Allen Fred D, Asnes Clara F, Chang Philip, Elson Elliot L, Lauffenburger Douglas A, Wells Alan
Division of Bioengineering and Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Wound Repair Regen. 2002 Jan-Feb;10(1):67-76. doi: 10.1046/j.1524-475x.2002.10701.x.
During wound healing, dermal fibroblasts switch from a migratory, repopulating phenotype to a contractile, matrix-reassembling phenotype. The mechanisms controlling this switch are unknown. A possible explanation is suggested by the finding that chemokines that appear late in wound repair prevent growth factor-induced cell-substratum de-adhesion by blocking calpain activation. In this study, we tested the specific hypothesis that fibroblast contraction of the matrix is promoted by a pro-repair growth factor, epidermal growth factor, and is modulated by calpain-mediated release of adhesions. We employed an isometric force transduction system designed to measure the contraction of a collagen matrix under tension by a population of NR6 fibroblasts transfected with the human epidermal growth factor receptor. By maintaining a fixed level of strain, we could monitor both the initial contraction and subsequent relaxation of the matrix. Epidermal growth factor stimulated a transient, dose-dependent increase in matrix contraction that peaked within 60 minutes and then decayed over the ensuing 3 to 6 hours. Calpain inhibitor I (ALLN) prevented epidermal growth factor-stimulated cell de-adhesion and resulted in a significantly slower decay of matrix contraction, with only a slight decrease of the peak magnitude of contraction. The mitogen-activated protein kinase kinase-1-selective inhibitor PD 98059 that blocks signaling through the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway, required for epidermal growth factor receptor-mediated activation of calpain and de-adhesion, does not significantly affect the magnitude of matrix contraction within minutes of epidermal growth factor addition, but slows the decay similarly to calpain inhibition. Epidermal growth factor receptor signaling thus stimulates the complementary mechanisms of intracellular contractile force generation and calpain-mediated de-adhesion, which are known to coordinately facilitate cell migration. These findings suggest that calpain can act as a functional switch for transmission of intracellular contractile force to the surrounding matrix, with calpain-mediated de-adhesion reducing this transmission and corresponding matrix contraction. Countervailing processes that down-regulate calpain activation can, accordingly, direct the transition of cell function from locomotion to matrix contraction.
在伤口愈合过程中，真皮成纤维细胞从迁移、重新填充表型转变为收缩、基质重组表型。控制这种转变的机制尚不清楚。伤口修复后期出现的趋化因子通过阻断钙蛋白酶激活来阻止生长因子诱导的细胞与基质脱黏附，这一发现提示了一种可能的解释。在本研究中，我们测试了一个特定的假说，即促修复生长因子表皮生长因子促进基质的成纤维细胞收缩，并受钙蛋白酶介导的黏附释放调节。我们采用了一种等长力转导系统，该系统旨在测量转染了人表皮生长因子受体的NR6成纤维细胞群体在张力作用下对胶原基质的收缩。通过维持固定的应变水平，我们可以监测基质的初始收缩和随后的松弛。表皮生长因子刺激基质收缩出现短暂的、剂量依赖性增加，在60分钟内达到峰值，然后在随后的3至6小时内衰减。钙蛋白酶抑制剂I（ALLN）阻止了表皮生长因子刺激的细胞脱黏附，并导致基质收缩的衰减明显减慢，收缩峰值幅度仅略有下降。丝裂原活化蛋白激酶激酶-1选择性抑制剂PD 98059可阻断通过细胞外信号调节激酶/丝裂原活化蛋白激酶途径的信号传导，这是表皮生长因子受体介导的钙蛋白酶激活和脱黏附所必需的，在添加表皮生长因子后几分钟内，它对基质收缩幅度没有显著影响，但与钙蛋白酶抑制类似，减缓了衰减。因此，表皮生长因子受体信号传导刺激了细胞内收缩力产生和钙蛋白酶介导的脱黏附这两种互补机制，已知这两种机制协同促进细胞迁移。这些发现表明，钙蛋白酶可以作为将细胞内收缩力传递到周围基质的功能开关，钙蛋白酶介导的脱黏附减少了这种传递和相应的基质收缩。相应地，下调钙蛋白酶激活的对抗过程可以引导细胞功能从运动向基质收缩转变。
