Extraocular muscle satellite cells are high performance myo-engines retaining efficient regenerative capacity in dystrophin deficiency

Abstract

Extraocular muscles (EOMs) are highly specialized skeletal muscles that originate from the head mesoderm and control eye movements. EOMs are uniquely spared in Duchenne muscular dystrophy and animal models of dystrophin deficiency. Specific traits of myogenic progenitors may be determinants of this preferential sparing, but very little is known about the myogenic cells in this muscle group. While satellite cells (SCs) have long been recognized as the main source of myogenic cells in adult muscle, most of the knowledge about these cells comes from the prototypic limb muscles. In this study, we show that EOMs, regardless of their distinctive Pax3-negative lineage origin, harbor SCs that share a common signature (Pax7+, Ki67−, Nestin-GFP+, Myf5nLacZ+, MyoD-positive lineage origin) with their limb and diaphragm somite-derived counterparts, but are remarkably endowed with a high proliferative potential as revealed in cell culture assays. Specifically, we demonstrate that in adult as well as in aging mice, EOM SCs possess a superior expansion capacity, contributing significantly more proliferating, differentiating and renewal progeny than their limb and diaphragm counterparts. These robust growth and renewal properties are maintained by EOM SCs isolated from dystrophin-null (mdx) mice, while SCs from muscles affected by dystrophin deficiency (i.e., limb and diaphragm) expand poorly in vitro. EOM SCs also retain higher performance in cell transplantation assays in which donor cells were engrafted into host mdx limb muscle. Collectively, our study provides a comprehensive picture of EOM myogenic progenitors, showing that while these cells share common hallmarks with the prototypic SCs in somite-derived muscles, they distinctively feature robust growth and renewal capacities that warrant the title of high performance myo-engines and promote consideration of their properties for developing new approaches in cell-based therapy to combat skeletal muscle wasting.

Isolation and Characterization of Satellite Cells from Rat Head Branchiomeric Muscles

“…the extraocular muscles) 24 . It has been clearly demonstrated that head and limb muscles possess highly different properties.…”

“…Masseter muscle from old animals seems to retain their regenerative capacity in comparison with limb muscles 25,26 . SCs from the extraocular muscles possess a robust proliferation and differentiation capacity comparable to SCs from head muscles, and show a larger engraftment potential than limb muscle SCs 24 .…”

“…Specific studies on branchiomeric head muscles are also important because it was recently demonstrated that they differ from other muscles in several aspects 24 .…”

Regulation and phylogeny of skeletal muscle regeneration

“…Here too it should be noted that the vast majority of studies on muscle regeneration are performed on the TA muscle. Given the genetic and phenotypic differences between muscles in different anatomical locations (Sambasivan et al, 2009), including the superior engraftment potential of extraocular derived 8 satellite cells compared to those from the TA muscle (Stuelsatz et al, 2015), careful consideration needs to be given to other muscle groups.…”

“…Here too it should be noted that the vast majority of studies on muscle regeneration are performed on the TA muscle. Given the genetic and phenotypic differences between muscles in different anatomical locations (Sambasivan et al, 2009), including the superior engraftment potential of extraocular derived 8 satellite cells compared to those from the TA muscle (Stuelsatz et al, 2015), careful consideration needs to be given to other muscle groups.The most commonly used acute injury models involve intramuscular injection of myotoxins (Cardiotoxin (CTX) and Notexin (NTX)), Barium chloride (BaCl 2 ), and mechanical injury (freeze, needle or crush injuries) Hardy et al, 2016) (Figure 1). …”