Objectives. In the vastus lateralis (VL) samples of control subjects and bronchiectasis (BQ) patients, we sought to study muscle phenotypic features including muscle regeneration muscle morphometry

Methods. Ten healthy subjects and twenty stable BQ patients were recruited. Nutritional and functional parameters were evaluated. In the VL of the participants, muscle fiber type, morphometry, and structural abnormalities were assessed; apoptotic-nuclei were quantified using the TUNEL assay and counting techniques (conventional immunohistochemistry) and total numbers of satellite cells were measured through identification of markers Pax7 and Myf5 (conventional immunofluorescence with specific antibodies and fluorochromes).

Results:Patients with BQ presented a reduction in nutritional and functional muscle parameters. The proportion of hybrid fibers was higher, and type II and hybrid fibers had smaller cross-sectional areas (CSA). Inner nuclei and TUNEL-positive nuclei proportions were increased in BQs. Quiescent cell (Pax7+/Myf5-) and total satellite cell counts were reduced.

Conclusions. In the lower limb muscles of BQ patients, there are significant alterations in the muscle phenotype and metabolic features being the most relevant the presence of greater proportions of hybrid fibers and smaller cross-sectional areas of type II and hybrid fibers. Moreover, BQ patients presented muscle structural abnormalities mainly by a rise in the proportions of internal nuclei and apoptotic nuclei (TUNEL). Finally, patients presented an increase of activated satellite cells, which suggest the trigger of muscle regeneration. These findings will help elucidate the impact of BQ in the muscle physiology and function.