Evidence of Innervation in Talc-Induced Pleural Adhesions: Discussion

Evidence of Innervation in Talc-Induced Pleural Adhesions: DiscussionClassically, pleural adhesions are considered to be collagenous formations binding between visceral and parietal pleura. They are thought to develop in the pleural cavity secondary to several inflammatory stimuli, including infection, malignancy, and trauma. Although they are commonly considered to play a critical role in the establishment of pleural symphysis, little is known about their histopatho-genesis. The present study provides a detailed morphologic and ultrastructural description of talc-induced pleural adhesions in rabbits. More
Although we have previously shown that pleurode-sis with a high talc dose is associated with an increased risk of pulmonary talc deposition in rab-bits, the dose used here was selected because 200 mg/kg is the minimum dose that induces an effective pleurodesis in this animal model. As early as 1 week after talc slurry instillation, adhesions were completely formed, showing bundles of collagen fibers, newly formed blood and lymphatic vessels, and complete epithelialization. Strikingly, the finding of nerve fibers in adhesions of 20% of the rabbits is reported for the first time.
A main result of the present study was the observation that nerve fibers, identified histologically and ultrastructurally, grow into rabbit pleural adhesions formed after the intrapleural administration of talc. Although nerve fibers have been found in murine and human peritoneal adhesions, to our knowledge this study is the first to report nerve growth into pleural adhesions. Our results further demonstrate that the anatomic location of the adhesion within the pleural cavity did not influence the presence of nerve fibers, given that nerves were observed in adhesions joining visceral pleura to both costal, mediastinal, and diaphragmatic parietal pleura.
After talc pleurodesis, we found the percentage of rabbits with nerve-containing pleural adhesions to be 20%. No data are available for our results to be compared with other experimental studies; however, in clinical series, between 38% and 100% of patients had peritoneal adhesions containing nerve fibers. The difference between the percentage of innervation found in the present study and those reported in clinical studies can be attributed to various factors, including biological and physiologic variations between rabbits and humans as well as anatomic differences between pleural and peritoneal cavities.

This entry was posted in Pulmonary Function and tagged adhesion, innervation, lymphangiogenesis, neovascularization, pleurodesis, talc, ultrastructure.