Histochemical and morphologic changes of porcine airway epithelial cells in response to infection with Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae causes pneumonia in pigs. The effect of infection by this organism on histochemical characteristics of airway mucin within epithelial cells was studied. Seven- to 10-week-old pigs were inoculated intratracheally with M hyopneumoniae or culture broth, and lung tissues were collected from inoculated and control pigs at 2, 4, and 6 weeks after inoculation. Tissue sections were stained with periodic acid-Schiff/Alcian blue, pH 2.5 or high iron diamine/Alcian blue. Histologic features of randomly selected bronchi, bronchioles, and submucosal glands were compared in sections stained with periodic acid-Schiff/Alcian blue. Bronchial goblet cell sulfomucin and sialomucin were quantitated by image analysis of sections stained with high iron diamine/Alcian blue. Bronchi and bronchioles of infected pigs contained proportionately fewer goblet cells with mucin at all stages of infection than age-matched control pigs. Goblet cells in bronchi of infected pigs contained significantly less total mucin and sialomucin, and significantly more sulfomucin than goblet cells of control pigs. Increased sulfated mucin in bronchial goblet cells may reflect altered glycoprotein production or secretion in response to infection with M hyopneumoniae.