Esen, O. | bioRxiv Science

bioRxiv2026

Microtubule architecture and detyrosination bidirectionally modulate sarcomere shortening in skeletal muscle fibers

Although microtubules (MT) are established regulators of striated muscle mechanics, how MT lattice organization and post-translational modifications (PTM) individually shape contractility in healthy skeletal muscle fibers remains incompletely understood. We used an ex vivo single muscle fiber culture under unloading, examining acetylation and detyrosination (deTyr). During long-term 2D culture, the MT lattice was disrupted by transverse MT depletion without changes in MT abundance. In individual fibers, MT structure, but not abundance, positively correlated with sarcomere shortening non-linearly. When fibers were cultured in 3D hydrogels, the MT lattice was similarly disrupted yet shortening was preserved, with increased longitudinal MTs and decreased deTyr-MTs. Pharmacologically, contractility increased with either a decrease (parthenolide) or an increase (Taxol) in deTyr-MTs, and Taxol further rescued the MT lattice. Our findings identify MT organization and detyrosination, rather than MT abundance, as key determinants of muscle fiber contractility, positioning deTyr-MT as a load-responsive, bidirectional marker relevant to disuse atrophy and aging.

physiology↗

bioRxiv2025

Embedding muscle fibers in hydrogel improves viability and preserves contractile function during prolonged ex vivo culture

Ex vivo culture of isolated muscle fibers can serve as an important model for in vitro research on mature skeletal muscle fibers. Nevertheless, this model has limitations for long-term studies due to structural loss and dedifferentiation following prolonged culture periods. This study aimed to investigate how ex vivo culture affects muscle fiber contraction and to improve the culture system to preserve muscle fiber morphology and sarcomere function. Additionally, we sought to determine which culture-induced changes can negatively affect muscle fiber contraction. We cultured isolated flexor digitorum brevis (FDB) muscle fibers in several conditions for up to 7 days, and investigated viability, morphology, the unloaded sarcomere shortening in intact fibers, along with force generation in permeabilized muscle fibers. In addition, we examined changes to the microtubule network. We found a time-dependent decrease in contractility and viability in muscle fibers cultured for 7 days on a laminin-coated culture dish (2D). Conversely, we found that culturing FDB muscle fibers in a low-serum, fibrin/Geltrex hydrogel (3D) reduces markers of muscle fiber dedifferentiation (i.e. sprouting), improves viability and retains contractility over time. We discovered that the loss of contractility of cultured muscle fibers was not the direct result of reduced sarcomere function but may be related to changes in the microtubule network. Collectively, our findings highlight the importance of providing muscle fibers with a 3D environment during ex vivo culture, particularly when testing pharmacological or genetic interventions to study viability or contractile function. SummaryIn this work, the authors demonstrate that a low-serum, 3D ex vivo culture model preserves muscle fiber viability and contractility while reducing dedifferentiation. This model system can be utilized to conduct prolonged ex vivo pharmacological or genetic interventions to study fundamental muscle fiber processes or disease mechanisms.

cell biology↗