MMP2 and Huntington disease: The mechanism of action can be explained as follows: first, more cells from the HD culture homed to and survived in the injured liver after injection (Fig. 5); second, a lower level of the pro-fibrogenic factors, TGF-β and PDGF-B, were expressed in the liver of the HD group (Fig. 4B); third, matrix degradation enzyme MMP-2 were highly expression in HD group (Fig. 4B); fourth, cell proliferation was stimulated through higher expression of HGF in the HD group (Fig. 6); and finally, more blood vessels were formed, induced by higher expressions of VEGF-A and Ang-1 in the HD group (Fig. 7B).