Endothelial Permeability Following Skeletal Muscle Injury in Males Versus Females Ages 4 weeks to 1 Year.

Abstract

Capillary permeability following skeletal muscle injury is necessary for the entry of blood cells and plasma factors necessary for healing. However, it is unclear how aging and sex differences affect capillary permeability after muscle injury.PURPOSETo compare endothelial permeability 48 hours post skeletal muscle injury between male and female mice at 1, 3, 6 and 12s month of ag between male and female mice.METHODSBarium chloride (BaCl2) was injected into the left tibialis anterior(TA) to create a chemical injury and sodium chloride (NaCl) was injected into the right leg as a control. Evans Blue (EB) dye was injected through the lateral tail vein at 48 hours post‐injury. The mouse was sacrificed 30 min following EB injection and both TA’s were removed, weighed and soaked in formamide to remove extravasated EB from the muscles. Absorbance of extravasated EB was measured. To determine the effect of testosterone and estradiol on permeability, castrated and ovariectomized mice at 12 weeks of age were tested for permeability using Evan’s Blue dye injection 48 hours after injury.RESULTSPermeability 48 hours post‐injection was significantly elevated in the BaCl2 injected muscles of mice aged 4 weeks compared to NaCl Male: 6.53±0.1.25 vs. 16.68±8.712 ngEB/mgTA, p<0.001; Female: 2.435±1.56 vs. 9.411±2.799, p<0.01). Permeability 48 hours post‐injection was significantly elevated in the BaCl2 injected muscles of mice aged 12 weeks compared to NaCl Female: 3.02 + 2.43 vs. 16.425 ± 6.63, p<0.0001). Permeability 48 hours post‐injection was significantly elevated in the BaCl2 injected muscles of mice aged 6 months compared to NaCl Male: 2.2743 + .0.932 vs. 8.37 ± 81.66 ngEB/mgTA, p<0.01; Female: 1.593 ±.0.991 vs. 6.3 ± 4.846, p<0.001). Permeability 48 hours post‐injection was significantly elevated in the BaCl2 injected muscles of mice aged 12 months compared to NaCl Male: 1.55 ± 0.32 vs. 4.371 ± 0.299 ngEB/mgTA, p<0.01; Female: 2.78 + 0.79 vs.. 12.02 ± 2.84, p<0.0001). Following castration, permeability in male mice at 12 weeks was not significantly different than non‐castrated mice (5.64 ± 1.033; 7.505 ± 2.131vs 4.927 ± 0.549 vs. 7.505 ± 2.131, respectively). Following ovariectomy, permeability in female mice at 12 weeks was not significantly different than non‐ovariectomized mice (3.02 + 2.43 vs. 16.53 ± 6.63; 4.927 ± 0.549 vs. 9.152 ± 2.96, respectively)CONCLUSIONBoth age and gender contribute to permeability 48 hrs post‐skeletal muscle injury. This affect does not appear to be dependent on testosterone or estradiol.