Recombinant TIMP-1 restores the NG2+ cell deficit observed in neural stem cells derived from TIMP-1 KO mice. A, Representative immunocytochemical labeling of oligodendrocyte progenitors (NG2+) derived from WT or TIMP-1 KO neurosphere cultures following 1 week of differentiation. B, A significant decrease in the number of neural stem cell-derived NG2+ cells was observed in the TIMP-1 KO cultures when plated on either fibronectin or laminin substrates. C, D, Administration of recombinant murine TIMP-1 (1 and 10 ng/ml), but not the pan-MMP inhibitor GM6001 [active (A)/inactive (I)], dose-dependently reversed the deficiency (a more than threefold increase) of NG2+ progenitor cells in TIMP-1 KO neurosphere cultures. Scale bars, 200 μm. ***p < 0.0001; *p < 0.05. n = 3/group. Error bars represent the mean ± SEM.