Time-dependent ultrastructural changes during venous thrombogenesis and thrombus resolution.

BACKGROUND: Deep vein thrombosis is a common vascular event that can result in debilitating morbidity and even death due to pulmonary embolism. Clinically, patients with faster resolution of a venous thrombus have improved prognosis, but the detailed structural information regarding changes that occur in a resolving thrombus over time is lacking. OBJECTIVES: To define the spatial-morphologic characteristics of venous thrombus formation, propagation, and resolution at the submicron level over time. METHODS: Using a murine model of stasis-induced deep vein thrombosis along with scanning electron microscopy and immunohistology, we determine the specific structural, compositional, and morphologic characteristics of venous thrombi formed after 4 days and identify the changes that take place during resolution by day 7. Comparison is made with the structure and composition of venous thrombi formed in mice genetically deficient in plasminogen activator inhibitor type 1. RESULTS: As venous thrombus resolution progresses, fibrin exists in different structural forms, and there are dynamic cellular changes in the compositions of leukocytes, platelet aggregates, and red blood cells. Intrathrombus microvesicles are present that are not evident by histology, and red blood cells in the form of polyhedrocytes are an indicator of clot contraction. Structural evidence of fibrinolysis is observed early during thrombogenesis and is accelerated by plasminogen activator inhibitor type 1 deficiency. CONCLUSION: The results reveal unique, detailed ultrastructural and compositional insights along with documentation of the dynamic changes that occur during accelerated resolution that are not evident by standard pathologic procedures and can be applied to inform diagnosis and effectiveness of thrombolytic treatments to improve patient outcomes.

Risk factors and treatment interventions associated with incomplete thrombus resolution and pulmonary hypertension after pulmonary embolism.

BACKGROUND: Residual pulmonary vascular occlusion (RPVO) affects one half of patients after a pulmonary embolism (PE). The relationship between the risk factors and therapeutic interventions for the development of RPVO and chronic thromboembolic pulmonary hypertension is unknown. METHODS: This retrospective review included PE patients within a 26-month period who had baseline and follow-up imaging studies (ie, computed tomography [CT], ventilation/perfusion scans, transthoracic echocardiography) available. We collected the incidence of RPVO, percentage of pulmonary artery occlusion (%PAO), baseline CT %PAO, most recent CT %PAO, and difference between the baseline and most recent %PAO on CT (Δ%PAO). RESULTS: A total of 354 patients had imaging reports available; 197 with CT and 315 with transthoracic echocardiography. The median follow-up time was 144 days (interquartile range [IQR], 102-186 days). RPVO was present in 38.9% of the 354 patients. The median Δ%PAO was -10.0% (IQR, -32% to -1.2%). Fewer patients with a provoked PE developed RPVO (P ≤ .01), and the initial troponin level was lower in patients who developed RPVO (P = .03). The initial thrombus was larger in the patients who received advanced intervention vs anticoagulation (baseline CT %PAO: median, 61.2%; [IQR, 27.5%-75.0%] vs median, 12.5% [IQR, 2.5%-40.0%]; P ≤ .0001). Catheter-directed thrombolysis (CDT; median Δ%PAO, -47.5%; IQR, -63.7% to -8.7%) and surgical pulmonary embolectomy (SPE; median Δ%PAO, -42.5; IQR, -68.1% to -18.7%) had the largest thrombus reduction compared with anticoagulation (P = .01). Of the 354 patients, 76 developed pulmonary hypertension; however, only 14 received pulmonary hypertension medications and 12 underwent pulmonary thromboendarterectomy. Cancer (odds ratio [OR], 1.7) and planned prolonged anticoagulation (>1 year; OR, 2.20) increased the risk of RPVO. In contrast, the risk was lower for men (OR, 0.61), patients with recent surgery (OR, 0.33), and patients treated with SPE (OR, 0.42). A larger Δ%PAO was found in men (coefficient, -8.94), patients with a lower body mass index (coefficient, -0.66), patients treated with CDT (coefficient, -18.12), and patients treated with SPE (coefficient, -21.69). A lower Δ%PAO was found in African-American patients (coefficient, 7.31). CONCLUSIONS: The use of CDT and SPE showed long-term benefit in thrombus reduction.

Diameter and depth of femoral vessels by duplex ultrasound.

BACKGROUND: The anatomy of the femoral artery and vein plays an integral role in vascular access. Both technical feasibility and complication rates are associated with femoral vessel diameter and depth. The goal of this study is to establish normative values for common femoral artery (CFA) and vein (CFV) depth and diameter using a large, diverse patient population. METHODS: A retrospective review of all patients undergoing lower extremity venous duplex imaging over a 1 year period were reviewed. Patients with inadequate imaging or with evidence of deep vein thrombosis were excluded. The index image of all studies was a non-compressed view of the common femoral vein at the saphenous-femoral junction. All measurements were taken from this still. Vessel diameters were measured from intima to intima. Depth was measured from skin to intima. BMI and BSA were calculated using standard formulas. Chi square was used for univariate analysis. Linear regression was used to establish correlation. RESULTS: Over the 1 year period, 983 patients met criteria for inclusion. The majority were male (53%) with a mean age of 55. The patients were 47% white and 44% black. The majority had hypertension (53%). The mean BMI and BSA were 29 and 2, respectively. Mean CFA depth was 1.7 cm, while mean CFV depth was 1.8 cm. The mean CFA and CFV diameters were 0.9 and 1.1 cm, respectively. Amongst height, weight, BMI, and BSA, weight correlated best with CFA (R = 0.548) and CFV (R = 0.552) depth, while BSA correlated best for diameter for both CFA (R = 0.390) and CFV (R = 0.440). CONCLUSIONS: This study establishes mean diameters and depths for the common femoral artery and vein using a large, diverse patient group. BSA was most closely associated with vessel diameter, while weight was correlated with depth. This study provides normative diameter and depth values for the common femoral vasculature, which may assist in vascular access planning for providers.

Intravascular ultrasound imaging for diagnosis and characterization of the popliteal compression syndrome.

Objective: Functional popliteal artery entrapment syndrome (fPAES) is a rare form of nonatherosclerotic claudication most often seen in young athletic patients. Diagnosis remains challenging, with various imaging modalities showing equivocal or subtle findings that may be missed. We sought to critically examine and quantitate the utility of intravascular ultrasound (IVUS) imaging, a common diagnostic tool for vascular compression syndromes, in diagnosis and characterization of fPAES. Methods: Patients presenting to a single tertiary care center between 2019 and 2022 with symptoms of PAES but without an anatomic etiology or equivocal workup were selected. Angiogram and IVUS with maneuvers were performed on affected extremities at rest, active plantarflexion/dorsiflexion, and plantarflexion/dorsiflexion against resistance. IVUS examination was recorded using a pull-back technique from the tibial vessels to the superficial femoral artery. The degree, length, and anatomic location of compression using the two imaging modalities were compared. Results: Angiogram and IVUS with maneuvers were performed on 17 lower extremities (9 left, 8 right) in 15 patients (88% female; mean age, 21.2 years). Evidence of arterial compression on angiography was noted in 88.2% (n = 15) of limbs (66.7% complete contrast cessation and 20% popliteal artery tapering); 13.3% (n = 2) only demonstrated sluggish flow as possible evidence of compression. Arterial compression was seen on IVUS imaging in 15 of 17 limbs, and all completely compressed around the IVUS catheter. The IVUS-measured mean length of compression was 10.5 cm ± 4.2 (median, 11 cm; range, 4-23 cm). Compression involved only the popliteal vessels in 86.7% (n = 13); one patient had both popliteal and tibioperoneal trunk compression, whereas another had tibioperoneal trunk and peroneal artery compression. Popliteal vein compression was 100%. The contrast cessation point on angiography and the proximal point of compression on IVUS imaging differed in 80% of cases (P < .05). The distal extent of compression was unable to be determined by angiogram findings but was clearly delineated by IVUS imaging in all cases. Conclusions: IVUS imaging is a more sensitive diagnostic and descriptive imaging modality compared with angiogram in patients with possible fPAES. IVUS and angiogram findings are greatly discordant; moreover, IVUS imaging can provide detailed information such as the precise extent and anatomic location of the arterial compression, which may be useful in aiding surgical planning. IVUS imaging should be considered the gold standard for diagnosing and characterizing fPAES before intervention planning.

Utilizing an office based laboratory (OBL) during the COVID-19 pandemic for vascular surgical patients.

COVID-19 pandemic brought new challenges in healthcare including the need to create tiered class recommendations about which types patients to treat urgently and which surgical cases to defer. This is a report of a single center's Office Based Laboratory (OBL) system to prioritize vascular patients and preserve acute care resources and personnel. In reviewing three months of data, it appears that by continuing to provide the urgent care needed for this chronically ill population, the insurmountable backup of surgical procedures is prevented in the operating room once elective surgeries resumed. The OBL was able to continue providing care at the same pre-pandemic rate to a large intercity population.

Evaluating the Safety of Transcarotid Artery Revascularization under Local Anesthesia Prior to Coronary Artery Bypass Grafting Surgery.

BACKGROUND: Controversy exists regarding the timing of intervention for patients with critical coronary artery disease (CAD) awaiting coronary artery bypass and severe carotid artery stenosis (CAS). Transcarotid artery revascularization (TCAR) is a minimally invasive revascularization alternative through direct transcervical carotid access that minimizes the chance of arch manipulation and consequent antegrade embolic stroke rate. While the TCAR procedure can be performed under local anesthesia (monitored anesthesia care [MAC]) versus general anesthesia, the hemodynamic benefits of local anesthesia in patients with severe CAD are significant. Patients receiving staged TCAR-coronary artery bypass grafting (CABG) have high-risk cardiovascular disease and require accurate perioperative neurological and hemodynamic evaluation that can be safely provided with local anesthesia. METHODS: In this retrospective single-center study, 14 patients were systematically identified to have undergone staged TCAR prior to CABG surgery from December 2018 to October 2021. All patients underwent TCAR with local anesthesia and minimal sedation. Relevant patient demographics, medical and surgical history, preoperative covariates, and type of anesthesia administered were obtained from patients' charts. CAD was confirmed by either carotid duplex imaging or computed tomography angiography (CTA) of the head/neck. RESULTS: Staged TCAR-CABG interventions were performed on 14 patients (64% male; mean age 65.0 years). No major adverse cardiac events were reported including transient ischemic attack (TIA), stroke, myocardial infarction (MI), or TCAR-related death in the interval between their TCAR and CABG as well as in a 12-month follow-up period. One patient required to return to the operating room (OR) for evacuation of a neck hematoma. CONCLUSIONS: This study demonstrated high success rate of TCAR under local anesthesia prior to CABG (100%) with no incidence of perioperative stroke, MI, or death at 1-month, 6-month, and 12-month follow-up intervals. The authors support the use of staged TCAR-CABG with local anesthesia as a safe and promising treatment option for patients with high-grade cardiac disease, high risk of stroke, or multiple comorbidities that preclude a carotid endarterectomy (CEA).

Can remote endarterectomy expand access to kidney transplantation in patients with severe iliac calcification?

Severe iliac artery calcification in patients with end-stage renal disease is a common barrier to listing for kidney transplant. While few surgical solutions to iliac calcification have been reported, improving treatment may thus improve access to transplant care. Here we present two cases of a novel application of remote endarterectomy of the external iliac artery to facilitate listing for renal transplant. Both patients were listed following remote endarterectomy, followed by successful renal transplants using the treated vessels.

Presentation and management of rare saccular superior mesenteric artery trunk and branch aneurysms.

Superior mesenteric artery (SMA) aneurysm is caused by degeneration of the visceral arteries. Although a rarely encountered entity, it requires timely management owing to the high mortality rate associated with rupture, particularly when the aneurysm is saccular in nature. As such, urgent treatment is generally indicated. We present five cases of SMA aneurysm arising from the main trunk or branches of the SMA.

Superior Mesenteric Artery Stenosis Due to Disseminated Tuberculosis in a Pediatric Patient.

Disseminated tuberculosis (TB) associated with mesenteric arteritis has not been established in children. We present the case of an 8-year-old woman who presented with TB and superior mesenteric artery stenosis. Although rare, large vessel involvement from Takayasu arteritis can occur in TB. Evaluation for mesenteric vessel involvement should be considered in pediatric patients presenting with widely disseminated TB and abdominal pain.

Transrectal intracolon cooling prevents paraplegia and mortality in a rat model of aortic occlusion-induced spinal cord ischemia.

OBJECTIVE: Spinal cord ischemia-reperfusion injury (SC-IRI) occurs in many medical conditions such as aneurysm surgical repair but no treatment of SC-IRI is available in clinical practice. The objective of the present study was to develop a novel medical device for the treatment of SC-IRI. METHODS: A rat model of SC-IRI was used. A novel transrectal intracolon (TRIC) temperature management device was developed to maintain an intracolon wall temperature at either 37°C (TRIC37°C) or 12°C (TRIC12°C). The upper body temperature was maintained as close as possible to 37°C in both groups. A 2F Fogarty balloon catheter was inserted via the left common carotid artery to block the distal aortic blood flow to the spinal cord. The proximal blood pressure was controlled by the withdrawal and infusion of blood via the jugular vein catheter, such that the distal tail artery blood pressure was maintained at ∼10 mmHg for 13 and 20 minutes, respectively. Next, the balloon was deflated, and TRIC temperature management was continued for an additional 30 minutes to maintain the colon wall temperature at either 37°C or 12°C during the reperfusion period. RESULTS: All the rats subjected to 13 minutes of spinal cord ischemia in the TRIC37°C group had developed paraplegia during the postischemic phase. In striking contrast, TRIC at 12°C completely prevented the paraplegia, dramatically improved the arterial blood gas parameters, and avoided the histopathologic injuries to the spinal cord in rats subjected to 13 minutes of spinal cord ischemia. Furthermore, TRIC12°C allowed for the extension of the ischemia duration from 13 minutes to 20 minutes, with significantly reduced functional deficits. CONCLUSIONS: Directly cooling the intestine focally with the TRIC device offered an exceptional survival rate and functional improvement after aortic occlusion-induced spinal cord ischemia.

Directly Cooling Gut Prevents Mortality in the Rat Model of Reboa Management of Lethal Hemorrhage.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a lifesaving technique for the management of lethal torso hemorrhage. Its benefit, however, must be weighed against the lethal distal organ ischemia-reperfusion injury (IRI). This study uses a novel direct gut cooling technique to manage the distal organ IRI. METHODS: A rat lethal hemorrhage model was established by bleeding of 50% of the estimated total blood volume via inferior vena cava. A novel TransRectal Intra-Colon (TRIC) temperature management device was positioned in the descending colon either to maintain intra-colon temperature at 37°C or 12°C. The upper body temperature was maintained at as close to 37°C as possible in both groups. A 2F Fogarty balloon catheter was inserted via the femoral artery into the descending thoracic aorta for the implementation of REBOA. After REBOA, the balloon was deflated, and the shed blood was returned. The temperature managements were continued for additional 180 to 270 min during the post-REBOA period. RESULTS: All rats subjected to REBOA management of lethal hemorrhage at 37°C had severe histopathological gut and abdominal organ IRI, severe functional deficits, and died within 24 h with 100% mortality. By contrast, directly cooling the colon to 10°C to 12°C with the novel TRIC device abolished mortality, and dramatically improved ABG parameters, prevented the abdominal organ injury, and reduced the functional deficits during the 7-day post-REBOA period. CONCLUSIONS: Direct trans-rectal colon cooling during REBOA management of lethal hemorrhage offers extraordinary functional improvement and amazing tissue protection, and abolishes mortality.

Preventing Retained Surgical Items During Endovascular Procedures: Bridging the Gap Between Guidelines and Practice.

A retained surgical item (RSI) can be a devastating and costly procedural complication. Although the current incidence of RSIs is unknown, perioperative personnel routinely perform surgical counts according to their facility's policies and procedures to prevent this sentinel event. The American College of Surgeons, The Joint Commission, and AORN emphasize the importance of communication and standardized protocols for the counting of surgical items. However, there is a lack of current evidence to support specific recommendations for the counting of items during endovascular procedures. After the occurrence of RSIs during endovascular procedures at our facility, we convened an interdisciplinary workgroup, conducted an analysis of root causes, reviewed the available literature, and revised the existing policy. This article reviews the available literature on RSIs, describes root causes, discusses recommendations from national organizations, and describes the process that we used to create the policy changes at our facility.

Depletion of CD4 and CD8 Positive T Cells Impairs Venous Thrombus Resolution in Mice.

Resolution of deep venous thrombosis involves coordinated inflammatory processes. T cells regulate inflammation in vivo and modulate vascular remodeling in other settings, but their role in venous thrombus resolution remains undefined. To determine the role of T cells in venous thrombus resolution in vivo, stasis induced thrombi were created by vena cava ligation in outbred CD-1 mice. CD4 and CD8 positive T cells, as determined by flow cytometry, were present in thrombi both during thrombus formation and resolution. Depletion of the CD4 and CD8 positive T cells by antibody treatment selectively impaired thrombus resolution compared to animals treated with isotype control antibodies, without an effect on venous thrombus formation. Quantitation of intra-thrombus macrophage numbers, fibrinolytic marker expression, and gelatinolytic activity by zymography revealed that T cell depletion decreased the number of macrophages, reduced the expression of fibrinolytic marker urokinase plasminogen activator (uPA), and decreased the activity of matrix metalloprotinease-9 (MMP-9). These data implicate CD4 and CD8 positive T cells in functionally contributing to venous thrombus resolution, thus representing a potential therapeutic target, but also underscoring potential risks involved in T cell depletion used clinically for solid organ and hematopoietic transplantation procedures.

Modeling variability in the inferior vena cava into fenestrated endografts for retrohepatic caval injuries.

OBJECTIVE: Injury of the retrohepatic inferior vena cava (IVC) is rare, but extremely fatal. Open repair of these injuries is challenging. Various maneuvers, including atriocaval shunting and total vascular isolation, have been described, but are poorly tolerated in the severely injured patient. Endovascular repair is an attractive alternative strategy, but effective hemostasis of complex injuries requires an endograft that excludes the injury while permitting flow from the hepatic veins. Unfortunately, IVC and hepatic vein anatomy is highly variable and has not been clearly described in injured patients. Our purpose was to characterize critical human IVC morphology in trauma patients, and develop the design parameters of an off-the-shelf fenestrated endograft intended for caval deployment. METHODS: One hundred consecutive adult trauma patients with an admission computed tomography scan including a portal venous phase of the abdomen were reviewed. Specific anatomic measurements including segmental IVC lengths and diameters were obtained. Multiple theoretical endografts were modeled to optimize caval coverage in the retrohepatic segment, assuming 10% to 40% oversizing for seal. RESULTS: This sample population had a mean age of 50 years, height of 173 cm, and weight 84 kg. Seventy-one percent were male and 89% had a blunt mechanism of injury. The median caval length from the renal veins to right atrium was 111 mm (interquartile range [IQR], 102-120 mm), diameter was 22 mm (IQR, 19-26 mm), and hepatic venous orifice area was 336 mm2 (IQR, 267-432 mm2). All patients had a landing zone of at least 12 mm in the suprahepatic and 10 mm in the suprarenal segments. Three models of graft length were developed to accommodate patients with segmental and overall dimensions in the smallest half, third quartile, and fourth quartile. These could provide 95% of patients with coverage of the retrohepatic segment without risk of hepatic or renal vein occlusion. Four graft diameters were developed for cross-sectional fit. Graft diameters of 20, 24, 30, and 38 mm could provide adequate coverage in, respectively, 11%, 35%, 49%, and 16% of patients. These combinations of graft length and diameter would accommodate 93% of patients. CONCLUSIONS: We defined human IVC morphology essential for endovascular therapy and developed parameters for fenestrated IVC endografts to address retrohepatic caval injuries in trauma patients. Although additional study and testing are required, this proof-of-concept study supports the hypothesis that exclusion of the most devastating retrohepatic IVC injuries can be achieved with a reasonable number of off-the-shelf fenestrated endografts. These findings form the basis for additional research toward the development of novel devices for endovascular therapy of these often lethal injuries.

Intraoperative Fragmentation and Retention of Endovascular Devices: Clinical Consequences and Preventative Strategies.

BACKGROUND: Expanded applications and increasing volumes of complex endovascular procedures have increased the risk of unintended intraoperative fragmentation and retention of catheters and sheaths. We describe a series of retained or fragmented endovascular devices, a quality improvement program to address this unmet need for improved detection of catheter fragmentation, and the results of this program. METHODS: Cases utilizing endovascular devices that resulted in a retained catheter fragment were identified and analyzed during divisional quality improvement review. One consistent area of concern was operating room (OR) staff unfamiliarity with verifying the integrity of an endovascular device. In response, a slide-based training protocol of focused, endovascular nursing education was implemented. Following perceived lack of improvement after this approach, we developed a handheld visual reference display of the tips of common catheters and sheaths. Staff was surveyed before and after intervention to assess the educational value of the display and the impact on staff device familiarity. RESULTS: All 4 described cases resulted in an unplanned return to the OR for retrieval of the fragmented catheter or sheath. No thromboembolic complications were observed, although associated intra-arterial thrombus was noted in 2 cases. Thirty-four OR nurses were polled to trial the visual reference display initiative, with 70% of those reporting primary surgical assignments outside of cardiovascular ORs. Introduction of the new visual reference display improved staff confidence in their ability to identify a broken device (2.4-3.7, P < .001). This improvement was most significant in OR staff with primary assignments in noncardiovascular services. CONCLUSION: Current OR standard operating procedures fail to address the potential for unintentionally retained catheters and wires during endovascular procedures. Our novel visual reference display of common endovascular items rather than conventional in-service training improved the ability of staff to identify device fragmentation at the time of the index procedure.

Fibrinolysis and Inflammation in Venous Thrombus Resolution.

Clinical observations and accumulating laboratory evidence support a complex interplay between coagulation, inflammation, innate immunity and fibrinolysis in venous thromboembolism (VTE). VTE, which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), and the subsequent complications of post-thrombotic syndrome (PTS), are significant causes of morbidity and mortality in patients. Clinical risk factors for VTE include cancer, major trauma, surgery, sepsis, inflammatory bowel disease, paralysis, prolonged periods of immobility, and aging. Abnormalities in venous blood flow or stasis initiates the activation of endothelial cells, and in concert with platelets, neutrophils and monocytes, propagates VTE in an intact vein. In addition, inflammatory cells play crucial roles in thrombus recanalization and restoration of blood flow via fibrinolysis and vascular remodeling. Faster resolution of the thrombus is key for improved disease prognosis. While in the clinical setting, anticoagulation therapy is successful in preventing propagation of venous thrombi, current therapies are not designed to inhibit inflammation, which can lead to the development of PTS. Animal models of DVT have provided many insights into the molecular and cellular mechanisms involved in the formation, propagation, and resolution of venous thrombi as well as the roles of key components of the fibrinolytic system in these processes. Here, we review the recent advances in our understanding of fibrinolysis and inflammation in the resolution of VTE.

Considerations beyond Stenosis for Carotid Endarterectomy in Treating Free-Floating Thrombus of the Carotid Artery.

BACKGROUND: Free-floating thrombus (FFT) of the carotid artery is an uncommon condition that can present with neurologic symptoms, often in the setting of ischemic stroke. The literature pertaining to the incidence and optimal treatment of this condition is limited. Herein, we report our contemporary experience with FFT across a range of degrees of carotid stenosis. METHODS: Medical records and imaging studies from a single academic medical center from January 2016 to July 2018 were retrospectively reviewed. Patient demographics, presentation, treatment, and follow-up were abstracted. RESULTS: Six cases of FFT of the carotid artery with and without hemodynamically significant atherosclerotic disease were identified. All cases presented with ischemic stroke; one case had a hemorrhagic conversion. In each case, the FFT was visualized by at least one imaging modality including computed tomography angiography, magnetic resonance angiography, and duplex ultrasound. Three patients had >50% carotid stenosis and three had <50%. All cases were treated with endarterectomy. Four of the six patients received preoperative anticoagulation. There were no postoperative complications. Median follow-up was 252 days, with one case lost to follow-up. Four of the six patients have been without restenosis, recurrence of the thrombus, nor worsening or recurrent stroke on follow-up. The fifth patient developed restenosis but remained clinically stable. CONCLUSIONS: Although current society guidelines do not recommend carotid endarterectomy as first-line treatment for symptomatic patients with <50% stenosis, it may be indicated in the context of FFT.

The myristoylated alanine-rich C kinase substrate differentially regulates kinase interacting with stathmin in vascular smooth muscle and endothelial cells and potentiates intimal hyperplasia formation.

OBJECTIVE: Restenosis limits the durability of all cardiovascular reconstructions. Vascular smooth muscle cell (VSMC) proliferation drives this process, but an intact, functional endothelium is necessary for vessel patency. Current strategies to prevent restenosis employ antiproliferative agents that affect both VSMCs and endothelial cells (ECs). Knockdown of the myristoylated alanine-rich C kinase substrate (MARCKS) arrests VSMC proliferation and paradoxically potentiates EC proliferation. MARCKS knockdown decreases expression of the kinase interacting with stathmin (KIS), increasing p27kip1 expression, arresting VSMC proliferation. Here, we seek to determine how MARCKS influences KIS protein expression in these two cell types. METHODS: Primary human coronary artery VSMCs and ECs were used for in vitro experiments. MARCKS was depleted by transfection with small interfering RNA. Messenger RNA was quantitated with the real-time reverse transcription polymerase chain reaction. Protein expression was determined by Western blot analysis. Ubiquitination was determined with immunoprecipitation. MARCKS and KIS binding was assessed with co-immunoprecipitation. Intimal hyperplasia was induced in CL57/B6 mice with a femoral artery wire injury. MARCKS was knocked down in vivo by application of 10 µM of small interfering RNA targeting MARCKS suspended in 30% Pluronic F-127 gel. Intimal hyperplasia formation was assessed by measurement of the intimal thickness on cross sections of the injured artery. Re-endothelialization was determined by quantitating the binding of Evans blue dye to the injured artery. RESULTS: MARCKS knockdown did not affect KIS messenger RNA expression in either cell type. In the presence of cycloheximide, MARCKS knockdown in VSMCs decreased KIS protein stability but had no effect in ECs. The effect of MARCKS knockdown on KIS stability was abrogated by the 26s proteasome inhibitor MG-132. MARCKS binds to KIS in VSMCs but not in ECs. MARCKS knockdown significantly increased the level of ubiquitinated KIS in VSMCs but not in ECs. MARCKS knockdown in vivo resulted in decreased KIS expression. Furthermore, MARCKS knockdown in vivo resulted in decreased 5-ethynyl-2'-deoxyuridine integration and significantly reduced intimal thickening. MARCKS knockdown enhanced endothelial barrier function recovery 4 days after injury. CONCLUSIONS: MARCKS differentially regulates the KIS protein stability in VSMCs and ECs. The difference in stability is due to differential ubiquitination of KIS in these two cell types. The differential interaction of MARCKS and KIS provides a possible explanation for the observed difference in ubiquitination. The effect of MARCKS knockdown on KIS expression persists in vivo, potentiates recovery of the endothelium, and abrogates intimal hyperplasia formation.

Iliofemoral deep venous thrombosis in kidney transplant patients can cause graft dysfunction.

We present a series of kidney transplant dysfunction secondary to lower extremity deep venous thrombosis (DVT). A 70-year-old man underwent living unrelated kidney transplantation and presented 2 months postoperatively with acute kidney injury (AKI) secondary to external iliac vein thrombosis. Graft function improved after endovascular intervention. A 43-year-old man underwent living unrelated kidney transplantation and presented 3 years postoperatively with AKI secondary to external iliac vein thrombosis. Graft function recovered after thrombolysis. A 42-year-old woman underwent simultaneous pancreas and kidney transplantation. Four weeks postoperatively, she had AKI secondary to common femoral vein DVT. Her graft function improved after common iliac vein stenting. A 67-year-old man underwent living unrelated kidney transplantation and presented a week later with lower extremity DVT and AKI. His graft function improved with anticoagulation. Iliofemoral DVT can cause allograft dysfunction. The cause may be multifactorial. Endovascular intervention is safe and feasible when anticoagulation fails.