Ishida-Yamamoto A, Hohl D, Roop D R, Iizuka H, Eady R A
Department of Dermatology, Asahikawa Medical College, Japan.
Arch Dermatol Res. 1993;285(8):491-8. doi: 10.1007/BF00376822.
Loricrin is a major component of the cornified cell envelope and is also expressed in the granular layer of human epidermis. In newborn mouse epidermis, loricrin accumulates in small round granules (L-granules) in the granular layer before being incorporated into the cornified cell envelope, but the expression of L-granules has not yet been demonstrated in human skin. In the present study we used postembedding immunoelectron microscopy to examine loricrin expression in normal human skin. We observed diffuse loricrin staining in the uppermost granular cell layer in interappendageal epidermis, that was not associated with any granular structures. In the cornified cells, most of the labelling was on the inner face of cornified cell envelopes. By contrast, in the upper segment of acrosyringia there were small granules (L-granules) that specifically labelled for loricrin. In the outer ductal cells, L-granules with a highly osmiophilic electron density were apparent in the nucleus as well as in the cytoplasm. In the inner ductal cells, L-granules were round or oval, less electron-dense and larger than the outer ductal L-granules, and present only in the cytoplasm. Some of the outer ductal L-granules and most of the inner ductal L-granules formed composite granules with filaggrin immunoreactive granules. These results suggest that in human interappendageal epidermis, loricrin might be rapidly incorporated into the cornified cell envelope without prior accumulation in any type of granule. By contrast, in acrosyringia loricrin accumulates in granules, perhaps reflecting increased synthesis or slower processing. The significance of the different morphological features of the L-granules in inner and outer acrosyringial cells remains to be clarified.
兜甲蛋白是角质化细胞包膜的主要成分，在人类表皮颗粒层中也有表达。在新生小鼠表皮中，兜甲蛋白在被整合到角质化细胞包膜之前，先在颗粒层的小圆形颗粒（L颗粒）中积累，但L颗粒在人类皮肤中的表达尚未得到证实。在本研究中，我们使用包埋后免疫电子显微镜检查正常人类皮肤中兜甲蛋白的表达。我们观察到在附属器间表皮最上层的颗粒细胞层中有弥漫性的兜甲蛋白染色，这与任何颗粒结构均无关。在角质化细胞中，大多数标记位于角质化细胞包膜的内表面。相比之下，在顶泌汗腺导管上段有特异性标记兜甲蛋白的小颗粒（L颗粒）。在导管外层细胞中，具有高嗜锇电子密度的L颗粒在细胞核以及细胞质中均可见。在导管内层细胞中，L颗粒呈圆形或椭圆形，电子密度较低，比导管外层的L颗粒大，且仅存在于细胞质中。一些导管外层的L颗粒和大多数导管内层的L颗粒与角蛋白聚集素免疫反应性颗粒形成复合颗粒。这些结果表明，在人类附属器间表皮中，兜甲蛋白可能在没有预先在任何类型颗粒中积累的情况下迅速整合到角质化细胞包膜中。相比之下，在顶泌汗腺导管中兜甲蛋白在颗粒中积累，这可能反映了合成增加或加工较慢。顶泌汗腺导管内层和外层细胞中L颗粒不同形态特征的意义仍有待阐明。
