VEGF-delivering PEG hydrogels promote vascularization in the porcine subcutaneous space

For cell therapies, the subcutaneous space is an attractive transplant site due to its large surface area and accessibility for implantation, monitoring, biopsy, and retrieval. However, its poor vascularization has catalyzed research to induce blood vessel formation within the site to enhance cell revascularization and survival. Most studies focus on the subcutaneous space of rodents, which does not recapitulate important anatomical features and vascularization responses of humans. Herein, we evaluate biomaterial-driven vascularization in the porcine subcutaneous space. Additionally, we report the first use of cost-effective fluorescent microspheres to quantify perfusion in the porcine subcutaneous space. We investigate the vascularization-inducing efficacy of vascular endothelial growth factor (VEGF)-delivering synthetic hydrogels based on 4-arm poly(ethylene) glycol macromers with terminal maleimides (PEG-4MAL). We compare three groups: a non-degradable hydrogel with a VEGF-releasing PEG-4MAL gel coating (Core+VEGF gel); an uncoated, non-degradable hydrogel (Core-only); and naïve tissue. After 2 weeks, Core+VEGF gel has significantly higher tissue perfusion, blood vessel area, blood vessel density, and number of vessels compared to both Core-only and naïve tissue. Furthermore, healthy vital signs during surgery and post-procedure metrics demonstrate the safety of hydrogel delivery. We demonstrate that VEGF-delivering synthetic hydrogels induce robust vascularization and perfusion in the porcine subcutaneous space.

Alginate-Encapsulated Mesenchymal Stromal Cells Improve Hind Limb Ischemia in a Translational Swine Model

BACKGROUND

Cellular therapies have been investigated to improve blood flow and prevent amputation in peripheral artery disease with limited efficacy in clinical trials. Alginate-encapsulated mesenchymal stromal cells (eMSCs) demonstrated improved retention and survival and promoted vascular generation in murine hind limb ischemia through their secretome, but large animal evaluation is necessary for human applicability. We sought to determine the efficacy of eMSCs for peripheral artery disease-induced limb ischemia through assessment in our durable swine hind limb ischemia model.

METHODS AND RESULTS

Autologous bone marrow eMSCs or empty alginate capsules were intramuscularly injected 2 weeks post-hind limb ischemia establishment (N=4/group). Improvements were quantified for 4 weeks through walkway gait analysis, contrast angiography, blood pressures, fluorescent microsphere perfusion, and muscle morphology and histology. Capsules remained intact with mesenchymal stromal cells retained for 4 weeks. Adenosine-induced perfusion deficits and muscle atrophy in ischemic limbs were significantly improved by eMSCs versus empty capsules (mean±SD, 1.07±0.19 versus 0.41±0.16, P=0.002 for perfusion ratios and 2.79±0.12 versus 1.90±0.62 g/kg, P=0.029 for ischemic muscle mass). Force- and temporal-associated walkway parameters normalized (ratio, 0.63±0.35 at week 3 versus 1.02±0.19 preligation; P=0.17), and compensatory footfall patterning was diminished in eMSC-administered swine (12.58±8.46% versus 34.85±15.26%; P=0.043). Delivery of eMSCs was associated with trending benefits in collateralization, local neovascularization, and muscle fibrosis. Hypoxia-cultured porcine mesenchymal stromal cells secreted vascular endothelial growth factor and tissue inhibitor of metalloproteinase 2.

CONCLUSIONS

This study demonstrates the promise of the mesenchymal stromal cell secretome at improving peripheral artery disease outcomes and the potential for this novel swine model to serve as a component of the preclinical pipeline for advanced therapies.

Modulation of type I interferon responses potently inhibits SARS-CoV-2 replication and inflammation in rhesus macaques

Type I interferons (IFN-I) are critical mediators of innate control of viral infections but also drive the recruitment of inflammatory cells to sites of infection, a key feature of severe coronavirus disease 2019. Here, IFN-I signaling was modulated in rhesus macaques (RMs) before and during acute SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection using a mutated IFN-α2 (IFN-modulator; IFNmod), which has previously been shown to reduce the binding and signaling of endogenous IFN-I. IFNmod treatment in uninfected RMs was observed to induce a modest up-regulation of only antiviral IFN-stimulated genes (ISGs); however, in SARS-CoV-2-infected RMs, IFNmod reduced both antiviral and inflammatory ISGs. IFNmod treatment resulted in a potent reduction in SARS-CoV-2 viral loads both in vitro in Calu-3 cells and in vivo in bronchoalveolar lavage (BAL), upper airways, lung, and hilar lymph nodes of RMs. Furthermore, in SARS-CoV-2-infected RMs, IFNmod treatment potently reduced inflammatory cytokines, chemokines, and CD163+ MRC1- inflammatory macrophages in BAL and expression of Siglec-1 on circulating monocytes. In the lung, IFNmod also reduced pathogenesis and attenuated pathways of inflammasome activation and stress response during acute SARS-CoV-2 infection. Using an intervention targeting both IFN-α and IFN-β pathways, this study shows that, whereas early IFN-I restrains SARS-CoV-2 replication, uncontrolled IFN-I signaling critically contributes to SARS-CoV-2 inflammation and pathogenesis in the moderate disease model of RMs.

TREM2+ and interstitial-like macrophages orchestrate airway inflammation in SARS-CoV-2 infection in rhesus macaques

The immunopathological mechanisms driving the development of severe COVID-19 remain poorly defined. Here, we utilize a rhesus macaque model of acute SARS-CoV-2 infection to delineate perturbations in the innate immune system. SARS-CoV-2 initiates a rapid infiltration of plasmacytoid dendritic cells into the lower airway, commensurate with IFNA production, natural killer cell activation, and a significant increase of blood CD14-CD16+ monocytes. To dissect the contribution of lung myeloid subsets to airway inflammation, we generate a longitudinal scRNA-Seq dataset of airway cells, and map these subsets to corresponding populations in the human lung. SARS-CoV-2 infection elicits a rapid recruitment of two macrophage subsets: CD163+MRC1-, and TREM2+ populations that are the predominant source of inflammatory cytokines. Treatment with baricitinib (Olumiant®), a JAK1/2 inhibitor is effective in eliminating the influx of non-alveolar macrophages, with a reduction of inflammatory cytokines. This study delineates the major lung macrophage subsets driving airway inflammation during SARS-CoV-2 infection.

Chronic rheumatologic disorders and cardiovascular disease risk in women

Cardiovascular disease (CVD) is a major health threat to women worldwide. In addition to traditional CVD risk factors, autoimmune conditions are increasingly being recognized as contributors to adverse CVD consequences in women. Chronic systemic autoimmune and inflammatory disorders can trigger premature and accelerated atherosclerosis, microvascular dysfunction, and thrombosis. The presence of comorbid conditions, duration of the autoimmune condition, disease severity, and treatment of underlying inflammation are all factors that impact CVD risk and progression. Early identification and screening of CVD risk factors in those with underlying autoimmune conditions may attenuate CVD in this population. Treatment with non-steroidal anti-inflammatory drugs, corticosteroids, disease modifying agents and biologics may influence CVD risk factors and overall risk. Multi-disciplinary and team-based care, clinical trials, and collaborative team-science studies focusing on systemic autoimmune conditions will be beneficial to advance care for women.

Hydrogel delivery of purinergic enzymes improves cardiac ischemia/reperfusion injury

RATIONALE

The innate immune response contributes to cardiac injury in myocardial ischemia/reperfusion (MI/R). Neutrophils are an important early part of the innate immune response to MI/R. Adenosine, an endogenous purine, is a known innate immune modulator and inhibitor of neutrophil activation. However, its delivery to the heart is limited by its short half-life (<30 s) and off-target side effects. CD39 and CD73 are anti-inflammatory homeostatic enzymes that can generate adenosine from phosphorylated adenosine substrate such as ATP released from injured tissue.

OBJECTIVE

We hypothesize that hydrogel-delivered CD39 and CD73 target the local early innate immune response, reduce neutrophil activation, and preserve cardiac function in MI/R injury.

METHODS AND RESULTS

We engineered a poly(ethylene) glycol (PEG) hydrogel loaded with the adenosine-generating enzymes CD39 and CD73. We incubated the hydrogels with neutrophils in vitro and showed a reduction in hydrogen peroxide production using Amplex Red. We demonstrated availability of substrate for the enzymes in the myocardium in MI/R by LC/MS, and tested release kinetics from the hydrogel. On echocardiography, global longitudinal strain (GLS) was preserved in MI/R hearts treated with the loaded hydrogel. Delivery of purinergic enzymes via this synthetic hydrogel resulted in lower innate immune infiltration into the myocardium post-MI/R, decreased markers of macrophage and neutrophil activation (NETosis), and decreased leukocyte-platelet complexes in circulation.

CONCLUSIONS

In a rat model of MI/R injury, CD39 and CD73 delivered via a hydrogel preserve cardiac function by modulating the innate immune response.

Ischemia and no obstructive coronary arteries (INOCA): A narrative review

Myocardial ischemia with no obstructive coronary arteries (INOCA) is a chronic coronary syndrome condition that is increasingly being recognized as a substantial contributor to adverse cardiovascular mortality and outcomes, including myocardial infarction and heart failure with preserved ejection fraction (HFpEF). While INOCA occurs in both women and men, women are more likely to have the finding of INOCA and are more adversely impacted by angina, with recurrent hospitalizations and a lower quality of life with this condition. Abnormal epicardial coronary vascular function and coronary microvascular dysfunction (CMD) have been identified in a majority of INOCA patients on invasive coronary function testing. CMD can co-exist with obstructive epicardial coronary artery disease (CAD), diffuse non-obstructive epicardial CAD, and with coronary vasospasm. Epicardial vasospasm can also occur with normal coronary arteries that have no atherosclerotic plaque on intravascular imaging. While all predisposing factors are not clearly understood, cardiometabolic risk factors, and endothelium dependent and independent mechanisms that increase oxidative stress and inflammation are associated with microvascular injury, CMD and INOCA. Cardiac autonomic dysfunction has also been implicated in abnormal vasoreactivity and persistent symptoms. INOCA is under-recognized and under-diagnosed, partly due to the heterogenous patient populations and mechanisms. However, diagnostic testing methods are available to guide INOCA management. Treatment of INOCA is evolving, and focuses on cardiac risk factor control, improving ischemia, reducing atherosclerosis progression, and improving angina and quality of life. This review focuses on INOCA, relations to HFpEF, available diagnostics, current and investigational therapeutic strategies, and knowledge gaps in this condition.

Modulation of type I interferon responses potently inhibits SARS-CoV-2 replication and inflammation in rhesus macaques

Type-I interferons (IFN-I) are critical mediators of innate control of viral infections, but also drive recruitment of inflammatory cells to sites of infection, a key feature of severe COVID-19. Here, and for the first time, IFN-I signaling was modulated in rhesus macaques (RMs) prior to and during acute SARS-CoV-2 infection using a mutated IFNα2 (IFN-modulator; IFNmod), which has previously been shown to reduce the binding and signaling of endogenous IFN-I. In SARS-CoV-2-infected RMs, IFNmod reduced both antiviral and inflammatory ISGs. Notably, IFNmod treatment resulted in a potent reduction in (i) SARS-CoV-2 viral load in Bronchoalveolar lavage (BAL), upper airways, lung, and hilar lymph nodes; (ii) inflammatory cytokines, chemokines, and CD163+MRC1-inflammatory macrophages in BAL; and (iii) expression of Siglec-1, which enhances SARS-CoV-2 infection and predicts disease severity, on circulating monocytes. In the lung, IFNmod also reduced pathogenesis and attenuated pathways of inflammasome activation and stress response during acute SARS-CoV-2 infection. This study, using an intervention targeting both IFN-α and IFN-β pathways, shows that excessive inflammation driven by type 1 IFN critically contributes to SARS-CoV-2 pathogenesis in RMs, and demonstrates the potential of IFNmod to limit viral replication, SARS-CoV-2 induced inflammation, and COVID-19 severity.

Abstract P3069: The Impact Of Lymphatic Vasculature Post-Cardiac Transplantation On Allograft Function, Fibrotic Remodeling, And Lymphatic Drainage

Lymphatic drainage inherently modulates cardiac function by maintaining the immune response and tissue-fluid homeostasis. During cardiac transplantation, the lymphatic collecting vessels are severed at the time of donor heart excision and not surgically reconstructed in the recipient. We hypothesize severed cardiac lymphatics contribute to transplant rejection and reduced cardiac function by influencing myocardial edema and immune cell transit.

Methods: A heterotopic abdominal heart transplant (HAHT) rodent model permitted the immunologic evaluation of transplant rejection as supported in past literature. Echocardiography confirmed allograft survival via active contraction, while histologic quantification of lymphatic vessels and fibrosis were obtained for native and transplanted rodent hearts (n=3). Lymphatic drainage was assessed via intramyocardial injection of fluorescein isothiocyanate (FITC)-dextran.

Results: Electrocardiographic impulses detected during the echocardiograms revealed additional QRS complexes attributed to contractions of the transplanted hearts. Histologic analysis of fibrosis in rodent allografts at an early timepoint exhibited increases in total tissue accumulation (1.48 – 5.15 fold) and significant increases in various focal regions (left ventricle, ***p < 0.001; interventricular septum, ****p < 0.0001) compared to the native hearts. Furthermore, large amounts of cellular infiltrate and marginal increases in cardiac diameter (1.10 – 1.42 fold) were observed in the transplants. While the scarcity of immunofluorescence signal for lymphatic markers has caused cardiac lymphatic quantification to be inconclusive, evaluation of lymphatic transport revealed fluctuating time-dependent circulating FITC levels (0.002 - 0.010 mg/mL; *p < 0.05) suggesting multi-teared compartmental release properties between the microcirculatory system, lymphatic system, and cardiac tissue.

Conclusion: The HAHT rodent model provides a promising modality to assess both lymphatic transport and transplant rejection. Moreover, these studies will progress understanding of transplant rejection’s pathological intricacies and provide the groundwork for lymphangiogenic-based therapeutic intervention.

Abstract P3077: The Role Of Neutrophils In Initiating Type I Interferon Response In Myocardial Ischemia/reperfusion

Background: Inflammation succeeding myocardial ischemia/reperfusion (MI/R) plays a significant role in damaging cardiomyocytes and influencing infarct size, with neutrophils being the most rapid and most numerous cells in the post-MI/R heart. While neutrophils play a role in wound healing, they can cause further damage through the generation of reactive oxygen species, proteolytic enzymes, and neutrophil extracellular traps (NETs). We thus hypothesize that double stranded DNA stemming from these NETs activates cGAS-STING signaling in a murine model of MI/R, leading to the production of type I interferons by neutrophils, which worsens reperfusion injury.

Methods: Single-cell RNA sequencing was performed on neutrophils isolated from the hearts of mice 24 hours post-MI/R. Additionally, mice underwent MI/R and heart tissues were harvested 6- and 24- hours after reperfusion for ELISA and qPCR analysis.

Results: Utilizing single-cell RNA sequencing to better characterize the role of neutrophils and NETs in MI/R, we identified a significant population of neutrophils with a strong type I interferon (IFN) signature recruited to the area of infarct 24 hours post MI/R in a murine model. To further investigate the IFN response seen in this population of neutrophils, we preformed protein and gene expression analysis on heart tissue samples isolated from mice at timepoints in which neutrophils would be present in the area of infarct. Analysis by qPCR shows an increased fold change in gene expression of IFNα (7.22 ± 6.05, n = 3; 3.83 ± 2.22, n = 4) and IFNβ (6.74 ± 5.39, n = 3; 3.64 ± 2.25, n = 4) at 6- and 24- hours post MI/R respectively, compared to sham mice. Furthermore, analysis by ELISA shows a significant increase in IFNβ protein levels in the heart after 6- hours (0.41pg/mg ± 0.04, n =8) compared to sham mice (0.16 pg/mg ± 0.06, n = 7; p ≤ 0.01, Student’s t-test).

Conclusions: These data show a rapid increase in type I IFN in the hearts of mice post-MI/R, which implicates neutrophils may be participating in the IFN signaling pathway. Identifying neutrophils as an early source of IFN can provide a potentially new therapeutic target in treating MI/R.

Sodium alginate microencapsulation of human mesenchymal stromal cells modulates paracrine signaling response and enhances efficacy for treatment of established osteoarthritis

Mesenchymal stromal cells (MSCs) have shown promise as osteoarthritis (OA) treatments; however, effective translation has been limited by high variability and heterogeneity of MSCs, suboptimal delivery strategies, and poor understanding of critical quality and potency attributes. Furthermore, most pre-clinical studies of MSC therapeutics for OA have focused on delaying OA development and not on treating established OA, which brings added clinical relevance. Thus, the objective of the current study was to assess the effects of sodium alginate microencapsulation on human MSC (hMSC) secretion of immunomodulatory cytokines in an OA microenvironment and therapeutic efficacy in treating established OA. A Medial Meniscal Transection (MMT) pre-clinical model of OA was implemented. Three weeks post-surgery, after OA was established, intra-articular injections of encapsulated hMSCs or nonencapsulated hMSCs were administered. Six weeks post-surgery, microstructural changes in the knee joint were quantified using microCT. Encapsulated hMSCs reduced articular cartilage degeneration and subchondral bone remodeling. A multiplexed immunoassay panel was used to profile the in vitro secretome of hMSCs in response to IL-1β. Nonencapsulated hMSCs showed an indiscriminate increase in all cytokines in response to IL-1β while encapsulated hMSCs showed a targeted secretory response with increased expression of pro-inflammatory (IL-1β, IL-6, IL-7, IL-8), anti-inflammatory (IL-1RA), and chemotactic (G-CSF, MDC, IP10) cytokines. These data show that sodium alginate microencapsulation can modulate hMSC paracrine signaling and enhance the therapeutic efficacy of the hMSCs in treating established OA. This cytokine profile provides a foundation for the identification of key factors affecting the overall potency of hMSC therapeutics for OA. STATEMENT OF SIGNIFICANCE: While there has been considerable interest in material based MSC encapsulation for treatment of OA, there are critical gaps in our translational understanding of these biomaterial-based technologies for OA. More specifically, previous studies have several important limitations: (1) they have been largely focused on preventing OA development, which limits their translational utility and (2) little prior work has been done to delineate potential routes/mechanisms by which material encapsulation alters MSC therapeutic action. In our manuscript, we aimed to fill these gaps in knowledge by testing the hypotheses that: (1) hMSC encapsulation can attenuate established disease progression, which is a more clinically relevant scenario and (2) hMSC encapsulation significantly changes the secreted paracrine factors from hMSCs.

A Swine Hind Limb Ischemia Model Useful for Testing Peripheral Artery Disease Therapeutics

Currently, there is no large animal model of sustained limb ischemia suitable for testing novel angiogenic therapeutics for peripheral artery disease (PAD) such as drugs, genes, materials, or cells. We created a large animal model suitable for efficacy assessment of these therapies by testing 3 swine hind limb ischemia (HLI) variations and quantifying vascular perfusion, muscle histology, and limb function. Ligation of the ipsilateral external and bilateral internal iliac arteries produced sustained gait dysfunction compared to isolated external iliac or unilateral external and internal iliac artery ligations. Hyperemia-dependent muscle perfusion deficits, depressed limb blood pressure, arteriogenesis, muscle atrophy, and microscopic myopathy were quantifiable in ischemic limbs 6 weeks post-ligation. Porcine mesenchymal stromal cells (MSCs) engineered to express a reporter gene were visualized post-administration via positron emission tomography (PET) in vivo. These results establish a preclinical platform enabling better optimization of PAD therapies, including cellular therapeutics, increasing bench-to-bedside translational success. A preclinical platform for porcine studies of peripheral artery disease therapies including (1) a hind limb ischemia model and (2) non-invasive MSC viability and retention assessment via PET.

TREM2+ and interstitial macrophages orchestrate airway inflammation in SARS-CoV-2 infection in rhesus macaques

The COVID-19 pandemic remains a global health crisis, yet, the immunopathological mechanisms driving the development of severe disease remain poorly defined. Here, we utilize a rhesus macaque (RM) model of SARS-CoV-2 infection to delineate perturbations in the innate immune system during acute infection using an integrated systems analysis. We found that SARS-CoV-2 initiated a rapid infiltration (two days post infection) of plasmacytoid dendritic cells into the lower airway, commensurate with IFNA production, natural killer cell activation, and induction of interferon-stimulated genes. At this early interval, we also observed a significant increase of blood CD14-CD16+ monocytes. To dissect the contribution of lung myeloid subsets to airway inflammation, we generated a novel compendium of RM-specific lung macrophage gene expression using a combination of sc-RNA-Seq data and bulk RNA-Seq of purified populations under steady state conditions. Using these tools, we generated a longitudinal sc-RNA-seq dataset of airway cells in SARS-CoV-2-infected RMs. We identified that SARS-CoV-2 infection elicited a rapid recruitment of two subsets of macrophages into the airway: a C206+MRC1-population resembling murine interstitial macrophages, and a TREM2+ population consistent with CCR2+ infiltrating monocytes, into the alveolar space. These subsets were the predominant source of inflammatory cytokines, accounting for ~75% of IL6 and TNF production, and >90% of IL10 production, whereas the contribution of CD206+MRC+ alveolar macrophages was significantly lower. Treatment of SARS-CoV-2 infected RMs with baricitinib (Olumiant ^® ), a novel JAK1/2 inhibitor that recently received Emergency Use Authorization for the treatment of hospitalized COVID-19 patients, was remarkably effective in eliminating the influx of infiltrating, non-alveolar macrophages in the alveolar space, with a concomitant reduction of inflammatory cytokines. This study has delineated the major subsets of lung macrophages driving inflammatory and anti-inflammatory cytokine production within the alveolar space during SARS-CoV-2 infection.

One sentence summary

Multi-omic analyses of hyperacute SARS-CoV-2 infection in rhesus macaques identified two population of infiltrating macrophages, as the primary orchestrators of inflammation in the lower airway that can be successfully treated with baricitinib.

Regeneration of infarcted mouse hearts by cardiovascular tissue formed via the direct reprogramming of mouse fibroblasts

Fibroblasts can be directly reprogrammed into cardiomyocytes, endothelial cells or smooth muscle cells. Here we report the reprogramming of mouse tail-tip fibroblasts simultaneously into cells resembling these three cell types using the microRNA mimic miR-208b-3p, ascorbic acid and bone morphogenetic protein 4, as well as the formation of tissue-like structures formed by the directly reprogrammed cells. Implantation of the formed cardiovascular tissue into the infarcted hearts of mice led to the migration of reprogrammed cells to the injured tissue, reducing regional cardiac strain and improving cardiac function. The migrated endothelial cells and smooth muscle cells contributed to vessel formation, and the migrated cardiomyocytes, which initially displayed immature characteristics, became mature over time and formed gap junctions with host cardiomyocytes. Direct reprogramming of somatic cells to make cardiac tissue may aid the development of applications in cell therapy, disease modelling and drug discovery for cardiovascular diseases.

A Hydrogel Strategy to Augment Tissue Adenosine to Improve Hindlimb Perfusion

[Figure: see text].

Baricitinib treatment resolves lower-airway macrophage inflammation and neutrophil recruitment in SARS-CoV-2-infected rhesus macaques

SARS-CoV-2-induced hypercytokinemia and inflammation are critically associated with COVID-19 severity. Baricitinib, a clinically approved JAK1/JAK2 inhibitor, is currently being investigated in COVID-19 clinical trials. Here, we investigated the immunologic and virologic efficacy of baricitinib in a rhesus macaque model of SARS-CoV-2 infection. Viral shedding measured from nasal and throat swabs, bronchoalveolar lavages, and tissues was not reduced with baricitinib. Type I interferon (IFN) antiviral responses and SARS-CoV-2-specific T cell responses remained similar between the two groups. Animals treated with baricitinib showed reduced inflammation, decreased lung infiltration of inflammatory cells, reduced NETosis activity, and more limited lung pathology. Importantly, baricitinib-treated animals had a rapid and remarkably potent suppression of lung macrophage production of cytokines and chemokines responsible for inflammation and neutrophil recruitment. These data support a beneficial role for, and elucidate the immunological mechanisms underlying, the use of baricitinib as a frontline treatment for inflammation induced by SARS-CoV-2 infection.

Baricitinib treatment resolves lower airway inflammation and neutrophil recruitment in SARS-CoV-2-infected rhesus macaques

Effective therapeutics aimed at mitigating COVID-19 symptoms are urgently needed. SARS-CoV-2 induced hypercytokinemia and systemic inflammation are associated with disease severity. Baricitinib, a clinically approved JAK1/2 inhibitor with potent anti-inflammatory properties is currently being investigated in COVID-19 human clinical trials. Recent reports suggest that baricitinib may also have antiviral activity in limiting viral endocytosis. Here, we investigated the immunologic and virologic efficacy of baricitinib in a rhesus macaque model of SARS-CoV-2 infection. Viral shedding measured from nasal and throat swabs, bronchoalveolar lavages and tissues was not reduced with baricitinib. Type I IFN antiviral responses and SARS-CoV-2 specific T cell responses remained similar between the two groups. Importantly, however, animals treated with baricitinib showed reduced immune activation, decreased infiltration of neutrophils into the lung, reduced NETosis activity, and more limited lung pathology. Moreover, baricitinib treated animals had a rapid and remarkably potent suppression of alveolar macrophage derived production of cytokines and chemokines responsible for inflammation and neutrophil recruitment. These data support a beneficial role for, and elucidate the immunological mechanisms underlying, the use of baricitinib as a frontline treatment for severe inflammation induced by SARS-CoV-2 infection.

Minimally Invasive Delivery of Hydrogel-Encapsulated Amiodarone to the Epicardium Reduces Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Although treatment options for AF exist, many patients cannot be maintained in normal sinus rhythm. Amiodarone is an effective medication for AF but has limited clinical utility because of off-target tissue toxicity.

METHODS

Here, we use a pig model of AF to test the efficacy of an amiodarone-containing polyethylene glycol-based hydrogel. The gel is placed directly on the atrial epicardium through the pericardial space in a minimally invasive procedure using a specially designed catheter.

RESULTS

Implantation of amiodarone-containing gel significantly reduced the duration of sustained AF at 21 and 28 days; inducibility of AF was reduced 14 and 21 days post-delivery. Off-target organ drug levels in the liver, lungs, thyroid, and fat were significantly reduced in animals treated with epicardial amiodarone gel compared with systemic controls in small-animal distribution studies.

CONCLUSIONS

The pericardium is an underutilized therapeutic site and may be a new treatment strategy for AF and other cardiovascular diseases.

Abstract 146: Investigating and Inhibiting Neutrophil Extracellular Trap Formation in the Heart

Neutrophil extracellular traps (NETs) have been observed in multiple diseases of the cardiovascular system, such as myocardial infarction and atherosclerosis. We have recently shown that adenosine (ADO) inhibits NET formation and may be an important endogenous regulator. CD73 is expressed on many cell types and catalyzes the extracellular formation of ADO from AMP. Here, we first attempt to implicate NETs in cardiac injury, and we posit that human NETs negatively impact cardiac function by influencing native leukocyte recruitment and activation. Second, we prototype a CD73-functionalized hydrogel delivery vehicle for adenosine and test its function in vitro. We introduced NETs obtained from stimulated neutrophils into healthy hearts by intramyocardial injection in two-month-old rats. We used echo to assess cardiac function at days 0, 1 and 3 of injection. We measured the abundance of cardiac leukocyte subpopulations by flow cytometry at days 1 and 3 after injection, with immunostaining for CD45 (all leukocytes), myeloperoxidase (MPO, neutrophils), CD68 (macrophages), CD3 (T-cells), B220 (B-cells) and citrullinated histone 3 (citH3, NETs). To deliver adenosine as a NET antagonist, we designed a polyethylene (PEG) hydrogel composed of a 4-armed PEG incorporating a VPM protease-degradable crosslinker for cargo release, and an RGD peptide to enhance gel-tissue attachment. We tested gel polymerization by measuring storage and loss moduli at 4% and 6% PEG content (w/v) and 0, 1 uM and 1mM RGD concentrations. We functionalized the gel with CD73 to test its adenosine production capability. We found a significant decreased in cardiac function assessed by global longitudinal strain at day 1 in the NET group compared to saline. By flow cytometry, we found an increase in neutrophils, macrophages and NET formation at day 1, while B- and T-cells were increased at day 3. We found that increasing the PEG content of our hydrogel, but not RGD, increases gel stiffness. We also found that the CD73 functionalized hydrogel successfully catalyzes the formation of adenosine in vitro. In conclusion, we found that NETs negatively impact cardiac function, and successfully tested an adenosine hydrogel source in vitro. Next, we will study the effect of our gel on NETs in vivo.

Adenosine from a biologic source regulates neutrophil extracellular traps (NETs)

Neutrophil extracellular traps (NETs) are implicated in autoimmune, thrombotic, malignant, and inflammatory diseases; however, little is known of their endogenous regulation under basal conditions. Inflammatory effects of neutrophils are modulated by extracellular purines such as adenosine (ADO) that is inhibitory or ATP that generally up-regulates effector functions. In order to evaluate the effects of ADO on NETs, human neutrophils were isolated from peripheral venous blood from healthy donors and stimulated to make NETs. Treatment with ADO inhibited NET production as quantified by 2 methods: SYTOX green fluorescence and human neutrophil elastase (HNE)-DNA ELISA assay. Specific ADO receptor agonist and antagonist were tested for their effects on NET production. The ADO _2A receptor (A_2A R) agonist CSG21680 inhibited NETs to a similar degree as ADO, whereas the A_2A R antagonist ZM241385 prevented ADO's NET-inhibitory effects. Additionally, CD73 is a membrane bound ectonucleotidase expressed on mesenchymal stromal cells (MSCs) that allows manipulation of extracellular purines in tissues such as bone marrow. The effects of MSCs on NET formation were evaluated in coculture. MSCs reduced NET formation in a CD73-dependent manner. These results imply that extracellular purine balance may locally regulate NETosis and may be actively modulated by stromal cells to maintain tissue homeostasis.

Therapeutic efficacy of intra-articular delivery of encapsulated human mesenchymal stem cells on early stage osteoarthritis

Mesenchymal stem cells (MSCs) represent a great therapeutic promise in pre-clinical models of osteoarthritis (OA), but many questions remain as to their therapeutic mechanism of action: engraftment versus paracrine action. Encapsulation of human MSCs (hMSCs) in sodium alginate microspheres allowed for the paracrine signaling properties of these cells to be isolated and studied independently of direct cellular engraftment. The objective of the present study was to quantitatively assess the efficacy of encapsulated hMSCs as a disease-modifying therapeutic for OA, using a medial meniscal tear (MMT) rat model. It was hypothesized that encapsulated hMSCs would have a therapeutic effect, through paracrine-mediated action, on early OA development. Lewis rats underwent MMT surgery to induce OA. 1 d post-surgery, rats received intra-articular injections of encapsulated hMSCs or controls (i.e., saline, empty capsules, non-encapsulated hMSCs). Microstructural changes in the knee joint were quantified using equilibrium partitioning of a ionic contrast agent based micro-computed tomography (EPIC-μCT) at 3 weeks post-surgery, an established time point for early OA. Encapsulated hMSCs significantly attenuated MMT-induced increases in articular cartilage swelling and surface roughness and augmented cartilaginous and mineralized osteophyte volumes. Cellular encapsulation allowed to isolate the hMSC paracrine signaling effects and demonstrated that hMSCs could exert a chondroprotective therapeutic role on early stage OA through paracrine signaling alone. In addition to this chondroprotective role, encapsulated hMSCs augmented the compensatory increases in osteophyte formation. The latter should be taken into strong consideration as many clinical trials using MSCs for OA are currently ongoing.

Engineering Vessels as Good as New?

Blood vessels convey essential nutrients to end organs, and when diseased, they must be replaced or bypassed. Traditionally plastic and synthetic materials have been used but are susceptible to thrombosis, stenosis, and poor patency rates. A recent report in Science Translational Medicine describes a decellularized matrix grown in vitro from commercially sourced fibroblasts that can be used as a vascular graft. Fibroblasts are grown for several weeks on a fibrin scaffold, laying down a collagen layer. After decellularization and transplantation as an arteriovenous fistula, this group showed that grafts remained patent for several weeks. The lack of cellular material in this graft at the time of transplantation reduced the risk of immune rejection. The matrix laid down by the fibroblasts can serve as a scaffold for recipient cells to colonize after implantation, but also provides structural support for arterial blood flow. Other tissue-engineered grafts of decellularized matrices have recently been tested in clinical trial. For these strategies, the cell type, scaffold material, and culture conditions are key components that dictate not only the type and quality of the end product, but also allow standardization and quality control necessary for widespread translation into clinical use. These off-the-shelf decellularized products may be the first in a new generation of therapies for patients with cardiovascular disease.

Adenosine Production by Biomaterial-Supported Mesenchymal Stromal Cells Reduces the Innate Inflammatory Response in Myocardial Ischemia/Reperfusion Injury

BACKGROUND

During myocardial ischemia/reperfusion (MI/R) injury, there is extensive release of immunogenic metabolites that activate cells of the innate immune system. These include ATP and AMP, which upregulate chemotaxis, migration, and effector function of early infiltrating inflammatory cells. These cells subsequently drive further tissue devitalization. Mesenchymal stromal cells (MSCs) are a potential treatment modality for MI/R because of their powerful anti-inflammatory capabilities; however, the manner in which they regulate the acute inflammatory milieu requires further elucidation. CD73, an ecto-5'-nucleotidase, may be critical in regulating inflammation by converting pro-inflammatory AMP to anti-inflammatory adenosine. We hypothesized that MSC-mediated conversion of AMP into adenosine reduces inflammation in early MI/R, favoring a micro-environment that attenuates excessive innate immune cell activation and facilitates earlier cardiac recovery.

METHODS AND RESULTS

Adult rats were subjected to 30 minutes of MI/R injury. MSCs were encapsulated within a hydrogel vehicle and implanted onto the myocardium. A subset of MSCs were pretreated with the CD73 inhibitor, α,β-methylene adenosine diphosphate, before implantation. Using liquid chromatography/mass spectrometry, we found that MSCs increase myocardial adenosine availability following injury via CD73 activity. MSCs also reduce innate immune cell infiltration as measured by flow cytometry, and hydrogen peroxide formation as measured by Amplex Red assay. These effects were dependent on MSC-mediated CD73 activity. Finally, through echocardiography we found that CD73 activity on MSCs was critical to optimal protection of cardiac function following MI/R injury.

CONCLUSIONS

MSC-mediated conversion of AMP to adenosine by CD73 exerts a powerful anti-inflammatory effect critical for cardiac recovery following MI/R injury.

A Minimally Invasive, Translational Method to Deliver Hydrogels to the Heart Through the Pericardial Space

Biomaterials are a new treatment strategy for cardiovascular diseases but are difficult to deliver to the heart in a safe, precise, and translatable way. We developed a method to deliver hydrogels to the epicardium through the pericardial space. Our device creates a temporary compartment for hydrogel delivery and gelation using anatomic structures. The method minimizes risk to patients from embolization, thrombotic occlusion, and arrhythmia. In pigs there were no clinically relevant acute or subacute adverse effects from pericardial hydrogel delivery, making this a translatable strategy to deliver biomaterials to the heart.

Abstract 146: Adenosine Production by Biomaterial-supported Mesenchymal Stromal Cells Reduces the Innate Inflammatory Response in Myocardial Ischemia/Reperfusion Injury

Rationale: During myocardial ischemia/reperfusion (MI/R) injury there is excessive release of immunogenic metabolites that activate cells of the innate immune system. These metabolites include adenine nucleotides such as adenosine triphosphate (ATP) and adenosine monophosphate (AMP) which up-regulate chemotaxis, migration, and effector function of early infiltrating inflammatory cells. These cells subsequently drive further tissue devitalization. Mesenchymal stromal cells (MSCs) are a potential treatment modality for MI/R due to their powerful anti-inflammatory capabilities; however, the manner in which they regulate the acute inflammatory milieu requires further elucidation. Surface membrane ecto-5’-nucleotidase CD73 may play a critical role in inflammatory regulation by converting pro-inflammatory AMP to anti-inflammatory adenosine (ADO). We hypothesized that the MSC-mediated conversion of AMP into ADO reduces inflammation in early MI/R, favoring a micro-environment that attenuates excessive innate immune cell activation and facilitates earlier cardiac recovery.

Objective: To determine the contribution of MSC-mediated production of ADO in regulating the innate inflammatory response following MI/R.

Methods and Results: Adult rats were subjected to 30 minutes of MI/R injury. MSCs were encapsulated within a hydrogel vehicle and implanted onto the myocardium. A subset of MSCs were treated with the CD73 inhibitor, α,β-methylene adenosine diphosphate, prior to implantation. Using liquid chromatography/mass spectrometry, we found MSCs increase myocardial ADO availability following injury via CD73 activity. We also demonstrated that MSCs reduce innate immune cell infiltration as measured by flow cytometry and hydrogen peroxide formation as measured by Amplex Red assay. These effects were also dependent on MSC-mediated CD73 activity. Furthermore, through echocardiography we found CD73 activity on MSCs was critical to optimal protection of cardiac function following MI/R injury.

Conclusion: MSC-mediated conversion of AMP to ADO by CD73 ecto-5’-nucleotidase activity exerts a powerful anti-inflammatory effect following MI/R injury.

Pheochromocytoma Masquerading as "Diabetic Ketoacidosis"

Diabetic ketoacidosis is a routinely encountered diagnosis in medicine. Physicians are trained early on to look for precipitants. Most clinicians assess for medication compliance, infection, ischemia, and the like. We present a case of pheochromocytoma presenting as “diabetic ketoacidosis.” The case serves as an example for broadening the differential diagnosis for patients with similar presentations. Additionally, the case helps inform our understanding of the so-called “stress reactions” that are commonly invoked in clinical rationale.

Cellular encapsulation enhances cardiac repair

Background

Stem cells for cardiac repair have shown promise in preclinical trials, but lower than expected retention, viability, and efficacy. Encapsulation is one potential strategy to increase viable cell retention while facilitating paracrine effects.

Methods and Results

Human mesenchymal stem cells (hMSC) were encapsulated in alginate and attached to the heart with a hydrogel patch in a rat myocardial infarction (MI) model. Cells were tracked using bioluminescence (BLI) and cardiac function measured by transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR). Microvasculature was quantified using von Willebrand factor staining and scar measured by Masson's Trichrome. Post‐MI ejection fraction by CMR was greatly improved in encapsulated hMSC‐treated animals (MI: 34±3%, MI+Gel: 35±3%, MI+Gel+hMSC: 39±2%, MI+Gel+encapsulated hMSC: 56±1%; n=4 per group; P<0.01). Data represent mean±SEM. By TTE, encapsulated hMSC‐treated animals had improved fractional shortening. Longitudinal BLI showed greatest hMSC retention when the cells were encapsulated (P<0.05). Scar size at 28 days was significantly reduced in encapsulated hMSC‐treated animals (MI: 12±1%, n=8; MI+Gel: 14±2%, n=7; MI+Gel+hMSC: 14±1%, n=7; MI+Gel+encapsulated hMSC: 7±1%, n=6; P<0.05). There was a large increase in microvascular density in the peri‐infarct area (MI: 121±10, n=7; MI+Gel: 153±26, n=5; MI+Gel+hMSC: 198±18, n=7; MI+Gel+encapsulated hMSC: 828±56 vessels/mm², n=6; P<0.01).

Conclusions

Alginate encapsulation improved retention of hMSCs and facilitated paracrine effects such as increased peri‐infarct microvasculature and decreased scar. Encapsulation of MSCs improved cardiac function post‐MI and represents a new, translatable strategy for optimization of regenerative therapies for cardiovascular diseases.

Alginate microencapsulation of human mesenchymal stem cells as a strategy to enhance paracrine-mediated vascular recovery after hindlimb ischaemia

Stem cell-based therapies hold great promise as a clinically viable approach for vascular regeneration. Preclinical studies have been very encouraging and early clinical trials have suggested favourable outcomes. However, significant challenges remain in terms of optimizing cell retention and maintenance of the paracrine effects of implanted cells. To address these issues, we have proposed the use of a cellular encapsulation approach to enhance vascular regeneration. We contained human mesenchymal stem cells (hMSCs) in biocompatible alginate microcapsules for therapeutic treatment in the setting of murine hindlimb ischaemia. This approach supported the paracrine pro-angiogenic activity of hMSCs, prevented incorporation of hMSCs into the host tissue and markedly enhanced their therapeutic effect. While injection of non-encapsulated hMSCs resulted in a 22 ± 10% increase in vascular density and no increase in perfusion, treatment with encapsulated hMSCs resulted in a 70 ± 8% increase in vascular density and 21 ± 7% increase in perfusion. The described cellular encapsulation strategy may help to better define the mechanisms responsible for the beneficial effects of cell-based therapies and provide a therapeutic strategy for inducing vascular growth in the adult. As hMSCs are relatively easy to isolate from patients, and alginate is biocompatible and already used in clinical applications, therapeutic cell encapsulation for vascular repair represents a highly translatable platform for cell-based therapy in humans.

Abstract P039: Encapsulation of Human Mesenchymal Stem Cells in Alginate Microspheres to Enhance Paracrine-Mediated Vascular Recovery

Bone marrow cells migrate to ischemic areas and facilitate revascularization mostly through paracrine mechanisms. As a result, therapeutic strategies for vascular repair have focused on increasing the concentration of these cells at the site of ischemia by direct injection. These strategies have led to encouraging results in clinical trials, yet the number of cells that remain at the site of delivery is very low.

The goal of this study is to design an effective cell delivery system to enhance revascularization by maintaining large numbers of cells at the ischemic site, thus increasing the local delivery of angiogenic factors. To achieve this goal, we encapsulated bone marrow derived human mesenchymal stem cells (hMSCs) in non-degradable, barium-gelled alginate spheres prior to delivery to the ischemic site. Our microspheres are biocompatible, do not generate a fibrotic response, and are stable for extended periods of time. They prevent incorporation of cells into the neighboring tissue and protect implanted cells from immune mediated clearance or wash out by the host capillary and lymphatic systems. The microspheres allow diffusion of molecules as large as 80 kDa (which includes most angiogenic factors) but not of larger molecules such as IgG. To test this cell delivery system in vivo, we used a model of murine hind limb ischemia in athymic nude mice. We delivered encapsulated hMSCs, or, as a control, empty capsules, to the ischemic muscle. At various time points, we retrieved the capsules by gentle scooping, then assessed the viability of the encapsulated cells and their protein secretion profile. Approximately 70% of the cells remained viable within the first week and 10-20% within the first month after implantation. In addition, encapsulated cells secreted angiogenic factors (VEGF, bFGF, HGF, angiogenin) in vitro and in vivo. We also assessed recovery of perfusion in the hind limb and found that delivery of encapsulated cells enhanced vascular recovery as compared to empty capsules.

The results obtained from this study show that microcapsules are an effective delivery vehicle of therapeutic cells for vascular repair. Encapsulation represents a powerful and highly translatable tool to enhance cell-based therapies in cardiovascular disease.

Computational protein design to reengineer stromal cell-derived factor-1α generates an effective and translatable angiogenic polypeptide analog

BACKGROUND

Experimentally, exogenous administration of recombinant stromal cell-derived factor-1α (SDF) enhances neovasculogenesis and cardiac function after myocardial infarction. Smaller analogs of SDF may provide translational advantages including enhanced stability and function, ease of synthesis, lower cost, and potential modulated delivery via engineered biomaterials. In this study, computational protein design was used to create a more efficient evolution of the native SDF protein.

METHODS AND RESULTS

Protein structure modeling was used to engineer an SDF polypeptide analog (engineered SDF analog [ESA]) that splices the N-terminus (activation and binding) and C-terminus (extracellular stabilization) with a diproline segment designed to limit the conformational flexibility of the peptide backbone and retain the relative orientation of these segments observed in the native structure of SDF. Endothelial progenitor cells (EPCs) in ESA gradient, assayed by Boyden chamber, showed significantly increased migration compared with both SDF and control gradients. EPC receptor activation was evaluated by quantification of phosphorylated AKT, and cells treated with ESA yielded significantly greater phosphorylated AKT levels than SDF and control cells. Angiogenic growth factor assays revealed a distinct increase in angiopoietin-1 expression in the ESA- and SDF-treated hearts. In addition, CD-1 mice (n=30) underwent ligation of the left anterior descending coronary artery and peri-infarct intramyocardial injection of ESA, SDF-1α, or saline. At 2 weeks, echocardiography demonstrated a significant gain in ejection fraction, cardiac output, stroke volume, and fractional area change in mice treated with ESA compared with controls.

CONCLUSIONS

Compared with native SDF, a novel engineered SDF polypeptide analog (ESA) more efficiently induces EPC migration and improves post-myocardial infarction cardiac function and thus offers a more clinically translatable neovasculogenic therapy.

A clinical commentary on the article "N-acetylglucosamine conjugated to nanoparticles enhances myocyte uptake and improves delivery of a small molecule p38 inhibitor for post-infarct healing" : N-acetylglucosamine conjugated nanoparticles: translational opportunities and barriers

Targeting drugs and nanoparticles to cardiomyocytes has been an elusive challenge. Cardiomyocytes are inherently non-phagocytic and their environment is subjected to contractile forces which tend to expel injected and catheter-delivered drugs. In this issue, a novel-targeting strategy, N-acetyl-glucosamine (GlcNAc) coating, is shown to enhance cardiomyocyte nanoparticle uptake both in vitro and in vivo. Many effective and proven therapies for myocardial infarction are in clinical use thus raising the bar for the translation of new technologies. Nevertheless, GlcNAc targeting represents a promising approach for improved targeting of drug therapies to cardiomyocytes.

Cardiovascular disease in young women: a population at risk

Ischemic heart disease (IHD) is a leading cause of morbidity in the United States and worldwide. In women, it is the leading cause of death in all age groups except young women who rarely have clinically evident disease. However, when young women less than age 50 develop IHD, they are at high risk for mortality. This may be due in part to delay in diagnosis or less aggressive treatment. Young women may be less aggressively treated with medical therapies and percutaneous or surgical interventions despite studies that have shown benefit in women as well as men. Young women are an especially important population to target for treatment and study since prevention of IHD during this stage of life can have great personal and societal health consequences. Epidemiological studies, including the INTERHEART study, have identified risk factors including hypertension, diabetes, metabolic syndrome, smoking, and sedentary lifestyle that explain much of IHD in women. Several factors, including diabetes, metabolic syndrome, and tobacco use, are stronger predictors of IHD in young women as compared with older women. Healthcare practitioners who encounter young women should aggressively treat risk factors, maintain an appropriate index of suspicion for IHD, and treat acute coronary syndromes promptly and intensively to reduce the burden of IHD in young women.

Oxygen-dependent quenching of phosphorescence used to characterize improved myocardial oxygenation resulting from vasculogenic cytokine therapy

This study evaluates a therapy for infarct modulation and acute myocardial rescue and utilizes a novel technique to measure local myocardial oxygenation in vivo. Bone marrow-derived endothelial progenitor cells (EPCs) were targeted to the heart with peri-infarct intramyocardial injection of the potent EPC chemokine stromal cell-derived factor 1α (SDF). Myocardial oxygen pressure was assessed using a noninvasive, real-time optical technique for measuring oxygen pressures within microvasculature based on the oxygen-dependent quenching of the phosphorescence of Oxyphor G3. Myocardial infarction was induced in male Wistar rats (n = 15) through left anterior descending coronary artery ligation. At the time of infarction, animals were randomized into two groups: saline control (n = 8) and treatment with SDF (n = 7). After 48 h, the animals underwent repeat thoracotomy and 20 μl of the phosphor Oxyphor G3 was injected into three areas (peri-infarct myocardium, myocardial scar, and remote left hindlimb muscle). Measurements of the oxygen distribution within the tissue were then made in vivo by applying the end of a light guide to the beating heart. Compared with controls, animals in the SDF group exhibited a significantly decreased percentage of hypoxic (defined as oxygen pressure ≤ 15.0 Torr) peri-infarct myocardium (9.7 ± 6.7% vs. 21.8 ± 11.9%, P = 0.017). The peak oxygen pressures in the peri-infarct region of the animals in the SDF group were significantly higher than the saline controls (39.5 ± 36.7 vs. 9.2 ± 8.6 Torr, P = 0.02). This strategy for targeting EPCs to vulnerable peri-infarct myocardium via the potent chemokine SDF-1α significantly decreased the degree of hypoxia in peri-infarct myocardium as measured in vivo by phosphorescence quenching. This effect could potentially mitigate the vicious cycle of myocyte death, myocardial fibrosis, progressive ventricular dilatation, and eventual heart failure seen after acute myocardial infarction.

Acute myocardial rescue with endogenous endothelial progenitor cell therapy

PURPOSE

Post-myocardial infarction heart failure is a major health concern with limited therapy. Molecular revascularisation utilising granulocyte-macrophage colony stimulating factor (GMCSF) mediated endothelial progenitor cell (EPC) upregulation and stromal cell derived factor-1α (SDF) mediated myocardial EPC chemokinesis, may prevent myocardial loss and adverse remodelling. Vasculogenesis, viability, and haemodynamic improvements following therapy were investigated.

PROCEDURES

Lewis rats (n=91) underwent LAD ligation and received either intramyocardial SDF and subcutaneous GMCSF or saline injections at the time of infarction. Molecular and haemodynamic assessments were performed at pre-determined time points following ligation.

FINDINGS

SDF/GMCSF therapy upregulated EPC density as shown by flow cytometry (0.12±0.02% vs. 0.06±0.01% circulating lymphocytes, p=0.005), 48hours following infarction. A marked increase in perfusion was evident eight weeks after therapy, utilising confocal angiography (5.02±1.7×10(-2)μm(3)blood/μm(3)myocardial tissue vs. 2.03±0.710(-2)μm(3)blood/μm(3)myocardial tissue, p=0.00004). Planimetric analysis demonstrated preservation of wall thickness (0.98±0.09mm vs. 0.67±0.06mm, p=0.003) and ventricular diameter (7.81±0.99mm vs. 9.41±1.1mm, p=0.03). Improved haemodynamic function was evidenced by echocardiography and PV analysis (ejection fraction: 56.4±18.1% vs. 25.3±15.6%, p=0.001; pre-load adjusted maximal power: 6.6±2.6mW/μl(2) vs. 2.7±1.4mW/μl(2), p=0.01).

CONCLUSION

Neovasculogenic therapy with GMCSF-mediated EPC upregulation and SDF-mediated EPC chemokinesis maybe an effective therapy for infarct modulation and preservation of myocardial function following acute myocardial infarction.

Asymptomatic central venous stenosis in hemodialysis patients

PURPOSE

To retrospectively evaluate the natural history of high-grade (>50%) asymptomatic central venous stenosis (CVS) in hemodialysis patients and the outcome of serial treatment of CVS with percutaneous transluminal angioplasty (PTA).

MATERIALS AND METHODS

The institutional review board granted exemption for this retrospective study, the need for informed consent was waived, and all data collection was in compliance with HIPAA. Patients with hemodialysis access requiring maintenance procedures between 1998 and 2004 and incidentally found to have ipsilateral (> or =50%) CVS were identified from a departmental database. Thirty-five patients (19 men, 16 women; mean age, 58.7 years) with 38 grafts met inclusion criteria, and 86 venograms were reviewed. CVS was measured by using venograms obtained before and after PTA, if performed. Patients with arm swelling, multiple CVS, indwelling catheters, and stents at the first encounter were excluded. CVS progression was calculated by dividing the change in the degree of stenosis by the time between venographic examinations. Wilcoxon rank sum test was used to evaluate differences in rate of CVS progression between treated and nontreated patients.

RESULTS

Mean degree of CVS before intervention was 71% (range, 50%-100%). Sixty-two percent (53 of 86) of lesions had associated collateral vessels; 28% (24 of 86) of CVSs were not treated. Mean degree of stenosis in this group was 72% (range, 30%-100%); mean progression was -0.08 percentage point per day. No untreated CVS progressed to symptoms, stent placement, or additional CVS. Seventy-two percent (62 of 86) of CVSs were treated with PTA. Mean degree of stenosis in this group was 74% (range, 50%-100%) before and 40% (range, 0%-75%) after treatment; mean progression was 0.21 percentage point per day after treatment (P = .03). Six (8%) of 62 treatments were followed by CVS escalation; one patient developed arm swelling, four required stents, and four developed additional CVS.

CONCLUSION

PTA of asymptomatic CVS greater than 50% in the setting of hemodialysis access maintenance procedures was associated with more rapid stenosis progression and escalation of lesions, compared with a nontreatment approach.