Differential effects of retinoic acid and growth factors on osteoblastic markers and CD10/NEP activity in stromal-derived osteoblasts.
The effects of retinoic acid (RA) on the expression of osteoblastic-related cell markers was examined. A marrow stromal osteogenic cell line, MBA-15, was analyzed by Northern blotting for the expression of bone matrix proteins. These cells constitutively express mRNA encoding for procollagen alpha 2 (I), osteonectin, osteopontin, biglycan, and alkaline phosphatase (ALK-P). Gene expression was unchanged in response to RA triggering for 24 hr. Furthermore, cell growth and enzymatic activities of ALK-P and neutral endopeptidase (CD10/NEP) were studied. These parameters were examined in MBA-15 and clonal populations representing different stages of differentiation. The cell's growth rate was unchanged, while ALK-P activity was greatly increased during the culture period under RA treatment in MBA-15 and in the clonal cell lines examined while CD10/NEP activity displayed a different pattern. MBA-15.4, a preosteoblast cell line, exhibited an inhibition in CD10/NEP activity at the beginning of the culture period, reaching basal level with time. This activity was greatly increased over control level in MBA-15.6, a mature stage of osteoblasts. Furthermore, the response of cell lines to various growth factors was tested subsequent to priming the cultures with RA. A synergistic effect was monitored for ALK-P activity in MBA-15.4 and MBA-15.6 cells under rh-bone morphogenic protein (BMP-2) and purified osteogenin (BMP-3), and an antagonist effect was measured when cells were exposed to transforming growth factor beta (TGF beta). Contrarily, BMP-2 and BMP-3 inhibited the CD10/NEP activity that had remained unchanged following priming of the cell with RA. Insulin-like growth factor I (IGF-I) and basic fibroblast growth factors (bFGF) did not affect either ALK-P nor CD10/NEP activities in both cloned cells. Cellular response to bone-seeking hormone, parathyroid hormone (PTH), and prostaglandin E2 (PGE2) was monitored by activation of intracellular cAMP. Treatment with RA caused a dramatic decrease in MBA-15.6 cell responses to PTH and PGE2, but no significant effects could be observed in other clonal lines.
Benayahu
D
D
Department of Histology and Cell Biology, Sackler Faculty of Medicine, Tel Aviv University, Israel.
Fried
A
A
Shamay
A
A
Cunningham
N
N
Blumberg
S
S
Wientroub
S
S
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000096:biosynthesis*; D000818:Animals; D015415:Biomarkers; D001854:Bone Marrow Cells; D019485:Bone Morphogenetic Proteins; D002460:Cell Line; D002999:Clone Cells; D000242:Cyclic AMP / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D015260:Neprilysin / Q000096:biosynthesis*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; D016326:Extracellular Matrix Proteins; D006133:Growth Substances; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D016222:Fibroblast Growth Factor 2; D014212:Tretinoin; D007334:Insulin-Like Growth Factor I; D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D015260:Neprilysin; D015056:1-Methyl-3-isobutylxanthine