15502-m-pleumeekers

Collagen, the most abundant protein present within the ECM, is of major importance, providing mechanical strength and guiding chondrogenic differentiation. [300] Additionally, the number of collagen cross-links contributes to the mechanical properties of newly formed cartilage. [301] Naturally, we expect these cross-links to be greater in scaffolds derived from native cartilage, than in synthetic scaffolds or ECM-derived scaffolds. Therefore, the retention of collagen during decellularization is crucial. Although collagen type I-elastin-GAG scaffolds were produced before [302], the dense elastic network that is interspersed with the collagen fibrils is not as highly organized as that of native ear cartilage [164, 303], while high magnification SEM showed that the decellularized EC retained the complex interaction between the elastic fibers and fine collagen network. Following decellularization, sGAG content decreased significantly which corresponds with previously reported findings by others [100, 101] and was most likely caused by the SDS-treatment during decellularization. Consequently with the sGAG reduction, the viscoelastic material properties of the decellularized EC scaffolds also reduced, which is in agreement with findings previously reported by others. [304] Depletion of sGAGs might be required to allow cells and cell residuals to leave the matrix. [305] Depending on the eventual application of the scaffold, sGAG depletion might also improve ingrowth of cells with chondrogenic capacity into the scaffold and thereby allowing matrix remodeling and revitalization of the graft. To completely assess functionality of the decellularized scaffold, mechanical properties were evaluated, since it should provide sufficient mechanical strength to compensate for that of the damaged tissue. After decellularization, biomechanical properties reduced significantly. Nevertheless, the decellularized b EC scaffolds presented superior mechanical properties compared to that of other commonly used natural or synthetic biomaterials for cartilage TE. For instance, low equilibrium moduli were found by unconfined compression in various hydrogels; maximum Eeq of 0.03 MPa in 2% alginate constructs [210], 0.3 MPa in 20% polyethylene glycol and 0.5 MPa in 15% agarose [306], showing that these hydrogels only reach a maximum of 50% of the Eeq of our decellularized EC scaffolds. Additionally, the Eeq of synthetic co-polymer scaffolds was 0.05-0.25 MPa [307], which was only 5.5-25% found in our decellularized b EC scaffolds. To assure long lasting properties and fully functional cartilage, eventual revitalization of the scaffold is a requirement. It is therefore important that we can prepare scaffolds that are non-cytotoxic after decellularization so cells can attach and survive. We showed that our decellularized scaffolds were non-cytotoxic and the seeded BMSCs were still viable after 21 days of culture. Furthermore, the scaffold allowed chondrogenic differentiation of BMSCs. We have used BMSCs in this work to evaluate the cell supportive capacity of our scaffold, the final choice of cell sources would mainly depend on the application and could be any cell with chondrogenic potential such as chondrocytes, perichondrium cells or adipose derived mesenchymal stem cells. [40, 54] Moreover, it would not be unlikely that seeding prior to implanting a decellularized scaffold is required, as it is the scaffold that could provide support for cells present at the implantation site to grow in. To revitalize and remodel the matrix, migration of cells throughout the matrices needs to be further optimized. In this respect, the reduction of sGAGs in the decellularized scaffolds will be advantageous [305], since it has been reported that chondrocyte adhesion is prevented by sGAGs. [308] Given that cell adhesion is 143 DECELLULARIZED CARTILAGE: AN ECM-DERIVED SCAFFOLD 7