R. WechslerS. Cohen, Y. Shachaf, O. Nadir and

A novel ‘Bead-In-Pellet’ model for tissue-implant interactions: Application for cartilage repair biomaterials

Introduction:

GelrinC™ is a biodegradable hydrogel intended for cartilage repair and

composed of water (>90%), cross-linked polyethylene-glycol-diacrylate

(PEG-DA) and denatured fibrinogen. To study its tissue interactions and

biodegradation in-vitro, a novel technique (‘Bead-In-Pellet‘) was developed

in which candidate materials are evaluated by encapsulating them within

pellet cultures. The purpose of the current work, beyond the study of

GelrinC-tissue interactions, was to demonstrate the utility of such a system

for the in-vitro characterization of other biomaterials that are intended for

cartilage repair.

Regentis Biomaterials, Or Akiva, Israel

Materials and methods: Single GelrinC/PEG-DA beads (d = 1mm) or fibrin clots were mixed with

suspension of primary ovine chondrocytes (passage 2, 1.5-2 x106 cells) or

human mesenchymal stem cells (passage 5, 0.25 x 106 cells) in a 15 ml tube

containing 0.5 ml chondrogenic medium (Bernstein et al., 2009; Sekiya et

al., 2005). Following low speed centrifugation (500g for 10 minutes), the

cell pellets with the beads were incubated for various time points. Paraffin-

embedded pellets were sectioned and stained with anti-PEG, anti-

fibrinogen, anti-collagen I and anti-collagen II antibodies followed by

staining using Envision™ G│2 System/AP Mouse Permanent Red

(DAKO).

Results:

Conclusions: Using GelrinC as a model material for cartilage repair,

the novel ‘Bead-In-Pellet’ system successfully evaluated the followings:

Material-tissue integration

Tissue infiltration into the material

Material degradation mechanism and degradation products

Material-mediated support for chondrogenic differentiation

Contribution of individual components

In-vivo behavior of the implant in the intended tissue

The ‘Bead-In-Pellet’ system can serve as an effective in-vitro model

for the study of biomaterials in the field of cartilage/bone repair.

I. ‘Bead-In-Pellet’: Tissue-material interaction (chondrocytes pellets)

II. ‘Bead-In-Pellet’: Effect on chondrogenic differentiation

III. ‘Bead-In-Pellet’: Kinetics of degradation (chondrocytes pellets)

IV. ‘Bead-In-Pellet’: A prediction of material behavior in-vivo

Chondrocytes Mesenchymal Stem Cells

GelrinC

GelrinC

PEG-DA

Fibrin

GelrinC

GelrinC

Pellet

Pellet

Pellet

Pellet

GelrinC

GelrinC

Pellet

Pellet

Pellet

Pellet

GelrinC Pellet

GelrinC

Pellet

GelrinC

Pellet

GelrinC degradation products

Acknowledgments: References:

Bernstein et al., Biotechnology Progress (2009) 25(4):1146-52

Sekiya et al, Cell Tissue Res (2005) 320: 269–276

The authors are grateful to Dr. E. Ivanir (Dror Seliktar Lab, BME Department,

Technion, Israel) for the PEG-DA/GelrinC beads preparation method.

This work was partially supported by the European FP7 grant (Biodesign Project)

GelrinC

Pellet

I

Implant (GelrinC)

Collagen capsule

C

I = Implant C = Collagen capsule

In-Vitro (5 Wks.) In-Vivo (6 Mos.)

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