Stimulation of SDF-1–dependent trans-Matrigel migration of CB and BM CD34⁺ cells and MMP secretion by SLPs. (A) CB and BM CD34⁺ cells preincubated with SLPs from 2 patients^1,2  were loaded into Boyden chambers and allowed to migrate toward a low (20 ng/mL) SDF-1 gradient in a trans-Matrigel assay. Unstimulated cells migrated across Matrigel toward media alone (control) or toward low or high (300 ng/mL) SDF-1 gradients. Each experiment was performed in triplicate using 4 chambers for each condition (*P < .0003). (B) Media conditioned by CB and BM CD34⁺ cells preincubated with SLP from patients 1 and 2 were analyzed by zymography. Bands indicating MMP-9 and MMP-2 activity were quantitated by densitometric analysis, and fold-increase in the presence of SLP was calculated relative to the control (SLP alone). Each experiment was performed 3 times, and representative data are shown.