Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
Stem Cells Transl Med. 2012 Aug;1(8):632-9. doi: 10.5966/sctm.2012-0039. Epub 2012 Jul 27.
The precise spatial and temporal presentation of growth factors is critical for cartilage development, during which tightly controlled patterns of signals direct cell behavior and differentiation. Recently, chondrogenic culture of human mesenchymal stem cells (hMSCs) has been improved through the addition of polymer microspheres capable of releasing growth factors directly to cells within cellular aggregates, eliminating the need for culture in transforming growth factor-β1 (TGF-β1)-containing medium. However, the influence of specific patterns of spatiotemporal growth factor presentation on chondrogenesis within microsphere-incorporated cell systems is unclear. In this study, we examined the effects of altering the chondrogenic microenvironment within hMSC aggregates through varying microsphere amount, growth factor concentration per microsphere, and polymer degradation time. Cartilage formation was evaluated in terms of DNA, glycosaminoglycan, and type II collagen in hMSCs from three donors. Chondrogenesis equivalent to or greater than that of aggregates cultured in medium containing TGF-β1 was achieved in some conditions, with varied differentiation based on the specific conditions of microsphere incorporation. A more spatially distributed delivery of TGF-β1 from a larger mass of fast-degrading microspheres improved differentiation by comparison with delivery from a smaller mass of microspheres with a higher TGF-β1 concentration per microsphere, although the total amount of growth factor per aggregate was the same. Results also indicated that the rate and degree of chondrogenesis varied on a donor-to-donor basis. Overall, this study elucidates the effects of varied conditions of TGF-β1-loaded microsphere incorporation on hMSC chondrogenesis, demonstrating that both spatiotemporal growth factor presentation and donor variability influence chondrogenic differentiation within microsphere-incorporated cellular constructs.
生长因子的精确时空呈现对于软骨发育至关重要，在此过程中，紧密控制的信号模式指导细胞行为和分化。最近，通过添加能够将生长因子直接释放到细胞聚集体内细胞的聚合物微球，改善了人骨髓间充质干细胞（hMSC）的软骨生成培养，从而消除了在含有转化生长因子-β1（TGF-β1）的培养基中培养的需要。然而，特定时空生长因子呈现模式对微球掺入细胞系统内软骨形成的影响尚不清楚。在这项研究中，我们通过改变微球数量、每个微球的生长因子浓度和聚合物降解时间来改变 hMSC 聚集体内的软骨生成微环境，从而检查了这一点。根据三个供体的 hMSC 的 DNA、糖胺聚糖和 II 型胶原评估软骨形成。在某些条件下，与在含有 TGF-β1 的培养基中培养的聚集体相比，实现了等同于或大于 TGF-β1 的软骨生成，并且基于微球掺入的具体条件，分化也有所不同。与具有更高 TGF-β1 浓度的每个微球的较小质量的微球相比，从较大质量的快速降解微球中更空间分布的 TGF-β1 传递可改善分化，尽管每个聚集体的生长因子总量相同。结果还表明，在供体之间，软骨生成的速度和程度存在差异。总体而言，这项研究阐明了不同条件的 TGF-β1 负载微球掺入对 hMSC 软骨生成的影响，表明时空生长因子呈现和供体变异性均会影响微球掺入细胞构建体中的软骨分化。
