Dottorato in MEDICINA MOLECOLARE

Titolo della tesi: Comparison of Immunohistochemical and Histopathological Findings Between Patients with Diabetic and Idiopathic Carpal Tunnel Syndrome

Introduction: Carpal tunnel syndrome (CTS) is the most common and widely studied nerve entrapment syndrome. It is caused by compression of the median nerve at the wrist as it passes through a space-limited osteofibrous canal. The exact cause of CTS is unknown, and a multifactorial origin is presumed; in such cases, CTS is defined as idiopathic. It affects 4-5% of the population especially between the ages of 45-60 years. There is strong evidence that patients with diabetes mellitus type 1 and 2 are at greater risk of developing CTS when compared to the general population. Although the exact cause of compression is unknown, oedema, neo-angiogenesis and increase in non-inflammatory fibrosis in the sub-synovial connective tissue (SSCT) remains the hallmark in the development and progression of CTS. Different studies showed an important role of vascular endothelial growth factor (VEGF) A as a promoter of vascular permeability and angiogenesis in the epineurium and SSCT especially in diabetic patients. The aim of our study was to compare the histopathological differences and correlate them to the expression of VEGF and its receptors 1 and 2 in the carpal tunnel environment between patients with idiopathic and diabetic related CTS. Materials & Methods: A total of 45 CTS patients matched the study inclusion criteria and were divided in to 3 groups: 1. CTS-I– 15 patients, 2. CTS-DM1– 15 patients 3. CTS-DM2– 15 patients. During surgery biopsy specimens were taken from Transverse ligament, Tenosynovium and Epineurium. For the histological examination, prepared sections were stained with hematoxylin–eosin and blind examination was performed for fibrosis, oedema, vascular proliferation, and vascular wall thickness, data was documented and scored in all specimens. For the Immunohistochemistry evaluation, sections were incubated with primary antibodies for 30 min at room temperature, rabbit polyclonal Abs to VEGF-A (1:100) (Biocare Medical), VEGFR-1 (1:25) (Diagnostic Biosystem) and VEGFR-2 (1:50) (Diagnostic Biosystem). Blind examination was performed for Cell type and percentage of expression in each tissue section were recorded. Results: Histopathological findings of the transverse ligament showed that vascular proliferation and vascular thickness were more expressed in the CTS-DM1 group when compared to the CTS-I group (p<0.01) and the CTS-DM2 group (p<0.05), while tenosynovium specimens revealed significantly higher oedema, vascular proliferation and vascular thickness in both CTS-DM1 and CTS-DM2 groups compared to the CTS-DM1 group (p<0.001). Epineurium samples evidenced no significant statistical differences in terms of oedema between the 3 groups, while significantly higher vascular proliferation and vascular thickness were seen in both CTS-DM1 and CTS-DM2 groups when compared to the CTS-I group (p<0.001). Immunohistochemical findings showed a significantly higher expression of VEGF and its receptors 1 and 2 on fibroblast and endothelial cells of both CTS-DM1 and CTS-DM2 groups when compared to the CTS-I group in all tissues (TL, Tenosynovium and Epineurium). Signific high expression was seen also in synovial cells at tenosynovium specimens of both CTS-DM1 and CTS-DM2 groups when compared to the CTS-I group. Conclusion: Our study evidenced an increased expression of VEGF and its receptors 1 and 2 in endothelial cells, fibroblast and synovial cells of the transverse ligament, tenosynovium e epineurium inside the carpal tunnel in patients with DM type 1 and 2 related CTS when compared with idiopathic CTS patients. We also noticed an increased oedema, vascular proliferation and vascular wall thickness and Tenosynovial fibrosis in these population of patients when comparing them with idiopathic CTS patients. Those Histological findings are known to be promoted by VEGF. These results may provide a potential pathophysiological basis for CTS in this group of patients and might even provide a therapeutic rationale for anti-VEGF therapy as an adjunct or alternative to the surgical treatment of CTS in these population of patients.