Left Internal Mammary Artery as an Endocrine Organ: Insights Into Graft Biology and Long-term Impact Following Coronary Artery Bypass Grafting.

The left internal mammary artery (LIMA) is considered the criterion standard vessel for use in coronary artery bypass grafting. In recent decades, countless studies have documented its superiority over other arterial and venous coronary artery bypass grafting conduits, although the full mechanisms for this superiority remain unknown. A growing body of literature has unveiled the importance of extracellular vesicles known as exosomes in cardiovascular signaling and various pathologic states. In this review, we briefly compare the clinical longevity of the LIMA relative to other conduits, explore the effects of varying grafting techniques on clinical and angiographic outcomes, and provide physiologic insights into graft function on a cellular and molecular level. Finally, we explore exosome signaling as it pertains to atherosclerosis in support of the LIMA as an "endocrine organ."

Exosome-Induced Vaginal Tissue Regeneration in a Porcine Mesh Exposure Model.

OBJECTIVES: The purpose of this study was to explore the utility of an injectable purified exosome product derived from human apheresis blood to (1) augment surgical closure of vaginal mesh exposures, and (2) serve as a stand-alone therapy for vaginal mesh exposure. METHODS: Sixteen polypropylene meshes (1×1-3×3 cm) were implanted in the vaginas of 7 Yorkshire-crossed pigs by urogynecologic surgeons (day 0). On day 7, group 1 underwent surgical intervention via vaginal tissue suture reclosure with (n=2 pigs, n=4 meshes) or without (n=2 pigs, n=4 meshes) exosome injection; group 2 underwent medical intervention with an exosome injection (n=3, n=8 meshes). One animal in group 2 was given oral 2'-deoxy-5-ethynyluridine to track cellular regeneration. Euthansia occurred at 5 weeks. RESULTS: Mesh exposures treated with surgical closure alone experienced reexposure of the mesh. Exosome treatment with or without surgical closure resulted in partial to full mesh exposure resolution up to 3×3 cm. Exosome-treated tissues had significantly thicker regenerated epithelial tissue (208 µm exosomes-only and 217 µm surgery+exosomes, versus 80 µm for surgery-only; P < 0.05); evaluation of 2'-deoxy-5-ethynyluridine confirmed de novo regeneration throughout the epithelium and underlying tissues. Capillary density was significantly higher in the surgery+exosomes group (P = 0.03). Surgery-only tissues had a higher inflammatory and fibrosis response as compared with exosome-treated tissues. CONCLUSIONS: In this pilot study, exosome treatment augmented healing in the setting of vaginal mesh exposure, reducing the incidence of mesh reexposure after suture closure and decreasing the area of mesh exposure through de novo tissue regeneration after exosome injection only. Further study of varied local tissue conditions and mesh configurations is warranted.

Percutaneous Axillary Intra-aortic Balloon Pump Insertion Technique as Bridge to Advanced Heart Failure Therapy.

In patients with advanced heart failure (HF), temporary mechanical circulator support (TMCS) is used to improve hemodynamics, via left ventricular unloading, and end-organ function as a bridge to definitive therapy. While listed for cardiac transplantation, use of TMCS may be prolonged, preventing adequate mobility. Here, we describe the technique for placement of a percutaneous axillary intra-aortic balloon pump (IABP) using single-site arterial access to facilitate ambulation and subsequent safe removal without surgery or a closure device. Retrospective review of the experience with this approach at a single institution between September 2017 and February 2020 documented feasibility and safety. Baseline demographics, hemodynamic data, and clinical outcomes were collected. Thirty-eight patients had a total of 56 IABPs placed. There were no significant access site or cerebrovascular complications. One fifth of IABPs (21.4%) had balloon failure or migration, requiring placement of a new device, though no patients had significant complications from balloon failure. The majority (81.6%) of patients in the cohort on axillary IABP support were ambulatory and ultimately received the intended therapy (63.2% transplant, 13.2% durable left ventricular assist device, 5.3% other cardiac surgery). Percutaneous, axillary IABP is feasible and associated with an acceptable complication rate as a bridge to definitive therapy.

Impact of Repeat Dosing and Mesh Exposure Chronicity on Exosome-Induced Vaginal Tissue Regeneration in a Porcine Mesh Exposure Model.

OBJECTIVE: The aim of the study was to compare vaginal wound healing after exosome injection in a porcine mesh exposure model with (1) single versus multiple dose regimens and (2) acute versus subacute exposure. METHODS: Six 80-kg Yorkshire-crossed swine each had 2 polypropylene meshes implanted to create the vaginal mesh exposure model. Animals were divided into 3 groups based on number and timing of exosome injection: (1) single purified exosome product (PEP) injection (acute-single), (2) weekly PEP injections (acute-weekly, 4 total injections), and (3) delayed single injection (subacute-single). Acute and subacute injections occurred 1 and 8 weeks after mesh implantation, respectively. EdU, a thymidine analog, was given twice weekly after the first injection to track tissue regeneration. Euthanasia and tissue analysis occurred 4 weeks after the first injection. ImageJ was used to quantify epithelial thickness, cellular proliferation, and capillary density. Statistical analysis was performed using analysis of variance and post hoc Tukey test. RESULTS: Acute-single PEP injection tissues mirrored pilot study results, validating replication of protocol. Within the acute groups, weekly dosing resulted in 1.5× higher epithelial thickness (nonsignificant), 1.8× higher epithelial proliferation (P < 0.05), and 1.5× higher regenerated capillary density (P < 0.05) compared with single injection. Regarding chronicity of the exposure, the subacute group showed 1.7× higher epithelial proliferation (nonsignificant) and similar capillary density and epithelial thickness as compared with the acute group. CONCLUSIONS: Exosome redosing resulted in significantly greater epithelial proliferation with significantly higher regenerated capillary density, leading to a trend toward thicker epithelium. Subacute exposure exhibited similar regeneration to acute exposure despite a delayed injection timeline. These results contribute to a growing body of preclinical research demonstrating utility of exosomes in pelvic floor disorders.

Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells.

Cardiac cell therapies involving bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promising results, although their mechanisms of action are still poorly understood. Here, we investigated direct interactions between hMSCs and cardiomyocytes in vitro. Using a genetic Ca(2+) indicator gCaMP3 to efficiently label hMSCs in co-cultures with neonatal rat ventricular myocytes (NRVMs), we determined that 25-40% of hMSCs (from 4 independent donors) acquired periodic Ca(2+) transients and cardiac markers through spontaneous fusion with NRVMs. Sharp electrode and voltage-clamp recordings in fused cells showed action potential properties and Ca(2+) current amplitudes in between those of non-fused hMSCs and NRVMs. Time-lapse video-microscopy revealed the first direct evidence of active fusion between hMSCs and NRVMs within several hours of co-culture. Application of blebbistatin, nifedipine or verapamil caused complete and reversible inhibition of fusion, suggesting potential roles for actomyosin bridging and Ca(2+) channels in the fusion process. Immunostaining for Cx43, Ki67, and sarcomeric α-actinin showed that fused cells remain strongly coupled to surrounding NRVMs, but downregulate sarcomeric structures over time, acquiring a non-proliferative and non-contractile phenotype. Overall, these results describe the phenotype and mechanisms of hybrid cell formation via fusion of hMSCs and cardiomyocytes with potential implications for cardiac cell therapy.