Differentiation of interstitial cells and stromal proteins in the secondary septum of early postnatal rat: effect of maternal chronic exposure to whole cigarette smoke

The intention of this investigation was to ascertain the effect of maternal exposure to cigarette smoke on the early postnatal morphogenesis of pulmonary interstitium in offspring. Female rats were chronically exposed to whole cigarette smoke. Offspring of these and control animals were sacrificed at postnatal day 15, and their tissues were prepared for quantitative and qualitative analyses. Results indicate a diminished quantitative representation of parenchymal tissue (P less than 0.01) and a slower pace of secondary septal growth (P less than 0.07) in the experimental lung. Furthermore, a greater cellular volume density (P less than 0.0002) and, inversely, a lesser quantitative representation of extracellular matrix (P less than 0.0002) was ascertained for the experimental septal interstitium. There was proportionately less of elastin substances (P less than 0.009), collagen together with basal laminae (P less than 0.0008), and nonfibrillar, amorphous matrix (P less than 0.02) in the experimental extracellular stroma. Fibrillar collagen and nonfibrillar matrix were represented quantitatively 6.3 times more in the experimental extracellular interstitium than elastin, whereas that ratio for the control tissue was only 4.2. Most experimental interstitial cells (80%) contained numerous lipid globules, which, in contrast, were only occasionally present in control cells (7.3%). Experimental cells, consequently, possessed a larger cross-sectional diameter and a smaller nucleus-to-cytoplasm volume ratio than control cells. These divergent developmental patterns are possibly suggestive of a delayed differentiation of interstitial cells and a modified production to degradation balance of stromal proteins in offspring of animals chronically exposed to whole cigarette smoke.