Conditional Loss of Pten in Myogenic Progenitors Leads to Postnatal Skeletal Muscle Hypertrophy but Age-Dependent Exhaustion of Satellite Cells

Abstract

Skeletal muscle stem cells (satellite cells [SCs]) are normally maintained in a quiescent (G₀) state. Muscle injury not only activates SCs locally, but also alerts SCs in distant uninjured muscles via circulating factors. The resulting G_Alert SCs are adapted to regenerative cues and regenerate injured muscles more efficiently, but whether they provide any long-term benefits to SCs is unknown. Here, we report that embryonic myogenic progenitors lacking the phosphatase and tensin homolog (Pten) exhibit enhanced proliferation and differentiation, resulting in muscle hypertrophy but fewer SCs in adult muscles. Interestingly, Pten null SCs are predominantly in the G_Alert state, even in the absence of an injury. The G_Alert SCs are deficient in self-renewal and subjected to accelerated depletion during regeneration and aging and fail to repair muscle injury in old mice. Our findings demonstrate a key requirement of Pten in G₀ entry of SCs and provide functional evidence that prolonged G_Alert leads to stem cell depletion and regenerative failure.

Keywords: Pten; aging; hypertrophy; regeneration; skeletal muscle; stem cells.