Vitamin a-poor lipocytes: a novel desmin-negative lipocyte subpopulation, which can be activated to myofibroblasts. Ramm, Grant A., Robert S. Britton, Rosemary O'neill, William S. Blaner, and Bruce R. Bacon. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Saint Louis University Health Sciences Center, St. Louis, MO 63110-0250, and Institute of Human Nutrition, Columbia University, New York, NY 10032
APStracts 2:0095G, 1995.
Lipocytes have been classified as vitamin A-storing, desmin-positive cells. In hepatic fibrogenesis, lipocytes transform into myofibroblasts, which express [alpha]-smooth muscle actin ([alpha] -SMA), and produce increased amounts of collagen. We isolated a population of vitamin A-poor lipocytes (VAPL) from normal rat liver and examined the morphological and biochemical differences between VAPL and vitamin A-replete lipocytes (VARL). Desmin and [alpha]-SMA expression were determined by Western blot in quiescent cells and in cells activated by culture on uncoated plastic. Both cell types were [alpha]-SMA-negative, however, in contrast to VARL, freshly isolated VAPL did not contain desmin. Desmin expression was induced in VAPL upon activation. With time in culture, both VAPL and VARL expressed [alpha]-SMA and produced collagen, indicative of transformation to myofibroblasts. Ferritin receptor expression was demonstrated in cultured VARL after 1 d and in VAPL after 5 d, indicating that this is an early marker of lipocyte activation. After 7 d, VARL and VAPL were indistinguishable in terms of desmin, ferritin receptor expression, and collagen production. This study demonstrates the first isolation and characterization of two distinct quiescent subpopulations of lipocytes from normal rat liver: desmin-negative VAPL and desmin-positive VARL. Both populations of cells can be activated to myofibroblasts, the phenotype associated with hepatic fibrogenesis. 

Received 29 August 1994; accepted in final form 28 March 1995.
APS Manuscript Number G328-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.