The 106b∼25 microRNA cluster is essential for neovascularization after hindlimb ischaemia in mice.

AIMS: MicroRNAs (miRNAs, miR) are endogenous short RNA sequences that regulate a wide range of physiological and pathophysiological processes. Several miRNAs control the formation of new blood vessels either by increasing or by inhibiting angiogenesis. Here, we investigated the possible role of the miR-106b∼25 cluster in postnatal neovascularization and in regulation of the angiogenic properties of adult bone marrow-derived stromal cells. METHODS AND RESULTS: To study the effect of miR-106b∼25 deletion on neovascularization, we used a miR-106b∼25 knockout (KO) mouse model. After inducing hindlimb ischaemia, we showed that vascularization in ischaemic mice devoid of miR-106b∼25 is impaired, as evident from the reduced blood flow on laser Doppler perfusion imaging. The miR-106b∼25 cluster was also shown here to be an essential player in the proper functioning of bone marrow-derived stromal cells through its regulation of apoptosis, matrigel tube formation capacity, cytokine secretion, and expression of the stem-cell marker Sca-1. In addition, we showed that capillary sprouting from miR-106b∼25 KO aortic rings is diminished. CONCLUSION: These results show that the miR-106b∼25 cluster regulates post-ischaemic neovascularization in mice, and that it does so in part by regulating the function of angiogenic bone marrow-derived stromal cells and of endothelial cells.

Accelerated renal fibrosis in cardiorenal syndrome is associated with long-term increase in urine neutrophil gelatinase-associated lipocalin levels.

BACKGROUND: Cardiac events are the main cause of death among patients with end-stage renal failure. Even a mild renal disease is currently considered a major risk factor for cardiovascular complications following myocardial infarction (MI). The aim of the present study was to detect histological, sera and urine characteristics of kidney injury in cardiorenal syndrome (CRS) compared to chronic kidney disease (CKD) with an intact cardiac function. METHODS: We employed a rat model for CRS, in which an acute MI (AMI) was induced 4 weeks after establishment of subtotal nephrectomy. Four weeks later, left ventricular function was assessed by echocardiography and changes in renal performance were examined using histological and biochemical parameters. RESULTS: Increased interstitial fibrosis as well as renal inflammation were observed in renal sections derived from CRS rats, compared to subtotal nephrectomy (CKD)-only animals. Moreover, we found that even though AMI on the background of CKD was not associated with a further decrease in creatinine clearance or a further increase in sera BUN levels compared to CKD only, a significant long-term elevation in urine neutrophil gelatinase-associated lipocalin (Ngal) levels was detectable post-MI induction. CONCLUSIONS: AMI in the CKD setting is associated with accelerated renal fibrosis and long-term elevated urine Ngal values, suggesting that cardiac dysfunction contributes to accelerated intrinsic kidney injury in CKD. The data indicate that elevated urine Ngal may potentially serve as an early non-invasive laboratory parameter for a left ventricular dysfunction-related renal injury.

Regulatory T cells influence blood flow recovery in experimental hindlimb ischaemia in an IL-10-dependent manner.

AIMS: Ischaemic damage is associated with up-regulation of pro-inflammatory cytokines, as well as invasion of leucocytes and lymphocytes to the injured muscle. Regulatory T cells (Tregs) exert suppressive effects on several immune and non-immune cellular elements. We hypothesized that adoptive Treg cell transfer and depletion will influence re-establishment of flow in the hindlimb ischaemia model, and that this effect would be mediated by the cytokine interleukin (IL)-10. METHODS AND RESULTS: To study the functional role of Tregs in hindlimb ischaemia, we either adoptively transferred Tregs or functionally blocked Tregs by antibodies to CD25. Initially, we showed that the number and function of Tregs is altered after the induction of ischaemia. Treg ablation resulted in reduced blood flow by laser Doppler at Day 7 that became more robust at Day 14. Adoptive Treg transfer led to a significant improvement of flow in the ligated limb. Treg-mediated improvement in flow was abolished by employing blocking anti-IL-10 antibodies. CONCLUSIONS: These results show that Tregs play an important role in processes that control flow re-establishment after inducible hindlimb ischaemia, and that IL-10 plays a requisite role mediating these effects.

Experimental myocardial infarction induces altered regulatory T cell hemostasis, and adoptive transfer attenuates subsequent remodeling.

BACKGROUND: Ischemic cardiac damage is associated with upregulation of cardiac pro-inflammatory cytokines, as well as invasion of lymphocytes into the heart. Regulatory T cells (Tregs) are known to exert a suppressive effect on several immune cell types. We sought to determine whether the Treg pool is influenced by myocardial damage and whether Tregs transfer and deletion affect cardiac remodeling. METHODS AND RESULTS: The number and functional suppressive activity of Tregs were assayed in mice subjected to experimental myocardial infarction. The numbers of splenocyte-derived Tregs in the ischemic mice were significantly higher after the injury than in the controls, and their suppressive properties were significantly compromised. Compared with PBS, adoptive Treg transfer to mice with experimental infarction reduced infarct size and improved LV remodeling and functional performance by echocardiography. Treg deletion with blocking anti-CD25 antibodies did not influence infarct size or echocardiographic features of cardiac remodeling. CONCLUSION: Treg numbers are increased whereas their function is compromised in mice with that underwent experimental infarction. Transfer of exogeneous Tregs results in attenuation of myocardial remodeling whereas their ablation has no effect. Thus, Tregs may serve as interesting potential interventional targets for attenuating left ventricular remodeling.