Abstract
BACKGROUND: Direct intra-articular injection (DIAI) of mesenchymal stem cells (MSCs) is a promising technique for cartilage repair. However, the repair process was hindered by the absence of scaffold and poor cell-matrix interactions. METHODS: In this study, we developed a pericellular collagen I coating (PCC) on MSCs. The overall performances of MSC-PCC homing, chondrogenic differentiation, and cartilage regeneration have been comprehensively evaluated in a New Zealand rabbit model. Firstly, we examined the morphology and physical characteristics of PCC. Secondly, MSC ex-vivo cartilage slice adhesion and in-vivo cartilage defect homing were observed using multiscale methods. Thirdly, the precartilage condensation of cell pellets formed by aggregation of MSCs was examined to evaluate the cartilage-inducing potential of PCC. Finally, the cartilage regeneration by DIAI of PCC-coated MSCs was observed and scored macroscopically and histologically. RESULTS: In general, the cell adhesion and homing assay revealed that PCC facilitated MSC adhesion on cartilage slices, enhancing MSC homing and retention to cartilage defect. This increased homing ratio was accompanied by an increasing cell-cell contact. Compared with naked MSCs, the cell pellets formed by PCC-coated MSCs exhibited more evident appearance of condensation. In pellets, cell-cell interaction has been significantly stimulated, inducing the expression of condensation marker N-cadherin, and subsequent chondrogenic marker collagen II and aggrecan. By 12 weeks after DIAI, cartilage defects have been repaired by MSCs to varying degrees. Overall, PCC significantly enhances the quality of cartilage regeneration judging from macroscopic observation, ICRS score, histological examination, and collagen type I, II, and X immunohistochemical staining. CONCLUSIONS: The capacity and viability of MSCs can be enhanced by collagen I coating, which provides cues for enhancing cell homing and differentiation. Our method provides a novel strategy for stem cell therapy.