Laminin alpha 1-chain shows a restricted distribution in epithelial basement membranes of fetal and adult human tissues

Two novel monoclonal antibodies were raised and used to study the expressio n of laminin (Ln) alpha 1-chain in developing and adult human tissues. In b oth fetal and adult kidney, a distinct immunoreactivity was seen in basemen t membranes (BM) of most proximal tubules but not in the distal tubular or glomerular BM or in the basal laminae of blood vessels. Immunoprecipitation of metabolically labeled cultured human renal proximal tubular cells showe d an abundant production and deposition of Ln alpha 1-chain to the extracel lular matrix, suggestive of an epithelial origin of kidney Ln-1. Quantitati ve cell adhesion experiments with JAR choriocarcinoma cells showed that pur ified human Ln-1 is a good substrate for cell adhesion that it is different ly recognized by integrin receptors when compared to mouse Ln-1. In fetal a nd adult testes immunoreactivity was solely confined to BM of the seminifer ous epithelium. In the airways BM-confined reaction was only seen in fetal budding bronchial tubules (16-19 weeks) at the pseudoglandular stage of dev elopment. In the skin a distinct immunoreactivity was confined to BM of dev eloping hair buds but not in epithelial BMs of adult epidermis or of epider mal appendages. In other adult tissues, immunoreactivity was found in BMs o f thyroid, salivary, and mammary glands as well as in BMs of endometrium an d endocervix, but not of ectocervix or vagina. No immunoreactivity was foun d in BMs of most of the digestive tract, including the fiver and pancreas, except for BMs of esophageal submucosal glands and duodenal Brunner's gland s. In fetal specimens, BMs of the bottoms of the intestinal and gastric gla nds were positive. Basal laminae of blood vessels were generally negative f or Ln alpha 1 chain with the exception of specimens of both fetal and adult central nervous system in which immunoreactivity for Ln alpha 1 chain was prominently confined to capillary walls. The results suggest that outside t he central nervous system, Ln alpha 1 chain shows a restricted and developm entally regulated expression in BMs of distinct epithelial tissues. (C) 200 0 Academic Press.