[The changes of cytoskeleton F-actin in rat bone marrow mesenchymal stem cells and calvarial osteoblasts under mechanical strain].
OBJECTIVE
To explore the response of rat bone marrow mesenchymal stem cells (MSCs and calvarial osteoblasts to mechanical strain and the consequent changes of cytoskeleton F-actin.


METHODS
Bone marrow MSCs and calvarial osteoblasts were isolated from SD rats and cultured in vitro. Mechanical stretch was performed on passage 3 cells at 2 000 microepsilon for 0, 2, 6 and 12 hours using four-point bending system. The response of cells and the distribution of F-actin were observed using fluorescent staining under laser scanning confocal microscope and the morphological parameters were quantified using image analysis software Laserpix.


RESULTS
Under mechanical stretch, the fluorescent staining decreased obviously at both MSCs and osteoblasts, and F-actin filaments were rearranged and became tenuous, thinner, and abnormally distributed. The outline of nucleus became unclear and apoptotic changes were observed at some of both cells. Cellular size decreased more significantly in MSCs than in osteoblasts. Quantity analysis showed that total area of cells, total fluorescent density and green fluorescent density (F-actin) were all significantly decreased in MSCs (P < 0.05 or P < 0.01), and total fluorescent density, green fluorescent density and red fluorescent density (nuclei) did also in osteoblasts (P < 0.05 or P < 0.01).


CONCLUSIONS
Mechanical stretch caused extensive response on both MSCs and osteoblasts which led to the rearrangement of F-actin filament and apoptosis in some of these cells. MSCs were more sensitive to mechanical strain than osteoblasts.
Qi
Meng-Chun
MC
Key Lab. of Oral Biomedical Engineering of Ministry of Education, Sichuan University, Chengdu 610041, China.
Hu
Jing
J
Zou
Shu-Juan
SJ
Han
Li-Chi
LC
Luo
En
E
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001854:Bone Marrow Cells; D002478:Cells, Cultured; D003599:Cytoskeleton; D059630:Mesenchymal Stem Cells; D008870:Microtubules; D010006:Osteoblasts; D051381:Rats; D013314:Stress, Mechanical
D000199:Actins