A CD31-Derived Peptide Prevents the Development of Antibody-Mediated Lesions in a Rat Model of Aortic Allograft.

BACKGROUND: Antibody-mediated rejection (AMR) is a major cause of graft loss. The development of donor-specific antibodies (DSAs) directed against the allogeneic HLA molecules expressed by the graft also leads to accelerated arteriosclerosis. CD31 is a protein expressed on endothelial and immune cells, ensuring homeostasis at this interface. When strong immune stimulation occurs, the regulatory function of CD31 is lost owing to cleavage of its extracellular portion. P8RI, a synthetic peptide that binds to the ectodomain of CD31, is able to restore the CD31 immunomodulatory function. In this study, we hypothesized that CD31 could represent an attractive molecular target in AMR and investigated whether P8RI could prevent the development of vascular antibody-mediated lesions. MATERIALS AND METHODS: A rat model of orthotopic aortic allograft was used, and P8RI was administered for 28 days. Circulating DSAs were quantified to assess the alloimmune humoral response, and histologic and immunohistochemical analyses of aortic allografts were performed to estimate antibody-mediated lesions in the allograft. RESULTS: Aorta-allografted rats receiving P8RI developed fewer DSAs than control animals (mean fluorescence intensity 344 vs 741). The density of nuclei in the media (3.4 x 10-5 vs 2.2 x 10-5 nuclei/px2) and media surface area (2.33 x 106 vs 2.02 x 106 px2) were higher in animals treated with P8RI than in control animals. CONCLUSIONS: These data support a therapeutic potential for molecules able to restore the CD31 signaling to fight AMR. P8RI, an agonist synthetic peptide targeting CD31, might prevent DSA production and have a beneficial effect in limiting arterial antibody-mediated lesions. CD31 agonists may become therapeutic tools to prevent and treat solid organ transplant arteriosclerosis.

Comparison of the linking arm effect on the biological performance of a CD31 agonist directly grafted on L605 CoCr alloy by a plasma-based multistep strategy.

Stents are cardiovascular implants deployed on atherosclerotic arteries that aid in reopening, sustaining, and avoiding their collapse. Nevertheless, postimplantation complications exist, and the risk of the renewal of the plaque subsists. Therefore, enhanced properties are mandatory requirements for clinics. For that purpose, a novel approach allowing the direct-grafting of bioactive molecules on cobalt-chromium devices (L605) has been developed. This original strategy involves the direct plasma functionalization of metallic surfaces with primary amines (-NH2). These groups act as anchor points to covalently graft biomolecules of interest, herein a peptide derived from CD31 (P23) with proendothelialization and antithrombotic properties. However, the biological activity of the grafted peptide could be impacted by its conformation. For this study, glutaric anhydride (GA), a short chain spacer, and polyethylene glycol (PEG) with antifouling properties were used as linking arms (LAs). The covalent grafting of the CD31 agonist on L605 by different LAs (GA-P23 and PEG-P23) was confirmed by XPS and ToF-SIMS analyses. The biological performance of these functionalized surfaces showed that, compared to the electropolished (EP) alloy, grafting the P23 with both LA increases adhesion and proliferation of endothelial cells (ECs) since day 1: EP = 68 ± 10%, GA-P23 = 101 ± 7%, and PEG-P23 = 106 ± 5% of cell viability. Moreover, ECs formed a complete monolayer at the surface, preventing clot formation (hemoglobin-free >80%). The potential of this plasma-based strategy for cardiovascular applications was confirmed by promoting a fast re-endothelialization, by improving the hemocompatibility of the alloy when coupled with the CD31 agonist and by its transfer onto commercial L605 stents, as confirmed by ToF-SIMS.

Macrophage CD31 Signaling in Dissecting Aortic Aneurysm.

BACKGROUND: The authors recently found that a CD31 agonist peptide reaches macrophages in injured aortas and exerts beneficial effects on apolipoprotein E-knockout (Apo E-/-) mice subjected to angiotensin (Ang) II infusion, a model of experimental acute aortic dissection and intramural hematoma (ADIM). OBJECTIVES: The purpose of this study was to evaluate the therapeutic potential of a drug-suitable agonist peptide in experimental ADIM. METHODS: P8RI, a retro-inverso sequence of the best candidate identified by functional in vitro screening of a peptide library, passed an absorption, distribution, metabolism, excretion and toxicology analysis. Apo E-/- mice (male, 28-week-old) implanted with Ang II-releasing pumps received P8RI (2.5 mg/kg/day) or vehicle from day 14 (n = 10/group). Leukocytes were analyzed by flow cytometry. Healing features of human and mouse dissected aortic segments were assessed by histology and immunofluorescence. The effect of CD31 on macrophages was evaluated using cells from CD31-/- mice and P8RI, in vitro. RESULTS: Human and experimental ADIM were characterized by the infiltration of proinflammatory macrophages. The absence of CD31 enhanced the proinflammatory polarization of macrophages, whereas the CD31 agonist P8RI favored reparative macrophages both in vitro and in vivo. The administration of P8RI after the occurrence of ADIM prevented aneurysmal transformation by promoting the resolution of intramural hematoma and the production of collagen in dissected aortas in vivo, associated with enrichment of M2 macrophages at the site of injury. CONCLUSIONS: CD31 signaling promotes the switching of proinflammatory macrophages to the reparative phenotype and favors the healing of experimental dissected aortas. Treatment with a drug-suitable CD31 agonist may facilitate the clinical management of ADIM.

MiR-497∼195 cluster regulates angiogenesis during coupling with osteogenesis by maintaining endothelial Notch and HIF-1α activity.

A specific bone vessel subtype, strongly positive for CD31 and endomucin (CD31hiEmcnhi), is identified as coupling angiogenesis and osteogenesis. The abundance of type CD31hiEmcnhi vessels decrease during ageing. Here we show that expression of the miR-497∼195 cluster is high in CD31hiEmcnhi endothelium but gradually decreases during ageing. Mice with depletion of miR-497∼195 in endothelial cells show fewer CD31hiEmcnhi vessels and lower bone mass. Conversely, transgenic overexpression of miR-497∼195 in murine endothelium alleviates age-related reduction of type CD31hiEmcnhi vessels and bone loss. miR-497∼195 cluster maintains the endothelial Notch activity and HIF-1α stability via targeting F-box and WD-40 domain protein (Fbxw7) and Prolyl 4-hydroxylase possessing a transmembrane domain (P4HTM) respectively. Notably, endothelialium-specific activation of miR-195 by intravenous injection of aptamer-agomiR-195 stimulates CD31hiEmcnhi vessel and bone formation in aged mice. Together, our study indicates that miR-497∼195 regulates angiogenesis coupled with osteogenesis and may represent a potential therapeutic target for age-related osteoporosis.