Fibroblast growth factor-2 promotes keratan sulfate proteoglycan expression by keratocytes in vitro.
Keratocytes of the corneal stroma produce a specialized extracellular matrix responsible for corneal transparency. Corneal keratan sulfate proteoglycans (KSPG) are unique products of keratocytes that are down-regulated in corneal wounds and in vitro. This study used cultures of primary bovine keratocytes to define factors affecting KSPG expression in vitro. KSPG metabolically labeled with [(35)S]sulfate decreased during the initial 2-4 days of culture in quiescent cultures with low serum concentrations (0.1%). Addition of fetal bovine serum, fibroblast growth factor-2 (FGF-2), transforming growth factor beta, or platelet derived growth factor all stimulated cell division, but only FGF-2 stimulated KSPG secretion. Combined with serum, FGF-2 also prevented serum-induced KSPG down-regulation. KSPG secretion was lost during serial subculture with or without FGF-2. Expression of KSPG core proteins (lumican, mimecan, and keratocan) was stimulated by FGF-2, and steady state mRNA pools for these proteins, particularly keratocan, were significantly increased by FGF-2 treatment. KSPG expression therefore is supported by exogenous FGF-2 and eliminated by subculture of the cells in presence of serum. FGF-2 stimulates KSPG core protein expression primarily through an increase in mRNA pools.
Long
C J
CJ
Division of Biology, Kansas State University, Manhattan Kansas, 66506-4901, USA.
Roth
M R
MR
Tasheva
E S
ES
Funderburgh
M
M
Smit
R
R
Conrad
G W
GW
Funderburgh
J L
JL
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000096:biosynthesis*; D003315:Cornea / Q000378:metabolism*; D015536:Down-Regulation; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D007632:Keratan Sulfate / Q000096:biosynthesis*; D000071234:Lumican; D017154:Stromal Cells / Q000378:metabolism; D015854:Up-Regulation
D011508:Chondroitin Sulfate Proteoglycans; D000071234:Lumican; D016222:Fibroblast Growth Factor 2; D007632:Keratan Sulfate