Cyr D G, Hermo L, Egenberger N, Mertineit C, Trasler J M, Laird D W
Centre de Recherche en Santé Humaine, Institut National de la Recherche Scientifique-Institut Armand Frappier, Université du Québec, Pointe Claire, Canada.
Endocrinology. 1999 Aug;140(8):3815-25. doi: 10.1210/endo.140.8.6903.
Cellular junctions in the testis and epididymis play crucial roles for the development and maturation of spermatozoa. In the testis, tight junctions between Sertoli cells form a functional blood testis barrier between 10 and 16 days of age, whereas the tight junctional blood epididymal barrier between adjacent epithelial cells is formed between days 18 and 21. In the present study, occludin, a constituent integral membrane protein of tight junctions, was localized by immunofluorescent confocal microscopy in embryonic (days 13.5-18.5), postnatal (days 5-23) and adult (day 70) mouse testes and epididymides to correlate its expression with the onset of tight junctions and eventual formation of these barriers. At embryonic days 13.5 and 16.5, low diffuse cytoplasmic levels of occludin were observed in cells of the testicular cords. By embryonic day 18.5, the level of occludin was still low but appeared as a filiform-like network streaming toward the center of the cord. At postnatal days 5 and 7 immunostaining became more intense and appeared to outline the periphery of Sertoli cells of seminiferous tubules. Postnatal day 14 marked the appearance of an intense, focal band-like localization of occludin at the base of the tubules, correlating with the appearance of a functional blood-testis barrier. By day 23 and in adults, expression of occludin was noted at the base of the tubule appearing as intense, wavy, discontinuous bands similar in appearance irrespective of the stage of the seminiferous epithelium cycle. In the developing epididymis, intense cytoplasmic immunostaining was present in epithelial cells of many epididymal tubules at embryonic day 13.5. By embryonic day 16.5, intense occludin immunostaining appeared along the lateral plasma membranes of epithelial cells, whereas at embryonic day 18.5, immunostaining was punctate and apically located, suggesting the presence of tight junctions by this age; similar immunostaining was noted at postnatal days 5 and 7. In the adult epididymis, distinct punctate apical staining was observed between adjacent principal cells of all epididymal regions except the proximal initial segment, where occludin was found only in association with narrow cells. These results indicate that in the epididymis, the appearance of occludin at apical sites between adjacent epithelial cells occurs during embryonic development suggesting that tight junctions form earlier than in the testis. While occludin was expressed in a similar pattern between Sertoli cells at all stages of the cycle in the adult testis, its expression in the adult epididymis was cell- and region-specific. Taken together these data suggest that different factors regulate occludin expression in the testis and epididymis.
睾丸和附睾中的细胞连接对于精子的发育和成熟起着至关重要的作用。在睾丸中，支持细胞之间的紧密连接在10至16日龄时形成功能性血睾屏障，而相邻上皮细胞之间的紧密连接性血附睾屏障则在18至21日龄时形成。在本研究中，紧密连接的组成性整合膜蛋白闭合蛋白通过免疫荧光共聚焦显微镜定位在胚胎期（13.5 - 18.5日龄）、出生后（5 - 23日龄）和成年（70日龄）小鼠的睾丸和附睾中，以将其表达与紧密连接的起始以及这些屏障的最终形成相关联。在胚胎期13.5和16.5日龄时，在睾丸索的细胞中观察到闭合蛋白的低水平弥漫性细胞质表达。到胚胎期18.5日龄时，闭合蛋白水平仍然较低，但呈现为丝状网络流向索的中心。在出生后5和7日龄时，免疫染色变得更强，似乎勾勒出曲细精管支持细胞的周边。出生后14日龄标志着闭合蛋白在曲细精管基部出现强烈的、局灶性的带状定位，这与功能性血睾屏障的出现相关。到23日龄及成年时，在曲细精管基部观察到闭合蛋白的表达，呈现为强烈的、波浪状的、不连续的带，无论曲细精管上皮周期处于何阶段，其外观相似。在发育中的附睾中，在胚胎期13.5日龄时，许多附睾管的上皮细胞中存在强烈的细胞质免疫染色。到胚胎期16.5日龄时，强烈的闭合蛋白免疫染色出现在上皮细胞的外侧质膜上，而在胚胎期18.5日龄时，免疫染色呈点状且位于顶端，表明在这个年龄存在紧密连接；在出生后5和7日龄时也观察到类似的免疫染色。在成年附睾中，除近端起始段外，在所有附睾区域相邻主细胞之间观察到明显的点状顶端染色，在近端起始段，闭合蛋白仅与窄细胞相关联。这些结果表明，在附睾中，相邻上皮细胞顶端部位闭合蛋白的出现发生在胚胎发育期间，这表明紧密连接的形成比在睾丸中更早。虽然在成年睾丸周期的所有阶段，支持细胞之间闭合蛋白的表达模式相似，但其在成年附睾中的表达具有细胞和区域特异性。综合这些数据表明，不同因素调节睾丸和附睾中闭合蛋白的表达。
