Platelet-derived growth factor receptor signaling is not involved in osteogenic differentiation of human mesenchymal stem cells.
Platelet-derived growth factor (PDGF) receptor signaling plays an important role in the regulation of proliferation and migration of skeletal cells such as osteoblasts or mesenchymal stem cells (MSCs). However, involvement of these receptors in the process of osteoblastic differentiation of MSCs is still a matter of debate. The aim of our study was to examine the role of PDGF receptor signaling in osteogenic differentiation of human MSCs. For this purpose, we performed PDGF receptor stimulation as well as inhibition experiments. Inhibition experiments were carried out with Tyrphostin AG1296, a potent and specific inhibitor of PDGF receptor activity. As expected, Tyrphostin AG1296 treatment caused a concentration-dependent decrease in fetal calf serum and PDGF-BB-induced proliferation of MSCs and effectively inhibited PDGF-BB-induced phosphorylation of extracellular-regulated kinase 1/2. However, PDGF receptor inhibition had no significant effect on osteoblastic differentiation of MSCs, as evaluated histochemically by von Kossa, Alizarin-Red, and osteocalcin stainings. Moreover, mineralized matrix production, as assayed by quantitative Ca(2+)-measurements, was also not modulated by Tyrphostin AG1296 treatment. These results were noticeable irrespective of whether MSCs were grown under nonosteogenic or osteogenic differentiation conditions. Similarly, PDGF-BB treatment of MSCs in receptor stimulation experiments also failed to modulate mineralization. However, expression of alkaline phosphatase was suppressed by Tyrphostin AG1296 treatment at later stages of osteogenesis but not in the early stages, as assessed by enzyme activity and mRNA expression assays. Expression of other osteogenic marker genes such as osteocalcin, runt-related transcription factor 2, osteopontin, collagen type I, and bone sialoprotein was almost unaffected in our perturbation studies. From these experiments, we conclude that PDGF receptor signaling sustains proliferation without affecting osteogenic differentiation of MSCs.
Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
Akhilesh
A
Kumar
Bharathi P
BP
Salimath
Gerhard Björn
GB
Stark
Günter
G
Finkenzeller
D000368:Aged; D000469:Alkaline Phosphatase / Q000378:metabolism; D000077214:Becaplermin; D015415:Biomarkers / Q000378:metabolism; D001857:Bone Matrix / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D015415:Biomarkers; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D015675:Osteocalcin; D000077214:Becaplermin; D017479:Receptors, Platelet-Derived Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000469:Alkaline Phosphatase