Loss of α-smooth muscle actin immunostaining is not a useful marker for functional impairment: a comparison from patients with and without small bowel motility disorder.

Objective: Prior studies have reported the loss of α-smooth muscle actin (α-SMA) immunoreactivity in the inner circular layer of the muscularis propria in small bowel motility disorder cases, but this remains controversial with conflicting data. In this study, we aimed to characterize α-SMA immunoreactivity in the muscularis propria of the small intestine-specifically, jejunum-in patients with and without small bowel motility disorder.

Methods: A total of 28 transmural proximal jejunum biopsy specimens from adult patients with clinical impression of upper gastrointestinal dysmotility disorder and 64 control tissues were evaluated. The controls were full-thickness, longitudinal tissue sections from segmental resections performed due to gunshot wounds, multivisceral transplant donation, and tumors. Immunostaining for α-SMA was performed with appropriate controls to confirm the presence of immunoreactivity in the circular and longitudinal muscle layers of the muscularis propria in each sample and recorded as retained or diminished.

Results: In the small bowel motility disorder and control cases, 42.9% (12/28) and 70.3% (49/64) of the cases showed no or minimal α-SMA immunoreactivity in the inner circular layer with peripheral accentuation, respectively.

Conclusions: Loss or diminished α-SMA immunoreactivity in the inner circular layer of the muscularis propria occurs with a similar frequency in cases with and without small bowel motility disorder and does not correlate with impairment of function.