Evidence of Innervation in Talc-Induced Pleural Adhesions

Evidence of Innervation in Talc-Induced Pleural AdhesionsPleurodesis is a well-established therapeutic method for the treatment of recurrent spontaneous pneumothoraces and relapsing symptomatic pleural effusions of different etiologies.,2 The goal of pleurodesis is to achieve the symphysis of visceral and parietal pleura in order to impede the accumulation of air or fluid in the pleural cavity. To date, many agents have been proposed as useful for pleurodesis, although many of them have only been tested in the experimental setting. For practical purposes, the two agents more commonly used for pleurodesis are talc and tetracycline. Since tetracycline is no longer available in most hospitals, talc has become the most frequently used sclerosing agent worldwide.
The strong point of talc as a good choice for pleu-rodesis is its efficacy. Data from several studies report a high success rate of approximately 90% regardless of the dose administered. Nevertheless, there is no unanimity on the definition of pleurodesis success, but for most authors,, it is the radiologic finding that no fluid has reaccumulated in the pleural space. Although this is reasonable on a clinical basis, the mechanisms responsible for producing pleurodesis remain poorly understood.
Pioneering studies’ demonstrated that 1 month after talc poudrage, dogs and cats showed obliteration of their pleural cavities. Bethune assayed talc poudrage in human patients and showed that complete pleural symphysis had been achieved 1 to 2 months after the procedure. A proposed theory from experimental studies explaining the mechanisms responsible for talc pleurodesis is as follows: talc particles activate the mesothelium, pleural macrophages and endothelium of the visceral and parietal pleura and a fibrinous exudate bridges both pleural surfaces. This exudate evolves to form a fibrin network by a process modulated by various coagulation and fibrinolytic factors; posteriorly, stabilization of the fibrin network and increased levels of basic fibroblast growth factor result in fibroblast recruitment and collagen deposition in the newly formed adhesion.
According to this theory, adhesions would be critical as the first step in keeping both pleural layers in contact and thus permitting pleural symphysis. In fact, in most experimental studies, pleurodesis success is graded as a score according to the number and appearance of adhesions observed macroscopi-cally. However, despite their clinical importance, little is known on the cellular and histologic processes underlying pleural adhesion formation. To this end, the present study was designed to ascertain, in a rabbit model, the morphologic and ultrastruc-tural characteristics of talc-induced pleural adhesions.

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