CXCL12 and ischemia: Interestingly, a knock-in mouse line carrying a mutated Cxcl12 that cannot bind heparin sulfate without effect on Cxcr4 signaling by the α, β, or γ isoform showed an increased number of circulating hematopoietic progenitor cells, but a reduction in the number of cells infiltrating ischemic tissue after acute hindlimb ischemia and associated revascularization (51).