Forum original research communication

Hypoxia serves as a physiologic cue to drive an angiogenic response via HIF- dependent mechanisms. Interestingly, minor elevation of lactate levels in the tissue produces the same effect under aerobic conditions. Aerobic glycolysis contributes to lactate accumulation in the presence of oxygen, especially under inflammatory conditions. We previously postulated that aerobic lactate accumulation, already known to stimulate collagen deposition, will also stimulate angiogenesis. If substantiated, this concept would advance understanding of wound healing and aerobic angiogenesis because lactate accumulation has many aerobic sources. In this study, Matrigel plugs containing a powdered, hydrolyzable lactate polymer were implanted into the subcutaneous space of mice. Lactate monomer concentrations in the implant were consistent with wound levels for more than 11 days. They induced little inflammation but considerable VEGF production and were highly angiogenic, as opposed to controls. Arterial hypoxia abrogated angiogenesis. Furthermore, inhibition of lactate dehydrogenase by using oxamate also prevented the angiogenic effects of lactate. Lactate monomer, at concentrations found in cutaneous wounds, stabilized HIF-1 alpha and increased VEGF levels in aerobically cultured human endothelial cells. Accumulated lactate, therefore, appears to convey the impression of metabolic need for vascularization, even in well- oxygenated and pH-neutral conditions. Lactate and oxygen together stimulate angiogenesis and matrix deposition.