S. Keisin Wang

Rationale and design of the MarrowStim PAD Kit for the Treatment of Critical Limb Ischemia in Subjects with Severe Peripheral Arterial Disease (MOBILE) trial investigating autologous bone marrow cell therapy for critical limb ischemia

Objective: Critical limb ischemia (CLI) continues to place a significant encumbrance on patients and the health care system as it progresses to limb loss and long‐term disability. Traditional methods of revascularization offer a significant benefit; however, for one‐third of CLI patients, these surgical options are not technically possible or patency is severely limited by disease burden (deemed “poor‐option” for revascularization). In a previous phase I trial, we demonstrated intramuscular injection of concentrated bone marrow aspirate (cBMA) via MarrowStim (Zimmer Biomet, Warsaw, Ind) harvest is safe and may decrease major amputation in patients with CLI unfit for surgical revascularization. Therefore, we describe and rationalize the MarrowStim PAD Kit for the Treatment of Critical Limb Ischemia in Subjects with Severe Peripheral Arterial Disease (MOBILE) trial, a study geared to provide the pivotal proof of efficacy of cBMA in CLI. Methods: MOBILE is a multicenter, randomized, double‐blind, placebo‐controlled trial designed to assess the efficacy of intramuscular injections of cBMA in promoting amputation‐free survival in patients with poor‐option CLI. Patients (aged >21 years) with rest pain or tissue loss resulting from advanced peripheral arterial disease, as characterized by ankle‐brachial index (<0.6), toe‐brachial index (<0.4), or transcutaneous pressure of oxygen (<50 mm Hg), were eligible for inclusion if surgical revascularization was not possible secondary to advanced disease. Results: Treatment and 1‐year follow‐up of 152 patients enrolled in MOBILE are completed. Long‐term follow‐up is ongoing. Currently, we are in the process of unblinding the initial results for preliminary data analysis. Conclusions: If successful, MOBILE could add definitive, high‐quality evidence in support of cBMA for the treatment of poor‐option CLI patients and provide an additional modality for patients who face amputation secondary to advanced limb ischemia.

Rationale and design of the Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial investigating the therapeutic mechanism of mesenchymal stromal cells in the treatment of critical limb ischemia

Objective: Currently, there are no accepted nonsurgical therapies that improve the delivery of blood‐derived nutrients to patients with critical limb ischemia. Here, we describe the ongoing phase 1/2 Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial, which will provide crucial evidence of the safety profile of mesenchymal stromal cells (MSCs) and explore their therapeutic mechanisms in the setting of critical limb ischemia requiring below‐knee amputation (BKA). Methods: In the CHAMP and the parallel marrowCHAMP trials (hereafter grouped together as CHAMP), a total of 32 extremities with rest pain or tissue loss requiring BKA will be enrolled to receive intramuscular injections of allogeneic MSCs (CHAMP; n = 16) or autogenous concentrated bone marrow aspirate (marrowCHAMP; n = 16) along the distribution of the BKA myocutaneous flap and proximal tibialis anterior. After treatment, subjects are randomized to BKA at four time points after injection (days 3, 7, 14, and 21). At the time of amputation, skeletal muscle is collected at 2‐cm increments from the tibialis injection site and used to determine proangiogenic cytokine description, MSC retention, quantification of proangiogenic hematopoietic progenitor cells, and histologic description. Clinical limb perfusion before and after treatment will be quantified using transcutaneous oximetry, toe‐brachial index, ankle‐brachial index, and indocyanine angiography. Additional clinical end points include all‐cause mortality, need for amputation revision, and gangrene incidence during the 6‐month post‐treatment follow‐up. Results: Enrollment is under way, with 10 patients treated per protocol thus far. We anticipate full conclusion of follow‐up within the next 24 months. Conclusions: CHAMP will be pivotal in characterizing the safety, efficacy, and, most important, therapeutic mechanism of allogeneic MSCs and autogenous concentrated bone marrow aspirate in ischemic skeletal muscle.

Institutional experience with the Zenith Fenestrated aortic stent graft

Objective: The Zenith Fenestrated (ZFEN; Cook Medical, Bloomington, Ind) aortic stent graft system was approved for commercial use by the Food and Drug Administration in April 2012. We report our single‐center experience of 100 consecutive patients treated with the ZFEN platform from October 2012 to March 2017. Methods: A retrospective review of our prospectively maintained fenestrated endovascular aneurysm repair (FEVAR) database at a tertiary care academic institution located in the Midwest United States was performed for descriptive analysis. All continuous variables are reported as a mean ± standard deviation and compared using two‐sided Student t‐tests. Categorical variables were compared using two‐sided Fisher exact tests. Results: All but one of the procedures were elective in nature. Overall intraoperative characteristics included a mean blood loss (estimated blood loss) of 388 ± 385 mL, fluoroscopy time of 63 ± 30 minutes, radiation dose of 437 ± 272 rad, contrast material volume of 99 ± 36 mL, and operative time of 236 ± 87 minutes. Average number of visceral arteries stented was 2.1 ± 0.5. Technical success was achieved in 98% of the patients. Statistically significant (P < .05) improvement in estimated blood loss (2.1‐fold) was observed in the second half of our series. Interestingly, no improvements were made in terms of fluoroscopy time, radiation exposure, contrast material use, or operative time. However, procedural difficulty increased in the last half by number of visceral arteries stented as a surrogate (1.9 vs 2.2; P < .05). Mean length of stay was 3.6 ± 4.3 days. Perioperative mortality at 30 days was 2%. Perioperative morbidity included a 5% incidence of any bowel ischemia, 1% of spinal cord ischemia, 3% of renal failure requiring hemodialysis, 1% of stroke, and 4% of myocardial infarction. Average follow‐up was 1.7 ± 1.4 years. Reintervention during the follow‐up phase was 20%. Of the 209 visceral arteries stented, we noted 6 instances of stent thrombosis, 6 of kinking or stenosis, and 1 of stent fracture in follow‐up. Endoleak, most commonly type II, was present or could not be excluded in 15% of all FEVARs at last available computed tomography angiography. Conclusions: In our experience, FEVAR with the ZFEN system continues to be safe and effective. There is a significant rate of reintervention observed, and close monitoring is fundamental to maintaining good clinical results.

Osteopontin may be a driver of abdominal aortic aneurysm formation

Objective: Previous in vitro and animal studies have suggested that osteopontin (OPN), an inflammatory extracellular matrix protein, is involved in the formation and growth of abdominal aortic aneurysms (AAAs). However, the mechanism by which this occurs continues to be nebulous. The relationship between OPN and inflammation‐suppressing lymphocytes present in the human AAA condition was investigated and presented herein. Methods: Serum OPN concentrations were measured in healthy, risk factor‐matched non‐AAA and AAA patients by enzyme‐linked immunosorbent assay (ELISA). Immunohistochemistry was used to determine the source of OPN secretion using aortic tissue collected from multiorgan donors and AAA patients undergoing open surgical repair. Vascular smooth muscle cells (VSMCs) were exposed to various inflammatory mediators, and OPN expression was evaluated by quantitative reverse transcriptase‐polymerase chain reaction and ELISA. The inflammatory nature of OPN and the aortic wall was determined using a TR1 suppressor cell induction assay as a surrogate and characterized by ELISA and fluorescence‐activated cell sorting. Results: OPN was found to be elevated in both the plasma and aortic homogenate of AAA patients compared with controls. On immunohistochemistry, OPN localized to the tunica media of the diseased aorta but was minimally expressed in healthy aorta. In vitro, cigarette smoke extract was the most potent stimulator of OPN secretion by VSMCs and increased both messenger RNA and supernatant concentrations. OPN demonstrated an ability to inhibit the induction of interleukin 10‐secreting TR1 lymphocytes, a depleted population in the AAA patient, from naive precursors. Last, neutralizing receptor targets of OPN in the setting of AAA homogenate coincubation abrogated the inhibition of TR1 induction. Conclusions: OPN, secreted by the VSMCs of the tunica media, is elevated in the circulating plasma and aortic wall of patients with AAA. It can inhibit the induction of the TR1 suppressor cell, leading to an overall proinflammatory state contributing to progressive aortic wall breakdown and dilation. Clinical Relevance: Little is known about the initiating event of abdominal aortic aneurysm formation. However, the early histology of the ectatic aorta is characterized by massive infiltration of mononuclear cells and elaboration of matrix metalloproteinases, collagenases, and elastases. This runaway inflammatory response directly leads to extracellular matrix degradation and loss of aortic integrity. In this study, we report elevations of osteopontin (OPN), an extracellular matrix glycoprotein associated with inflammation in other pathologic processes. In addition, OPN demonstrated an ability to inhibit the expression of the TR1 lymphocyte, a potent suppressor of inflammation. Therefore, we argue that accumulation of OPN in the aortic wall may be a potent driver for abdominal aortic aneurysm propagation.

Getting A Leg Up on Cell Therapy for Critical Limb Ischemia

Critical limb ischemia (CLI) is the most severe form of peripheral arterial disease and is associated with an excessively high risk for death and amputation of the affected extremity.1 The clinical hallmarks of CLI are rest pain and tissue loss because of progressive occlusion of the arteries in the leg as a result of atherosclerosis and, less frequently, autoimmune and inflammatory disorders.2 The estimated annual incidence of CLI in Western society is 500 to 1000 new cases, which is expected to increase as the population ages and obesity and diabetes mellitus become more prevalent.3 Treatment strategies for CLI have traditionally focused on surgical bypass or endovascular interventions that improve limb perfusion to prevent amputation of the affected leg. Unfortunately, 40% of patients with CLI will not have options for these procedures, and as a result, over 53 000 amputations are performed annually in the United States. Patients with diabetes mellitus, Rutherford class 5 or 6 disease (tissue loss), and renal dysfunction are at highest risk for limb loss.3,4 Article, see p 1326 …

Fenestrated Aortic Endografts in the Last 3 Years: An Update

Purpose of ReviewFenestrated endovascular aortic aneurysm repair (FEVAR) is an accepted treatment option for patients who are not suitable for conventional endovascular aortic aneurysm repair or open surgical repair (OSR). Five years ago, the FDA approved the use of FEVAR in patients with inadequate infrarenal aortic seal zones (short necks). This procedural paradigm continues to gain in popularity compared to OSR for complex aortic disease. We seek to define the current state of fenestrated endovascular repair by reviewing relevant literature over the past 3 years.Recent FindingsFEVAR continues to prove to be efficacious with reasonable durability as a therapy for patients who are not candidates for OSR. As a second-line treatment, FEVAR is less morbid in the short-term with trade-off of high reintervention rates in the follow-up period. Mid- to long-term outcomes have proven to be comparable to OSR in selected patients with persistent excellent patency of the visceral target vessels. Recent publications have thrust FEVAR into consideration as the primary interventional modality in juxtarenal abdominal aortic aneurysms, a traditional indication for OSR.SummaryAs FEVAR continues to evolve from surgeon-modified devices to custom built and eventually off-the-shelf grafts, it is anticipated to be employed widely for managing complex aortic aneurysms. Compared to OSR, FEVAR carries a low risk of perioperative morbidity while demonstrating continued safety and durability in early to mid-term reports.

Successful Treatment of an Infected Zenith Fenestrated Endograft Without Explantation

Current surgical dogma for infected aortic endografts consists of complete explantation concurrent with revascularization via extra-anatomic bypass or in situ infection-resistant conduit. However, this treatment paradigm is associated with high rates of postoperative mortality and major morbidity. Therefore, patients with prohibitive operative risk are often not offered surgical intervention. In the following manuscript, we report the successful treatment of an 85-year-old gentleman with a fenestrated aortic endograft (Cook Medical, Bloomington, Indiana) infected secondary to the formation of an aortoenteric fistula with primary bowel repair, washout, and lifelong antibiotics and followed for nearly 2 years after intervention. Therefore, this nonexplantation approach can be considered for patients who may otherwise have no surgical recourse.

Metformin does not reduce inflammation in diabetics with abdominal aortic aneurysm or at high risk of abdominal aortic aneurysm formation

Introduction The protective effect of diabetes mellitus on abdominal aortic aneurysm formation and growth has been repeatedly observed in population studies but continues to be poorly understood. However, recent investigations have suggested that metformin, a staple antihyperglycemic medication, may be independently protective against abdominal aortic aneurysm formation and growth. Therefore, we describe the effect of metformin in abdominal aortic aneurysm and at-risk patients on markers of inflammation, the driver of early abdominal aortic aneurysm formation and growth. Methods Peripheral blood was collected from patients previously diagnosed with abdominal aortic aneurysm or presenting for their U.S. Preventive Task Force-recommended abdominal aortic aneurysm screening. Plasma and circulating peripheral blood mononuclear cells were isolated using Ficoll density centrifugation. Circulating plasma inflammatory and regulatory cytokines were assessed with enzyme-linked immunosorbent assays. CD4+ cell phenotyping was performed using flow cytometric analysis and expressed as a proportion of total CD4+ cells. To determine the circulating antibody to self-antigen response, a modified enzyme-linked immunosorbent assay was performed against antibodies to collagen type V and elastin fragments. Results Peripheral blood was isolated from 266 patients without diabetes mellitus (n=182), with diabetes mellitus not treated with metformin (n=34), and with diabetes mellitus actively taking metformin (n=50) from 2015 to 2017. We found no differences in the expression of Tr1, Th17, and Treg CD4+ fractions within diabetics ± metformin. When comparing inflammatory cytokines, we detected no differences in IL-1β, IL-6, IL-17, IL-23, IFN-γ, and TNF-α. Conversely, no differences were observed pertaining to the expression to regulatory cytokines IL-4, IL-10, IL-13, TSG-6, or TGF-β. Lastly, no differences in expression of collagen type V and elastin fragment antigen and/or antibodies were detected with metformin use in diabetics. Conclusion Metformin in diabetics at-risk for abdominal aortic aneurysm or diagnosed with abdominal aortic aneurysm does not seem to alter the peripheral inflammatory environment.

Description of human AAA by cytokine and immune cell aberrations compared to risk-factor matched controls

Background: The pathogenesis driving the formation of abdominal aortic aneurysms continues to be poorly understood. Therefore, we systemically define the cytokine and circulating immune cell environment observed in human abdominal aortic aneurysm compared with risk‐factor matched controls. Methods: From 2015 to 2017, a total of 274 patients donated blood to the Indiana University Center for Aortic Disease. Absolute concentrations of circulating cytokines were determined, using enzyme‐linked immunosorbent assays while the expression of circulating immune cell phenotypes were assayed via flow cytometric analysis. Results: Human abdominal aortic aneurysm is characterized by a significant depletion of the antigen‐specific, CD4+ Tr1 regulatory lymphocyte that corresponds to an upregulation of the antigen‐specific, inflammatory Th17 cell. We found no differences in the incidence of Treg, B10, and myeloid‐derived suppressor regulatory cells. Similarly, no disparities were noted in the following inflammatory cytokines: IL‐1&bgr;, C‐reactive protein, tumor necrosis factor &agr;, interferon &ggr;, and IL‐23. However, significant upregulation of the inflammatory cytokines osteopontin, IL‐6, and IL‐17 were noted. Additionally, no changes were observed in the regulatory cytokines IL‐2, IL‐4, IL‐13, TNF‐stimulated gene 6 protein, and prostaglandin E2, but we did observe a significant decrease in the essential regulatory cytokine IL‐10. Conclusion: In this investigation, we systematically characterize the abdominal aortic aneurysm–immune environment and present preliminary evidence that faulty immune regulation may also contribute to aneurysm formation and growth.

Adjunctive visceral artery chimney in patients undergoing Zenith Fenestrated aortic repair

Objective: Visceral artery chimneys have been employed as an adjunct to endovascular aneurysm repair (EVAR) to treat short‐neck infrarenal and juxtarenal aortic aneurysms for more than two decades. With the widespread introduction of fenestrated endovascular aneurysm repair by the Food and Drug Administration‐approved Zenith Fenestrated endograft (ZFEN; Cook Medical, Bloomington, Ind) to the United States in 2012, clinicians gained the ability to apply the chimney technique to these custom devices for difficult anatomy. The purpose of this report was to demonstrate feasibility and to provide evidence on the performance of chimneys for the treatment of complex juxtarenal aneurysms that could not be adequately treated with ZFEN alone. Methods: A retrospective analysis was performed of a prospectively maintained institutional ZFEN database capturing 110 fenestrated endovascular aneurysm repairs from October 2012 to January 2018 to identify patients undergoing a concomitant visceral artery chimney. All patients with <12 months of follow‐up were excluded from further analysis. Demographic, anatomic, intraoperative, perioperative, and follow‐up characteristics were tabulated and analyzed. Results: Six patients met criteria and were included in this investigation. They were universally male with a mean age of 76.2 years at the time of ZFEN/chimney. Chimneys were placed in a total of six visceral arteries (n = 1 per patient) consisting of three renal arteries, two celiac arteries, and one accessory renal artery. Mean estimated blood loss and operative time were 283 mL and 298 minutes, respectively. Technical success was achieved in all cases. Two small type IA “gutter” endoleaks were detected early; both spontaneously resolved on follow‐up. We observed no instances of chimney migration, stenosis, or thrombosis perioperatively or on follow‐up. Two reinterventions were performed in these six patients; these consisted of a repeated renal stent for ostial stenosis at a main body fenestration and a common femoral artery endarterectomy and patch angioplasty for an access‐related common femoral artery occlusion. Conclusions: Use of ZFEN in conjunction with a singular chimney is safe, feasible, and durable in patients with difficult anatomy who do not meet instructions for use as demonstrated in this limited series.