Transdifferentiation of alternatively activated macrophages into lymphatic endothelial cells induced by VEGF-C / 解放军医学杂志

ABSTRACT

Objective To explore whether alternatively activated macrophages (aaMphi) can transdifferentiate into lymphatic endothelial cells (LEC) under the inducement of VEGF-C, and to investigate the possible mechanisms involved in aaMphi-induced lymphangiogenesis. Methods An aaMphi model constructed by treating mouse macrophage cells RAW264.7 with mouse recombinant IL-4 for 24h was treated with different concentrations of recombinant mouse vascular endothelial growth factor-C (VEGF-C). After the clustering formed and the tube-like structures were detected in the matrigel, the aaMphi transdifferentiation system was finally decided to be constructed with the VEGF-C in the concentration of 100ng/ml. The mRNA expression of LEC specific markers, VEGFR-3 and Prox1, and aaMphi specific marker, Fizz1, were detected by real time quantitative RT-PCR on the 0, 7th, 14th, and 28th day, respectively, after VEGF-C stimulation. Formation of tube-like structure in the matrigel was observed with inverted phase contrast microscope in 28 consecutive days. Results The VEGF-C induced transdifferention system, incubated in EBM-2 medium and sustained by the matrigel, was successfully established. In this system, it was found that the mRNA expression of VEGFR-3 and Prox1 gradually increased, whilst that of Fizz1 decreased. The mRNA expression of VEGFR-3 and Prox1 reached the peak value, whilst that of the Fizz1 went down to the nadir, on the 14th day. No significant difference in values was found between the 14th day and the 28th day. During the period of the 7th day to the 28th day, distinct tube-like structures were gradually formed in the matrigel and the numbers increased in a time-dependant manner. Conclusion VEGF-C can induce the transdifferentiation of aaMphi into LEC by up-regulating the mRNA expression of VEGFR-3 and Prox1 in aaMphi, which is one of the possible mechanisms involved in aaMphi-induced lymphangiogenesis.