Leptomeningeal and skin fibroblasts: two different cell types?

Leptomeningeal and skin fetal (E16-17) fibroblasts were subcultured in vitro either in DMEM/F12 basal medium (with or without 10% FCS) or in astroglial conditioned medium (ACM). Both populations were characteristically composed of flat, undifferentiated, fibronectin(+), GFAP(-)cells where cultured in fetal serum supplemented basal media. When exposed to ACM leptomeningeal cells developed a population of thin, elongated, fibronectin(+) cells with radial type long processes while skin fibroblasts did not show significant changes in their characteristic morphotype. Exposure to db cAMP in basal medium resulted within 3 hr in their transformation to an astrocytic-like morphotype characterized by a condensed soma and multiple, short processes. Twenty-four hours later skin fibroblasts had returned to their flat appearance while leptomeningeal ones showed elongated, radial-like forms. Results indicate the possible existence of different receptors (to ACM factors) and/or cytoskeletal properties, and suggest that ACM-reactive fibroblasts of leptomeningeal origin represent a different cell type from those of skin origin. The hypothetical role of leptomeningeal cells during brain development is considered.