What Is Sauce for the Gander Is Not Sauce for the Goose: Sexual Dimorphism of Skeletal Muscle Stem Cells in Age and Exercise - The 2016 Wingate Congress of Exercise and Sport Sciences

Gabi Shefer ^1,2,3 Yonit Marcus ^1,2 Eli Carmeli ⁴ Naftali Stern ^1,2 Dafna Benayahu ² Eli Carmeli Naftali Stern Zipora Yablonka-Reuveni ³

¹Institute of Endocrinology, Metabolism and Hypertension, Tel Aviv Souraski Medical Center, Israel
²Sackler School of Medicine, Tel Aviv University, Israel
³Biological Structure, University of Washington School of Medicine, USA
⁴Physical Therapy, Faculty of Social Welfare and Health Sciences, University of Haifa, Israel

Background: Aging is associated with sarcopenia, a progressive decline in muscle mass and strength. The repair of myofibers, functional units of skeletal-muscles, depends on satellite cells (SCs), or muscle stem cells. Human and rodent studies show an age-associated decline in SC-numbers which may play a role in sarcopenia.

Aim: to investigate gender-related differences in SCs in response to age and endurance exercise.

Methods: Gastrocnemius or extensor-digitorum-longus muscles of rats and mice were assessed for the effect of age, gender and exercise on SCs. Rodents ran on a treadmill for 20 minutes/day/6days/week, for 13-weeks. Ages (months) at the end of exercise were in rats 6.5, 18-20 and in mice 8, 18-20.

Results: Age: There was an age-associated decline in SC-numbers of sedentary males and females and a sharp increase in myofibers lacking SCs. Myostatin-null-mice with large muscle mass were not spared from age-associated SC decline. Gender: (1) Average number of SCs was 2-3-fold higher in males vs. females in both ages; (2) At old age, male myofibers exhibited a 64% decline in SC-numbers compared to a 34% decline in females. Exercise: In male rats, exercise induced a 25% and 100% increase in SC-numbers, compared to 66% and 50% increases in young and old rats. In mice, gender differences were more dramatic with an increase of 66% and 100% in SCs in males at both ages and only 20% and 40% in females. Our studies underscore the need to further explore the role of sex-hormones in attempted preservation of skeletal-muscle in aging.