Alessandra Puggioni

Increased shear stress with upregulation of VEGF-A and its receptors and MMP-2, MMP-9, and TIMP-1 in venous stenosis of hemodialysis grafts

Venous injury and subsequent venous stenosis formation are responsible for hemodialysis graft failure. Our hypothesis is that these pathological changes are in part related to changes in wall shear stress (WSS) that results in the activation of matrix regulatory proteins causing subsequent venous stenosis formation. In the present study, we examined the serial changes in WSS, blood flow, and luminal vessel area that occur subsequent to the placement of a hemodialysis graft in a porcine model of chronic renal insufficiency. We then determined the corresponding histological, morphometric, and kinetic changes of several matrix regulatory proteins including VEGF-A, its receptors, matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of matrix metalloproteinase (TIMP)-1, and TIMP-2. WSS was estimated by obtaining blood flow and luminal vessel area by performing phase-contrast MRI with magnetic resonance angiography in 21 animals at 1 day after graft placement and prior to death on day 3 (n = 7), day 7 (n = 7), and day 14 (n = 7). At all time points, the mean WSS at the vein-to-graft anastomosis was significantly higher than that at the control vein (P < 0.05). WSS had a bimodal distribution with peaks on days 1 and 7 followed by a significant reduction in WSS by day 14 (P < 0.05 compared with day 7) and a decrease in luminal vessel area compared with control vessels. By day 3, there was a significant increase in VEGF-A and pro-MMP-9 followed by, on day 7, increased pro-MMP-2, active MMP-2, and VEGF receptor (VEGFR)-2 (P < 0.05) and, by day 14, increased VEGFR-1 and TIMP-1 (P < 0.05) at the vein-to-graft anastomosis compared with control vessels. Over time, the neointima thickened and was composed primarily of alpha-smooth muscle actin-positive cells with increased cellular proliferation. Our data suggest that hemodialysis graft placement leads to early increases in WSS, VEGF-A, and pro-MMP-9 followed by subsequent increases in pro-MMP-2, active MMP-2, VEGFR-1, VEGFR-2, and TIMP-1, which may contribute to the development of venous stenosis.

How often is deep venous reflux eliminated after saphenous vein ablation

BACKGROUND AND PURPOSE Deep venous reflux resolution after great saphenous vein surgery has been reported, but the studies evaluated mainly patients with deep segmental reflux. We prospectively analyzed the effects of greater saphenous vein ablation on coexisting primary deep axial venous reflux compared with segmental venous reflux. Patients and methods Between February 1997 and June 2001, patients with primary deep venous reflux scheduled for greater saphenous vein surgery were included in the study. Limbs of patients with a history of deep venous thrombosis, thrombophlebitis, trauma, and orthopedic or venous surgery were excluded. After surgery, duplex scanning was repeated and patients were examined for persistent deep venous reflux. RESULTS Thirty-three patients (38 limbs) were followed up with duplex scanning. Follow-up ranged from 2 weeks to 38 months. Preoperative axial deep reflux was present in 17 extremities, and segmental reflux was present in 21. The total number of incompetent segments was 59. Overall reflux abolishment rate was similar in extremities with axial and segmental reflux (30% vs 36%; P >.05). When segments were analyzed individually, abolishment of superficial femoral vein reflux was observed more often in extremities with segmental reflux than those with axial reflux (odds ratio, 4). In the extremities where deep reflux was not abolished with greater saphenous vein ablation, degree of reflux did not change significantly (P >.1). Duplex scanning was performed more than once during follow-up in 9 patients. In 3 of these patients reflux resolved by the second follow-up evaluation, and in 2 reflux was decreased at the second and third follow-up evaluations. CONCLUSION In patients with concomitant deep and superficial venous reflux, saphenous vein ablation results in resolution of deep reflux in about a third of patients. Superficial femoral vein reflux is seldom corrected in limbs with axial reflux compared with those limbs with segmental reflux. To appreciate the effects of greater saphenous vein ablation, longer follow-up may be needed.

Increased Expression of Hypoxia-inducible Factor-1α in Venous Stenosis of Arteriovenous Polytetrafluoroethylene Grafts in a Chronic Renal Insufficiency Porcine Model

PURPOSE To create a more clinically relevant model of hemodialysis graft failure in pigs by creating chronic renal insufficiency before polytetrafluoroethylene (PTFE) hemodialysis graft placement and to determine the expression of hypoxia-inducible factor-1 alpha (HIF-1 alpha) at the vein-to-graft anastomosis (VGA). MATERIALS AND METHODS Chronic renal insufficiency was created in 14 castrated juvenile male pigs with complete embolization of the left renal artery and the partial embolization of the right renal artery by infusing 150-250-mum polyvinyl acrylide spherical particles. The efficacy of the embolization was assessed by determining the amount of polyvinyl acrylide particles used per kidney, the weight of the kidneys at sacrifice, and kidney function (blood urea nitrogen [BUN] and creatinine levels). Twenty-eight days after embolization, PTFE grafts were placed from the carotid artery to the ipsilateral jugular vein and removed 3, 7, and 14 days after graft placement. Western blot for HIF-1 alpha was performed in the VGA and control vessel. RESULTS The left kidney required two times the polyvinyl acrylide particles than did the right kidney (P < .05). The right kidney weighed nearly three times more than the left (P < .05). The BUN and creatinine levels at graft placement were significantly higher than those at baseline (P < .05). Four grafts were patent at day 3, four at day 7, and four at day 14. By day 7, the mean HIF-1 alpha at the VGA had increased significantly when compared with that of control vessels (P < .05). CONCLUSIONS A more clinically relevant porcine model of hemodialysis graft failure was created, and there was significantly increased expression of HIF-1 alpha by day 7 at the VGA.

Adventitial transplantation of blood outgrowth endothelial cells in porcine haemodialysis grafts alleviates hypoxia and decreases neointimal proliferation through a matrix metalloproteinase-9-mediated pathway—a pilot study

Purpose. We hypothesized that adventitial transplantation of blood outgrowth endothelial cells (BOEC) to the vein-to-graft anastomosis of polytetrafluoroethylene grafts will reduce neointimal hyperplasia by reducing hypoxia inducible factor-1α (HIF-1α), by increasing angiogenesis in a porcine model of chronic renal insufficiency with haemodialysis polytetrafluoroethylene grafts. Because matrix metalloproteinases (MMPs) have been shown to be involved with angiogenesis, the expression of MMPs and their inhibitors was determined. Methods. Chronic renal insufficiency was created by subtotal renal infarction and 28 days later, arteriovenous PTFE grafts were placed bilaterally from the carotid artery to the jugular vein. Autologous blood outgrowth endothelial cells labeled with Lac Z were transplanted to the adventitia of the vein-to-graft anastomosis using polyglycolic acid scaffolding and scaffolding only to other side (control). Animals were killed 14 days later and vessels were explanted from the vein-to-graft anastomosis of both sides and underwent immunohistochemical analysis, western blotting and zymography for HIF-1α, MMP-2, MMP-9, TIMP-1 and TIMP-2. BOEC were also made hypoxic and normoxic for 12, 24 and 48 h to determine protein expression for MMPs and TIMPs. Results. Under hypoxia, BOEC significantly increased the expression of pro MMP-2 by 12 h and TIMP-2 by 24 h when compared to normoxic cells (P < 0.05). Transplantation of BOEC resulted in a significant decrease in both HIF-1α and intima-to-media ratio with a significant increase in both pro and active MMP-9 when compared to control vessels (P < 0.05). MMP-9 activity was localized to the neointima of the transplanted vessels by immunohistochemistry. There was increased CD31 density with engraftment of BOEC cells into the neointima of both the transplanted vessels compared to controls (P = NS). Conclusion. Transplantation of BOEC resulted in a significant decrease in intimal hyperplasia and HIF-1α with a significant increase in both pro and active MMP-9 that was localized to the neointima of transplanted vessels. The increase in MMP-9 offers a possible mechanism for angiogenesis and the reduced intima-to-media ratio. Furthermore, we observed that BOEC had homed to the neointima of the contralateral vessels that had increased levels of HIF-1α, suggesting that hypoxia may be an important stimulus for BOEC migration.

Large Symptomatic Carotid Body Tumor Resection Aided by Preoperative Embolization and Mandibular Subluxation

Carotid body tumors (CBT) are rare and usually benign neoplasms (60%-90%), originating from the mesoderm and neural ectoderm. In view of the extensive and unrelenting growth of unresected CBT, encasing vital neurovascular structures, and the significant incidence of malignancy (> or = 10%), surgical excision is the standard treatment of choice. Despite progress in CBT imaging and surgical technique, cranial nerve deficit, stroke, and death continue to affect 10% to 40% of patients undergoing curative surgical resection, particularly in large tumors proximal to the skull base. In such cases, CBT shrinkage by preoperative embolization, improved surgical access utilizing mandibular subluxation, and electroencephalographic monitoring combined with meticulous surgical technique may enable curative tumor resection, without prohibitive morbidity. In light of associated disability, preoperative acknowledgment of the ever-present substantial risk of cranial nerve injury cannot be overemphasized. We report on a patient with a large symptomatic CBT treated surgically with the aid of mandibular subluxation and preoperative embolization.

Proteomic Profiling in Early Venous Stenosis Formation in a Porcine Model of Hemodialysis Graft

PURPOSE To use proteomic analysis to identify up- and downregulated proteins in early venous stenosis formation in a porcine model of hemodialysis graft failure. MATERIALS AND METHODS Pigs had chronic renal insufficiency created by subtotal renal infarction caused by renal artery embolization. Arteriovenous polytetrafluoroethylene grafts were placed 28 days later and the animals were killed after a further 3 days (n = 4), 7 days (n = 4), or 14 days (n = 4). Proteomic analysis with isotope-coded affinity tags and multidimensional liquid chromatography followed by tandem mass spectrometry was performed on the venous stenosis and control vessels. Expression of proteins was further confirmed by Western blot analysis. The blood urea nitrogen (BUN) and creatinine levels were determined before renal artery embolization and at the time of graft placement. RESULTS At graft placement, mean BUN and creatinine levels were significantly higher than before embolization (P < .05). Six proteins were identified that were common to all four animals at the same time point. Five proteins (alpha-fetoprotein, fetuin A, macrophage migration inhibitory factor, pyruvate dehydrogenase E1 component, and lactoferrin) were upregulated and one protein (decorin) was downregulated. Expression of macrophage migration inhibitory factor, alpha-fetoprotein, and lactoferrin was further validated with Western blotting. By day 14, lactoferrin and fetuin-A expression were increased significantly in early venous stenosis formation. CONCLUSIONS Significantly increased expression of lactoferrin and fetuin-A were observed in early venous stenosis by day 14. Understanding the role of lactoferrin and fetuin-A in hemodialysis vascular access failure could help in improving outcomes in patients undergoing hemodialysis.

Subfascial Endoscopic Perforator Vein Surgery (SEPS) for Chronic Venous Insufficiency

Publisher Summary Initial exuberance with subfascial endoscopic perforator vein surgery (SEPS) focuses much needed attention on chronic venous disease, and the underlying venous anatomy and pathophysiology. Limitations of perforator ablations alone in treating patients with ulcers have also been recognized. Without doubt, SEPS should be combined with ablation of the incompetent superficial system, performed either as staged or as combined procedures. Results have been excellent on both ulcer healing and recurrence in primary valvular incompetence without associated femoropopliteal reflux, but long-term ulcer healing could not be achieved in half of the operated patients with postthrombotic syndrome. Incompetent perforators are one of the contributing factors to ambulatory venous hypertension, and in patients with postthrombotic syndrome and deep vein occlusion, they likely are important outflow channels that should be preserved to assure the collateral venous circulation. Introduction of less invasive techniques for perforator ablation, such as ultrasound-guided sclerotherapy or radiofrequency ablation, may diminish the role of SEPS in the future, but results should be compared and analyzed before the use of a safe and effective endoscopic technique for ablation of the perforating veins is diminished.

Ultrasound-Guided Sclerotherapy (USGS) of Perforating Veins in Chronic Venous Insufficiency

Publisher Summary This chapter presents the review of a nonsurgical treatment option for incompetent perforating veins, ultrasound-guided sclerotherapy, which combines the precision of surgical approach with minimal invasiveness of an injection. Recent development of new treatment options for reflux in the superficial venous system have established a new standard where patients can be treated in the office without a need for general anesthesia, can ambulate immediately after treatment, have insignificant postoperative pain, and have almost no negative impact on quality of life immediately after treatment. When venous stripping was the only choice for patients with saphenous insufficiency, surgical interruption of perforating veins, either by subfascial endoscopic surgery (SEPS) or through small incisions, was considered minimally invasive. In a new clinical environment, invasiveness and wound complication risk of these surgical techniques exceeds that of the treatment of saphenous veins. Achieving this goal theoretically should convert the patient into being asymptomatic, eliminate or reverse existing signs, and prevent progression to more advanced stages of venous disease. Practical challenges that face the surgeon who will treat a patient with chronic venous disease include selection of which vein to treat and which technique to employ.