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Synthesis of and response to 1,25 dihydroxycholecalciferol by subpopulations of murine epidermal keratinocytes: Existence of a paracrine system for 1,25 dihydroxycholecalciferol
Author(s) -
RizkRabin Marthe,
Zineb Rougui,
Zhor Bouizar,
Michele Garabedian,
Jana Pavlovitch
Publication year - 1994
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041590117
Subject(s) - epidermis (zoology) , paracrine signalling , keratinocyte , biology , acridine orange , calcitriol , calcitriol receptor , microbiology and biotechnology , receptor , cellular differentiation , flow cytometry , cell culture , medicine , endocrinology , biochemistry , vitamin d and neurology , apoptosis , anatomy , genetics , gene
The epidermis is both a target tissue for and a source of 1,25 dihydroxycholecal‐ciferol. The present study determines which of the epidermal cell populations synthesizes 1,25 dihydroxycholecalciferol and which responds to this hormone. Epidermal keratinocytes from new born rat epidermis were separated by unit gravity sedimentation into poorly differentiated cells, slow‐cycling more differentiated cells, actively proliferating cells, and terminally differentiating subpopulations. The keratinocyte populations were characterized by cell size analysis, cell morphology, and DNA and RNA contents (acridine orange flow cytometry). 1,25(OH) 2 D 3 synthesis was studied by measuring the conversion of [ 3 H] 25(OH)D 3 to [ 3 H] 1,25(OH) 2 D 3 . The purified product was tested for its ability to compete with synthetic [ 3 H] 1,25(OH) 2 D 3 for binding to chick intestinal cytosol. The responses of the keratinocyte subpopulations to exogeneous 1,25(OH) 2 D 3 were evaluated by the increase in 25(OH)D 3 ‐24 hydroxylase activity. Furthermore the expression of 1,25(OH) 2 D 3 receptors (VDR) was examined in these cell populations. The results show that only the least differentiated cells produced 1,25(OH) 2 D 3 . In contrast, immunocytochemical detection of VDR, the VDR mRNA, and a 25(OH)D 3 ‐24 hydroxylase response to 1,25(OH) 2 D 3 were mainly found in the more differentiated cells. Thus, the ability of epidermis to synthesize 1,25(OH) 2 D 3 and be simultaneously sensitive to it depends on the state of cell differentiation. This suggests that the mammalian epidermis contains a paracrine system in which the more differentiated keratinocytes are sensitive to the 1,25(OH) 2 D 3 produced locally by neighboring immature ones. © 1994 wiley‐Liss, Inc.