Vein distensibility is superior to vein diameter for predicting unassisted maturation of arteriovenous fistulae.

BACKGROUND: A mature arteriovenous fistula (AVF) is the preferred hemodialysis access owing to its durability and lower risk of complications. Various factors have been implicated as predictors for maturation, including vein diameter and access type. Vein distensibility, which refers to the ability of the vein to dilate in response to changes in blood flow and pressure, has been proposed as a potential predictor for maturation, but its utility remains poorly studied. METHODS: This is a single-institution retrospective study of AVFs performed under regional anesthesia. Vein distensibility was defined as the absolute and relative difference in target vein diameter (TVD) between the preoperative ultrasound vein mapping performed with tourniquet and a repeat ultrasound examination after a regional block before AVF creation and without a tourniquet. RESULTS: Forty-six patients underwent first-time AVF surgery with distensibility recorded in a prospectively maintained database. The mean initial preoperative TVD was 2.7 mm, and after the block 3.4 mm. The unassisted maturation rate for the entire cohort was 76%. In patients with an absolute change of TVD of <0.5 mm (Δ<0.5), the unassisted maturation rate was 63% (12/19), even though 95% of the group had a preoperative TVD of >3 mm. In those with ≥0.5 mm, the unassisted maturation rate was 85% (23/27; P = .08), even though the preoperative vein map TVD was 2.3 mm and 75% had a vein map TVD of <3 mm. For radiocephalic AVFs (n = 26), the unassisted maturation rate was 75% for Δ<0.5 vs 94% for Δ≥0.5 (P = .16), despite a preoperative vein map TVD of >3 mm in 92% vs 75%, respectively. The receiver operatring characteristic area under the curve for unassisted maturation with a Δ≥0.5 mm was 0.68 (P = .26). CONCLUSIONS: Quality in dialysis access surgery requires optimizing the unassisted maturation rate. A physiological measure that accounts for the dynamic process of maturation may be more informative than anatomic measurements alone. The results shown here demonstrate that vein distensibility may be a better predictor than absolute vein diameter on standard vein mapping ultrasound examinations.

Toward endovascular treatment of type A aortic dissection with smaller landing zones and more patient eligibility.

OBJECTIVE: Type A or ascending aortic dissection is an acute life-threatening condition with high morbidity and mortality. Open surgery remains the standard of care. The development of minimally invasive endografts for type A aortic dissection (TAAD) will require a detailed understanding of the dissection and aortic root anatomy to determine patient eligibility and optimal device specifications. METHODS: Computed tomography images of TAAD cases at our institution from 2012 to 2019 were identified, and three-dimensional reconstructions were performed using OsiriX, version 10.0 (Pixmeo SARL, Bernex, Switzerland). We analyzed key anatomic structures, including centerline length measurements, ascending aorta and aortic root dimensions, and the location and extent of dissection in relationship to the coronary ostia. RESULTS: A total of 53 patients were identified (mean ± standard deviation age, 60.4 ± 17.1 years; 36 men and 17 women), 46 of whom had undergone surgery for TAAD. Four patients had died within 30 days of surgery. In 47 patients (88.7%), the entry tear was distal to the highest coronary ostium. These cases were retrospectively considered for endovascular intervention using a nonbranched, single endograft stent. The proximal landing zone (LZ) was defined as the distance from the highest coronary ostium to the entry tear. Of the 53 patients, 35 (66.0%) had a proximal LZ length of ≥2.0 cm, 38 (71.7%) had a proximal LZ length of ≥1.5 cm, and 42 (79.2%) had a proximal LZ length of ≥1.0 cm. The median proximal and distal LZ diameters of the sinotubular junction (STJ) and distal ascending aorta regions were 3.29 cm (interquartile range [IQR], 2.73-4.10 cm) and 3.49 cm (IQR, 3.09-3.87 cm, respectively), with a median length from the STJ to the innominate takeoff of 8.08 cm (IQR, 6.96-9.40 cm). The median ascending aorta radius of curvature was 6.48 cm (IQR, 5.27-8.00 cm). Of the 53 patients, 25 (47.2%) could be treated with a straight tube graft with a ≤20% diameter mismatch between the proximal and distal LZs. CONCLUSIONS: Almost 80% of the patients with TAAD had had a proximal LZ of ≥1.0 cm. Of these patients, 47.2% had anatomy amenable for endovascular therapy with a nontapered straight tube graft using commercially available devices. To increase patient eligibility for TAAD endovascular intervention, enhanced precision deployment with an adequate seal in shorter LZs will be required. Our results can serve as a guide for endovascular device specifications designed to treat this devastating condition.

Functional outcomes of arteriovenous fistulas recruited with regional anesthesia.

OBJECTIVE: Regional anesthesia (RA)-induced vasodilation increases the proportion of patients with vein anatomy suitable for arteriovenous fistula (AVF) creation. The functional outcomes of AVFs created with veins initially small for size on preoperative duplex ultrasound mapping (≤2.4 mm) that are recruited under RA have not been clearly defined. We aimed to evaluate freedom from revision or thrombosis, time to first cannulation, and reintervention rates of AVFs created with veins recruited after induction of RA. METHODS: A prospectively maintained quality improvement database from a single institution was queried for patients who had dialysis access created under RA. We compared AVFs created according to the original surgical plan (preoperative minimum vein diameter >2.5 mm) with AVFs recruited with RA (preoperative minimum vein diameter ≤2.4 mm). End points included freedom from revision or thrombosis, time to first cannulation, and reintervention rates. RESULTS: Between May 2014 and April 2018, there were 208 dialysis access cases performed under RA. Excluding grafts, revisions, patients with previous ipsilateral AVFs, and those without preoperative ultrasound vein mapping, 135 patients were included in our analysis. Induction of RA with intraoperative duplex ultrasound allowed a change in surgical plan in 55 of 135 (42%) patients (recruited with RA), including 31 patients originally scheduled for an arteriovenous graft (mean preoperative distal upper arm cephalic vein diameter of 1.8 mm [standard deviation, 0.2 mm]) who were converted to an AVF (12 brachiobasilic, 11 brachiocephalic, and 8 radiocephalic). The remaining patients in the group of AVFs recruited with RA included 13 scheduled for brachiobasilic configurations who were converted to brachiocephalic or radiocephalic AVFs and 11 scheduled for brachiocephalic AVFs who were converted to radiocephalic AVFs. Comparing AVFs created according to the original surgical plan vs AVFs recruited with RA, there were no differences in reintervention rates (48% vs 49%; P = .90) or functional outcomes at 6 months (60% vs 65% used on hemodialysis [P = .58] and 7% vs 2% primary failure [P = .19]). CONCLUSIONS: In this series, RA increased the proportion of patients who underwent AVF creation without compromising functional outcomes. Routine use of RA in access surgery could have significant implications in meeting national guidelines for autogenous access in the prevalent hemodialysis population.

Natural history of acute pediatric iliofemoral artery thrombosis treated with anticoagulation.

OBJECTIVE: Acute iliofemoral artery thrombosis (IFAT) can occur in critically ill neonates and infants who require indwelling arterial cannulas for monitoring or as a consequence of cardiac catheterization. Guidelines suggest treatment with anticoagulation, but evidence supporting the optimal duration of therapy and the role of surveillance ultrasound is limited. The objectives of this study were to characterize the kinetics of thrombus resolution and to define an appropriate duration of anticoagulation and interval for surveillance ultrasound. METHODS: This was a single-center retrospective cohort study of pediatric patients with acute IFAT from 2011 to 2019. Medical records and vascular laboratory studies were reviewed. Patients with one or more surveillance ultrasound examinations were included. Thrombus resolution was defined as multiphasic flow throughout the index limb without evidence of echogenic intraluminal material by ultrasound. Time to resolution of thrombus was assessed using Kaplan-Meier analysis. RESULTS: Fifty-four limbs in 50 patients were identified with acute IFAT. The median age was 9.9 weeks (interquartile range, 3.1-21.7 weeks), with a median weight of 4.2 kg (interquartile range, 3.3-5.5 kg). The majority of limbs (65%) with acute IFAT presented with a diminished pedal Doppler signal, commonly after cardiac catheterization (55%). Forty-eight (89%) limbs had complete arterial occlusion on index ultrasound, and flow could not be detected below the ankle in 48%. The median number of ultrasound examinations per limb was three (range, two to seven), and 61% of limbs had a surveillance ultrasound within 7 days of diagnosis. At 14 and 30 days, 33% and 64% of patients, respectively, treated with anticoagulation had an estimated complete resolution of thrombus. Nine (17%) patients did not receive anticoagulation, and only two of these patients experienced IFAT resolution. At the time of diagnosis, one patient underwent open thrombectomy because of a contraindication to anticoagulation, and one patient was treated with thrombolysis. There were no instances of tissue loss or amputation CONCLUSIONS: Management of IFAT with anticoagulation resulted in successful short-term outcomes. Based on the observed rate of resolution, management should start with anticoagulation, followed by surveillance ultrasound at 2-week intervals. With treatment by anticoagulation, resolution can be expected to occur in one-third of patients every 2 weeks.

Patients with abdominal aortic aneurysms have reduced levels of microRNA 122-5p in circulating exosomes.

OBJECTIVE: There are currently no specific biomarkers to identify patients with abdominal aortic aneurysms (AAAs). Circulating exosomes contain microRNAs (miRNA) that are potential biomarkers for the presence of disease. This study aimed to characterize the exosomal miRNA expression profile of patients with AAAs in order to identify novel biomarkers of disease. METHODS: Patients undergoing duplex ultrasound (US) or computed tomography (CT) for screening or surveillance of an AAA were screened to participate in the study. Cases with AAA were defined as having a max aortic diameter >3 cm. Circulating plasma exosomes were isolated using Cushioned-Density Gradient Ultracentrifugation and total RNA was extracted. Next Generation Sequencing was performed on the Illumina HiSeq4000 SE50. Differential miRNA expression analysis was performed using DESeq2 software with a Benjamini-Hochberg correction. MicroRNA expression profiles were validated by Quantitative Real-Time PCR. RESULTS: A total of 109 patients were screened to participate in the study. Eleven patients with AAA and 15 non-aneurysmal controls met study criteria and were enrolled. Ultrasound measured aortic diameter was significantly larger in the AAA group (mean maximum diameter 4.3 vs 2.0 cm, P = 6.45x10-6). More AAA patients had coronary artery disease (5/11 vs 1/15, P = 0.05) as compared to controls, but the groups did not differ significantly in the rates of peripheral arterial disease and chronic obstructive pulmonary disease. A total of 40 miRNAs were differentially expressed (P<0.05). Of these, 18 miRNAs were downregulated and 22 were upregulated in the AAA group compared to controls. After false discovery rate (FDR) adjustment, only miR-122-5p was expressed at significantly different levels in the AAA group compared to controls (fold change = 5.03 controls vs AAA; raw P = 1.8x10-5; FDR P = 0.02). CONCLUSION: Plasma exosomes from AAA patients have significantly reduced levels of miRNA-122-5p compared to controls. This is a novel exosome-associated miRNA that warrants further investigation to determine its use as a diagnostic biomarker and potential implications in AAA pathogenesis.

Activation of autophagy in mesenchymal stem cells provides tumor stromal support.

Recent studies have implicated multipotential mesenchymal stem cells (MSCs) as an aid to breast cancer cell proliferation and metastasis, partly as a result of the MSCs secretome. As the tumor gets beyond 2 mm in diameter, the stromal cells could undergo starvation due to the lack of sufficient nutrients in solid tumor microenvironment. In this study, we investigated the survival mechanisms used by stressed stromal cells in breast cancers. We used serum-deprived mesenchymal stem cells (SD-MSCs) and MCF-7 breast cancer cells as model system with a hypothesis that stromal cells in the nutrient-deprived core utilize survival mechanisms for supporting surrounding cells. We tested this hypothesis using in vivo tumor xenografts in immunodeficient mice, which indicated that SD-MSCs supported MCF-7 tumor growth by protection from apoptosis. Histochemical assays showed that SD-MSCs-injected tumors exhibited higher cellularity, decreased apoptosis and decreased differentiation. Beclin-1 staining indicated autophagic areas surrounded by actively proliferating cells. Furthermore, in vitro studies demonstrate that SD-MSCs survive using autophagy and secrete paracrine factors that support tumor cells following nutrient/serum deprivation. Western blot and immunocytochemistry analysis of SD-MSCs demonstrated upregulation and perinuclear relocation of autophagy key regulators such as beclin-1, ATG10, ATG12, MAP-LC3 and lysosomes. Electron microscopic analysis detected a time-dependent increase in autophagosome formation and HDAC6 activity assays indicated the upregulation of autophagy. Taken together, these data suggest that under nutrient-deprived conditions that can occur in solid tumors, stromal cells utilize autophagy for survival and also secrete anti-apoptotic factors that can facilitate solid tumor survival and growth.

Human multipotent stromal cells from bone marrow and microRNA: regulation of differentiation and leukemia inhibitory factor expression.

We observed that microRNAs (miRNAs) that regulate differentiation in a variety of simpler systems also regulate differentiation of human multipotent stromal cells (hMSCs) from bone marrow. Differentiation of hMSCs into osteoblasts and adipocytes was inhibited by using lentiviruses expressing shRNAs to decrease expression of Dicer and Drosha, two enzymes that process early transcripts to miRNA. Expression analysis of miRNAs during hMSC differentiation identified 19 miRNAs that were up-regulated during osteogenic differentiation and 20 during adipogenic differentiation, 11 of which were commonly up-regulated in both osteogenic and adipogenic differentiation. In silico models predicted that five of the up-regulated miRNAs targeted leukemia inhibitory factor (LIF) expression. The prediction was confirmed for two of the miRNAs, hsa-mir 199a and hsa-mir346, in that over-expression of the miRNAs decreased LIF secretion by hMSCs. The results demonstrate that differentiation of hMSCs is regulated by miRNAs and that several of these miRNAs target LIF.

Contemporary outcomes after venography-guided treatment of patients with May-Thurner syndrome.

OBJECTIVE: Patients with May-Thurner syndrome (MTS) present with a spectrum of findings ranging from mild left leg edema to extensive iliofemoral deep venous thrombosis (DVT). Whereas asymptomatic left common iliac vein (LCIV) compression can be seen in a high proportion of normal individuals on axial imaging, the percentage of these persons with symptomatic compression is small, and debate exists about the optimal clinical and diagnostic criteria to treat these lesions in patients with symptomatic venous disease. We evaluated our approach to venography-guided therapy for individuals with symptomatic LCIV compression and report the outcomes. METHODS: All patients with suspected May-Thurner compression of the LCIV between 2008 and 2015 were analyzed retrospectively. Patients with chronic iliocaval lesions not associated with compression of the LCIV were excluded from analysis. Criteria for intervention included LCIV compression in the setting of (1) leg edema/venous claudication with associated venographic findings (collateralization, iliac contrast stagnation, and contralateral cross cross-filling), or (2) left leg deep venous thrombosis. Outcome measures included presenting Clinical, Etiology, Anatomy, Pathophysiology (CEAP) score, postintervention CEAP score, primary patency, and secondary patency. Technical success was defined as successful stent implantation without intraoperative device complications, establishment of in-line central venous flow, and less than 30% residual LCIV stenosis. RESULTS: Of the 63 patients evaluated, 32 (51%) had nonthrombotic MTS and presented with leg edema (100%) or venous claudication (47%). Thirty-one patients (49%) had thrombotic MTS and presented with acute (26%) or chronic (71%) DVT, leg edema (100%), or venous claudication (74%). The mean presenting CEAP score was 3.06 and 3.23 for nonthrombotic and thrombotic MTS, respectively. Forty-four patients (70%) underwent successful intervention with primary stenting (70%) or thrombolysis and stenting (30%); 14 nonthrombotic MTS patients were treated conservatively with compression therapy alone, and 5 thrombotic MTS patients were treated with lysis or angioplasty alone. Clinical improvement and decrease in CEAP score occurred in 95% and 77% of stented patients compared with 58% and 32% of nonstented patients. Complete symptom resolution was achieved in 48% of patients overall, or 64% of stented patients and only 21% of nonstented patients. Complications included two early reocclusions. Primary and secondary 2-year patency rates were 93% and 97% (mean follow-up, 20.3 months) for stented patients. CONCLUSIONS: Venography-guided treatment of MTS is associated with excellent 1-year patency rates and a significant reduction in symptoms and CEAP score. Treating symptomatic MTS patients on the basis of physiologically relevant venographic findings rather than by intravascular ultrasound imaging alone results in excellent long-term patency and clinical outcomes but may result in undertreatment of some patients who could benefit from stent implantation.

Drosha regulates hMSCs cell cycle progression through a miRNA independent mechanism.

Recently we demonstrated that the miRNA regulate human mesenchymal stem cells (hMSCs) differentiation. To determine the role of the miRNA pathway in hMSCs proliferation, Drosha and Dicer knockdown hMSCs were generated using a lentiviral based tetracycline inducible shRNA. hMSCs with reduced Drosha expression had a significantly reduced proliferation rate, while hMSCs with reduced Dicer expression displayed a proliferation rate similar to untransduced cells. Cell cycle analysis identified that unlike Dicer knockdown, Drosha knockdown hMSCs contained an increased number of G1 phase cells, with a reduced level of cells in S phase, compared to controls. ELISAs of hMSCs revealed decreased levels of pRB and stable levels of total RB with Drosha knockdown. Two key regulators of the G1/S phase transition, cyclin dependent kinase inhibitor 2A (p16) and cyclin dependent kinase inhibitor 2B (p15), were increased in Drosha knockdown cells but not in Dicer knockdown. Transcripts of 28S and 18S rRNA were significantly reduced in Drosha knockdown hMSCs, with no change in rRNA levels in Dicer knockdown hMSCs. 45S pre-rRNA transcripts were not significantly different in either knockdown model. The above results indicate that Drosha modifies hMSCs proliferation through a miRNA independent mechanism, potentially by regulating rRNA processing.

CREB phosphorylation and c-Fos expression in the hippocampus of rats during acquisition and recall of a socially transmitted food preference.

In the present study, phosphorylation of cAMP-response element binding protein (pCREB) and expression of c-Fos were measured in the dorsal and ventral hippocampus, as well as in a control region, the retrosplenial cortex, of rats following acquisition and recall of a socially transmitted food preference (STFP). Behavioral analyses revealed that STFP-trained rats showed a stronger preference for the demonstrated food than did rats in social-control or odor-control conditions. Rats in a social + odor control condition displayed an intermediate preference that was not significantly different from either STFP-trained rats or the social- or odor-controls. Immunocytochemical analyses revealed increased pCREB-immunoreactivity (ir) in the ventral hippocampus of STFP-trained rats in comparisons with rats in all three control conditions and increased pCREB-ir in the dorsal hippocampus in comparisons with the social- and odor-control conditions. In contrast, c-Fos-ir was greater in the dorsal hippocampus of STFP-trained rats in comparisons with all three control conditions and greater in the ventral hippocampus than rats in the social- and odor-control conditions. Comparisons of pCREB-ir and c-Fos-ir were made also between STFP-trained rats and social-controls following either acquisition or a 48-h recall test. c-Fos-ir was greater in STFP-trained rats after both acquisition and recall, whereas pCREB was greater after recall only. There were no differences in either c-Fos-ir or pCREB-ir in comparisons between trained and control rats in the retrosplenial cortex. The current results indicate that the activity of transcription factors in the hippocampus is related to both acquisition and retention of a socially transmitted food preference.