Introduction/aims: Traditional methods of sampling skeletal muscle tissue are invasive. This study aimed to evaluate a sub-millimeter core-biopsy (microbiopsy) as a potentially more tolerable method, with further regard to tissue yield and analyzability of RNA expression.
Methods: Children (9-13 years, n = 11) and adults (18-50 years, n = 16) were recruited. Microbiopsy and venipuncture were performed, with prior application of local anesthesia cream. Additionally, adults underwent a Bergström muscle biopsy, with infiltrative local anesthesia. Pain was rated using the visual analog scale (VAS), reported as medians (95% CI). Microbiopsy samples were freeze-dried and weighed. To evaluate RNA sequencing performance at low tissue sample weights, a six-step incremental tissue ladder (10-500 μg) was analyzed.
Results: Children rated venipunctures and microbiopsies low, at VAS = 0.1 (0.0-0.6) and 1.6 (0.9-3.9), respectively. Microbiopsy pain ratings were slightly higher than venipuncture, p < 0.001. Pain ratings in adults were 0.0 (0.0-0.5), 1.8 (1.3-2.4), 2.9 (2.4-3.8), and 2.7 (2.2-3.8) for venipuncture, microbiopsy, Bergström biopsy, and infiltrative local anesthesia, respectively. Microbiopsy was rated less painful than Bergström biopsy and local anesthesia (p < 0.05). Children did not rate microbiopsy more painful than adults (p = 0.82). Microbiopsies yielded on average 303 (SD 121.8) μg. RNA sequencing detected similar transcriptomic signatures across the tissue ladder.
Discussion: The generally low pain ratings for the microbiopsy procedure support its use as a tolerable method of acquiring skeletal muscle samples in both children and adults. It represents a less painful alternative to Bergström biopsies while still rendering adequate material for RNA sequencing.
Keywords: RNA sequencing; microbiopsies; muscle biopsies; pain; visual analog scale.
© 2026 The Author(s). Muscle & Nerve published by Wiley Periodicals LLC.