Abstract 1540: Midkine Possesses a Potent Angiogenetic Action through Activation of Akt and ERK
Background: Midkine (MK) is a heparin-binding growth factor involved in diverse biological phenomena, such as neural survival, tissue repair and carcinogenesis. We reported recently that MK improves the long-term survival of mice after myocardial infarction and increases micro vessels in infarct area (AHA 2005). In this present study, we investigated the mechanisms of MK for angiogenesis and examined the possibility for angiogenic therapy of ischemic peripheral arterial disease.
Methods and results: Addition of MK (100 ng/ml) to HUVEC cultured on growth factor-depleted Matrigel in absence of serum resulted in a considerable acceleration of formation of visible rings and cords. In this in vitro assay, phosphorilation of Akt and ERK were shown to be significantly increased in Western blotting (phospho-Akt/total-Akt: 3.30±0.21 fold vs. control, n=5, p<0.05. p-ERK/t-ERK: 9.88±0.19 fold vs. control, n=5, p<0.05). To assess the angiogenic properties of MK in vivo, Matrigel pellets with or without MK were inserted into mouse abdominal walls. Incorporation of MK (500ng/ml) into the Matrigel led to significant increase in number of vessels after 7 days (3.31±0.18 fold vs. control, n=7, p<0.05). In mouse hindlimb ischemia model, Laser Doppler perfusion analyses showed significant decrease in the ratio of ischemic/non-ischemic hindlimb blood flow in MK-knockout mice (MKKO) compared with wild-type mice (WT) at 14 days after ligature (0.19±0.01 in MKKO vs. 0.41±0.03 in WT, n=9, p<0.05). Direct injection of adenovirus encoding MK into the ischemic hindlimb muscle of rat showed an appreciate improvement of blood flow compared with null virus injection group.
Conclusion: MK enhances angiogenesis via the activation of Akt and ERK. Exogenous application of MK might be a new therapeutic strategy to ameliorate peripheral obstructive arterial disease.