Background

Despite improved health outcomes associated with arteriovenous fistulas, 80% of Americans initiate hemodialysis using a catheter, influenced by low socioeconomic status among other factors. Risk factors for incident catheter use in safety-net populations are unknown. Our objective was to identify factors associated with incident catheter use among hemodialysis patients at one safety-net hospital, with a goal of informing fistula placement initiatives targeted at safety-net populations more generally.

Methods

We performed a retrospective review of all incident hemodialysis patients at a single urban safety-net hospital from January 1, 2010 - December 31, 2015 (n = 241), as well as semi-structured interviews with a multi-lingual convenience sample of patients (n = 10) from this cohort. The primary outcome was incident vascular access modality. Multivariable logistic regression was used to identify factors associated with incident catheter use. Interview transcripts were coded using a directed content analysis framework based on a model describing barriers to healthcare access.

Results

Subjects were 61.8% male, racially/ethnically diverse (19.5% white, 29.5% black, 28.6% Hispanic, 17.4% Asian), with a mean age of 52.4 years. Eighty-eight percent initiated hemodialysis using a catheter. In multivariable analysis, longer duration of nephrology care was associated with decreased catheter use (>12 months vs. 0-6 months: adjusted Odds Ratio [aOR] 0.07, 95% CI 0.02-0.23, p < 0.001), whereas uninsured status increased odds of catheter use (aOR 3.96, 1.23-12.76, p = 0.02). There was a decrease in catheter use after vascular surgery services became available in-hospital (OR 0.40, 95% CI 0.16-0.98, p = 0.04), however this association was not significant in multivariable analysis (aOR 0.48, 0.17-1.36, p = 0.17). During interviews, patients cited emotional responses to disease, lack of social and financial resources, and limited health knowledge as barriers to obtaining fistula surgery.

Conclusions

The rate of catheter use in this urban safety-net population is above the national average. Access to health insurance, early referrals to nephrology, and provision of in-hospital vascular surgery should be prioritized in the safety-net. Additionally, services that support patients' emotional and learning needs may decrease delays in fistula placement.

Diffusion-based bioartificial pancreas (BAP) devices are limited by poor islet viability and functionality due to inadequate mass transfer resulting in islet hypoxia and delayed glucose-insulin kinetics. While intravascular ultrafiltration-based BAP devices possess enhanced glucose-insulin kinetics, the polymer membranes used in these devices provide inadequate ultrafiltrate flow rates and result in excessive thrombosis. Here, we report the silicon nanopore membrane (SNM), which exhibits a greater hydraulic permeability and a superior pore size selectivity compared to polymer membranes for use in BAP applications. Specifically, we demonstrate that the SNM-based intravascular BAP with ∼10 and ∼40 nm pore sized membranes support high islet viability (>60%) and functionality (<15 minute insulin response to glucose stimulation) at clinically relevant islet densities (5700 and 11 400 IE per cm²) under convection in vitro. In vivo studies with ∼10 nm pore sized SNM in a porcine model showed high islet viability (>85%) at clinically relevant islet density (5700 IE per cm²), c-peptide concentration of 144 pM in the outflow ultrafiltrate, and hemocompatibility under convection. These promising findings offer insights on the development of next generation of full-scale intravascular devices to treat T1D patients in the future.

Correction for 'An intravascular bioartificial pancreas device (iBAP) with silicon nanopore membranes (SNM) for islet encapsulation under convective mass transport' by Shang Song et al., Lab Chip, 2017, 17, 1778-1792.

Objective

Antegrade femoral artery access is often used for ipsilateral infrainguinal peripheral vascular intervention. However, the use of closure devices (CD) for antegrade access (AA) is still considered outside the instructions for use for most devices. We hypothesized that CD use for antegrade femoral access would not be associated with an increased odds of access site complications.

Methods

The Vascular Quality Initiative was queried from 2010 to 2019 for infrainguinal peripheral vascular interventions performed via femoral AA. Patients who had a cutdown or multiple access sites were excluded. Cases were then stratified into whether a CD was used or not. Hierarchical multivariable logistic regressions controlling for hospital-level variation were used to examine the independent association between CD use and access site complications. A sensitivity analysis using coarsened exact matching was performed using factors different between treatment groups to reduce imbalance between the groups.

Results

Overall, 11,562 cases were identified and 5693 (49.2%) used a CD. Patients treated with a CD were less likely to be white (74.1% vs 75.2%), have coronary artery disease (29.7% vs 33.4%), use aspirin (68.7% vs 72.4%), and have heparin reversal with protamine (15.5% vs 25.6%; all P < .05). CD patients were more likely to be obese (31.6% vs 27.0%), have an elective operation (82.6% vs 80.1%), ultrasound-guided access (75.5% vs 60.6%), and a larger access sheath (6.0 ± 1.0 F vs 5.5 ± 1.0 F; P < .05 for all). CD cases were less likely to develop any access site hematoma (2.55% vs 3.53%; P < .01) or a hematoma requiring reintervention (0.63% vs 1.26%; P < .01) and had no difference in access site stenosis or occlusion (0.30% vs 0.22%; P = .47) compared with no CD. On multivariable analysis, CD cases had significantly decreased odds of developing any access site hematoma (odds ratio, 0.75; 95% confidence interval, 0.59-0.95) and a hematoma requiring intervention (odds ratio, 0.56; 95% confidence interval, 0.38-0.81). A sensitivity analysis after coarsened exact matching confirmed these findings.

Conclusions

In this nationally representative sample, CD use for AA was associated with a lower odds of hematoma in selected patients. Extending the instructions for use indications for CDs to include femoral AA may decrease the incidence of access site complications, patient exposure to reintervention, and costs to the health care system.

Clinical islet transplantation for treatment of type 1 diabetes (T1D) is limited by the shortage of pancreas donors and need for lifelong immunosuppressive therapy. A convection-driven intravascular bioartificial pancreas (iBAP) based on highly permeable, yet immunologically protective, silicon nanopore membranes (SNM) holds promise to sustain islet function without the need for immunosuppressants. Here, we investigate short-term functionality of encapsulated human islets in an iBAP prototype. Using the finite element method (FEM), we calculated predicted oxygen profiles within islet scaffolds at normalized perifusion rates of 14-200 nl/min/IEQ. The modeling showed the need for minimum in vitro and in vivo islet perifusion rates of 28 and 100 nl/min/IEQ, respectively to support metabolic insulin production requirements in the iBAP. In vitro glucose-stimulated insulin secretion (GSIS) profiles revealed a first-phase response time of <15 min and comparable insulin production rates to standard perifusion systems (~10 pg/min/IEQ) for perifusion rates of 100-200 nl/min/IEQ. An intravenous glucose tolerance test (IVGTT), performed at a perifusion rate of 100-170 nl/min/IEQ in a non-diabetic pig, demonstrated a clinically relevant C-peptide production rate (1.0-2.8 pg/min/IEQ) with a response time of <5 min.

With the aggressive resource conservation necessary to face the coronavirus disease 2019 pandemic, vascular surgeons have faced unique challenges in managing the health of their high-risk patients. An early analysis of patient outcomes after pandemic-related practice changes suggested that patients with chronic limb threatening ischemia have been presenting with more severe foot infections and are more likely to require major limb amputation compared with 6 months previously. As our society and health care system adapt to the new changes required in the post-coronavirus disease 2019 era, it is critical that we pay special attention to the most vulnerable subsets of patients with vascular disease, particularly those with chronic limb threatening ischemia and limited access to care.

Objectives

HIV and hepatitis C virus (HCV) have been associated with cardiovascular disease (CVD), but it is unclear whether HIV and HCV are also associated with peripheral artery disease (PAD). We examined the association of HIV, HCV, and traditional CVD risk factors with PAD in the Women's Interagency HIV Study, a multicenter US cohort.

Methods

In this cross-sectional study, ankle-brachial index was estimated using Doppler ultrasound and manual sphygmomanometer in 1899 participants aged more than 40 years with HIV/HCV coinfection, HCV or HIV monoinfection, or neither infection. Multivariable logistic regression was used to estimate the odds of PAD (ankle-brachial index ≤0.9) after controlling for demographic, behavioral, and CVD risk factors.

Results

Over two-thirds were African-American, median age was 50 years, and PAD prevalence was 7.7% with little difference by infection status. After multivariable adjustment, neither HIV nor HCV infection was associated with greater odds of PAD. Factors associated with PAD included older age [adjusted odds ratio (aOR): 2.01 for age 61-70 vs. 40-50 years; 95% confidence interval (CI): 1.04, 3.87], Black race (aOR: 2.30; 95% CI: 1.15, 4.63), smoking (aOR: 1.27 per 10-pack-year increment; 95% CI: 1.09, 1.48), and higher SBP (aOR: 1.14 per 10 mmHg; 95% CI: 1.01, 1.28).

Conclusion

The high PAD prevalence in this nationally representative cohort of women with or at risk for HIV is on par with general population studies in individuals a decade older than our study's median age. HIV and HCV infection are not associated with greater PAD risk relative to uninfected women with similar risk factors. Modifiable traditional CVD risk factors may be important early intervention targets in women with and at risk for HIV.

Reliable models of renal failure in large animals are critical to the successful translation of the next generation of renal replacement therapies (RRT) into humans. While models exist for the induction of renal failure, none are optimized for the implantation of devices to the retroperitoneal vasculature. We successfully piloted an embolization-to-implantation protocol enabling the first implant of a silicon nanopore membrane hemodialyzer (SNMHD) in a swine renal failure model. Renal arterial embolization is a non-invasive approach to near-total nephrectomy that preserves retroperitoneal anatomy for device implants. Silicon nanopore membranes (SNM) are efficient blood-compatible membranes that enable novel approaches to RRT. Yucatan minipigs underwent staged bilateral renal arterial embolization to induce renal failure, managed by intermittent hemodialysis. A small-scale arteriovenous SNMHD prototype was implanted into the retroperitoneum. Dialysate catheters were tunneled externally for connection to a dialysate recirculation pump. SNMHD clearance was determined by intermittent sampling of recirculating dialysate. Creatinine and urea clearance through the SNMHD were 76-105 mL/min/m² and 140-165 mL/min/m², respectively, without albumin leakage. Normalized creatinine and urea clearance measured in the SNMHD may translate to a fully implantable clinical-scale device. This pilot study establishes a path toward therapeutic testing of the clinical-scale SNMHD and other implantable RRT devices.

The definitive treatment for end-stage renal disease is kidney transplantation, which remains limited by organ availability and post-transplant complications. Alternatively, an implantable bioartificial kidney could address both problems while enhancing the quality and length of patient life. An implantable bioartificial kidney requires a bioreactor containing renal cells to replicate key native cell functions, such as water and solute reabsorption, and metabolic and endocrinologic functions. Here, we report a proof-of-concept implantable bioreactor containing silicon nanopore membranes to offer a level of immunoprotection to human renal epithelial cells. After implantation into pigs without systemic anticoagulation or immunosuppression therapy for 7 days, we show that cells maintain >90% viability and functionality, with normal or elevated transporter gene expression and vitamin D activation. Despite implantation into a xenograft model, we find that cells exhibit minimal damage, and recipient cytokine levels are not suggestive of hyperacute rejection. These initial data confirm the potential feasibility of an implantable bioreactor for renal cell therapy utilizing silicon nanopore membranes.

Background

Th17 cells are permissive to HIV-1 infection and their depletion from the gut of infected individuals leads to microbial translocation, a major cause for non-AIDS co-morbidities. Most recent evidence supports the contribution of long-lived Th17 cells to HIV persistence during antiretroviral therapy (ART). However, the identity of long-lived Th17 cells remains unknown.

Results

Here, we performed an in-depth transcriptional and functional characterization of four distinct Th17 subsets and investigated their contribution to HIV reservoir persistence during ART. In addition to the previously characterized CCR6(+)CCR4(+) (Th17) and CCR6(+)CXCR3(+) (Th1Th17) subsets, we reveal the existence of two novel CCR6(+) subsets, lacking (double negative, CCR6(+)DN) or co-expressing CXCR3 and CCR4 (double positive, CCR6(+)DP). The four subsets shared multiple Th17-polarization markers, a fraction of cells proliferated in response to C. albicans, and exhibited lineage commitment and plasticity when cultured under Th17 and Th1 conditions, respectively. Of note, fractions of CCR6(+)DN and Th17 demonstrated stable Th17-lineage commitment under Th1-polarization conditions. Among the four subsets, CCR6(+)DN expressed a unique transcriptional signature indicative of early Th17 development (IL-17F, STAT3), lymph-node homing (CCR7, CD62L), follicular help (CXCR5, BCL6, ASCL2), and self-renewal (LEFI, MYC, TERC). Cross sectional and longitudinal studies demonstrated that CCR6(+)DN cells were the most predominant CCR6(+) subset in the blood before and after ART initiation; high frequencies of these cells were similarly observed in inguinal lymph nodes of individuals receiving long-term ART. Importantly, replication competent HIV was isolated from CCR6(+)DN of ART-treated individuals.

Conclusions

Together, these results provide new insights into the functional heterogeneity of Th17-polarized CCR6(+)CD4(+) T-cells and support the major contribution of CCR6(+)DN cells to HIV persistence during ART.