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BackgroundScaffold-free cell-dense implants, termed “cell sheets”, are routinely fabricated using temperature-responsive commercial cell culture surfaces. In vivo regenerative capacity of human juvenile cartilage-derived chondrocyte (JCC) sheets is reported in both human clinical studies and nude rat defect models. How human cell source variables affect sheet tissue regeneration remains unelucidated.PurposeTo evaluate the variation of detailed histological neo-cartilage outcomes in an established rat defect model treated with human JCC sheets fabricated from various donors and different JCC passages.Study DesignDescriptive laboratory study.MethodsJCCs were isolated from 8 amputated human polydactylous digits. Passage 2 (P2) JCC sheets from all donors and P9 JCC sheets from one donor were transplanted into nude rat chondral defects for 4 weeks. Defect-only group served as control. Histological samples were stained for safranin-O, collagen 1 (COL1), and collagen 2 (COL2). Modified O’Driscoll scores, %COL1 and %COL2 areas, and COL2/1 ratios were applied for histological semi-quantitative evaluations. (1) All samples were scored and correlation coefficients for each score calculated. (2) Donors treated with P2 JCC sheets were divided into “more effective” and “less effective” groups based on these scores. Then, differences between each group in each category of modified O’Driscoll scoring were evaluated. (3) Scores of P2 and P9 samples from the same JCC donor were compared.Results(1) Mean modified O’Driscoll score, IHC %COL1 and COL2 areas, and COL2/1 ratio was 20.7±3.8, 37.9±27.5, 63.1±30.1, and 3.9±4.0, respectively. Modified O’Driscoll scores were negatively correlated with %COL1 area, and positively correlated with %COL2 area and COL2/1 ratio. (2) Four of 8 donors exhibited significantly higher modified O’Driscoll scores and %COL2 areas compared to the defect-only control group. JCC donors were divided into two groups by average score values: groups 3, 4, 6, and 7 (group ‘more effective’) and groups 1, 2, 5, and 8 (group less effective’). Significant differences between the two groups were observed in Modified O’Driscoll categories of “Nature of predominant”, “Reconstruction of subchondral bone”, and “Safranin-O staining”. (3) Modified O’Driscoll scores and COL2/1 ratio for JCC P2 were significantly higher than that from P9.ConclusionThe combined histological evaluation method employed is useful for detailedin vivoefficacy assessments of cartilage defect regeneration models. The analysis demonstrated that regenerative effects with JCC sheets varied both by JCC donor and passage number. Variations in histological evaluations among JCC donors were correlated to the quality of regenerated cartilage hyaline structure and subchondral bone remodeling observed in the nude rat defect model.Clinical RelevanceThis study provides a useful screening and prediction algorithm for cartilage regenerative success from human cell-derived implants in a rodent defect model.What is known about the subjectHuman juvenile cartilage-derived chondrocyte (JCC) sheets have shown safety and cartilage regenerative capacity in both nude rat chondral defects and a recent limited allogenic human clinical research study. Allogenic cell source variability is known to affect cell-based cartilage regeneration outcomes. Few predictive correlates exist to predict cell source regenerative success. Both Passage 2 (P2) and Passage 9 (P9) JCC-derived chondrogenic pellets exhibit strong characteristic safranin-O staining, but cultured P9 cultured pellet size is smaller than that of P2 pellets.What this study adds to existing knowledgeCartilage regenerative effects vary highly with banked cell source. Current cartilage regenerative strategies in preclinical models do not predict human performance and are clinically unreliable; few off-the-shelf, scalable “living” options are available. Cartilage regeneration using banked human JCC sheets represents a scalable, allogenic, scaffold-free approach now successfully tested both in nude rat and human chondral defects. This study shows that histological evaluation of sheets from several JCC donor demonstrated variable regenerated cartilage hyaline structure and subchondral bone remodeling in a nude rat across donor and passage. Tools to better predict cell-based cartilage regenerative reliability by screening banked allogenic human cell sources in a rat model are described. |
