Decellularized Osteochondral Sheets as a Bioscaf-fold Support Mesenchymal Stem Cell Proliferation and Dif-ferentiation in A Rabbit Model

Background: Decellularized osteochondral tissue is believed to be the best natural extra cellular matrix (ECM) for restoration of the osteoarthritis defects. Biomechanical feature, presence of differentiation-stimulating signals, preserved connection of bone-to-cartilage border, and existence of a tissue-specific structure are the most valuable innate properties of osteochon-dral tissue to be used as a bioscaffold as compared to artificial ones. Despite the advantages, osteochondral is a compact skele-tal tissue with low porosity particularly in the cartilaginous seg-ment which causes whole-organ decellularization, cell-seeding and subsequent cell-penetration challenges coming forward. This study aimed to develop a new construct of decellularized osteochondral tissue incorporated by bone marrow derived-mesenchymal stem cells (MSCs), as an osteochondral allograft, for preserving the cartilage–subchondral bone interface integra-tion.Materials and Methods: For this purpose, whole osteochon dral tissues were collected from rabbit knee joints; then, carti-laginous parts were sheeted in 200- 250 µm sections while con-nected to subchondral bone and were fully decellularized. The MSCs were derived from rabbit bone marrow, cultured and ex-panded by successive subcultures and characterized. Passage-3 cells were then seeded into the bioscaffold and incubated for 3 weeks; Moreover, some cell-derived-ECM were subcutane-ously implanted into the back of the rabbit and maintained for 4 weeks.Results: We found that constructed sheets were completely decellularized. In vitro and in vivo histological and scanning electron microscopy (SEM) assessments indicated that the cells could successfully penetrate into the bone and cartilage lacunas in implanted grafts. Importantly, gene expression analysis re-sults indicated that seeded cells differentiated into osteoblasts and chondroblasts in both bone and cartilage segments follow-ing exposure to native ECM elements and growth factors. Fur-ther, cartilage-to-bone border integrity was largely preserved. Conclusion: These results indicate that ECM-sheeted decellu-larized osteochondral constructs could be employed as a useful scaffold for promoting regeneration of osteochondral defects.

Keywords:

Decellularized Osteochondral Tissue , Allograft , Mesenchymal Stem Cells , Subcutaneous Implantation , Recel-lularization