Background: Cell therapy remains the most promising approach against ischemic heart injury. However, the poor survival of engrafted stem cells in the ischemic environment limits their therapeutic efficacy for cardiac repair after myocardial infarction. CTRP9 (C1q/tumor necrosis factor–related protein-9) is a novel prosurvival cardiokine with significantly downregulated expression after myocardial infarction. Here we tested a hypothesis that CTRP9 might be a cardiokine required for a healthy microenvironment promoting implanted stem cell survival and cardioprotection. Methods: Mice were subjected to myocardial infarction and treated with adipose-derived mesenchymal stem cells (ADSCs, intramyocardial transplantation), CTRP9, or their combination. Survival, cardiac remodeling and function, cardiomyocytes apoptosis, and ADSCs engraftment were evaluated. Whether CTRP9 directly regulates ADSCs function was determined in vitro. Discovery-drive approaches followed by cause-effect analysis were used to uncover the molecular mechanisms of CTRP9. Results: Administration of ADSCs alone failed to exert significant cardioprotection. However, administration of ADSCs in addition to CTRP9 further enhanced the cardioprotective effect of CTRP9 ( P <0.05 or P <0.01 versus CTRP9 alone), suggesting a synergistic effect. Administration of CTRP9 at a dose recovering physiological CTRP9 levels significantly prolonged ADSCs retention/survival after implantation. Conversely, the number of engrafted ADSCs was significantly reduced in the CTRP9 knockout heart. In vitro study demonstrated that CTRP9 promoted ADSCs proliferation and migration, and it protected ADSCs against hydrogen peroxide–induced cellular death. CTRP9 enhances ADSCs proliferation/migration by extracellular regulated protein kinases (ERK)1/2–matrix metallopeptidase 9 signaling and promotes antiapoptotic/cell survival via ERK–nuclear factor erythroid-derived 2—like 2/antioxidative protein expression. N-cadherin was identified as a novel CTRP9 receptor mediating ADSCs signaling. Blockade of either N-cadherin or ERK1/2 completely abolished the previously noted CTRP9 effects. Although CTRP9 failed to promote ADSCs cardiogenic differentiation, CTRP9 promotes superoxide dismutase 3 expression and secretion from ADSCs, protecting cardiomyocytes against oxidative stress-induced cell death. Conclusions: We provide the first evidence that CTRP9 promotes ADSCs proliferation/survival, stimulates ADSCs migration, and attenuates cardiomyocyte cell death by previously unrecognized signaling mechanisms. These include binding with N-cadherin, activation of ERK-matrix metallopeptidase 9 and ERK-nuclear factor erythroid-derived 2—like 2 signaling, and upregulation/secretion of antioxidative proteins. These results suggest that CTRP9 is a cardiokine critical in maintaining a healthy microenvironment facilitating stem cell engraftment in infarcted myocardial tissue, thereby enhancing stem cell therapeutic efficacy.

Diabetic retinopathy (DR) is a severe complication of chronic diabetes. The C1q/TNF-related protein family (CTRPs) has been demonstrated to exert protective effects against obesity and atherosclerosis in animal studies. Heretofore, the association between circulating CTRPs and DR patients has been unexplored. In the current study, we attempt to define this association, as well as the effect of CTRPs upon DR pathophysiology. The present investigation is a case control study that enrolled control subjects and type 2 diabetes mellitus (T2DM) patients diagnosed with DR. Serum CTRPs and sVACM-1 were determined by ELISA. Serum CTRP3 and CTRP5 levels were markedly decreased in patients with T2DM compared to controls (p<0.05) and inversely associated with T2DM. Furthermore, mutivariate regression and ROC analysis revealed CTRP3 deficiency, not CTRP5, was associated with proliferative diabetic retinopathy (PDR). Spearman’s rank correlation assay demonstrated an inverse association between CTRP3 and sVCAM-1. Finally, exogenous CTRP3 administration attenuated high glucose high lipid (HGHL)-induced VCAM-1 production in an AMPK-dependent manner in cultured human retinal microvascular endothelial cells (HRMECs). CTRP3 may serve as a novel biomarker for DR severity. CTRP3 may represent a future novel therapeutic against DR, a common ocular complication of diabetes.

Background The impairment of the inner blood–retinal barrier (iBRB) increases the pathological development of diabetic retinopathy (DR), a severe complication in diabetic patients. Identifying approaches to preserving iBRB integrity and function is a significant challenge in DR. C1q/tumor necrosis factor-related protein-3 (CTRP3) is a newly discovered adipokine and a vital biomarker, predicting DR severity. We sought to determine whether and how CTRP3 affects the pathological development of non-proliferative diabetic retinopathy (NPDR). Methods To clarify the pathophysiologic progress of the blood–retinal barrier in NPDR and explore its potential mechanism, a mouse Type 2 diabetic model of diabetic retinopathy was used. The capillary leakage was assessed by confocal microscope with fluorescent-labeled protein in vivo. Furthermore, the effect of CTRP3 on the inner blood–retinal barrier (iBRB) and its molecular mechanism was clarified. Results The results demonstrated that CTRP3 protects iBRB integrity and resists the vascular permeability induced by DR. Mechanistically, the administration of CTRP3 activates the AMPK signaling pathway and enhances the expression of Occludin and Claudin-5 (tight junction protein) in vivo and in vitro. Meanwhile, CTRP3 improves the injury of human retinal endothelial cells (HRMECs) induced by high glucose/high lipids (HG/HL), and its protective effects are AMPK-dependent. Conclusions In summary, we report, for the first time, that CTRP3 prevents diabetes-induced retinal vascular permeability via stabilizing the tight junctions of the iBRB and through the AMPK-dependent Occludin/Claudin-5 signaling pathway, thus critically affecting the development of NPDR.

Background: Retinal ischemia-reperfusion (I/R) injury often results in intractable visual impairments. The survival of retinal capillary endothelial cells is crucial for the treatment of retinal I/R injury. How to protect retinal endothelia from damage is a challenging work. Withaferin A, a small molecule derived from plants, has antibacterial and anti-inflammatory effects and has been used for about millennia in traditional medicine. The present study aimed to investigate the potential protective effect of withaferin A on retinal I/R injury. Methods: The drug-likeness of withaferin A was evaluated by the SwissADME web tool. The potential protective effect of withaferin A on the I/R-induced injury of human retinal microvascular endothelial cells (HRMECs) was investigated using multiple approaches. RNA sequencing was performed and associated mechanistic signaling pathways were analyzed based on the Kyoto Encyclopedia of Genes and Genomes data. The analytical results of RNA sequencing data were further validated by in vitro and in vivo experiments. Results: Withaferin A reduced the I/R injury-induced apoptotic death of HRMECs in vitro with a good drug-like property. RNA sequencing and experimental validation results indicated that withaferin A increased the production of the crucial antioxidant molecules heme oxygenase 1 (HO-1) and peroxiredoxin 1 (Prdx-1) during I/R. In addition, withaferin A activated the Akt signaling pathway and increased the expression of HO-1 and Prdx-1, thereby exerting an antioxidant effect, attenuated the retinal I/R injury, and decreased the apoptosis of HRMECs. The blockade of Akt completely abolished the effects of withaferin A. Conclusions: The study identified for the first time that withaferin A can protect against the I/R-induced apoptosis of human microvascular retinal endothelial cells via increasing the production of the antioxidants Prdx-1 and HO-1. Results suggest that withaferin A is a promising drug candidate for the treatment of retinal I/R injury.