Reasearch Awards nomination

Email updates

Keep up to date with the latest news and content from Stem Cell Research & Therapy and BioMed Central.

Open Access Research

Myostatin genetic inactivation inhibits myogenesis by muscle-derived stem cells in vitro but not when implanted in the mdx mouse muscle

James Tsao1, Dolores A Vernet13, Robert Gelfand13, Istvan Kovanecz23, Gaby Nolazco1, Kevin W Bruhn3 and Nestor F Gonzalez-Cadavid123*

Author Affiliations

1 Department of Internal Medicine, Charles Drew University (CDU), 1731 East 120th Street, Los Angeles, CA 90059, USA

2 Department of Urology, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA

3 Los Angeles Biomedical Research Institute (LABioMed) at Harbor-UCLA Medical Center, 1124 West Carson Street, Torrance, CA 90502, USA

For all author emails, please log on.

Stem Cell Research & Therapy 2013, 4:4  doi:10.1186/scrt152

Published: 7 January 2013

Abstract

Introduction

Stimulating the commitment of implanted dystrophin+ muscle-derived stem cells (MDSCs) into myogenic, as opposed to lipofibrogenic lineages, is a promising therapeutic strategy for Duchenne muscular dystrophy (DMD).

Methods

To examine whether counteracting myostatin, a negative regulator of muscle mass and a pro-lipofibrotic factor, would help this process, we compared the in vitro myogenic and fibrogenic capacity of MDSCs from wild-type (WT) and myostatin knockout (Mst KO) mice under various modulators, the expression of key stem cell and myogenic genes, and the capacity of these MDSCs to repair the injured gastrocnemius in aged dystrophic mdx mice with exacerbated lipofibrosis.

Results

Surprisingly, the potent in vitro myotube formation by WT MDSCs was refractory to modulators of myostatin expression or activity, and the Mst KO MDSCs failed to form myotubes under various conditions, despite both MDSC expressing Oct 4 and various stem cell genes and differentiating into nonmyogenic lineages. The genetic inactivation of myostatin in MDSCs was associated with silencing of critical genes for early myogenesis (Actc1, Acta1, and MyoD). WT MDSCs implanted into the injured gastrocnemius of aged mdx mice significantly improved myofiber repair and reduced fat deposition and, to a lesser extent, fibrosis. In contrast to their in vitro behavior, Mst KO MDSCs in vivo also significantly improved myofiber repair, but had few effects on lipofibrotic degeneration.

Conclusions

Although WT MDSCs are very myogenic in culture and stimulate muscle repair after injury in the aged mdx mouse, myostatin genetic inactivation blocks myotube formation in vitro, but the myogenic capacity is recovered in vivo under the influence of the myostatin+ host-tissue environment, presumably by reactivation of key genes originally silenced in the Mst KO MDSCs.