Journal of Dental Research, Vol 64, 1186-1190, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Retinoic acid stimulates degradation of interstitial collagen fibrils by rat mucosal keratinocytes in vitro
B. R. Wells and H. Birkedal-Hansen
A large body of evidence suggests that retinoids modulate the phenotypic
expression of epithelial cells of skin and mucous membranes. The purpose of
this study was to investigate the effect of retinoic acid on
keratinocyte-mediated collagen breakdown. Keratinocytes derived from the
ventral surfaces of the tongues of 4-6 week-old male Wistar rats were
established in culture under conditions which are restrictive to growth of
fibroblasts, and they were eventually cloned by limiting dilution. The
cells were seeded (100,000 cells/cm2) in dishes coated with 3H-labeled,
reconstituted type I collagen fibrils and incubated in serum-free medium
over a 3-5 day period. Dissolution of the collagen fibrils was monitored by
the release of radioactivity to the culture medium. Unstimulated cells
metabolized the collagen rather slowly, but addition of retinoic acid in
concentrations from 10(-6)M to 10(-8)M resulted in marked acceleration of
the degradative process, with complete solubilization of the collagen
fibrils in four or five days. The effect of 10(-6)M retinoic acid was of
the same order of magnitude as that obtained by addition of a proteolytic
activating system either in the form of plasmin or of plasminogen, which is
converted to catalytic plasmin by endogenous activators. The effects of
retinoic acid and plasminogen/plasmin, however, were not additive.
Keratinocytes rendered vitamin A-deficient by cultivation in sera from
deficient rats were clearly less effective in degrading the collagen
substrate than were "sufficient" cells. Addition of retinoic acid (10(-7)M)
enhanced collagen breakdown in both sets of cultures and partially restored
the collagenolytic activity of the deficient cells.
