Functional effects of collagen & SDF-1 microsphere matrix treatments in vivo . At early time points after treatment ( A ; days 1-4), animals receiving SDF-1 microsphere-matrix (SDF-1) had greater numbers of circulating CPCs. This was also observed at later time points ( B ; days 7-14). By 7 d post-op, hindlimb perfusion was restored to baseline levels with matrix treatments ( C ; n = 8-9 per group). * p < 0.05 versus PBS; ** p < 0.05 versus PBS & collagen.