Collateral artery development is the body's natural adaptive response to bypass major artery blockage. However, this process restores about 30% of the original blood flow, which is insufficient to avoid end-organ ischemia. Therefore, there is a great need for better understanding of the angiogenesis process. Overexpression of the p27kip1 (p27 or cdkn1b) gene inhibits angiogenesis in mice, and p27 knock-out mice (p27-/- or KO) have improved angiogenesis and arteriogenesis. We previously showed that p27-/- mouse vascular smooth muscle cells (VSMC) have increased matrix metalloproteinase 2 (MMP2) mRNA and migrate more effectively than wild type (WT) VSMC. We wanted to better understand the link between p27, MMP2, and cell repair capability. We hypothesized that decreasing the p27 genetic dose would result in increased MMP2 expression. Experiments were performed on p27+/+ (WT), p27+/- (HET), and KO VSMC isolated from 8-10 wk old female mouse aortae. All groups were tested for MMP2 mRNA and protein expression level using qRT-PCR and Western blot respectively. A cytoplasmic fraction was used for protein analysis. MMP2 mRNA expression in HET VSMC was significantly higher than in WT (194±9 vs. 101±3%, p<0.001), and significantly lower than in KO VSMC (280±38%, p<0.001). TIMP1 and TIMP2 mRNA expression was significantly lower in the KO VSMC than in the HET and WT cells (p<0.01). In the cytoplasmic fraction there was no significant difference between MMP2 protein levels between KO and HET VSMC, but both were significantly higher than the level in WT (2.55±0.27 vs. 2.15±0.22 and 1.14±0.3 respectively, p<0.05). Decreasing genetic dose of p27 in VSMC leads to higher levels of MMP2 mRNA and protein levels. This suggests that p27’s effect on VSMC migration in vitro and possibly its effect on angiogenesis and arteriogenesis is through regulation of MMP2 expression. TIMP1 and TIMP2 may also play a role in this process.