Key result
AQP4 expression was highly variable, present in 64-99% of MHC-fast positive fibers and 5-72% of MHC-slow positive fibers, and could not be predicted by MHC type alone.
Cross-Sectional (n=6)
Variable AQP4 expression challenges MHC-based fiber assumptions; leaves open its functional and disease relevance in human muscle.
INTRODUCTION: Aquaporins (AQPs) are a family of transmembrane proteins involved in the maintenance of osmotic gradients. AQP4 is abundant in skeletal muscle, where it seems to be associated with glycolytic metabolism. We investigated the pattern of expression of AQP4 in normal human myofibers relative to the main forms of myosin heavy chain (MHC). METHODS: Six normal human muscle biopsies were analyzed by double immunofluorescence for co-expression of AQP4 and slow or fast MHC. RESULTS: A high percentage (64-99%) of MHC-fast positive fibers showed immunoreaction for AQP4. Immunoreactivity for AQP4 was also present in MHC-slow positive fibers, but with a higher variability (5-72%) among biopsies. DISCUSSION: The expression pattern of AQP4 in human myofibers is highly variable among different patients and cannot be predicted for single fibers depending on MHC type expression. Other factors, possibly related to muscle activity, may modulate AQP4 expression. Muscle Nerve 57: 856-859, 2018.
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Vizzaccaro et al. (2017) conducted a cross-sectional in Normal human skeletal muscle (n=6). Myosin heavy chain (MHC) type was evaluated on Co-expression of AQP4 and slow or fast MHC. AQP4 expression was highly variable, present in 64-99% of MHC-fast positive fibers and 5-72% of MHC-slow positive fibers, and could not be predicted by MHC type alone.
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