Materials Science and Engineering Program, Texas A&M University, College Station, TX, USA.
Acta Biomater. 2012 Dec;8(12):4397-404. doi: 10.1016/j.actbio.2012.07.048. Epub 2012 Aug 5.
Growth factors have been shown to be powerful mediators of mesenchymal stem cell (MSC) osteogenic differentiation. However, their use in tissue engineered scaffolds not only can be costly but also can induce undesired responses in surrounding tissues. Thus, the ability to specifically promote MSC osteogenic differentiation in the absence of exogenous growth factors via the manipulation of scaffold material properties would be beneficial. The current work examines the influence of select extracellular matrix (ECM) proteins on MSC osteogenesis toward the goal of developing scaffolds with intrinsically osteoinductive properties. Fibrinogen (FG), fibronectin (FN) and laminin-1 (LN) were chosen for evaluation due to their known roles in bone morphogenesis or bone fracture healing. These proteins were conjugated into poly(ethylene glycol) diacrylate (PEGDA) hydrogels and their effects on encapsulated 10T½ MSCs were evaluated. Specifically, following 1week of culture, mid-term markers of various MSC lineages were examined in order to assess the strength and specificity of the observed osteogenic responses. PEG-LN gels demonstrated increased levels of the osteogenic transcription factor osterix relative to day 0 levels. In addition, PEG-FG and PEG-LN gels were associated with increased deposition of bone ECM protein osteocalcin relative to PEG-FN gels and day 0. Importantly, the osteogenic response associated with FG and LN appeared to be specific in that markers for chondrocytic, smooth muscle cell and adipocytic lineages were not similarly elevated relative to day 0 in these gels. To gain insight into the integrin dynamics underlying the observed differentiation results, initial integrin adhesion and temporal alterations in cell integrin profiles were evaluated. The associated results suggest that α(2), α(v) and α(6) integrin subunits may play key roles in integrin-mediated osteogenesis.
生长因子已被证实是间充质干细胞（MSC）成骨分化的有力介质。然而，它们在组织工程支架中的应用不仅成本高昂，而且还可能引起周围组织的不良反应。因此，能够通过操纵支架材料特性在不存在外源性生长因子的情况下特异性地促进 MSC 成骨分化将是有益的。目前的工作研究了选择的细胞外基质（ECM）蛋白对 MSC 成骨的影响，以期开发具有内在成骨特性的支架。纤维蛋白原（FG）、纤连蛋白（FN）和层粘连蛋白-1（LN）由于它们在骨形态发生或骨骨折愈合中的已知作用而被选择进行评估。这些蛋白质被共轭到聚乙二醇二丙烯酸酯（PEGDA）水凝胶中，并评估了它们对封装的 10T½ MSC 的影响。具体来说，在培养 1 周后，检测了各种 MSC 谱系的中期标志物，以评估观察到的成骨反应的强度和特异性。与第 0 天相比，PEG-LN 凝胶表现出更高水平的成骨转录因子osterix。此外，与 PEG-FN 凝胶和第 0 天相比，PEG-FG 和 PEG-LN 凝胶与骨 ECM 蛋白骨钙素的沉积增加有关。重要的是，与 FG 和 LN 相关的成骨反应似乎是特异性的，因为在这些凝胶中，软骨细胞、平滑肌细胞和脂肪细胞谱系的标志物相对于第 0 天并没有同样升高。为了深入了解观察到的分化结果背后的整合素动力学，评估了初始整合素粘附和细胞整合素谱的时间变化。相关结果表明，α(2)、α(v)和α(6)整合素亚基可能在整合素介导的成骨中发挥关键作用。
