SPECIFIC STIMULATION OF BASAL LAMINA HEPARAN-SULFATE PROTEOGLYCAN IN MOUSE UTERINE EPITHELIUM BY MATRIGEL AND BY TRANSFORMING GROWTH-FACTOR-BETA-1

The basal lamina of differentiated epithelium normally turns over only slowly unless stimulated by tissue repair and growth. We show here th at one mechanism of this stimulation, as modeled by basal lamina prote oglycan synthesis, may be the release of basal lamina-bound transformi ng growth factor (TGF-beta). A large heparan sulfate proteoglycan (HSP G, 0.2 K-a upsilon on Sepharose CL-4B) that was extractable from mouse uterine epithelium with 4 M guanidine-HC1 or 1 M KC1 was recognized b y a specific monoclonal antibody to the basal lamina HSPG, perlecan. T his HSPG was metabolically inactive with respect to [S-35]-sulfate lab eling in pieces of whole uterus during 4 h of culture, but it was labe led in isolated cells under the same conditions, provided that the cel ls had been cultured at least 6 to 12 h before labeling. The rate of l abeling was then constant during at least 4 days in culture in serum-c ontaining medium. Cultures on Matrigel showed an enhanced [S-35]-sulfa te labeling 2 K-a upsilon HSPG fraction. Partial stimulation was obtai ned with a serum-free medium extract of Matrigel, which fractionated o n Sephadex G-50 in two components; a major one >30 kDa and the other a t about 15 to 25 kDa. The specific stimulation was mimicked by the add ition of 10 ng/ml of TGF-beta 1, but there was no specific stimulation by basic fibroblast growth factor (bFGF), epidermal growth factor (EG F), insulinlike growth factor-1 (IGF-1), or interleukin-1 (IL-1). TGF- beta 1 was identified as a 12.5 kDa monomer in thiol-reduced Matrigel and Matrigel extracts by polyclonal blocking antibodies on transblots following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. F ailure of excess amounts of these antibodies to block Matrigel-stimula ted basal lamina HSPG synthesis indicates that TGF-beta 1 may be only one component of Matrigel that is important in stimulating basal lamin a HSPG synthesis in culture. We suggest that in vivo TGF-beta 1 is bou nd to macromolecular components of mouse uterine epithelial basal lami na, where it may be sequestered until microenvironmental changes make it available to promote basal lamina HSPG synthesis.