RICERCA DI NUOVI TARGET TERAPEUTICI PER LA TERAPIA DEL DOLORE CRONICO

Chronic low back pain (CLBP) is a painful condition arising from spinal structures and due to traumatic, degenerative, or inflammatory diseases, whose etiopathogenetic mechanisms are not completely known. Although several ion channels are implicated in nociception, among them transient receptor potential (TRP) channels, a superfamily of trans-membrane Ca2+-permeable channels, are one of the most studied group. Indeed, TRP channels act as sensor of various exogenous and endogenous stimuli, regulating pain sensation. In the first phase of this research, morphological, ultrastructural, histochemical, immunohistochemical and gene expression analyses were performed on sample tissues collected during the necessary surgery in patients affected by CLBP. An increase in TRP channel mRNAs and proteins was observed in pathological tissues compared with tissues retrieved from the non-symptomatic areas, in almost all patients. The most expressed channels were TRPV4 and TRPM8, associated with a greater infiltration of nervous fibers in pathological tissues. In a second phase using tissue samples collected from coxofemoral joint during hip replacement surgery of a patient affected by hip osteoarthritis, we assessed whether the same morphological changes and the same TRPV4 and TRPM8 expression pattern were maintained. By performing morphological and immunohistochemical analyses, the presence of numerous nerve fibres in the pathological tissues and a higher expression of TRPV4 and TRPM8 in samples from the capsule compared to the labrum were highlighted. Finally, using Xenopus laevis oocytes as a heterologous expression system, electrophysiological analyses were performed to better characterized the TRPV4 and TRPM8 functionalities. The response to different substances of X. laevis oocytes was first evaluated after TRPV4 and/or TRPM8 cRNA microinjection and then after the injection of membranes obtained from pathological coxofemoral tissues, in order to observe any possible difference. Immunofluorescence analyses were also performed to confirm the presence of these channels on oocyte membranes. The currents recorded in membranesinjected oocytes were different from those injected with cRNAs, suggesting a functional alteration of the channels considered. Our data, although preliminary, offer a model for studying TRP channels and their possible interactions by replicating a situation similar to that occurring in vivo. This model study would allow to identify and characterize specific modulators of TRP channels for the treatment of chronic pain