635. Effects of Mechanical Strain on Zmpste24-Deficient Prematurely Aged Muscle-Derived Stem Cells

Abstract

Mice deficient in Zmpste24, a metalloproteinase involved with formation of lamin A, are a model for aging and for Hutchinson-Gilford Progeria Syndrome, a human disorder caused by a similar defect. Z24-/- muscle-derived stem cells (MDSCs) are defective in proliferation and differentiation potential. Stretching stem cells prior to implantation has been shown to improve outcomes. Based on these results, stretching may be able to rejuvenate aged stem cells. Therefore, examining the response of stretched and non-stretched Z24-/- MDSCs to stress can show if stretching rescues some of the negative processes involved with aging.Z24-/- MDSCs were seeded on BioFlex plates (Flexcell Inc) at a density of 50,000 cells per well. Cells were stretched for 24 hours with 10% uniaxial elongation and a 0.5Hz frequency. Z24-/- mice had increased cell senescence and muscle stem cell depletion in the skeletal muscle. Muscle stem cells isolated from Z24-/- mice have increased activation of ROS (reactive oxygen species). Cells mechanically strained for 24 hours appeared to be more resistant to oxidative stress and express higher levels of RhoA, which is a mediator of cell stress: more senescent cells were observed in the non-flexed vs. flexed groups under standard conditions and under oxidative stress. The flexed cells also had a better survival rate following oxidative stress for 24h. These results indicate that flexing compensates for some of the progeria phenotype. Flexing appears to prime the cells so they are more resistant to stressors like H2O2. The lower number of senescent flexed vs. non-flexed cells seems to indicate that the flexing protects the cells from entering senescence. Mechanical strain also appears to give the cells greater resistance to reactive oxidative species. PCR results of TNE-α showed that non-flexed cells expressed the pro-inflammatory cytokine 1.33-fold compared to flexed cells. This indicates that mechanical stimulation may improve the cells’ response to stressors and reduce inflammation. These preliminary results indicate that mechanical strain may rejuvenate and rescue the cells from defects in cell proliferation and differentiation. Based on these results, flexing cells in vitro may improve the quality and outcome of stem cells implanted into patients, especially in older donors whose cells may behave similar to the Z24-/- cells.View Large Image | Download PowerPoint SlideView Large Image | Download PowerPoint Slide