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A team of researchers from the National Institutes for Quantum Science and Technology (QST) and Tokyo Metropolitan University has developed a biomaterial that could change how we treat muscle degeneration and metabolic disorders.

By mimicking the softness and microstructure of slow-twitch muscle tissue, the team successfully cultivated muscle cells in the lab that exhibit the genetic and metabolic traits of slow-twitch fibers—cells crucial for posture, endurance, and glucose regulation.

The paper is in the journal Scientific Reports.

Slow-twitch muscles are vital for maintaining mobility and metabolic health, especially in aging populations and patients with chronic conditions. However, replicating their unique properties in vitro has long been a challenge. Traditional culture methods fail to reproduce the soft, fibrous environment of native muscle, limiting the ability to study or regenerate these cells effectively.

Led by Dr. Mitsumasa Taguchi, the QST team used a radiation-induced crosslinking technique to create a gelatin-based gel with tunable elasticity and microgrooves. When muscle precursor cells (C2C12 myotubes) were cultured on the softest version of this gel (10 kPa), they expressed genes typical of slow-twitch fibers—such as MYH7 and MYH2—and metabolic markers like GLUT4 and myoglobin. These cells also showed increased levels of PGC-1α, a key regulator of slow-twitch muscle formation.

"Our gel provides a microenvironment that closely resembles the physical conditions inside the body," said Dr. Taguchi. "This allows muscle cells to develop in a way that mirrors natural slow-twitch muscle formation, which has never been achieved with conventional materials."

The study also found that adding microgrooves to the gel surface enhanced cell alignment and differentiation, although it did not independently trigger the slow-twitch gene expression. This suggests that elasticity is the primary driver of fiber-type shifts, while topography supports structural organization.

The implications of this research are far-reaching. Artificial slow-twitch muscle tissues could be used in regenerative medicine, drug screening, and even muscle transplantation therapies. Because the gel is biocompatible and biodegradable, it may one day serve as a scaffold for repairing damaged muscle in patients suffering age-related muscle loss.

"In the long term, this technology could help extend healthy life expectancy and improve quality of life," said Dr. Taguchi. "It opens new doors for personalized medicine and advanced biomedical engineering."