Activation of Muscle α7-Integrin Restores Sarcolemma Integrity and Improves Dystrophic Pathology


Pre-Clinical Research

Poster Number: S47


Claudio Perez, PhD, Pliant Therapeutics, Martin Decaris, PhD, Pliant Therapeutics, Mahru An, PhD, Pliant Therapeutics, Richard Ahn, PhD, Pliant Therapeutics, Gail Lee, Pliant Therapeutics, Penney Gilbert, PhD, University of Toronto, Jose Lopez, MD. PhD, Mount Sinai Medical Center, Fernando Rock, PhD, Pliant Therapeutics, Christopher Ward, PhD, University of Maryland, Scott Turner, PhD, Pliant Therapeutics

The α7β1 integrin complex is a surface receptor in striated muscle that links the intracellular actin cytoskeleton to the extracellular matrix (ECM) to stabilize sarcolemmal membrane. This critical role underlines the therapeutic potential of targeting the α7β1 integrin complex to overcome the absence of dystrophin, a sarcolemmal-cytoskeletal linker protein whose absence in Duchenne muscular dystrophy (DMD) destabilizes sarcolemma integrity. Here we show that activation of α7-integrin in dystrophic muscle cells with an agonist anti α7-integrin antibody (PLN-101325) resulted in enhanced sarcolemma membrane integrity and improved resistance to stress-induced muscle damage. Treatment of cultured DMD and mdx myotubes in vitro revealed a dose-specific effect of PLN-101325 on normalizing the resting cytosolic calcium [Ca2+] and sodium [Na+] levels, the repolarization of the sarcolemma resting membrane potential, reducing reactive oxygen species (ROS) production, and improving both glucose uptake and the sarcolemmal membrane resistance to mechanically-induced damage. Similarly, PLN-101325 treatment reduced diastolic [Ca2+] and [Na+] levels in cardiomyocytes from aged mdx mice. Further studies in dystrophic D2.mdx mice in vivo show PLN-101325 is efficacious in reducing contraction induced muscle injury and enhancing diaphragm and respiratory function. Aligned with the in vivo protection we identified decreased fibrosis and inflammation in the muscle, as well as reduced stress-induced sarcolemma membrane damage. This is further supported by transcriptomic evidence showing that PLN-101325 treatment regulates signaling pathways related to membrane excitability, ECM remodeling and metabolism. These results demonstrate that PLN-101325 improves the DMD phenotype by strengthening the link between muscle cell cytoskeleton and the ECM to improve sarcolemma membrane integrity and restore intracellular ionic balance, leading to enhanced resistance to muscle injury. Altogether, these data demonstrate agonists to human α7-integrin represent an effective strategy to ameliorate the myopathic phenotype of DMD.