RETINOBLASTOMA PROTEIN - A MOLECULAR REGULATOR OF CHRONIC VENOUS INSUFFICIENCY

Purpose. Chronic venous insufficiency (CVI) and varicose vein (VV) for mation is characterized histologically by the transformation of smooth muscle cells (SMC) from a contractile to a secretory phenotype and by intense collagen deposition. The subcellular regulation point for the se processes may be the retinoblastoma protein (pRb), a known inhibito r of cellular proliferation and regulator of differentiation. We hypot hesize that pRb phosphorylation is associated with VV formation and fu nctions as a possible subcellular regulator. Methods. Patients were se parated into two groups, Group 1 (n = 6) consisted of vein specimens o btained from patients undergoing coronary artery bypass, grafting. Gro up 2 (n = 6) consisted of patients with symptomatic CVI and duplex con firmed refluxing greater saphenous veins (GSVs) who required GSV strip ping.. Western blots of GSV protein extracts were performed with anti- human pRb monoclonal antibodies and the degree of nonphosphorylated an d phosphorylated pRb was determined. Results were quantified using ima ge analysis of band intensities (computer calibrated intensity units). The ultrastructural appearance of SMCs and the vein wall architecture were qualitatively analyzed with electron microscopy in both,groups. Results. Phosphorylated pRb from varicose GSVs exhibited intensities o f 523 +/- 188 units, while phosphorylated pRb from normal GSVs demonst rated intensities of 153 +/- 41 units (P < 0.05). SMCs in varicosed GS Vs were surrounded by disorganized collagen deposits and displayed a s ecretory phenotype with spherical vacuolated cells. SMCs from normal G SVs appeared spindle shaped with a purported contractile phenotype and a well-structured extracellular matrix. Conclusion. Our data demonstr ate that VV formation, in patients with CVI, is associated with phosph orylated pRb and the transformation of SMCs from a contractile to a se cretory ultrastructural morphology. The data suggest that SMC dediffer entiation is regulated by pRb and that disinhibition of this protein ( phosphorylation) may be an significant factor in the development of lo wer extremity varicosities. (C) 1998 Academic Press.