Analysis of cellular location and concentration in vocal fold lamina propria.

Studies have shown that the lamina propria plays an important role in voice production. Recent studies have analyzed the presence of different proteins and quantified their extent in the lamina propria, but no similar study has yet been done on cellular makeup. The distribution of three different cell types in the lamina propria of 22 human vocal folds was studied. These types are fibroblasts, macrophages, and myofibroblasts. The roles of these cells in the extracellular matrix are described. Their distribution was quantified with use of an image-analysis system. We arbitrarily divided the lamina propria into five sections (each representing 20% of the lamina propria) and compared cell numbers among these sections. Gender comparisons were also made. From these studies it is evident that the cellular distribution in the lamina propria is not uniform. Fibroblasts were more abundant in the deepest 20% of the lamina propria (p < 0.008), myofibroblasts were more abundant in the most superficial 20% (p < 0.016), and in the 36% of our samples that contained macrophages in the lamina propria, there was a significantly higher number of macrophages in the first 20% of the lamina propria (p < 0.003). The only significant gender difference was that women had twice as many macrophages in the most superficial 20% of the lamina propria as men (p < 0.05). The higher myofibroblast activity in the first 20% could indicate that the superficial layer is a region of constant repair. The increased number of macrophages in the superficial layer likely indicates an inflammatory response to inhalants (because of the role of macrophages in the inflammatory response and the fact that only 36% of the patients showed any macrophage activity at all).