Hepatocyte Growth Factor and p38 Promote Osteogenic Differentiation of Human Mesenchymal Stem Cells

Abstract

Hepatocyte growth factor (HGF) is a paracrine factor involved in organogenesis, tissue repair, and wound healing. We report here that HGF promotes osteogenic differentiation through the transcription of key osteogenic markers, including osteocalcin, osterix, and osteoprotegerin in human mesenchymal stem cells and is a necessary component for the establishment of osteoblast mineralization. Blocking endogenous HGF using PHA665752, a c-Met inhibitor (the HGF receptor), or an HGF-neutralizing antibody attenuates mineralization, and PHA665752 markedly reduced alkaline phosphatase activity. Moreover, we report that HGF promotion of osteogenic differentiation involves the rapid phosphorylation of p38 and differential regulation of its isoforms, p38α and p38β. Western blot analysis revealed a significantly increased level of p38α and p38β protein, and reverse transcription quantitative PCR revealed that HGF increased the transcriptional level of both p38α and p38β. Using small interfering RNA to reduce the transcription of p38α and p38β, we saw differential roles for p38α and p38β on the HGF-induced expression of key osteogenic markers. In summary, our data demonstrate the importance of p38 signaling in HGF regulation of osteogenic differentiation.

Hepatocyte growth factor and alternative splice variants - expression, regulation and implications in osteogenesis and bone health and repair

“…Moreover, using phospho-p38α specific antibodies we found that HGF treatment rapidly activated and phosphorylated p38α in hMSC in a dose- and time-dependent manner 37 . Interestingly, HGF treatment of hMSC also induced an increase in protein levels of p38α, p38β, p38δ, and p38γ, with the peak at 24hrs post-HGF treatment 37 . An increase in p38α, p38β and p38γ RNA was also seen within 48hrs after HGF treatment, in contrast to a decrease in p38δ 37 .…”

“…Our group was the first to show that HGF treatment leads to the rapid activation of total p38 in hMSC 37 . Moreover, using phospho-p38α specific antibodies we found that HGF treatment rapidly activated and phosphorylated p38α in hMSC in a dose- and time-dependent manner 37 .…”

“…Our group was the first to show that HGF treatment leads to the rapid activation of total p38 in hMSC 37 . Moreover, using phospho-p38α specific antibodies we found that HGF treatment rapidly activated and phosphorylated p38α in hMSC in a dose- and time-dependent manner 37 . Interestingly, HGF treatment of hMSC also induced an increase in protein levels of p38α, p38β, p38δ, and p38γ, with the peak at 24hrs post-HGF treatment 37 .…”

“…Interestingly, HGF treatment of hMSC also induced an increase in protein levels of p38α, p38β, p38δ, and p38γ, with the peak at 24hrs post-HGF treatment 37 . An increase in p38α, p38β and p38γ RNA was also seen within 48hrs after HGF treatment, in contrast to a decrease in p38δ 37 . The data suggest that the HGF-induced rapid phosphorylation of p38 leads to the downstream maintenance of p38 protein expression.…”

“…Subsequently, the phosphorylation of tyrosine residues Y1349 and Y1356 causes the induction of downstream signals. The activation of the cMET receptor and consequent pathways is cell-type specific and can result in such actions as: cell migration, decreased proliferation, and loss of stem cell markers 1, 37, 38 . After activation, cMET is degraded by MET-specific proteases.…”