**Ornella Cappellari** †**, Paola Mantuano** † **and Annamaria De Luca \***

Section of Pharmacology, Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", via Orabona 4—Campus, 70125 Bari, Italy; ornella.cappellari@uniba.it (O.C.); paola.mantuano@uniba.it (P.M.)

**\*** Correspondence: annamaria.deluca@uniba.it; Tel.: +39-080-544-22-45

† These authors contributed equally to this work.

Received: 31 May 2020; Accepted: 2 July 2020; Published: 9 July 2020

**Abstract:** The muscle stem cells niche is essential in neuromuscular disorders. Muscle injury and myofiber death are the main triggers of muscle regeneration via satellite cell activation. However, in degenerative diseases such as muscular dystrophy, regeneration still keep elusive. In these pathologies, stem cell loss occurs over time, and missing signals limiting damaged tissue from activating the regenerative process can be envisaged. It is unclear what comes first: the lack of regeneration due to satellite cell defects, their pool exhaustion for degeneration/regeneration cycles, or the inhibitory mechanisms caused by muscle damage and fibrosis mediators. Herein, Duchenne muscular dystrophy has been taken as a paradigm, as several drugs have been tested at the preclinical and clinical levels, targeting secondary events in the complex pathogenesis derived from lack of dystrophin. We focused on the crucial roles that pro-inflammatory and pro-fibrotic cytokines play in triggering muscle necrosis after damage and stimulating satellite cell activation and self-renewal, along with growth and mechanical factors. These processes contribute to regeneration and niche maintenance. We review the main effects of drugs on regeneration biomarkers to assess whether targeting pathogenic events can help to protect niche homeostasis and enhance regeneration efficiency other than protecting newly formed fibers from further damage.

**Keywords:** muscle regeneration; muscle stem cells; stem cells niche; muscle homeostasis; neuromuscular disorders; Duchenne muscular dystrophy; pharmacological approach
