Effect of Aging on the Plasma Membrane Repair Process in Multiple Cell Types

Abstract

Plasma membrane repair mechanisms play a vital role in supporting the structure and function of most mammalian cells by repairing changes in the permeability of the cell membrane and maintaining its barrier function. Breakdown of the barrier function of the membrane can lead to death of the cell and accumulation (or prevention) of such cell death events can contribute to the progression of various diseases, including cancer, bacterial infection, Alzheimer's disease, heart failure, and muscular dystrophies. Many of these disease states are also exacerbated by the aging process which can alter intracellular vesicle trafficking, an essential cellular process that mediates plasma membrane repair. Here we tested if membrane repair efficiency changed in Mus musculus muscle tissue cells (myocytes) from young and aged mice. Skeletal muscles in the hindlimb of aged mice were injured by treadmill running and the amount of Evan's Blue dye influx into six different anatomical muscles was measured. This experiment showed increased dye influx into the myocytes within gluteus muscles of aged (24 months old) mice compared to younger mice (12 months old) used as controls. Additional studies using laser microscopy injury on Mus musculus muscle tissue cells show an increased FM4-64 dye influx (∆F/F0) following the injury of myocytes from 24-month-old mice compared to 12-month-old mice. Further experimentation was conducted on the effects of senescence, or premature aging, on primary human fibroblasts from young volunteers. Fibroblast cells were treated with hydroxyurea, which causes growth arrest in the S phase of the cell cycle, every 72 hours for 12 days. Membrane repair capacity was tested using laser microscopy injury on senescent cells compared to young untreated control cells. Preliminary findings show decreased plasma membrane repair in cells treated with hydroxyurea. The results of this experiment will guide future research to determine the mechanism of reduced membrane repair during aging and provide a new therapeutic target for aging-related diseases.