Abstract Body (Do not enter title and authors here): The anti-angiogenic impact of neutrophil elastase clouded the understanding of the role of neutrophils in promoting neovascularization (NV) and fibrinolysis in patients with chronic limb-threatening ischemia (CLTI). The impact of significant neutrophilia was not studied during clinical trials using Granulocyte Colony Stimulating Factor (G-CSF) to boost the deficient circulating endothelial progenitor cell count. Only recently have activated human neutrophils been documented to release pro-angiogenic factors such as VEGFA, Hepatocyte Growth Factor (HGF), MMP-9, angiopoietin (Ang1). They also stimulate and modulate fibrinolysis through release of proteases, and by promoting endothelial cell release of plasmin.
The purpose of this abstract is to link clinical evidence* to these observations. Proteomic and cytometry data were obtained in 14 CLTI patients treated with Filgrastim 7-10 mcg/kg SQ every 72 h for up to a month. The absolute neutrophil count (ANC) increased a mean of 6-fold a day after each injection, returning to baseline within 72 hours. Significant (p < 0.05) increases in the concentration of VEGFA, HGF, MMP-9, Ang1 was measured by ELISA a day after both the 5th and the 10th Filgrastim doses as compared to baseline. The ANC peak was measured at the same time, as well as was the significant (p < 0.01) increases in the plasma concentration of plasmin (>10-fold) and Fibrin Degradation Products (FDP) (>5-fold). Since these patients also wore an infra-geniculate programmed compression pump (PCP) for 3 hours daily, these data were compared to 19 CLTI patients treated with PCP alone. PCP was used to improve the ischemic micro-environment and to provide endothelial shear stress as a strategy to induce arteriogenesis. PCP use did not influence the concentration of any of these proteins and did not induce neutrophilia. Resolution of ischemic rest pain and healing of ischemic ulcers contributed to limb salvage. Arterial hemodynamic improvement was supported by angiographic evidence of NV (enlarged corkscrew collaterals, improved contrast transit through the ischemic tissue). Segmental arterial recanalization indicated fibrinolysis. No hemorrhage occurred over the 30 day course. A prospective investigation of the uncovered link between neutrophilia, NV, and fibrinolysis is justified. * J Tissue Eng Regen Med. 2022 May;16(5):496-510. doi: 10.1002/term.3284