Ishida-Yamamoto Akemi, Igawa Satomi
Department of Dermatology, Asahikawa Medical University, Midorigaoka-Higashi 2-1-1-1, Asahikawa, Japan,
Cell Tissue Res. 2015 Jun;360(3):477-82. doi: 10.1007/s00441-014-2037-z. Epub 2014 Nov 19.
The stratum corneum of the epidermis is composed of stacked dead corneocytes embedded in lipid layers and is the main protective shield of the skin. The thickness of the stratum corneum is maintained fairly constantly through the balance between new cell creation and old cell removal. Corneodesmosomes are the main intercellular adhesive structures in the stratum corneum. They are transformed from desmosomes at the most superficial layer of the stratum granulosum of the epidermis. The major compositional distinction from desmosomes is the presence of corneodesmosin in the extracellular portion. Furthermore, corneodesmosomes are structurally different from desmosomes in that (1) they do not have a tri-lamellar desmoglea but rather one that is homogeneously electron-dense and (2) attachment plaques are integrated into a part of the cornified cell envelopes. When the extracellular regions of corneodesmosomes are fully degraded, desquamation occurs. The degradation process of corneodesmosomes is carefully controlled by a number of proteases and their inhibitors. The most important proteases involved in this process are the kallikrein-related peptidases. Their main inhibitor is the lympho-epithelial Kazal-type related inhibitor. Other regulators of this process include matriptase, meprin and mesotrypsin.
表皮的角质层由嵌入脂质层的堆叠死亡角质形成细胞组成，是皮肤的主要保护屏障。角质层的厚度通过新细胞生成与旧细胞清除之间的平衡得以相当稳定地维持。角质桥粒是角质层中的主要细胞间黏附结构。它们由表皮颗粒层最表层的桥粒转化而来。与桥粒的主要成分区别在于细胞外部分存在角质桥粒蛋白。此外，角质桥粒在结构上与桥粒不同，在于：（1）它们没有三层板状的桥粒芯，而是具有均匀电子致密的结构；（2）附着斑整合到角质化细胞包膜的一部分中。当角质桥粒的细胞外区域完全降解时，就会发生脱屑。角质桥粒的降解过程受到多种蛋白酶及其抑制剂的严格控制。参与此过程的最重要蛋白酶是激肽释放酶相关肽酶。其主要抑制剂是淋巴细胞上皮Kazal型相关抑制剂。此过程的其他调节因子包括matriptase、meprin和间胰蛋白酶。
