Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5609, USA.
J Cell Biochem. 2012 Sep;113(9):3011-8. doi: 10.1002/jcb.24179.
Dermal fibroblasts produce a collagen-rich extracellular matrix, which confers mechanical strength and resiliency to human skin. During aging, collagen production is reduced and collagen fragmentation is increased, which is initiated by matrix metalloproteinase-1 (MMP-1). This aberrant collagen homeostasis results in net collagen deficiency, which impairs the structural integrity and function of skin. Cysteine-rich protein 61 (CCN1), a member of the CCN family, negatively regulates collagen homeostasis, in primary human skin dermal fibroblasts. As replicative senescence is a form of cellular aging, we have utilized replicative senescent dermal fibroblasts to further investigate the connection between elevated CCN1 and aberrant collagen homeostasis. CCN1 mRNA and protein levels were significantly elevated in replicative senescent dermal fibroblasts. Replicative senescent dermal fibroblasts also expressed significantly reduced levels of type I procollagen and increased levels of MMP-1. Knockdown of elevated CCN1 in senescent dermal fibroblasts partially normalized both type I procollagen and MMP-1 expression. These data further support a key role of CCN1 in regulation of collagen homeostasis. Elevated expression of CCN1 substantially increased collagen lattice contraction and fragmentation caused by replicative senescent dermal fibroblasts. Atomic force microscopy (AFM) further revealed collagen fibril fragmentation and disorganization were largely prevented by knockdown of CCN1 in replicative senescent dermal fibroblasts, suggesting CCN1 mediates MMP-1-induced alterations of collagen fibrils by replicative senescent dermal fibroblasts. Given the ability of CCN1 to regulate both production and degradation of type I collagen, it is likely that elevated-CCN1 functions as an important mediator of collagen loss, which is observed in aged human skin.
真皮成纤维细胞产生富含胶原蛋白的细胞外基质，为人类皮肤提供机械强度和弹性。随着年龄的增长，胶原蛋白的产生减少，胶原蛋白的片段增加，这是由基质金属蛋白酶-1（MMP-1）引发的。这种异常的胶原蛋白动态平衡导致净胶原蛋白缺乏，从而损害皮肤的结构完整性和功能。富含半胱氨酸的蛋白 61（CCN1）是 CCN 家族的成员之一，它在原代人皮肤真皮成纤维细胞中负调控胶原蛋白动态平衡。由于复制性衰老也是一种细胞衰老形式，因此我们利用复制性衰老的真皮成纤维细胞进一步研究了 CCN1 升高与异常胶原蛋白动态平衡之间的联系。复制性衰老的真皮成纤维细胞中 CCN1 的 mRNA 和蛋白水平显著升高。复制性衰老的真皮成纤维细胞还表达了显著降低的 I 型前胶原水平和增加的 MMP-1 水平。在衰老的真皮成纤维细胞中敲低升高的 CCN1 可部分使 I 型前胶原和 MMP-1 的表达正常化。这些数据进一步支持了 CCN1 在调节胶原蛋白动态平衡中的关键作用。升高的 CCN1 表达大大增加了复制性衰老的真皮成纤维细胞引起的胶原蛋白晶格收缩和片段化。原子力显微镜（AFM）进一步显示，通过在复制性衰老的真皮成纤维细胞中敲低 CCN1，可大大防止胶原纤维的片段化和紊乱，这表明 CCN1 通过复制性衰老的真皮成纤维细胞介导 MMP-1 诱导的胶原纤维改变。鉴于 CCN1 能够调节 I 型胶原蛋白的产生和降解，因此升高的 CCN1 可能作为胶原蛋白丢失的重要介质发挥作用，这种胶原蛋白丢失在老年人类皮肤中观察到。
