Purpose: Scaffold-free cartilage tissue engineering circumvents issues with scaffold seeding, potential toxicity response, and impaired host integration. However, precisely controlling and maintaining a scaffold-free construct shape have been challenging. We explored the feasibility of microneedle arrays to print tissue using cellular microspheroids as building blocks.Materials and Methods: Human embryonic-derived mesenchymal stem cells or infrapatellar fat pad mesenchymal stem cells were used to create microspheroids of 500 µm in diameter, which were assembled on microneedle arrays in a predefined arrangement using a robotic system under computer vision. Microspheroids on microneedles were cultured to permit fusion into a tissue construct. Infrapatellar fat pad mesenchymal stem cell constructs were either implanted into chondral defects created in human osteoarthritic cartilage explants or maintained on the microneedle array for 3 weeks. Embryonic-derived mesenchymal stem cell constructs were designed to be press-fit into 3 mm subchondral defects in New Zealand White rabbits and maintained for up to 8 weeks to assess retention, early tissue repair, and more mature cartilage regeneration.Results: Microspheroids of both cell types fused together in culture to form neotissues of predefined shape and size. Infrapatellar fat pad mesenchymal stem cell neotissues expressed high levels of chondrogenic genes and integrated with the surrounding osteoarthritic host cartilage. Embryonic-derived mesenchymal stem cell constructs generated chondrogenic neotissue in vivo as early as 2 weeks and more mature tissue by 8 weeks with increased glycosaminoglycan deposition.Conclusions: We constructed defined scaffold-free shapes by bioprinting and fusing microspheroids. Proof of concept was shown in the repair of ex vivo osteoarthritic human cartilage and in vivo rabbit osteochondral (OC) defects.

中文翻译：

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结合微球体积木和微针阵列的软骨组织工程。

目的：无支架软骨组织工程避免了支架接种、潜在毒性反应和宿主整合受损等问题。然而，精确控制和保持无支架构造形状一直具有挑战性。我们探索了使用细胞微球体作为构建块的微针阵列打印组织的可行性。 材料和方法：使用人类胚胎来源的间充质干细胞或髌下脂肪垫间充质干细胞制造直径为 500 µm 的微球体，并组装在使用计算机视觉下的机器人系统以预定义排列的微针阵列。培养微针上的微球体以允许融合成组织构建体。髌下脂肪垫间充质干细胞构建体要么被植入人骨关节炎软骨外植体中产生的软骨缺损中，要么在微针阵列上维持 3 周。胚胎来源的间充质干细胞构建体被设计为压入新西兰白兔的 3 毫米软骨下缺损并维持长达 8 周以评估保留、早期组织修复和更成熟的软骨再生。结果：两者的微球体细胞类型在培养中融合在一起，形成预定形状和大小的新组织。髌下脂肪垫间充质干细胞新组织表达高水平的软骨基因并与周围的骨关节炎宿主软骨整合。胚胎源性间充质干细胞构建体最早在 2 周内在体内产生软骨形成新组织，在 8 周内产生更多的成熟组织，糖胺聚糖沉积增加。结论：我们通过生物打印和融合微球体构建了明确的无支架形状。在体外骨关节炎人类软骨和体内兔骨软骨 (OC) 缺陷的修复中显示了概念证明。