Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland.
Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland; Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, University Hospital Basel, Basel, Switzerland.
Biomaterials. 2023 Dec;303:122387. doi: 10.1016/j.biomaterials.2023.122387. Epub 2023 Nov 6.
Endochondral ossification (ECO), the major ossification process during embryogenesis and bone repair, involves the formation of a cartilaginous template remodelled into a functional bone organ. Adipose-derived stromal cells (ASC), non-skeletal multipotent progenitors from the stromal vascular fraction (SVF) of human adipose tissue, were shown to recapitulate ECO and generate bone organs in vivo when primed into a hypertrophic cartilage tissue (HCT) in vitro. However, the reproducibility of ECO was limited and the major triggers remain unknown. We studied the effect of the expansion of cells and maturation of HCT on the induction of the ECO process. SVF cells or expanded ASC were seeded onto collagen sponges, cultured in chondrogenic medium for 3-6 weeks and implanted ectopically in nude mice to evaluate their bone-forming capacities. SVF cells from all tested donors formed mature HCT in 3 weeks whereas ASC needed 4-5 weeks. A longer induction increased the degree of maturation of the HCT, with a gradually denser cartilaginous matrix and increased mineralization. This degree of maturation was highly predictive of their bone-forming capacity in vivo, with ECO achieved only for an intermediate maturation degree. In parallel, expanding ASC also resulted in an enrichment of the stromal fraction characterized by a rapid change of their proteomic profile from a quiescent to a proliferative state. Inducing quiescence rescued their chondrogenic potential. Our findings emphasize the role of monolayer expansion and chondrogenic maturation degree of ASC on ECO and provides a simple, yet reproducible and effective approach for bone formation to be tested in specific clinical models.
软骨内成骨（ECO）是胚胎发生和骨修复过程中的主要成骨过程，涉及到软骨模板的形成，该软骨模板经过重塑成为功能性骨器官。脂肪来源的基质细胞（ASC）是来自人脂肪组织基质血管部分（SVF）的非骨骼多能祖细胞，当体外被诱导为肥大软骨组织（HCT）时，它们被证明可以重现 ECO 并在体内产生骨器官。然而，ECO 的再现性有限，主要触发因素仍不清楚。我们研究了细胞扩增和 HCT 成熟对诱导 ECO 过程的影响。SVF 细胞或扩增的 ASC 接种到胶原海绵上，在软骨形成培养基中培养 3-6 周，并异位植入裸鼠，以评估它们的成骨能力。所有测试供体的 SVF 细胞在 3 周内形成成熟的 HCT，而 ASC 需要 4-5 周。更长的诱导时间增加了 HCT 的成熟度，软骨基质逐渐变得更加致密，矿化程度增加。这种成熟度高度预测了它们在体内的成骨能力，只有中间成熟度才能实现 ECO。同时，扩增 ASC 也导致基质部分的富集，其特征是其蛋白质组谱从静止状态到增殖状态的快速变化。诱导静止状态可恢复其软骨形成潜能。我们的发现强调了 ASC 的单层扩增和软骨形成成熟度对 ECO 的作用，并提供了一种简单、可重复且有效的方法来在特定的临床模型中测试骨形成。
