Bone Homeostasis and Pathology - Rochester, NY · § Factors regulang bone homeostasis § Disorders...
Transcript of Bone Homeostasis and Pathology - Rochester, NY · § Factors regulang bone homeostasis § Disorders...
BoneHomeostasisandPathology
Instructor:RomanEliseev
Outline:§ Boneanatomyandcomposi<on§ Boneremodeling§ Factorsregula<ngbonehomeostasis§ Disordersofbonehomeostasis:
-Boneloss-Abnormalboneacquisi<on
§ MethodsandMouseModels
AdultSkeletonAxialSkeleton
AppendicularSkeleton
Imagefromwww.pngall.com
206bones
AdultBoneArchitecture
Diaphysis
Epiphysis
Cor<calboneMarrowcavity
Trabecularbone
Metaphysis
BoneHistology
Trabecularbone
Cor<calbone
Marrowfat
Bonemarrow
Subchondralbone
BoneComposi<onBoneisamineralizedorganicmatrixcomposedof:
• TypeIcollagenandnon-collagenousproteins(osteoid)• Hydroxyapa<tecrystals(Ca5(PO4)3(OH))
Bone-formingcellsareosteoblasts(OB)thatproducecollagenIanddepositHA
Osteoblasts
Bone
BoneisFormedbyOsteoblasts
Wagneretal.,PPARRes.,2010
OBsoriginatefromBoneMarrowStromal(a.k.a.MesenchymalStem)Cells(BMSC)andterminallydifferen<ateintoosteocytes(OT).
BoneisResorbedbyOsteoclasts
ImagefromSciencePhotoLibrary
Osteoclasts(OC)areboneresorbingmul<nucleatedcellsthatoriginatefromhematopoie<ccells(monocyte/macrophage)
BoneForma<onvsResorp<on=DynamicEquilibrium(~10%ofadulthumanskeletonis
replacedannually)
Homeostasis=equilibrium(Greek:ὁμοίως+στάσις)
Boneforma<on
Bonerosorp<on
LiningcellsOB
BONE
BloodvesselBMSC
BMSC–bonemarrowstromal(a.k.a.mesenchymalstem)cell
OB–osteoblastOT–osteocyte
TGFb,IGF1,OCN CollagenI
OT
IntactBone
Apoptosis(~70%)
LiningcellsOB
BONE
BloodvesselBMSC
BMSC–bonemarrowstromal(a.k.a.mesenchymalstem)cell
OB–osteoblastOT–osteocyteHSC–hematopoie<cstemcell
OCP–osteoclastprecursor
OT
Remodeling:Ini<alPhase
HSC
OCPRANKL,m-CSF?
OB
BONE
BloodvesselBMSC
BMSC–bonemarrowstromal(a.k.a.mesenchymalstem)cell
OB–osteoblastOT–osteocyteOC–osteoclast
OT
Remodeling:Resorp<onPit
pH≤4
OC
pH≤4
OC
OBOB
BONE
BloodvesselBMSC
TGFb,IGF1
Remodeling:Recruitment/Ac<va<onofBMSCsintoOsteogenicLineage
OB
BONE
BloodvesselBMSC
OT
Remodeling:NewBoneForma<on
Newbone
Osteoblast
Osteocyte
Osteoclast
TRAP Staining
HistologyofBoneRemodeling
Image–courtesyofDr.J.Jonason
PhasesofRemodeling
FactorsRegula<ngBoneHomeostasis
Harada S and Rodan GA., (2003) Nature 423: 349-355.
DisordersofBoneHomeostasis
Boneforma<onbyosteoblastsBone
rosorp<onbyosteoclasts
BONELOSS
Bonerosorp<onbyosteoclasts Bone
forma<onbyosteoblasts
BONEGAIN
• Osteogenesis Imperfecta (aka, Brittle Bone Disease) • Most commonly inherited bone disorder • Autosomal dominant mutations (over 800 identified) in the genes encoding the α1
and α2 chains of type I collagen • Clinical features include; skeletal fragility with increased fracture risk, blue sclera,
hearing loss, dental imperfections, joint laxity
• Osteopetrosis (aka, Marble Bone Disease)
• Osteoporosis
• Paget Disease
• Hyperparathyroidism
DisordersofBoneHomeostasis
CourtesyofDr.J.Jonason
• Osteogenesis Imperfecta (aka, Brittle Bone Disease)
• Osteopetrosis (aka, Marble Bone Disease) • Rare genetic disease characterized by reduced bone resorption • Autosomal dominant or recessive mutations affecting osteoclast numbers or function • Clinical features include; frequent fractures, scoliosis, cranial nerve deficits, anemia • First genetic disease treated with a bone marrow transplant
• Osteoporosis
• Paget Disease
• Hyperparathyroidism
DisordersofBoneHomeostasis
CourtesyofDr.J.Jonason
• Osteogenesis Imperfecta (aka, Brittle Bone Disease)
• Osteopetrosis (aka, Marble Bone Disease)
• Osteoporosis • Common disease associated with decreased bone mass and increased fracture risk • Caused by both genetic and environmental factors • High societal burden with ~2 million fractures in the US annually due to osteoporosis,
at a cost of around 22 billion dollars to treat
• Paget Disease
• Hyperparathyroidism
DisordersofBoneHomeostasis
CourtesyofDr.J.Jonason
• Osteogenesis Imperfecta (aka, Brittle Bone Disease)
• Osteopetrosis (aka, Marble Bone Disease)
• Osteoporosis
• Paget’s Disease • Uncontrolled bone remodeling leading, ultimately, to areas of high bone mass that
are architecturally unsound • Onset in late adulthood with causes unknown (likely to be a combination of genetic
and environmental factors) • Most prominent clinical feature is bone pain, but can also lead to fracture, bone
deformities, and nerve compression
• Hyperparathyroidism
DisordersofBoneHomeostasis
CourtesyofDr.J.Jonason
• Osteogenesis Imperfecta (aka, Brittle Bone Disease)
• Osteopetrosis (aka, Marble Bone Disease)
• Osteoporosis
• Paget’s Disease
• Hyperparathyroidism • Excess parathyroid hormone (PTH) in the bloodstream due to over-activity of the
parathyroid glands • Can be primary (due to hyperplasia or tumor of the glands) or secondary (due to
hypocalcemia and compensatory increases in PTH secretion) • Results in increased bone resorption leading to increased fracture risk
DisordersofBoneHomeostasis
CourtesyofDr.J.Jonason
ImagesfromBionewsTexas
-Fracture-Delayed
repair
Osteoporosis
§ Osteoporosisisfoundin70%oftheelderlypopula6on
§ Post-menopausalwomenaremostaffected(25millionAmericanwomenwithOsteoporosis)
§ 1.9millionfracturesannuallyduetolowbonemass.
§ 1of3womenwilldevelopavertebralfracturebyage65,and1of3womenwilldevelopahipfracturebyage85.
§ $22billiondollarsperyearisspentontrea6ngOsteoporosis.
EpidemiologyofOsteoporosis
Journal of Bone and Mineral Research Volume 29, Issue 9, pages 1917-1925, 20 AUG 2014 DOI: 10.1002/jbmr.2286 http://onlinelibrary.wiley.com/doi/10.1002/jbmr.2286/full#jbmr2286-fig-0001
EpidemiologyofOsteoporosis
C57Bl/6Jmice:
DEXA Dual Energy X-ray Absorptiometry
T-score = comparison to healthy young bone Z-score = comparison to a reference group of
the same age, race, and gender as the patient
DiagnosisofOsteoporosis
CourtesyofDr.J.Jonason
An<-resorp<vedrugs:Bisphosphonates
TreatmentofOsteoporosis
Watts NB and Diab DL., (2010) Journal of Clinical Endocrinology and Metabolism. (95)4: 1555-1565.
SERMS
TreatmentofOsteoporosis
SERMS:Selec<veEstrogenReceptorModulators
Ac6on:Drugsthatactasestrogenagonists,ac<va<ngtheestrogenreceptorinordertoreduceosteoclastac<vityandboneresorp<on.
Drug:Raloxifene(Evista)
Dose:60mg/dayformanyyears
Notes:Notaseffec<veasbisphosphonates.Onlyappearstoprotectspineandnothipsfromfracture.
TreatmentofOsteoporosis
Boneanabolicagents
PTH: rPTH(1-34); Forteo. Under clinical investigation for the use in fracture non-union repair, treatment of osteoporosis.
BMPs: rBMP2 and rBMP7. Under clinical investigation and use for the repair of fracture non-union (InFuse). Recent complications in spinal fusion.
Neutralizing antibodies for Wnt inhibitors: anti-Dkk1 and anti-SOST. Under research and pre-clinical investigation for treatment of OA and fracture repair.
LabMethodstoAssessBoneHomeostasis
DEXA
LabMethodstoAssessBoneHomeostasis
micro-CT
Shumetal.,PLoSOne,2016
LabMethodstoAssessBoneHomeostasis
Histology/Histomorphometry
Shumetal.,PLoSOne,2016
PrimaryMeasurements:-BoneArea(B.Ar.)vsTotalArea(T.Ar.)-Surface,i.e.BoneSurface(BS)-CellNumberperSurface/Area
=OB.N.=OT.N.
OsteoMeasureorVisiopharm
LabMethodstoAssessBoneHomeostasis
Histology/Histomorphometry
Shumetal.,PLoSOne,2016
PrimaryMeasurements:-Surface:OsteoclastSurfaceperBoneSurface(OC.S./BS)-CellNumber:OsteoclastNumberperBoneSurface(N.OC/BS)
LabMethodstoAssessBoneHomeostasis
DynamicBoneLabeling(BoneForma<on)
MiceareinjectedwithAlizarinRed10dbeforesacrifice&withCalcein5dbeforesacrifice.Bonearefrozenandsec<oned.Labeledboneisvisualizedusingfluorescencemicroscopy.
Shumetal.,PLoSOne,2016
DerivedIndices:-MineralizingSurface(MS/BS)-MineralApposi<onRate(MAR)-BoneForma<onRate(BFR)
LabMethodstoAssessBoneHomeostasis
BoneTurnoverSerumMarkers
Forma<on: Resorp<on:
P1NP CTXPerrecommendaKonoftheInternaKonalOsteoporosisFoundaKon(IOF)andtheInternaKonalFederaKonforClinicalChemistry(IFCC)
UsefulMouseModels
Osteolineage-specificCreModels:• BMSC:Prx1,Nes<n,LepR,aSMA,Osx• OB:Osx(early),Col13.2kb(early),Col1
2.3kb(late),OCN(late)• OT:DMP1
UsefulMouseModels
Osteoclast-specificCreModels:• CD11b• Lyzm• Trap
Take-HomeMessage
Bonehomeostasisisadynamicequilibriumdueto
opposingac<onsandcouplingofbone-formingOBsandbone-resorbingOCs.