Matrix-associated autologous chondrocyte implantation (MACI) achieves good clinical efficacy in young patients with focal cartilage injury; however, phenotypic de-differentiation of chondrocytes cultured in monolayer and the treatment of older OA patients are still challenges in the field of cartilage tissue engineering. This study aimed to assess the in vitro re-differentiation potential and in vivo chondrogenic capacity of human OA chondrocytes inoculated into collagen I scaffolds with different cellular phenotypes and seeding densities. OA chondrocytes and articular chondrocyte-laden scaffolds were cultured over 2 weeks in in vitro. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and histological staining were used to detect the mRNA expression profiles and extracellular matrix secretion of chondrocyte-specific markers. OA chondrocyte-laden collagen I scaffolds with different cellular phenotypes, and seeding densities were implanted into SCID mice over 4 weeks to evaluate the chondrogenic capacity in vivo. Increased COL2a1, ACAN, COMP, SOX9, and BMP2 expression levels and decreased COL1a1, VCAN, MMP13, and ADAMTS5 amounts were observed in OA chondrocytes seeded in collagen I scaffolds; Implantation of phenotypically superior OA chondrocytes in collagen I scaffolds at high density could improve the chondrogenic capacity of human OA chondrocytes, as confirmed by RT-qPCR assessed gene expression patterns in vitro and histological evaluation in vivo. Freshly isolated chondrocytes from OA patients could be a source of replacement for articular chondrocytes being commonly used in MACI. Implantation of phenotypically superior OA chondrocytes in collagen I scaffolds at high density could be a promising tool for the treatment of elderly OA patients.

中文翻译：

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细胞表型和接种密度对I型胶原支架中人骨关节炎软骨细胞软骨形成能力的影响

基质相关的自体软骨细胞植入（MACI）在年轻的局灶性软骨损伤患者中取得了良好的临床疗效。然而，在软骨组织工程领域，单层培养的软骨细胞的表型去分化和老年OA患者的治疗仍然是挑战。这项研究旨在评估接种到具有不同细胞表型和播种密度的I型胶原支架中的人OA软骨细胞的体外再分化潜能和体内软骨形成能力。在体外培养超过2周的OA软骨细胞和载有关节软骨细胞的支架。逆转录酶定量聚合酶链反应（RT-qPCR）和组织学染色用于检测软骨细胞特异性标记物的mRNA表达谱和细胞外基质分泌。将具有不同细胞表型的OA软骨细胞载有胶原蛋白I支架，并在4周内将接种密度植入SCID小鼠中，以评估其体内软骨形成能力。在胶原I支架中接种的OA软骨细胞中观察到COL2a1，ACAN，COMP，SOX9和BMP2表达水平升高，而COL1a1，VCAN，MMP13和ADAMTS5含量降低。RT-qPCR评估体外基因表达模式和体内组织学评估证实，表型优越的OA软骨细胞以高密度植入胶原I支架中可以提高人OA软骨细胞的成软骨能力。来自OA患者的新鲜分离的软骨细胞可以替代MACI中常用的关节软骨细胞。