CELLULAR HYPERTROPHY AND HYPERPLASIA OF AIRWAY SMOOTH MUSCLES UNDERLYING BRONCHIAL-ASTHMA - A 3-D MORPHOMETRIC STUDY

In order to study whether hyperplasia or hypertrophy of cells is respo nsible for the thickening of airway muscles, 3-D morphometry of airway muscle cells was performed on resin-embedded semithin serial sections of autopsied lungs from 10 asthmatics and five control subjects. Ther e were five Type I and five Type II asthmatic lungs, as defined in an earlier study, thickened muscles being found only in the central bronc hi in Type I and distributed over the whole airway tree in Type II. Th e analysis was based on ''unbiased'' 3-D morphometry to obtain the num erical density N(V) of muscle cells using a ''disector,'' a spatial pr obe introduced by Sterio in 1984, which we modified into a stack of se rial sections. The mean number N(L) of cells per unit airway length an d the mean volume V(C) of a single muscle cell were also determined. I n Type I asthmatics, the number of cells increased in the larger bronc hi unaccompanied by cellular hypertrophy at any level of the airway tr ee. In contrast, in Type II asthmatics, hypertrophy was shown to preva il over the whole airway, but it was most remarkable in the bronchiole s, whereas hyperplasia was mild and localized only in the bronchi. The two types of asthmatic lungs may therefore result from different path ogeneses.