Ghrelin, MicroRNAs, and Critical Limb Ischemia: Hungering for a Novel Treatment Option

Pro-angiogenic approach for skeletal muscle regeneration

The angiogenesis process is a phenomenon in which numerous molecules participate in the stimulation of the new vessels' formation from pre-existing vessels. Angiogenesis is a crucial step in tissue regeneration and recovery of organ and tissue function. Muscle diseases affect millions of people worldwide overcome the ability of skeletal muscle to self-repair. Pro-angiogenic therapies are key in skeletal muscle regeneration where both myogenesis and angiogenesis occur. These therapies have been based on mesenchymal stem cells (MSCs), exosomes, microRNAs (miRs) and delivery of biological factors. The use of different calls of biomaterials is another approach, including ceramics, composites, and polymers. Natural polymers are use due its bioactivity and biocompatibility in addition to its use as scaffolds and in drug delivery systems. One of these polymers is the natural rubber latex (NRL) which is biocompatible, bioactive, versatile, low-costing, and capable of promoting tissue regeneration and angiogenesis. In this review, the advances in the field of pro-angiogenic therapies are discussed.

Cell Therapy for Critical Limb Ischemia: Advantages, Limitations, and New Perspectives for Treatment of Patients with Critical Diabetic Vasculopathy

PURPOSE OF REVIEW

To provide a highlight of the current state of cell therapy for the treatment of critical limb ischemia in patients with diabetes.

RECENT FINDINGS

The global incidence of diabetes is constantly growing with consequent challenges for healthcare systems worldwide. In the UK only, NHS costs attributed to diabetic complications, such as peripheral vascular disease, amputation, blindness, renal failure, and stroke, average £10 billion each year, with cost pressure being estimated to get worse. Although giant leaps forward have been registered in the scope of early diagnosis and optimal glycaemic control, an effective treatment for critical limb ischemia is still lacking. The present review aims to provide an update of the ongoing work in the field of regenerative medicine. Recent advancements but also limitations imposed by diabetes on the potential of the approach are addressed. In particular, the review focuses on the perturbation of non-coding RNA networks in progenitor cells and the possibility of using emerging knowledge on molecular mechanisms to design refined protocols for personalized therapy. The field of cell therapy showed rapid progress but has limitations. Significant advances are foreseen in the upcoming years thanks to a better understanding of molecular bottlenecks associated with the metabolic disorders.

Thrombospondin-4 (TSP4) gene-modified bone marrow stromal cells (BMSCs) promote the effect of therapeutic angiogenesis in critical limb ischemia (CLI) of diabetic rats

Critical limb ischemia (CLI) is the leading cause of lower limb amputation. Traditional treatments for CLI have limitations. Studies have shown that thrombospondin-4 (TSP4) can promote the growth of neovascularization. In this study, we observed the angiogenesis efficiency of TSP4-overexpressing BMSC transplantation in CLI treatment. The recombinant FT106-tsp4-gfp lentiviral vector plasmid was constructed and transfected into 293FT cells. Primary BMSCs were successfully infected with the tsp4 virus, and TSP4 overexpression was confirmed before TSP4-BMSCs infusion. A rat CLI model was established, and 60 CLI rats were randomly divided into the CLI, BMSC + CLI and TSP4-BMSC + CLI groups. The effect of TSP4-BMSC on angiogenesis was detected by the motor function, immunohistochemistry and immunofluorescence staining assays. Neovascular density was detected by digital subtraction angiography (DSA). Our results demonstrated that TSP4-BMSCs improved the motor function score of the CLI rats and increased MMP2, MMP9, Ang-1, VEGF and vWF protein expression in tissue of the ischaemic area. Meanwhile, new blood vessels can be observed around the ischemic area after TSP4-BMSCs treatment. Our data illustrate that TSP4-BMSCs can promote the recovery of motor function in diabetic hind limb ischaemic rats. TSP4-BMSCs have better therapeutic effects than BMSCs.

Dysregulation of ghrelin in diabetes impairs the vascular reparative response to hindlimb ischemia in a mouse model; clinical relevance to peripheral artery disease

Type 2 diabetes is a prominent risk factor for peripheral artery disease (PAD). Yet, the mechanistic link between diabetes and PAD remains unclear. This study proposes that dysregulation of the endogenous hormone ghrelin, a potent modulator of vascular function, underpins the causal link between diabetes and PAD. Moreover, this study aimed to demonstrate the therapeutic potential of exogenous ghrelin in a diabetic mouse model of PAD. Standard ELISA analysis was used to quantify and compare circulating levels of ghrelin between (i) human diabetic patients with or without PAD (clinic) and (ii) db/db diabetic and non-diabetic mice (lab). Db/db mice underwent unilateral hindlimb ischaemia (HLI) for 14 days and treated with or without exogenous ghrelin (150 µg/kg/day.) Subsequently vascular reparation, angiogenesis, hindlimb perfusion, structure and function were assessed using laser Doppler imaging, micro-CT, microangiography, and protein and micro-RNA (miRNA) analysis. We further examined hindlimb perfusion recovery of ghrelin KO mice to determine whether an impaired vascular response to HLI is linked to ghrelin dysregulation in diabetes. Patients with PAD, with or without diabetes, had significantly lower circulating levels of endogenous ghrelin, compared to healthy individuals. Diabetic db/db mice had ghrelin levels that were only 7% of non-diabetic mice. The vascular reparative capacity of diabetic db/db mice in response to HLI was impaired compared to non-diabetic mice and, importantly, comparable to ghrelin KO mice. Daily therapeutic treatment of db/db mice with ghrelin for 14 days post HLI, stimulated angiogenesis, and improved skeletal muscle architecture and cell survival, which was associated with an increase in pro-angiogenic miRNAs-126 and -132. These findings unmask an important role for endogenous ghrelin in vascular repair following limb ischemia, which appears to be downregulated in diabetic patients. Moreover, these results implicate exogenous ghrelin as a potential novel therapy to enhance perfusion in patients with lower limb PAD, especially in diabetics.

[Ghrelin deficiency in patients with type 2 diabetes: the relationships with obesity, adipose tissue dysfunction and glucose variability]

AIM

Ghrelin, a peptide hormone mostly produced by stomach, plays an important role in regulation of feeding behavior, energy balance and glucose homeostasis.

THE AIM

to determine the relationships between fasting serum levels of ghrelin, body composition, adipose tissue endocrine function and glucose variability (GV) in type 2 diabetic subjects with and without obesity.

MATERIALS AND METHODS

We observed 124 individuals with type 2 diabetes, including 42 non - obese subjects and 82 patients with obesity. Thirty non - obese healthy subjects were acted as control. The concentrations of ghrelin, leptin, resistin, and visfatin in the fasting serum were determined by Multiplex analysis. Body composition was assessed with DEXA. The 24-hour and nocturnal GV parameters were derived from continuous glucose monitoring.

RESULTS AND DISCUSSION

Ghrelin levels in patients with diabetes were decreased significantly as compared to control (p.

Ghrelin and vascular protection

Ghrelin is a small peptide with important roles in the regulation of appetite, gut motility, glucose homeostasis as well as cardiovascular protection. This review highlights the role that acyl ghrelin plays in maintaining normal endothelial function by maintaining the balance of vasodilator-vasoconstrictor factors, inhibiting inflammatory cytokine production and immune cell recruitment to sites of vascular injury and by promoting angiogenesis.

Alagebrium targets the miR-27b/TSP-1 signaling pathway to rescue Nε-carboxymethyl-lysine-induced endothelial dysfunction

N^ε-carboxymethyl-lysine (CML), a major isoform of advanced glycation end products (AGEs), plays a crucial role in the functional damage of diabetes mellitus. However, it is not clear whether ALT-711 (alagebrium), an inhibitor of AGEs, is capable to rescue CML-induced poor angiogenesis, as well as the underlying mechanism. MicroRNA-27b (miR-27b) promotes angiogenesis through down-regulation of anti-angiogenic protein thrombospondin-1 (TSP-1). Here, we used diabetic mice with hindlimb ischemia to investigate whether miR-27b/TSP-1 signaling is involved in the pathology of critical limb ischemia (CLI) in diabetes mellitus. We additionally examined the effect of ALT-711 on the tube formation of endothelial cells treated with CML-BSA. Compared with control group, the lower blood flow recovery was observed in the ischemic lower limbs of diabetic mice, with decreased expression of vascular endothelial growth factor (VEGF) and miR-27b and increased TSP-1 expression. CML-BSA reduced the tube formation ability of endothelial cells, decreased VEGF and miR-27b expression, and increased TSP-1 expression, whereas this trend was reversed by ALT-711. The miR-27b mimic promoted tube formation, increased VEGF expression, and decreased TSP-1 expression, whereas these effects were abolished by TSP-1 overexpression. Moreover, miR-27b silencing suppressed ALT-711-induced promotion of tube formation under CML-BSA treatment, with reduced VEGF and augmented TSP-1 expression. Taken together, the present study demonstrated that ALT-711 can rescue CML-induced functional angiogenesis damage via miR-27b/TSP-1 signaling cascades. These results indicate new therapeutic strategies for diabetes patients with CLI.

On the Cutting Edge: Wound Care for the Endovascular Specialist

Clinical outcomes in patients with critical limb ischemia (CLI) depend not only on endovascular restoration of macrovascular blood flow but also on aggressive periprocedural wound care. Education about this area of CLI therapy is essential not only to maximize the benefits of endovascular therapy but also to facilitate participation in the multidisciplinary care crucial to attaining limb salvage. In this article, we review the advances in wound care products and therapies that have granted the wound care specialist the ability to heal previously nonhealing wounds. We provide a primer on the basic science behind wound healing and the pathogenesis of ischemic wounds, familiarize the reader with methods of tissue viability assessment, and provide an overview of wound debridement techniques, dressings, hyperbaric therapy, and tissue offloading devices. Lastly, we explore emerging technology on the horizons of wound care.

Circulating MicroRNA-4739 May Be a Potential Biomarker of Critical Limb Ischemia in Patients with Diabetes

Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease, which is common but rarely diagnosed. Noninvasive biomarkers are urgently required to assist in the diagnosis of CLI. Accumulating evidence indicates that miRNAs play an important role in the development of various diseases. In this study, microarray profiling revealed 11 miRNAs with significantly altered expression in four T2DM patients with CLI compared with that in four sex- and age-matched T2DM patients without CLI. In independent cohorts, qRT-PCR validation confirmed the increased miRNA-4739 level in patients with CLI versus patients without CLI. miRNA-4739 levels increased with FPG and HbA1c (all P < 0.05). After adjusting for the risk factors, miRNA-4739 levels were found to be associated with an increased odds ratio (OR) of T2DM with CLI (OR =12.818, 95% confidence intervals (CI) 1.148 to 143.143, P = 0.038). ROC curve analysis revealed that the area under the curve (AUC) of miR-4739+confounding risk factors was 0.94 (95% CI 0.891 to 0.998, P < 0.001), which was higher than that of confounding risk factors (AUC 0.94 vs. 0.91, 95% CI -0.122 to 0.060, P > 0.05) and of miR-4739 (AUC 0.94 vs. 0.69, 95% CI -0.399 to -0.101, P < 0.001), respectively. We conclude that elevated plasma miRNA-4739 levels are independently associated with CLI in T2DM patients. miRNA-4739 is implicated as a novel diagnostic marker and a potential therapeutic target for CLI in diabetes.