Introduction and Objective: Loss of muscle function is detrimental to the human body and understanding its molecular underpinnings and identifying therapeutic avenues to modify these is of major importance. To enable this, we aimed to develop a translatable drug discovery model that circumvents limitations by species-driven biological differences and demonstrates high sensitivity to readouts related to muscle function.
Methods: A human primary myoblast-based engineered muscle tissue model was established, differentiated, and cultured for weeks. We characterized tissue maturity through contractility and gene and protein expression longitudinally and under various electrical stimulation regimens. Key physiological features such as force-frequency relationship, post-tetanic potentiation, and fatigue during exercise was assessed. Finally, functionality of the tissues following two different atrophy-inducing interventions was studied.
Results: Differentiated tissues maintained stable maximal force production for over 30 days. Maturity markers (muscle AMPK isoforms and mitochondrial, contractile and Ca2+ handling proteins) increased during a 23-day evaluation. Electrical stimulation also increased maturity, including improved maximal contractile force. The tissues exhibited expected physiological responses (force-frequency relationship, post tetanic potentiation and fatigue following exercise mimicking electrical stimulation). Activation of glucocorticoid (by dexamethasone) and activin (by Activin A) signaling pathways dose dependently caused a decline in maximal force development which was mitigated by antagonism. Intriguingly, the model demonstrated sensitivity to detect significant force changes with effect sizes below 15%.
Conclusion: Our human-based engineered muscle tissue model offers a robust platform with high sensitivity for elucidating mechanisms related to muscle function decline and therapeutic exploration.
M. Højfeldt: Employee; Novo Nordisk A/S. J. Birk: None. C. Segeritz-Walko: None. J.F.P. Wojtaszewski: Consultant; Pfizer Inc. Stock/Shareholder; Pfizer Inc., Novo Nordisk A/S. C. Pehmøller: Employee; Novo Nordisk A/S. J.R. Knudsen: Employee; Novo Nordisk A/S.
