Hepatocyte growth factor stimulates chemotactic response in mouse embryonic limb myogenic cells in vitro

In this study we investigate the influence of Hepatoctye Growth Factor (HGF ) on the motility of embryonic forelimb myoblasts. Using Blindwell chemotac tic chambers, it was found that HGF at concentrations of 1-50 ng/ml dramati cally enhanced the ability of myogenic cells to migrate. This stimulatory e ffect was elicited in a dose-dependent fashion and the effect was reversed with the addition of HGF neutralizing antibodies. A checkerboard analysis w as performed and it revealed that HGF's effect on limb myoblast motility wa s through both chemokinesis and chemotaxis. HGF was also examined for its a bility to stimulate myogenic cell proliferation, using MF20 antibody as the myogenic marker. At all concentrations tested, HGF did not stimulate an ov erall increase in the numbers of MF20-positive myoblasts in culture. To exa mine the chemokinetic effect of HGF on cell migration in the limb, cells we re isolated from the proximal regions of the limb (areas rich in myogenic c ells), exposed to HGF, labeled with DiI and transplanted into 11.5 day mous e forelimbs. After 36 h of culture, it was found that DiI-labeled limb cell s, pretreated with HGF, migrated significantly further in the limb than lab eled cells that have not been exposed to HGF. The chemotactic effect of HGF was also investigated by implanting beads loaded with and without HGF into the 11.5 day limb. Proximal to the beads, DiI-labeled limb cells were also transplanted. It was found that HGF was able to chemotactically attract an d direct the migration of DiI-labeled limb cells. Immunohistological staini ng was performed with HGF antibodies to determine the distribution of HGF i n the 11.5 day mouse forelimb. It was found that HGF was strongly expressed by the apical ectodermal ridge (AER), the ectoderm and the mesenchyme dire ctly beneath the AFR. Positive staining was also obtained for the myogenic regions. However, the pattern was heterogeneous-punctuated with myogenic ce lls expressing and not expressing HGF. J. Exp. Zool. 283:170-180, 1999. (C) 1999. Wiley-Liss,Inc.