Delivery system for autologous growth factors fabricated with low-molecular-weight heparin and protamine to attenuate ischemic hind-limb loss in a mouse model

Frozen and thawed platelet-rich plasma (PRP) contains high concentrations of various growth factors, such as fibroblast growth factor (FGF)-2, vascular endothelial growth factor, and hepatocyte growth factor. We previously reported that low-molecular-weight heparin/protamine microparticles (LH/P MPs) are useful as biodegradable carriers for the controlled release of FGF-2. In this study, we examined the ability of PRP/LH/P MPs to prevent limb loss in an induced ischemic hind-limb model that used adult BALB/c-nu/nu male mice. One day after inducing ischemia, intramuscular injections of a PRP/LH/P MPs solution were administered into several sites of the ischemic hind limb. Seven days and onward after the injections, the PRP/LH/P MPs-treated and PRP-treated groups recovered from ischemia, as reflected by the improved oxygen saturation. In the PRP-treated group, however, the level of recovery of oxygen saturation after ischemia decreased after 14 days. From the 21st day onward, there was a significant difference between those two groups. In the LH/P MPs-treated group, a partial recovery occurred only in the early period. The saline-treated group (i.e., the control) and the noninjection group (i.e., ischemia only) exhibited no recovery. The limb survival rate at 1 year in the ischemia-induced mice injected with PRP/LH/P MPs was approximately 25 % (two of eight mice) but was absent in the other groups.