Mechanical signals modulated vascular endothelial growth factor-A (VEGF-A) alternative splicing in osteoblastic cells through actin polymerisation.
Since VEGF-A is involved in mechanically induced bone gain and because vegf exists under 6 isoforms exerting various biological effects, we studied vegf isoform expression and VEGF protein production in osteoblastic cells (rat Ros17/2.8 and human osteoblasts) submitted to 4 mechanical regimens. Mechanical regimens (1% stretch deformation) were designed with a fixed number of cycles (450) delivered at various frequencies (0.05 to 5 Hz). We found a negative correlation (R(2)=0.76, p<0.0001) between production of soluble VEGF and mechanical stretch frequency and a positive correlation (R(2)=0.99, p<0.0001) between production of matrix-bound VEGF and mechanical stretch frequency. mRNA expressions of soluble VEGF isoforms (121, 165) were specifically expressed under low frequency while matrix-bound VEGF isoforms (206, 189, 165, 145) were specifically expressed under high frequency in human osteoblasts. As f-actin stress fiber formation was significantly increased selectively in high frequency conditions, we disrupted actin fibers in Ros17/2.8 and found that immobilisation of VEGF was abolished. Conversely, Jasplakinolide treatment which increases stress fiber formation was able to mimic high frequency stretch-induced immobilisation of VEGF. Thus, we speculate that the stretch-induced increase in cell tension is responsible for matrix-bound vegf isoform production. Mechanically induced selection of soluble or matrix-bound VEGF production may modify osteoblast and endothelial cell crosstalk crucial during osteogenesis and fracture healing.
Faure
Céline
C
INSERM U890, St-Etienne, F-42023, France.
Linossier
Marie-Thérèse
MT
Malaval
Luc
L
Lafage-Proust
Marie-Hélène
MH
Peyroche
Sylvie
S
Vico
Laurence
L
Guignandon
Alain
A
D000199:Actins / Q000378:metabolism*; D017398:Alternative Splicing; D000818:Animals; D002460:Cell Line; D002648:Child; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D022502:Stress Fibers / Q000378:metabolism*; D013314:Stress, Mechanical; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D020033:Protein Isoforms; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat