Telomerase activity is more significant for predicting the outcome of ...

1

Telomerase activity is more significant for predicting the outcome of IVF 1

treatment than telomere length in granulosa cells 2

Wenjun WANG1,2,3

, Hong CHEN2,4

, Ruiqi LI3, Nengyong OUYANG

3, Jinghua CHEN

3, Lili 3

HUANG 3, Meiqi MAI

3, Ningfeng ZHANG

3, Qingxue ZHANG

3, Dongzi YANG

3 4

1. Corresponding author. Email: [email protected] 5

2. Equal contribution 6

3. Reproductive Medicine Centre, Department of Obs. & Gyn., Sun YatSen Memorial Hospital，7

Sun YatSen University, Guangzhou, P. R. China 8

4. Now works in the Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, 9

Shanghai Jiaotong University, Shanghai, P.R. China, finished the study in Sun Yat-Sen 10

Memorial Hospital 11

12

Abstract 13

Our previous study demonstrated that luteinised granulosa cells (GCs) have the potential to 14

proliferate and that the telomerase activity (TA) of luteinised GCs may predict the clinical 15

outcomes of in vitro fertilisation (IVF) treatment. However, in the field of telomere research, there 16

have always been different opinions regarding the significance of TA and telomere length (TL). 17

Thus, the current study compared the effects of these two parameters on the outcome of IVF 18

treatment in the same individuals. TL did not differ significantly between the pregnancy group and 19

the non-pregnancy group. The TA, number of retrieved oocytes and rate of blastocyst transfer 20

were significantly higher in the pregnancy group (0.8825 OD × mm, 12.75 ± 2.20 and 34.48%, 21

respectively, in the pregnancy group vs. 0.513 OD × mm, 11.60 ± 0.93 and 14.89%, respectively, 22

in the non-pregnancy group (P < 0.05)), while basal follicle-stimulating hormone (FSH) levels 23

were lower in the pregnancy group than in the non-pregnancy group. The subjects did not differ in 24

ovarian stimulation or other clinical characteristics. A TA increase of 1 OD × mm increased the 25

chance of becoming pregnant 4.769-fold (OR: 5.769, 95% CI: 1.434–23.212, P < 0.014). The 26

areas under the receiver operating characteristic (ROC) curves were 0.576 for TL and 0.674 for TA 27

of 29 Reproduction Advance Publication first posted on 28 January 2014 as Manuscript REP-13-0223

Copyright © 2014 by the Society for Reproduction and Fertility.

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(P = 0.271 and P < 0. 012, respectively). The corresponding cut-off points were 4.470 for TL and 28

0.650 OD × mm for TA. These results demonstrated that TA is a better predictor than TL of 29

pregnancy outcome following IVF. No other clinical parameters, including age, baseline FSH 30

level or peak estradiol level, distinguished between the pregnant and non-pregnant groups as 31

effectively as TA. 32

33

Key words: telomerase activity / telomere length / in vitro fertilisation / pregnancy 34

35

Introduction 36

Telomeres are the physical ends of eukaryotic chromosomes. They consist of a 5 to 15 kb 37

long tandem repeat hexanucleotide sequence (TTAGGG)n that protects the ends of the 38

double-stranded DNA (Blackburn,2001) Hence, telomeres play essential roles in maintaining 39

chromosomal stability and cell viability. 40

A possible relationship between telomeres and reproduction has recently been reported. There 41

is evidence that telomere length (TL) is longer in oocytes from women who become pregnant than 42

in those who fail to become pregnant after IVF treatment (Keefe, et al.,2007). A study of human 43

sister oocytes collected during IVF procedures found that TL can predict oocyte development 44

(Keefe, et al.,2007). Even the TLs of spare oocytes are associated with pregnancy following IVF 45

(Keefe, et al.,2006). Dorland’s study showed that women with fertility disorders had significantly 46

longer lymphocyte TLs than did a group of fertile women of similar ages (Dorland, et al.,1998). 47

This result indicates that TL studies examining actual embryo transfers may be more accurate than 48

TL studies using spare oocytes, sister oocytes or other somatic cells. Only one study (Treff, et 49

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al.,2011) showed that TL in polar bodies predicted aneuploidy in linked embryos. There is 50

evidence suggesting that short telomeres resulting from a telomerase deficiency can disturb oocyte 51

function by acting on cumulus cells peripherally distributed over oocytes (Liu, et al.,2002). 52

However, this result does not mean that longer telomeres are better. Wan S et al. (Wan, et al.,2012) 53

reported that chromosomes from cirrhotic cases had a significantly longer relative telomere 54

lengths (RTLs) than those from non-cirrhotic controls. Subjects with long RTLs had a significantly 55

increased cirrhosis risk. This result suggested that in certain conditions, TL predisposes subjects to 56

unfavourable outcomes. A widely accepted model holds that compensation for TL mainly depends 57

on telomerase, a specialised ribonucleoprotein complex. 58

Granulosa cells (GCs) are the most important somatic cells for determining the final size of 59

preovulatory follicles. We therefore sought to determine whether TL and telomerase activity (TA) 60

in GCs is associated with oocyte quality, embryo quality or IVF outcomes. To date, only 61

case-control studies have been used to investigate GC TL in women with or without diminished 62

ovarian reserves. The GC telomeres of women with diminished ovarian reserves have been found 63

to be significantly shorter than those of controls (S. Buttsa,2006). In addition, several studies have 64

demonstrated detectable TA in the GCs of diverse species, including pigs, cattle and humans 65

(Lavranos, et al.,1999; Liu and Zhu,2003; Tomanek, et al.,2008). There have been no reports of 66

predicting IVF outcomes via TA and TL. 67

Our previous study showed that luteinised GCs have the potential to proliferate and that the 68

TA of luteinised GCs may predict the clinical outcomes of IVF treatment (Chen, et al.,2011). We 69

therefore undertook the current study to determine whether TL and TA are correlated with oocyte 70

and embryo quality and with pregnancy following IVF in a population of women with normal 71

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ovarian function. In addition, we ascertained which measure (TL or TA) was more valuable for 72

predicting IVF outcomes. 73

Methods 74

Patient selection This study was conducted with patients who enrolled in the assisted reproduction 75

program at the Reproductive Medicine Centre of Sun-Yat-Sen Memorial Hospital from September 76

of 2009 to April of 2013. During the study period, 76 females between the ages of 23 and 38 years 77

who underwent their first fresh cycle of in vitro fertilisation (IVF) were recruited, and informed 78

consent for using their follicular fluid in this study was obtained. The inclusion criteria were a 79

regular menstrual cycle (every 24 to 33 days), a normal level of basal serum follicle stimulating 80

hormone (FSH ≤ 8.78 IU/L) and conventional IVF treatment using the long GnRH agonist 81

protocol. The exclusion criteria included using medication, having a history of ovarian surgery 82

known to impact ovarian function in the three months prior to the study and diagnosed 83

gynaecological disease such as polycystic ovary syndrome, hyperprolactinemia, endometrial cysts, 84

functional or organic ovarian cysts and uterine myoma. A total of 76 women were divided into a 85

pregnancy group and a non-pregnancy group. 86

Treatment procedure The long GnRH agonist protocol described below was followed. Prior to 87

combined follicle stimulating hormone (Merck Serono, Geneva, Switzerland or Puregon, Organon, 88

Barcelona, Spain) and human menopausal gonadotropin (Livzon, Zhuhai, China) stimulation, 89

which was used to enhance multiple follicle development, the patients underwent pituitary 90

desensitisation through an intramuscular injection of triptorelin acetate (Diphereline; Ipsen 91

Pharma Biotech. France). The gonadotropin dose was adjusted according to the ovarian response, 92

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which was monitored by transvaginal ultrasound and serum estradiol concentrations. Ovulation 93

was induced by human chorionic gonadotropin (Livzon, Zhuhai, China or Ovidrel, Merck Serono) 94

when no spontaneous luteinising hormone surge was detected. The cumulus-oocyte complexes 95

were retrieved 36 hours after the hCG injection by aspiration under transvaginal ultrasound 96

guidance. The oocytes were classified as “mature” if they had a fully expanded and had a 97

stretchable, homogeneous cumulus with a radiating corona layer and a visible polar body. 98

Fertilisation was assessed 16–18 hours after IVF or ICSI by searching the oocytes for evidence of 99

pronucleus formation and a second polar body. The zygotes with one or two pronuclei were 100

cultured, and embryo cleavage was assessed after 24 hours. The embryos were identified as grade 101

I (good quality) if they had 2–4 blastomeres of equal size and less than 20% fragmentation on day 102

2, more than 6 blastomeres of equal size and less than 20% fragmentation on day 3 or formed 103

compact/morula embryos or early blastocysts on day 4. The embryo transfer was performed 2–3 or 104

5 days after the oocyte collection. Three embryos were transferred in the patients who were 35 105

years or older, and two embryos were transferred in the patients who were younger than 35 years 106

old. Clinical pregnancy was determined by the presence of a gestational sac and a heartbeat by a 107

transvaginal ultrasound performed seven weeks after the embryo transfer. 108

Assay methods Independent investigators who were blinded to the clinical histories measured TL 109

by quantitative real-time PCR and determined TA using the telomeric repeat amplification 110

protocol (TRAP) followed by nondenaturing polyacrylamide gel electrophoresis silver staining. 111

GC Isolation A pooled collection of Follicular Fluid (FF) was obtained from each patient by 112

follicular aspirates collected during the oocyte retrieval. After completion of the ovum collection 113

and the isolation of the cumulus-oocyte complexes, the FF was immediately transported for 114

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analysis in a thermo-container at a constant temperature of 37°C. The GCs were isolated by 50% 115

density-gradient centrifugation in a Ficoll solution (Lymphoprep™, AXIS-SHIELD, Oslo, 116

Norway) for 15 min at 2000 rpm at room temperature and were then washed two to three times 117

with phosphate-buffered saline (PBS; SAGE, USA). The red blood cells interspersed with the GCs 118

were lysed by the addition of 1–3 mL of a lysis buffer (Beyotime, Haimen, China). The GC 119

viability, as assessed by trypan blue (Sigma, St. Louis, USA) staining, was approximately 75% (or 120

approximately 2×105 cells) in all of the patients. The purified GCs were snap frozen in liquid 121

nitrogen and stored at −80°C until protein isolation processing. 122

TA assay TA was assayed using a commercial kit (TRAPeze, Telomerase Detection Kit, Roche 123

Applied Science, Germany) that employed a modified TRAP. Briefly, cell extracts were prepared 124

by lysing the GCs with ice-cold lysis reagent, and 175 µL of the supernatant was collected to 125

ensure that no cellular debris from the pelleted cells was transferred. The protein concentrations 126

were measured using BCA kits (Shenergy Biocolor Bioscience & Technology Company, 127

Shanghai, China), flash frozen with liquid nitrogen in aliquots and stored at -80°C until assayed. 128

The cell extracts were heat-treated for 10 min at 85°C prior to the TRAP reaction to inactivate the 129

telomerase protein and create a negative control. The positive control (human kidney 293 cells) 130

was provided by the assay kit. For each sample and control, 14.63 µg of total cell protein was 131

added to 25 µL of a reaction mixture (Tris-buffer, telomerase substrate, primers, nucleotides, Taq 132

polymerase for one-step telomerase-mediated primer elongation, biotin-labelled P1-TS primer, P2 133

primer and DNA/RNA-free sterile water (Promega, Madison, Wisconsin, USA)) to a final volume 134

of 50 µL per assay for the PCR amplification. The mixture was transferred to a Biometra 135

Tgradient PCR thermocycler (Biometra, Germany) for primer elongation at 37°C for 30 min, 136

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telomerase deactivation at 94°C for 5 minutes, 33 cycles of amplification (94°C for 30 seconds, 137

50°C for 30 seconds and 72°C for 90 seconds) and 1 cycle of 72°C for 10 min. Non-denaturing 138

polyacrylamide gel electrophoresis (Native PAGE) on a 15% polyacrylamide gel was used to 139

visualise and analyse the PCR products. Specifically, 10 µL of each DNA sample was mixed with 140

2 µL of 6 × DNA loading buffer (TAKARA, Kyoto, Japan) and separated by electrophoresis with 141

a constant electric power of 30 W at 4°C for 3.5 hours after 1 hour of pre-electrophoresis under the 142

same conditions. After the electrophoretic migration was completed, the polyacrylamide gel was 143

incubated with silver stain to identify the telomere DNA bands. The samples were considered to 144

be TA-positive if the DNA ladders in the polyacrylamide gel had 6 bp intervals, as in Figure 3. A 145

relative quantitative analysis of the bands was performed using the Quantity One 4.6.2 software 146

(Bio-Rad, California, USA). 147

Quantitative real-time PCR (qPCR) methodology for detecting TL The measurement of TL by 148

qPCR was performed as described (Harle-Bachor and Boukamp,1996). Genomic DNA was 149

extracted from the GCs using the PureLink™ Genomic DNA kit (Invitrogen, California, USA), and 150

its quantity and quality were determined by 260/280 UV spectrophotometry. After extraction, the 151

isolated DNA samples were stored at -80°C until the analysis. The TL of the DNA samples was 152

analysed using the quantitative real-time amplification procedure previously described 153

(Cawthon,2002), with the following modifications. Standard curves were shown as Figure 2. All 154

of the samples, including the reference DNA sample, were analysed using a LightCycler 480 155

system (Roche, Germany). The qPCR reactions were analysed in triplicate using 20 µL of a 156

solution containing the following: 35 ng of the DNA sample, 1 × SYBR Green kit (TAKARA, 157

Kyoto, Japan), 0.2 µM of the telomere forward primer (CGG TTT GTT TGG GTT TGG GTT 158

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TGG GTT TGG GTT TGG GTT) and 0.2 µM of telomere reverse primer (GGC TTG CCT TAC 159

CCT TAC CCT TAC CCT TAC CCT TAC CCT). The single-copy 36B4 gene, which encodes the 160

acidic ribosomal phosphoprotein P0, was used as the amplification reference gene. Primers for this 161

gene were added to obtain a final concentration of 0.2 µM. The forward primer was 36B4u 162

(5'-CAG CAA GTG GGA AGG TGT AATCC-3'), and the reverse primer was 36B4d (5'-CCC ATT 163

CTA TCA TCA ACG GGT ACAA-3'). For both the telomere and 36B4 products, the cycling 164

conditions were 30 s at 95°C, followed by 40 cycles of 95°C for 5 s, 60°C for 20 s and 83°C for 5 165

s. All of the transition rates were set to 4°C/s. One standard curve was generated for each plate. 166

We performed standard curves for all plates as in Figure 2. The reference gene was 36B4, and the 167

target gene was the telomere. Additionally, we chose one sample divided into two parts for testing 168

in two plates to correct for variance between the two plates. Each sample was spotted in three 169

wells. Positive controls and negative controls were included in each plate. The standard curves for 170

TL and 36B4 were generated by the Light Cycler software using the second derivative method 171

( [ ] tCBt

Ctelomerest

C ∆−−

= 22/21)436()(

). The single-copy gene amplification reactions from a 172

reference DNA sample were serially 10-fold diluted with DNase/RNase free water (Promega, 173

Madison, Wisconsin, USA) to produce five concentrations of DNA ranging from 2.08 × 10-4

to 174

2.08 ng/µL. The ratio of the telomere repeat copy number (T) to the single-copy gene copy 175

number (S), which is proportional to the average TL in each sample, was then determined by the 176

standard curve method. 177

Hormone assays Blood samples were obtained from each patient prior to the initiation of a 178

stimulation cycle, either during days 1 to 5 of the menstrual cycle or at another time during the 179

treatment process depending on follicular development. A Beckman Coulter UniCel DxI 800 and 180

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the associated reagents (Beckman Coulter, Los Angeles, USA) were used to determine the serum 181

sex hormones levels by chemiluminescence. The serum specimens that were not immediately 182

assayed were stored at -80°C until use. 183

ELISA Assay of telomerase activity by telomeric repeat amplification protocol- enzyme- linked 184

immunosorbent assay. From January to April 2013, we continued to collect granulosa cells from 185

approximately 50 patients. However, only 22 specimens yielded a sufficient number of granulosa 186

cells. Telomeric repeat amplification protocol-enzyme-linked immunosorbent assay 187

(TRAP-ELISA) was performed using the telomerase kit Telo TAGGG Telomerase PCR 188

ELISA PLUS (Roche Diagnostics, Mannheim, Germany) according to the manufacturer’s 189

instructions. For negative controls, values routinely found are less than 0.1 A450nm to A690nm units. 190

For positive controls, the values is obtained with 1ul of the control template, low, and 1ml of the 191

control template, high, should be in the range of 0.2 – 0.5 and 2.0 – 4.0, respectively, after 10 min 192

substrate reaction. All samples were repeated three times and absorbance values were reported as 193

the A450 nm and 690nm reading and the final values were TA ∆A=A450nm-A690nm.. After 194

validation of method with these samples, assay of samples from 22 patients was performed. These 195

22 samples were also used for determining telomerase activity and telomere length based on the 196

methods mentioned above. 197

Data analysis and statistical methods The statistical analyses were performed using the 198

SPSS (Statistical Product and Service Solutions, Chicago, USA) 16.0 software. The normally 199

distributed data are reported as the mean ± standard error of the mean (S.E.M.), and the 200

non-normally distributed data are reported as the median (range). The pregnancy and 201

non-pregnancy groups were compared using independent samples T Test or a Mann-Whitney U 202

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test depending on the data distribution. The blastocyst transfer rates were compared using the 203

Pearson Chi-squared test. A binary logistic regression model was used to analyse the pregnancy 204

probability. The likelihood ratio test was used to calculate the significance of the regression model, 205

and the Nagelkerke R2 coefficient was used to evaluate and explain the variance. Receiver 206

operating characteristic (ROC) curves were used to analyse the predictive values of TL and TA for 207

clinical pregnancy, and their accuracies were evaluated by sensitivity, specificity and the 208

Youden’s index. Significance was defined as a (two-tailed) P value less than 0.05. 209

Results 210

Clinical characteristics of study subjects The mean age of the subjects was 30.49 ± 0.46 years, 211

the mean body mass index was 21.00 ± 0.49 kg/m2 and the mean basal FSH was 6.71 ± 0.17 IU/L. 212

A significant basal serum FSH difference was observed between the two groups; it was 6.61 ± 213

0.47 IU/L in the pregnancy group and 7.58 ± 0.32 IU/L in the non-pregnancy group (P < 0.025). 214

The peak estradiol level was lower in the pregnancy group than that in the non-pregnancy group 215

(2665.40 ± 396.21 vs. 2766.27 ± 563.36, P < 0.034). The groups did not differ significantly by age, 216

BMI, basal LH, E2, T or the starting dose, total dose or duration of gonadotropin (P > 0.05, as 217

shown in Table 1). 218

TL, TA and IVF laboratory parameters The TA, number of retrieved oocytes and the rate of 219

blastocyst transfer were higher in the pregnancy group (0.8825 OD × mm, 12.75 ± 2.20 and 220

34.48%, respectively) than in the non-pregnancy group (0.513 OD × mm, 11.60 ± 0.93 and 221

14.89%, respectively), (P < 0.05). TLs and the numbers of retrieved oocytes, mature oocytes, two 222

pronuclei and good quality embryos were comparable between the two groups (P > 0.05, as shown 223

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in Table 2). Tls, the numbers of retrieved oocytes, the numbers of metaphase II oocyte, the 224

presence of two pronuclei and number of good quality embryos were comparable between two 225

groups (P>0.05, as shown in Table 2) 226

Correlations between TL, TA and the clinical pregnancy rate The associations between TL and 227

TA and the clinical pregnancy rate were analysed by binary logistic regression and were assessed 228

by the odds ratios (Exp(B)) and 95% confidence intervals (CI). Given that age, the basal serum 229

FSH level, BMI, total Gn dose, peak estradiol level, the LH and FSH levels on the HCG day and 230

the number of retrieved oocytes may have confounded the associations with the pregnancy rate, 231

these variables were included in a multivariate regression equation using a forward stepwise 232

(conditional) method. After adjusting for the confounding factors, we found that a TA increase of 233

1 OD × mm increased the probability of pregnancy by 4.769-fold (OR: 5.769, 95% CI: 234

1.434–23.212, P < 0.014) and that the odds ratio coefficient for the peak estradiol level was 0.999 235

(95% CI: 0.998–1.000, P < 0.002). There were no significant correlations between TL, female age, 236

basal serum FSH, the total Gn dose or duration and the clinical pregnancy rate (P > 0.05, as shown 237

in Table 3). 238

Predictive value of TL and TA for clinical pregnancy The areas under the ROC curve were 0.576 239

(Youden’s index: 0.21, sensitivity: 85%, specificity: 36%) for TL and 0.674 (Youden’s index: 0.38, 240

sensitivity: 81.0%, specificity: 57.0%) for TA (P = 0.271 and P < 0.012, respectively). The ROC 241

curves are shown in Figure 1. The corresponding cut-off points were 4.47 for TL and 0.65 OD × 242

mm for TA (Table 4). These results demonstrated that TA better predicts pregnancy outcome 243

following IVF than TL. No other clinical parameters, including age, the baseline FSH level or the 244

peak estradiol level, distinguished between the pregnant and non-pregnant groups as effectively as 245

TA. 246

Methodologies Validation of TA assessment using ELISA. We get the results from 22 samples 247

after statistics. The results were obtained by the methodologies (ELISA and non-denaturing 248

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polyacrylamide gel silver staining) in agreement. Spearman correlation showed that these two 249

methods were concordant (r=0.917, P<0.05). Then, we further analyses the data from 22 250

specimens between pregnancy group and non-pregnancy group. The results were shown that TA 251

in pregnancy group was significant higher than that in non-pregnancy group in two methods 252

(Table5 and Figure4). We compared the square of ROC curve from TA (by ELISA and 253

Native-PAGE, respectively) and TL. Area of TA by ELISA was 0.497, area of TA by 254

Native-PAGE was 0.528, and area of TL was 0.090. 255

256

Discussion 257

According to classical theories, TA and TL are thought to be associated with age 258

(Keefe,2007; Keefe, et al.,2007). Thus, this study was designed to restrict the cohort age range to 259

diminish the age effect on TA. Consequently, there were no significant differences between the 260

ages within our study. However, this factor does not contradict the theory that TA and TL are 261

related to age. Thus, only IVF patients with fallopian tube occlusion who were 23–38 years old 262

were recruited. 263

The reason for selecting luteinised GCs for the prediction of IVF outcomes and for the 264

evaluation of egg and embryo quality is that the egg is fertilised to form the embryo for the 265

purpose of embryo transfer; a large number of luteinised GCs are typically discarded. In addition, 266

the development of GCs is synchronised with that of oocytes, and it can indirectly reflect oocyte 267

development. We analysed both telomere parameters, TL and TA, simultaneously for each patient. 268

Our data indicated that TA predicts pregnancy outcomes following IVF better than TL. The cases 269

were divided into a pregnant group and a non-pregnant group, thereby facilitating the 270

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identification of unique clinical features for patients with each pregnancy outcome. As shown in 271

Table 1, the two groups displayed no significant differences in a variety of parameters including 272

age, BMI, basal serum LH, basal serum E2, serum T, starting dose of Gn, total dose of Gn, 273

duration of COH (days) and peak estradiol level. The traditional view holds that basal FSH (bFSH) 274

reflects the ovarian reserve and can predict IVF outcomes (Brodin, et al.,2009). Our data were in 275

agreement with a study by Kassab et al. in which the authors demonstrated (Kassab, et al.,2009) 276

that the bFSH level significantly correlated with the clinical pregnancy rate. However, other 277

studies have argued that bFSH is not adequate to predict IVF outcomes because bFSH level 278

elevation may coincide with a good ovarian response (Thum, et al.,2009). 279

In most cells, TL correlates with cell division potential such that the shorter the length, the 280

older the cells (Mondello, et al.,1997; Baird, et al.,2003; Keefe, et al.,2007). Human tissues often 281

display age-dependent telomere shortening (Keefe and Liu,2009; Takubo, et al.,2010). A lack of 282

GC TA was associated with occult ovarian insufficiency (Butts, et al.,2009). Our previous study 283

suggested that patients with higher levels of TA in the GCs had a greater likelihood of pregnancy 284

than those with less TA. In our current study, we compared both TA and TL in GCs from the same 285

individuals, and we found that TA better predicts the outcome of IVF than TL. We considered that 286

TA was more significant than TL and may be a potential biomarker of IVF outcome. However, the 287

sample size was so limited (76 cases) that we did not observe the normal range of TA in 288

reproductive age women. Previous studies have indicated that TL positively correlates with 289

reproductive potential (Aydos, et al.,2005). TL has been reported to be superior to many clinical 290

parameters for prediction of post-IVF pregnancy outcome including bFSH, age and BMI (Aydos, 291

et al.,2005; Keefe, et al.,2007). Telomeric DNA deficiency is associated with genomic instability 292

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in somatic cells and plays a role in the development of the aneuploidies commonly found in 293

female germ cells and human embryos (Treff, et al.,2011). Interestingly, some studies have 294

revealed that patients with recurrent spontaneous abortions had shorter TLs. However, other 295

studies reported that the TLs of POF patients were longer that those of the control group (Hanna, 296

et al.,2009). Additional studies reported that infertile women undergoing controlled ovarian 297

hyperstimulation treatment had significantly longer telomeres in comparison to healthy women of 298

a similar age (Dorland, et al.,1998). In general, most studies agreed that female fertility disorders 299

are likely to be associated with fewer cell divisions. A possible explanation is that the cells may 300

have prolonged cell cycle durations. This controversy also showed that TL alone was not enough 301

to fully reveal the reproductive potential when we compared the pregnant and non-pregnant group. 302

Moreover, the two groups were relatively indistinguishable in terms of the numbers of harvested 303

oocytes, the proportion of mature eggs, the fertilisation rate, the embryonic cleavage rate, and the 304

proportion of high quality embryos (Table 2). In contrast, the data in Table 3 revealed that TA 305

positively correlated with the pregnancy rate such that an increase of every 1 OD × mm in TA 306

resulted in a 4.769-fold increased likelihood of pregnancy. Many factors have previously been 307

implicated in IVF outcome, such as TL, age, basal FSH, BMI, total Gn dose, peak estradiol level, 308

the LH and FSH levels on the HCG day and the number of retrieved oocytes, but these factors did 309

not affect post-IVF pregnancy rates. Together, the data suggest that TA is a better indicator of 310

pregnancy than other factors and that TL alone is not a sufficient proxy for ovarian reserves and 311

reproductive potential. Importantly, our results show clear differences in comparison to the data 312

from Aydos et al. Those authors examined peripheral leucocytes in women who were 313

approximately 50 years old and investigated the connections between TL and reproductive 314

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lifespan (Aydos, et al.,2005). In contrast, our study examined GCs, which grow synchronously 315

with oocytes, and restricted the age of our subjects to less than 38 years old. Although there was 316

no effect of TL on pregnancy, TA was higher in the pregnancy group than in the non-pregnancy 317

group. Therefore, telomere shortening may be compensated for by an elevation of TA. Dong C.K. 318

suggested that telomerase may re-activate when cells suffer from a crisis to stabilise the TLs 319

(Dong, et al.,2005). Only clones with stabilised telomeres, which apparently occurred by the 320

activation of telomerase, continued to proliferate indefinitely (Counter CM, et al.,1994). 321

Thus far, there are no reports explicitly comparing TA and TL in cellular proliferative and 322

differentiation potentials. Telomerase can compensate for telomere shortening resulting from cell 323

division, maintain genetic integrity (Mondello et al. 1997) and synthesise TTAGGG repeats, 324

which assists with the prevention of chromosomal fusion (Mondello, et al.,1997; Cottliar and 325

Slavutsky,2001). Treff et al. (Treff, et al.,2011) studied several SNPs in the hTERT gene, 326

rs2736122, rs4246742, rs4975605, rs10069690, rs2736100, rs2853676 and rs7726159, and 327

examined changes in TL. Moreover, Choudhary B et al. (Choudhary, et al.,2012) proposed that the 328

postnatal decrease in TA leads to telomere shortening, which contributes to senescence. Further 329

analysis of the expression of the major telomerase genes Tert and TR would help validate the TA 330

assay in this study. This experiment might suggest that the alteration of TA precedes the alteration 331

of TL. 332

Our data indicate that the pregnant group had significantly higher average TA and 333

proportions of blastocyst transfer than did the non-pregnant group. TA better predicts the post-IVF 334

outcome than TL, which was statistically indistinguishable between the pregnant and 335

non-pregnant groups. However, because telomerase maintains telomere stability, higher TA leads 336

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to longer TL (Hiyama and Hiyama,2007; Miyashita, et al.,2011). Thus, it remains inconclusive 337

whether TA or TL is more important. One possible reason is that the TL and length range as well 338

as the level of TA have yet to be established in a normal proliferative state. 339

As shown in Table 3, there was no correlation between pregnancy and any of the following 340

factors: age, basal FSH, BMI, total Gn dose, peak estradiol level, LH and FSH levels on the HCG 341

day and the number of retrieved oocytes. Our results indicate that TA, but not TL, significantly 342

correlated with the outcome of pregnancy. As illustrated by the ROC shown in Fig. 1, TA had a 343

notable impact on post-IVF pregnancy outcomes and was therefore a better pregnancy indicator 344

than TL. For example, some studies have found that mutations in the RNA template for telomerase 345

could be passed onto the corresponding telomere fragments. These mutated telomeres may result 346

in a pre-anaphase cell cycle arrest phenotype, indicating that TL might not change immediately in 347

response to an alteration in TA (Blackburn,2005). Lin et al. (Liu, et al.,2002) discovered that 348

infertility in telomerase knockout mice is associated with gradual telomere shortening. These 349

observations have implicated TL and TA in infertility because impairing the elongation and 350

maintenance of telomeres may eventually lead to infertility. Some scholars (Cao, et al.,2002; 351

Calado and Chen,2006) have hypothesised that telomerase also plays an essential role in cell 352

viability. Some studies(Yamagata, et al.,2002) have suggested that telomerase in GCs possibly 353

plays an important role in maintaining the normal development of ovarian follicles, as telomerase 354

plays versatile roles in various reproduction pathways. 355

On the reliability of the methodologies for TA detection, we referred the methods and 356

followed the process from the papers which had been published (Kim, et al.,1994; Harle-Bachor 357

and Boukamp,1996). Furthermore, we used ELISA to validate our methods on 22 new samples 358

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17

and the results were obtained by the methodologies (ELISA and non-denaturing polyacrylamide 359

gel silver staining) in agreement. It suggested that TA assessment was reliable. For the limitation 360

of the sample size (22 samples), there might be certain bias. We considered that the semi-quantity 361

method (non-denaturing polyacrylamide gel silver staining) was not a perfect method and we will 362

use ELISA to test TA in the following specimens and the following study. The patients recruited 363

in this study were all under 38 years old, and thus the sample size should be expanded to evaluate 364

the outcomes of pregnancy for IVF-recipient women with a wider age range. Thus, the TL and TA 365

values that are more indicative for the general population should be generated for predicting 366

pregnancy in the general population. 367

368

Competing interests 369

The authors declare that they have no competing interests. 370

Acknowledgements: 371

We thank Mo Yaqin Ph.D. and Wang Jing for laboratory technical assistance and Huang 372

Baoyun for data collection. 373

Funding: 374

This work was supported in part by grants from the Science Technology Research and 375

Development Project of Guangdong Province (2010B031600043), the found of science research 376

of population and family planning commission of Guangdong Province (2009231) and the 377

National Science Technology Research Project (81070466) in China. 378

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ReferencesReferencesReferencesReferences

Aydos SE, Elhan AH, Tukun A. 2005. Is telomere length one of the determinants of

reproductive life span. Arch Gynecol Obstet. 272(2): 113-6.

Baird DM, Rowson J, Wynford-Thomas D, Kipling D. 2003. Extensive allelic

variation and ultrashort telomeres in senescent human cells. Nat Genet. 33(2):

203-7.

Blackburn EH. 2001. Switching and signaling at the telomere. Cell. 106(6): 661-73.

Blackburn EH. 2005. Telomeres and telomerase: their mechanisms of action and the

effects of altering their functions. FEBS Lett. 579(4): 859-62.

Brodin T, Bergh T, Berglund L, Hadziosmanovic N, Holte J. 2009. High basal LH

levels in combination with low basal FSH levels are associated with high

success rates at assisted reproduction. Hum Reprod. 24(11): 2755-9.

Butts S, Riethman H, Ratcliffe S, Shaunik A, Coutifaris C, Barnhart K. 2009.

Correlation of telomere length and telomerase activity with occult ovarian

insufficiency. J Clin Endocrinol Metab. 94(12): 4835-43.

Calado RT, Chen J. 2006. Telomerase: not just for the elongation of telomeres.

Bioessays. 28(2): 109-12.

Cao Y, Li H, Deb S, Liu JP. 2002. TERT regulates cell survival independent of

telomerase enzymatic activity. Oncogene. 21(20): 3130-8.

Cawthon RM. 2002. Telomere measurement by quantitative PCR. Nucleic Acids Res.

30(10): e47.

Chen H, et al. 2011. Women with high telomerase activity in luteinised granulosa

cells have a higher pregnancy rate during in vitro fertilisation treatment. J

Assist Reprod Genet. 28(9): 797-807.

Choudhary B, Karande AA, Raghavan SC. 2012. Telomere and telomerase in stem

cells: relevance in ageing and disease. Front Biosci (Schol Ed). 4: 16-30.

Cottliar AS, Slavutsky IR. 2001. [Telomeres and telomerase activity: their role in

aging and in neoplastic development]. Medicina (B Aires). 61(3): 335-42.

Counter CM BFM, Wang P HCB, Bacchetti S. 1994. Stabilization of short telomeres

and telomerase activity accompany immortalization of Epstein-Barr

virus-transformed human B lymphocytes. journal of virology. 68(5):

3410-3414.

Dong CK, Masutomi K, Hahn WC. 2005. Telomerase: regulation, function and

transformation. Crit Rev Oncol Hematol. 54(2): 85-93.

of 29

19

Dorland M, van Kooij RJ, te VER. 1998. General ageing and ovarian ageing.

Maturitas. 30(2): 113-8.

Hanna CW, Bretherick KL, Gair JL, Fluker MR, Stephenson MD, Robinson WP. 2009.

Telomere length and reproductive aging. Hum Reprod. 24(5): 1206-11.

Harle-Bachor C, Boukamp P. 1996. Telomerase activity in the regenerative basal layer

of the epidermis inhuman skin and in immortal and carcinoma-derived skin

keratinocytes. Proc Natl Acad Sci U S A. 93(13): 6476-81.

Harle-Bachor C, Boukamp P. 1996. Telomerase activity in the regenerative basal layer

of the epidermis inhuman skin and in immortal and carcinoma-derived skin

keratinocytes. Proc Natl Acad Sci U S A. 93(13): 6476-81.

Hiyama E, Hiyama K. 2007. Telomere and telomerase in stem cells. Br J Cancer.

96(7): 1020-4.

Kassab A, Sabatini L, Tozer A, Zosmer A, Mostafa M, Al-Shawaf T. 2009. The

correlation between basal serum follicle-stimulating hormone levels before

embryo cryopreservation and the clinical outcome of frozen embryo transfers.

Fertil Steril. 92(4): 1269-75.

Keefe DL. 2007. Telomeres and meiosis in health and disease. Cell Mol Life Sci.

64(2): 115-6.

Keefe DL, Liu L. 2009. Telomeres and reproductive aging. Reprod Fertil Dev. 21(1):

10-4.

Keefe DL, Liu L, Marquard K. 2007. Telomeres and aging-related meiotic

dysfunction in women. Cell Mol Life Sci. 64(2): 139-43.

Keefe DL, Marquard K, Liu L. 2006. The telomere theory of reproductive senescence

in women. Curr Opin Obstet Gynecol. 18(3): 280-5.

Kim NW, et al. 1994. Specific association of human telomerase activity with

immortal cells and cancer. Science (80- ). 266(5193): 2011-5.

Lavranos TC, Mathis JM, Latham SE, Kalionis B, Shay JW, Rodgers RJ. 1999.

Evidence for ovarian granulosa stem cells: telomerase activity and localization

of the telomerase ribonucleic acid component in bovine ovarian follicles. Biol

Reprod. 61(2): 358-66.

Liu L, Blasco M, Trimarchi J, Keefe D. 2002. An essential role for functional

telomeres in mouse germ cells during fertilization and early development. Dev

Biol. 249(1): 74-84.

Liu W, Zhu GJ. 2003. [Expression of telomerase in human ovarian luteinized

granulosa cells and its relationship to ovarian function]. Zhonghua Fu Chan

of 29

20

Ke Za Zhi. 38(7): 402-4.

Miyashita N, et al. 2011. Cloned cows with short telomeres deliver healthy offspring

with normal-length telomeres. J Reprod Dev. 57(5): 636-42.

Mondello C, Riboni R, Casati A, Nardo T, Nuzzo F. 1997. Chromosomal instability

and telomere length variations during the life span of human fibroblast clones.

Exp Cell Res. 236(2): 385-96.

S. Buttsa ASSM. 2006. Telomere length and the aging granulosa cell: Correlation with

diminished ovarian reserve .（2006）Fertility and Sterility Volume 86, Issue 3,

Supplement 1, September 2006, Page S406. 86(3 Supplement 1): Page S406.

Takubo K, et al. 2010. Changes of telomere length with aging. Geriatr Gerontol Int.

10 Suppl 1: S197-206.

Thum MY, Kalu E, Abdalla H. 2009. Elevated basal FSH and embryo quality: lessons

from extended culture embryos: raised FSH and blastocyst quality. J Assist

Reprod Genet. 26(6): 313-8.

Tomanek M, Chronowska E, Kott T, Czernekova V. 2008. Telomerase activity in pig

granulosa cells proliferating and differentiating in vitro. Anim Reprod Sci.

104(2-4): 284-98.

Treff NR, Su J, Taylor D, Scott RT Jr. 2011. Telomere DNA deficiency is associated

with development of human embryonic aneuploidy. PLoS Genet. 7(6):

e1002161.

Wan, S., Hann, H.W., Myers, R.E., Fu, X., Hann, R.S., Kim, S.H., Tang, H., Xing, J.,

& Yang, H. (2012). Telomere length in circulating serum DNA as a novel

non-invasive biomarker for cirrhosis: a nested case-control analysis. Liver Int,

32(8):1233-1241.

Yamagata Y, et al. 2002. Changes in telomerase activity in experimentally induced

atretic follicles of immature rats. Endocr J. 49(6): 589-95.

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Table 1

The baseline characteristics and controlled ovarian stimulation

Characteristics Pregnancy group

(n=29)

Non-pregnancy

group

(n=47)

Fd/Z

e P value

Age (y)a 29.13±1.32 28.80±1.74 0.001 0.149

BMI (kg/m2) a 22.50±1.32 19.62±0.92 2.377 0.425

Basal serum FSH (IU/L) a,b 6.61±0.47 7.58±0.32 2.125 <0.025

Basal serum LH (IU/L) a 3.50±0.44 4.68±1.03 0.679 0.353

Basal serum E2 (pg/mL)^

37.20

(16.69-363.82)

30.07 (16.33-72.77) -0.692 0.489

Serum T(nmol/L) a 1.35±0.13 1.38±0.17 1.046 0.336

PRL 13.33±2.20 18.26±4.12 0.987 0.740

Starting Gn dose (IU) c 150(100-225) 112.50 (100-300) -0.964 0.335

Total Gn dose (IU) a 1884.38±266.13 1807.50±479.77 1.756 0.394

Duration of COH (days) c 11.5(7-12) 12 (7-12) -1.352 0.176

Peak estradiol level (pg/mL) a,b 2665.40±396.21 2766.27±563.36 6.173 <0.034

BMI=body mass index; FSH=follicle stimulating hormone, LH=luteinising hormone.

a The values are means ± standard deviations.

b A significant difference was detected between the pregnancy and non-pregnancy groups by the

independent-samples T Test (P<0.05).

c The values are medians (ranges).

d For the Pearson Chi-Squared test.

e For the Mann-Whitney U.

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Table 2

The telomere length, telomerase activity and in vitro fertilisation laboratory parameters

Variables Pregnancy group

(n=29)

Non-pregnancy group

(n=47)

Fd/Ze P value

TL (T/S Ratio) 3.60±0.84 3.18±0.70 3.18 0.154

TA (OD×mm)a 0.8825 (0-1.33) 0.513 (0-1.54) -2.679 <0.007

Retrieved oocytes (n) 12.75±2.20 11.60±0.93 0.277 0.045

Metaphase II oocytes (n) 10.50±1.66 9.40±1.17 0.149 0.216

Rate of mature oocytes (%)a 85.71(57-100) 90.19(4-100) -0.622 0.534

Number of two pronuclei 8.93±1.28 7.60±1.32 0.643 0.133

Fertilisation rate (%)a 77.27(29-100) 83.77(8-100) -1.236 0.216

Rate of good quality embryos (%)a 21.05(0-67) 22.48(0-68) -0.604 0.546

Utilisation rate of embryos (%) 72.88±3.62 67.35±2.93 0.004 0.24

Rate of blastocyst transferral (%)b,c

34.48(10/29) 14.89(7/47) 3.963 <0.047

The fertilisation rate was calculated by one of the following expressions: number of mono-pronucleus + number

of two-pronuclei + number of multi-pronuclei + number of late cleavage)/ number of oocytes retrieved when IVF

cycles were performed, or (number of mono-pronucleus + number of two-pronuclei + number of multi-pronuclei)/

number of metaphase II oocytes when ICSI cycles were performed. The embryo utilisation rate was calculated by

the following expression: (number of cryopreserved embryos + number of embryos transferred)/ number of

oosperm. The blastocyst transferral rate was calculated as the fraction of blastocysts transferred out of the total

number of embryos transferred. Consistent with previously published findings, a high-quality embryo was defined

by the absence of multinucleated blastomeres, four or five blastomeres on day 2, seven or more cells on the

following day, and < 20% fragments(Van Royen E, De Neubourg D, Van de Meerssche M, & Eestermans W,1999;

Ebner, Moser, Sommergruber, & Tews,2003)

a The values are medians (ranges) and are compared using the Mann-Whitney U test.

b The values are percentages and are compared using the Pearson Chi-Squared test.

c A significant difference was detected between the pregnancy and non-pregnancy groups by the

independent-samples T Test (P<0.047).

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Table 3

The associations between the stepwise regression variables and the clinical pregnancy rate

Variables Coefficient (B) OR (Exp(B)) (95% CI) Wald (χ2

) P value

Telomerase activity 1.753 5.769 (1.434-23.212) 6.088 <0. 014

Total Gn dose -0.001 0.999(0.998-1.000) 3.754 0.053

LH level on HCG day 0.000 1.000(0.999-1.000) 0.155 0.694

Peak estradiol level 0.000 0.999(0.998-1.000) 9.526 <0.002

Constant 4.034 56.462 5.347 0.021

Telomere length, telomerase activity, female age, basal FSH, BMI, total Gn dose, peak estradiol level, LH and FSH

level on HCG day, number of retrieved oocytes were retained in the forward stepwise (conditional) logistic

regression equation and were treated as continuous variables. Telomerase activity and peak estradiol level were

significant. The -2 log likelihood = 61.364, and the Nagelkerke R2 = 0.41.

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Table 4

The predictive values of telomere length and telomerase activity for pregnancy

Objects Telomerase activity Telomere length

Area under the ROC Curve 0.674 0.576

Cut-off point 0.650 4.470

Sensitivity (%) 81.0 85.0

Specificity (%) 57.0 36

Youden’s index 0.38 0.207

SE 0.066 0.072

P value a <0. 012 0.271

aThe null hypothesis was true area = 0.5.

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Table 5 TA assessment using Native-PAGE and ELISA.

Pregnancy group

(n=4)

Non-pregnancy group

(n=18)

Fb P value

Native-PAGE (OD×mm) 0.58±0.28 a 0.13±0.06

a

4.30 <0.05

ELISA(abs A450 nm– A690 nm) 0.109±0.02

a 0.069±0.003

a 9.47 <0.05

Notes: a: The values are means ± standard deviations. b: For the independent-samples T Test.

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Figure1 Diagonal segments are produced by ties.

254x137mm (96 x 96 DPI)

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Figure2 Standard curve used to measure the relative T/S ratio. Five DNA concentrations over a 10-fold range were generated by serial dilution from 2.08×104 to 2.08ng/ul and aliquoted to microtiter plate wells; the final amounts per well 35ng of the DNA sample, with the middle quantity approximately matching that of

the samples being assayed. The Ct of a DNA sample is the frational number of PCR cycles to which the sample must be subjected in order to accumulate enough products to cross a set threshold of magnitude of fluorescent signal. Any individual or pooled human DNA sample may be used to create the standard curves, as long as the Ct of each assayed sample falls within the range of Ct values of the standard curves. Circles,

single copy gene 36B4; triangles, telomere. 183x232mm (96 x 96 DPI)

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Figure3 Levels of TA in GCs 125x150mm (96 x 96 DPI)

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Figure4 Means of TA in Native-PAGE and ELISA 217x77mm (96 x 96 DPI)

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