Expression patterns of tight junction associated proteins, occludin and claudins in ameloblasts during amelogenesis of mouse incisor.

紧密连接(TJ)主要作为上皮细胞间细胞旁转运的屏障，由TJ相关蛋白、occludin(OLD)和Claudins(CLDs)组成。CLD形成一个有24个成员的家族，表现出组织或细胞特异性表达。起源于口腔上皮的成釉细胞形成釉质，在成釉细胞发生过程中，釉质蛋白和矿物质通过成釉细胞层运输。我们用免疫组织化学方法检测了成釉细胞中TJ的分布模式以及OLD和CLDs(CLD-1到CLD-10)的表达模式。分泌性成釉细胞在细胞远端呈老状、CLD-1、-8和-9。在成熟的成釉细胞中，OLD、CLD-1、-6、-7、-8、-9和-10主要分布在细胞的远端和近端，无论是皱褶端还是光滑端的成釉细胞。成熟的成釉细胞仅近端染色，呈阳性反应。这些结果表明成釉细胞显著改变了CLDs的表达模式和TJs在分泌型成釉细胞和成熟成釉细胞之间的分布模式，并提示这些差异反映了这些细胞类型的细胞功能，特别是对釉质形成的蛋白质和离子的运输。

Tight junctions (TJs) function primarily as a barrier against paracellular transports between epithelial cells and are composed of TJ associated proteins, occludin (OLD) and claudins (CLDs). CLDs form a family with 24 members and show tissue or cell specific expression. Ameloblasts originated from oral epithelium form enamel, and enamel proteins and minerals are transported across the ameloblastic layer during amelogenesis. We immunohistochemically examined the distribution patterns of TJs and expression patterns of OLD and CLDs (CLD-1 to CLD-10) in the ameloblasts. Secretory ameloblasts showed OLD, CLD-1, -8 and -9 at the distal end of the cell. In mature ameloblasts, OLD, CLD-1, -6, -7, -8, -9 and -10 were shown mainly at both distal and proximal ends of the cell, regardless of ruffle-ended or smooth-ended ameloblasts. The mature ameloblasts that only proximal ends were positively stained by these OLD and CLDs were also found. These results indicate that ameloblasts drastically change the expression patterns of CLDs and the distribution patterns of TJs between secretory and mature ameloblasts, and suggest that these differences reflect the cell functions of these cell types, specifically the transports of proteins and ions for enamel formation.