De Lisio Michael, Jensen Tor, Sukiennik Richard A, Huntsman Heather D, Boppart Marni D
Stem Cell Res Ther. 2014 Jun 6;5(3):74. doi: 10.1186/scrt463.
Mesenchymal stem cells (MSCs) reside in a variety of tissues and provide a stromal role in regulating progenitor cell function. Current studies focus on identifying the specific factors in the niche that can alter the MSC secretome, ultimately determining the effectiveness and timing of tissue repair. The purpose of the present study was to evaluate the extent to which substrate and mechanical strain simultaneously regulate MSC quantity, gene expression, and secretome.
MSCs (Sca-1+CD45-) isolated from murine skeletal muscle (muscle-derived MSCs, or mMSCs) via fluorescence-activated cell sorting were seeded onto laminin (LAM)- or collagen type 1 (COL)-coated membranes and exposed to a single bout of mechanical strain (10%, 1 Hz, 5 hours).
mMSC proliferation was not directly affected by substrate or strain; however, gene expression of growth and inflammatory factors and extracellular matrix (ECM) proteins was downregulated in mMSCs grown on COL in a manner independent of strain. Focal adhesion kinase (FAK) may be involved in substrate regulation of mMSC secretome as FAK phosphorylation was significantly elevated 24 hours post-strain in mMSCs plated on LAM but not COL (P <0.05). Conditioned media (CM) from mMSCs exposed to both LAM and strain increased myoblast quantity 5.6-fold 24 hours post-treatment compared with myoblasts treated with serum-free media (P <0.05). This response was delayed in myoblasts treated with CM from mMSCs grown on COL.
Here, we demonstrate that exposure to COL, the primary ECM component associated with tissue fibrosis, downregulates genes associated with growth and inflammation in mMSCs and delays the ability for mMSCs to stimulate myoblast proliferation.
间充质干细胞（MSC）存在于多种组织中，在调节祖细胞功能方面发挥着基质作用。目前的研究重点是确定微环境中能够改变MSC分泌组的特定因素，最终确定组织修复的有效性和时机。本研究的目的是评估基质和机械应变同时调节MSC数量、基因表达和分泌组的程度。
通过荧光激活细胞分选从鼠骨骼肌中分离出的MSC（Sca-1+CD45-，即肌肉来源的MSC或mMSC）接种到层粘连蛋白（LAM）或I型胶原（COL）包被的膜上，并暴露于单次机械应变（10%，1Hz，5小时）。
mMSC的增殖不受基质或应变的直接影响；然而，在COL上生长的mMSC中，生长和炎症因子以及细胞外基质（ECM）蛋白的基因表达以与应变无关的方式下调。粘着斑激酶（FAK）可能参与mMSC分泌组的基质调节，因为在接种于LAM而非COL上的mMSC中，应变后24小时FAK磷酸化显著升高（P<0.05）。与用无血清培养基处理的成肌细胞相比，暴露于LAM和应变的mMSC的条件培养基（CM）在处理后24小时使成肌细胞数量增加了5.6倍（P<0.05）。在用COL上生长的mMSC的CM处理的成肌细胞中，这种反应延迟。
在此，我们证明，暴露于与组织纤维化相关的主要ECM成分COL会下调mMSC中与生长和炎症相关的基因，并延迟mMSC刺激成肌细胞增殖的能力。
