Immunohistochemical characterization of the human posterior tracheal wall reveals a possible muscularis mucosae: a...

The microscopic structure of the human posterior tracheal wall remains incompletely described despite its role in airway function. This pilot study aimed to characterize the posterior tracheal wall using α-smooth muscle actin (α-SMA) immunohistochemistry (IHC) and digital image analysis.

Posterior membranous tracheal specimens from patients undergoing total laryngectomy were analysed. Routine Haematoxylin and Eosin (H&E) staining was performed on (N = 12) specimens, while α-SMA IHC was performed on (N = 11). Morphometric measurements of the mucosubmucosal complex (MC), trachealis muscle (TM), adventitial (Adv) layer, and muscularis mucosae (MMu) were obtained using ImageJ. Demographic associations were explored using statistical tests.

α-SMA IHC provided clearer visualization of smooth muscle than routine H&E staining. A superficial smooth muscle layer within the mucosa, consistent with a possible muscularis mucosae (MMu), was observed in all 11 IHC specimens, while nerve fibres were morphologically identified in 58.33% of the 12 H&E specimens. A three layer muscle arrangement was identified in 36.36% of cases. The mean total posterior tracheal wall thickness was 4.55 ± 1.45 mm. The TM and MMu had similar fibre sizes (p = 0.86), although the TM showed significantly greater muscle density and α-SMA staining intensity than the MMu (both p < 0.01). Age was negatively correlated with TM staining intensity (r = - 0.62, p = 0.04).

This pilot study explores histological data from the human posterior tracheal wall and expands the current description of its microscopic structure, which may support future anatomical, biomechanical, and tissue engineering research.