Liu Frances D, Pishesha Novalia, Poon Zhiyong, Kaushik Tanwi, Van Vliet Krystyn J
Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
BioSystems and Micromechanics (BioSyM) Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore 138602.
ACS Biomater Sci Eng. 2017 Dec 11;3(12):3292-3306. doi: 10.1021/acsbiomaterials.7b00644. Epub 2017 Oct 24.
Human mesenchymal stem cells (MSCs) exhibit morphological and phenotypic changes that correlate with mechanical cues presented by the substratum material to which those cells adhere. Such mechanosensitivity has been explored to promote differentiation of MSCs along tissue cell lineages for direct tissue repair. However, MSCs are increasingly understood to facilitate indirect tissue repair through paracrine signaling via secreted biomolecules. Here we leveraged cell-material interactions to induce human bone marrow-derived MSCs to preferentially secrete factors that are beneficial to hematopoietic cell proliferation. Specifically, we varied the viscoelastic properties of cell-culture-compatible polydimethylsiloxane (PDMS) substrata to demonstrate modulated MSC expression of biomolecules, including osteopontin, a secreted phosphoprotein implicated in tissue repair and regeneration. We observed an approximately 3-fold increase in expression of osteopontin for MSCs on PDMS substrata of lowest stiffness (elastic moduli <1 kPa) and highest ratio of loss modulus to storage modulus (tan(δ) > 1). A specific subpopulation of these cells, shown previously to express increased osteopontin and to promote bone marrow recovery , also exhibited up to a 5-fold increase in osteopontin expression when grown on compliant PDMS relative to heterogeneous MSCs on polystyrene. Importantly, this mechanically modulated increase in protein expression preceded detectable changes in the terminal differentiation capacity of MSCs. In coculture with human CD34+ hematopoietic stem and progenitor cells (HSPCs) that repopulate the blood cell lineages, these mechanically modulated MSCs promoted proliferation of HSPCs without altering the multipotency for either myeloid or lymphoid lineages. Cytokine and protein expression by human MSCs can thus be manipulated directly by mechanical cues conferred by the material substrata prior to and instead of tissue lineage differentiation. This approach enables enhanced production of both mesenchymal and hematopoietic stem and progenitor cells that aid regenerative clinical applications.
人间充质干细胞（MSCs）表现出形态和表型变化，这些变化与细胞所粘附的基质材料呈现的机械信号相关。人们已经探索了这种机械敏感性，以促进MSCs沿组织细胞谱系分化，用于直接组织修复。然而，人们越来越认识到MSCs通过分泌生物分子的旁分泌信号促进间接组织修复。在这里，我们利用细胞-材料相互作用，诱导人骨髓来源的MSCs优先分泌有利于造血细胞增殖的因子。具体而言，我们改变了与细胞培养兼容的聚二甲基硅氧烷（PDMS）基质的粘弹性特性，以证明MSCs对生物分子的表达受到调节，包括骨桥蛋白，一种与组织修复和再生有关的分泌性磷蛋白。我们观察到，在最低硬度（弹性模量<1 kPa）和最高损耗模量与储能模量之比（tan(δ)>1）的PDMS基质上培养的MSCs，其骨桥蛋白表达增加了约3倍。这些细胞的一个特定亚群，先前已显示其骨桥蛋白表达增加并能促进骨髓恢复，当在顺应性PDMS上生长时，相对于聚苯乙烯上的异质性MSCs，其骨桥蛋白表达也增加了高达5倍。重要的是，这种机械调节的蛋白质表达增加先于MSCs终末分化能力的可检测变化。在与能够重建血细胞谱系的人CD34+造血干细胞和祖细胞（HSPCs）共培养时，这些经机械调节的MSCs促进了HSPCs的增殖，而不改变髓系或淋巴系的多能性。因此，人MSCs的细胞因子和蛋白质表达可以在组织谱系分化之前，直接通过材料基质赋予的机械信号进行操纵，而不是通过组织谱系分化来操纵。这种方法能够增强间充质和造血干细胞及祖细胞的产生，有助于再生临床应用。
