RNA‐binding proteins like human antigen R (HuR) are key regulators in post‐transcriptional control of gene expression in several pathophysiological conditions. Diabetes adversely affects monocyte/macrophage biology and function. It is not known whether diabetic milieu affects cellular/exosome‐HuR and its implications on cardiac inflammation and fibrosis. Here, we evaluate in vitro and in vivo effects of diabetic milieu on macrophage cellular/exosome‐HuR, alterations in intercellular cross talk with fibroblasts, and its impact on cardiac remodeling. Human failing hearts show higher HuR levels. Diabetic milieu activates HuR expression in cardiac‐ and cultured bone marrow‐derived macrophages (BMMØ) and stimulates HuR nuclear‐to‐cytoplasmic translocation and exosome transfer. Exosomes from macrophages exposed to diabetic milieu (high glucose or db/db mice) significantly increase inflammatory and profibrogenic responses in fibroblast (in vitro) and cardiac fibrosis in mice. Intriguingly, Exo‐HuR deficiency (HuR knockdown in macrophage) abrogates the above effects. In diabetic mice, macrophage depletion followed by reconstitution with BMMØ‐derived HuR‐deficient exosomes inhibits angiotensin II‐induced cardiac fibrosis response and preserves left ventricle function as compared to control‐exosome administration. To the best of our knowledge, this is the first study to demonstrate that diabetes activates BMMØ HuR expression and its transfer into exosome. The data suggest that HuR might be targeted to alleviate macrophage dysfunction and pathological fibrosis in diabetes.

No abstract

Rationale: After myocardial ischemic injury, improper phagocytic clearance of dying cardiac cells and the ensuing lack of inflammation resolution results in adverse cardiac remodeling and dysfunction that might lead to heart failure. Therefore, therapeutic strategies to ameliorate immune cell phagocytic function is critical for augmenting cardiac repair after injury. Objective: To determine if mesenchymal stem cell-derived exosomes (MSC-Exo) act as opsonin for apoptotic cells and/or trigger "eat me" phagocytic signaling in resident/recruited phagocytes after myocardial ischemic injury. Methods and Results: We evaluated MSC-Exo-mediated opsonization of apoptotic cardiomyocytes; and invitro and invivo effects of milk fat globule- epidermal growth factor-factor VIII (MFGE8)-deficient mouse MSC-Exo on macrophage engulfment of apoptotic cardiomyocytes and its implications on cardiac remodeling, repair and function. Microscopy and FACS analyses show that opsonization of apoptotic cardiomyocytes with MSC-Exo enhances their engulfment by macrophages. Furthermore, pre-incubation of macrophages with MSC-Exo reprogrammed the signaling pathways involved in phagocytosis and expression of pro-reparative cytokines. Protein analysis of MSC-Exo reveals expression of MFGE8, a glycoprotein which bridges externalized phosphatidylserine (PS) on the apoptotic cell surface to alphaVbeta3 or alphaVbeta5 integrins on the phagocyte. Most intriguingly, siRNA inhibition of MFGE8 significantly reduced the MSC-Exo-mediated augmentation of dead cell engulfment, associated signaling and pro-reparative phenotype. After myocardial ischemic injury, intramyocardial administration of MSC-Exo increases macrophage uptake of apoptotic bodies in the border zone of infarct and is associated with reduced proinflammatory response, increase in neovascularization, lower infarct size and an improvement in cardiac function and MFGE8-deficient MSC-Exo administration failed to protect mice against MI. Conclusions: Our data demonstrates that exosome-associated MFGE8 on one hand enhances opsonization of dead cells and on the other activates phagocytic signaling thus augmenting removal of apoptotic cells, resolution of inflammation and therefore efficient cardiac recovery after injury.

No abstract

No abstract

Traumatic peripheral nerve injury (TPNI) represents a major medical problem that results in loss of motor and sensory function, and in severe cases, limb paralysis and amputation. To date, there are no effective treatments beyond surgery in selective cases. In repurposing studies, we found that daily systemic administration of the FDA-approved drug 4aminopyridine (4-AP) enhanced functional recovery after acute peripheral nerve injury. This study was aimed at constructing a novel local delivery system of 4-AP using thermogelling polymers. We optimized a thermosensitive (4-AP)−poly(lactide-co-glycolide)−b-poly(ethylene glycol)−b-poly(lactide-co-glycolide) (PLGA−PEG−PLGA) block copolymer formulation. (4-AP)− PLGA−PEG exhibited controlled release of 4-AP both in vitro and in vivo for approximately 3 weeks, with clinically relevant safe serum levels in animals. Rheological investigation showed that (4-AP)−PLGA−PEG underwent a solution to gel transition at 32 °C, a physiologically relevant temperature, allowing us to administer it to an injured limb while subsequently forming an in situ gel. A single local administration of (4-AP)−PLGA−PEG remarkably enhanced motor and sensory functional recovery on post-sciatic nerve crush injury days 1, 3, 7, 14, and 21. Moreover, immunohistochemical studies of injured nerves treated with (4-AP)-PLGA-PEG demonstrated an increased expression of neurofilament heavy chain (NF-H) and myelin protein zero (MPZ) proteins, two major markers of nerve regeneration. These findings demonstrate that (4-AP)−PLGA−PEG may be a promising long-acting local therapeutic agent in TPNI, for which no pharmacologic treatment exists.

No abstract

No abstract