Ku Ching-Hsin, Johnson Philip H, Batten Puspa, Sarathchandra Padmini, Chambers Rachel C, Taylor Patricia M, Yacoub Magdi H, Chester Adrian H
Department of Cardiothoracic Surgery, Heart Science Centre, Harefield Hospital, NHLI, Imperial College London, UK.
Cardiovasc Res. 2006 Aug 1;71(3):548-56. doi: 10.1016/j.cardiores.2006.03.022. Epub 2006 Apr 7.
The synthesis of appropriate extracellular matrix by cells in tissue engineered heart valve constructs will be important for the maintenance of valve cusp integrity and function. We have examined and compared the capacity of mesenchymal stem cells to synthesise collagen in response to stretch in comparison with native aortic valve interstitial cells.
Cells were stretched on a Flexercell FX4000 apparatus and total collagen synthesis was measured by the incorporation of [3H]-proline. The effect of stretch on gene expression of different collagen types was assessed by RT-PCR.
There was a significant (p<0.01) increase in [3H]-proline incorporation into stretched valve cells at 10%, 14% and 20% stretch. The response of mesenchymal stem cells at 14% stretch was similar to that seen in the valve cells. Incorporation of [3H]-proline into soluble proteins in the cell media was significantly higher (p<0.01) only at 14% and 20% stretch in valve interstitial cells. These effects were shared with mesenchymal stem cells at 14% stretch. RT-PCR experiments demonstrated that 14% stretch up-regulated levels of mRNA for COL3A1 gene (type III collagen) but did not increase the expression of COL1A1 gene (type I collagen) in valve interstitial cells. However, both collagen genes could be detected in non-stretched and stretched mesenchymal stem cells. There was no evidence that the mesenchymal stem cells had started to adopt an osteoblastic cell phenotype in response to stretch.
Collagen synthesis by valve interstitial cells is dependent upon the degree and duration of stretch. This response can be mimicked closely by exposure of mesenchymal stem cells to the same stretching profile. These properties could have important implications for the choice of cells and programme of conditioning with which to tissue engineer heart valves.
组织工程心脏瓣膜构建物中的细胞合成合适的细胞外基质对于维持瓣膜叶的完整性和功能至关重要。我们已经研究并比较了间充质干细胞与天然主动脉瓣间质细胞在受到拉伸时合成胶原蛋白的能力。
在Flexercell FX4000仪器上对细胞进行拉伸，并通过掺入[3H]-脯氨酸来测量总胶原蛋白合成。通过逆转录聚合酶链反应（RT-PCR）评估拉伸对不同类型胶原蛋白基因表达的影响。
在10%、14%和20%的拉伸程度下，拉伸瓣膜细胞中[3H]-脯氨酸的掺入量显著增加（p<0.01）。间充质干细胞在14%拉伸时的反应与瓣膜细胞相似。仅在瓣膜间质细胞中，当拉伸程度为14%和20%时，[3H]-脯氨酸掺入细胞培养基中可溶性蛋白质的量显著更高（p<0.01）。间充质干细胞在14%拉伸时也有同样的效果。RT-PCR实验表明，14%的拉伸上调了瓣膜间质细胞中COL3A1基因（III型胶原蛋白）的mRNA水平，但未增加COL1A1基因（I型胶原蛋白）的表达。然而，在未拉伸和拉伸的间充质干细胞中均能检测到这两种胶原蛋白基因。没有证据表明间充质干细胞因拉伸而开始呈现成骨细胞表型。
瓣膜间质细胞的胶原蛋白合成取决于拉伸的程度和持续时间。间充质干细胞暴露于相同的拉伸模式下可紧密模拟这种反应。这些特性对于组织工程心脏瓣膜所选用的细胞和预处理方案可能具有重要意义。
