The experimental study of adipose-derived stem cells promoting vascular growth in irradiated skeletal muscle

Objective To investigate the mechanisms in the function of adipose-derived stem cells (ASCs) in angiogenesis of the radiation-induced skeletal muscle injury.Methods Totally 64 New Zealand rabbits were randomly divided into ASCs and PBS group (each with 32) after a monodose irradiation of 80 Gy by electron beam.The irradiated buttocks were injected with 5 × 107 allogeneic ASCs labeled with CM-Dil suspended in 1 ml PBS or 1 ml PBS respectively via local intramuscular 24 h after irradiation.Immunohistochemical staining was performed to evaluate the expression of VEGF,bFGF and CD31 in the muscular tissues.Western blot was performed to evaluate the expression of VEGF and bFGF protein in the muscular tissues.ELISA was used to test VEGF and bFGF secreted by ASCs in conditioned medium.Results After irradiation,the density of microvessel positively stained with CD31 showed remarkable increased after ASCs implantation at 4,8 and 26 weeks compared with PBS group,respectively (t =8.14,7.44,18.58,P ＜ 0.05).The integrated optimal density (IOD) of VEGF and bFGF was all significantly higher than PBS group at 1,4,8,and 26 weeks on each section of ASCs group,respectively (VEGF:t=3.13,4.66,2.19,6.79,P ＜0.05; bFGF:t =3.14,3.84,4.28,3.61,P ＜0.05).Moreover,the expression levels of VEGF protein which detected using western blot increased at 1,4,8 and 26 weeks in the ASCs groups compared with those of the PBS group (t =4.28,5.02,4.24,4.56,P ＜ 0.05).The expression levels of bFGF protein detected using Western blot showed increase at 4,8,and 26 weeks in the ASCs groups compared with PBS group (t =3.36,3.16,5.77,P ＜ 0.05).The expression levels of VEGF secreted by ASCs in irradiated muscle supernatant were higher than those secreted by ASCs in normal muscle supernatant at 48,72,and 96 h,respectively (t =2.81,9.96,4.75,P ＜ 0.05).The expression levels of bFGF secreted by ASCs in irradiated muscle supernatant were higher than those in normal muscle supernatant at 72 h and 96 h,respectively (t =3.80,4.33,P ＜ 0.05).Conclusions ASCs transplantation could up-regulate the expressions of VEGF and bFGF,and promote the angiogenesis of the irradiated muscle tissues,which may be partly associated with the repair of radiationinduced skeletal muscle injury. Key words: Adipose-derived stem cells ;  Skeletal muscles ;  Radiation injury ;  Angiogenesis ; Rabbit model