Vascular endothelium summary statement VI: Research directions for the 21st century

Challenges in vascular tissue engineering for diabetic patients

Hyperglycemia and dyslipidemia coexist in diabetes and result in inflammation, degeneration, and impaired tissue remodeling, processes which are not conducive to the desired integration of tissue engineered products into the surrounding tissues. There are several challenges for vascular tissue engineering such as non-thrombogenicity, adequate burst pressure and compliance, suturability, appropriate remodeling responses, and vasoactivity, but, under diabetic conditions, an additional challenge needs to be considered: the aggressive oxidative environment generated by the high glucose and lipid concentrations that lead to the formation of advanced glycation end products (AGEs) in the vascular wall. Extracellular matrix-based scaffolds have adequate physical properties and are biocompatible, however, these scaffolds are altered in diabetes by the formation AGEs and impaired collagen degradation, consequently increasing vascular wall stiffness. In addition, vascular cells detect and respond to altered stimuli from the matrix by pathological remodeling of the vascular wall. Due to the immunomodulatory effects of mesenchymal stem cells (MSCs), they are frequently used in tissue engineering in order to protect the scaffolds from inflammation. MSCs together with antioxidant treatments of the scaffolds are expected to protect the vascular grafts from diabetes-induced alterations. In conclusion, as one of the most daunting environments that could damage the ECM and its interaction with cells is progressively built in diabetes, we recommend that cells and scaffolds used in vascular tissue engineering for diabetic patients are tested in diabetic animal models, in order to obtain valuable results regarding their resistance to diabetic adversities.

STATEMENT OF SIGNIFICANCE

Almost 25 million Americans have diabetes, characterized by high levels of blood sugar that binds to tissues and disturbs the function of cardiovascular structures. Therefore, patients with diabetes have a high risk of cardiovascular diseases. Surgery is required to replace diseased arteries with implants, but these fail after 5-10 years because they are made of non-living materials, not resistant to diabetes. New tissue engineering materials are developed, based on the patients' own stem cells, isolated from fat, and added to extracellular matrix-based scaffolds. Our main concern is that diabetes could damage the tissue-like implants. Thus we review studies related to the effect of diabetes on tissue components and recommend antioxidant treatments to increase the resistance of implants to diabetes.

Endothelial dysfunction: a unifying hypothesis for the burden of cardiovascular diseases in sub-Saharan Africa

It is well established that the leading causes of death and disability worldwide are cardiovascular diseases (CVD), chief among which is ischaemic heart disease. However, it is also recognised that ischaemic heart disease frequently coexists with other vascular conditions, such as cerebrovascular, renovascular and peripheral vascular disease, thus raising the notion of a common underlying pathobiology, albeit with differing manifestations, dictated by the implicated vascular bed.

The understanding that common metabolic and behavioural risk factors as well as social determinants and drivers are convergent in the development of CVD evokes the idea that the dysfunction of a common bio-molecular platform is central to the occurrence of these diseases. The state of endothelial activation, otherwise known as endothelial dysfunction, occurs when reactive oxygen signalling predominates due to an uncoupled state of endothelial nitric oxide synthase (eNOS). This can be a physiological response to stimulation of the innate immune system or a pathophysiological response triggered by cardiovascular disease risk factors.

The conventional wisdom is that the endothelium plays an important role in the initiation, progression and development of CVD and other non-communicable diseases. Consequently, the endothelium has remarkable relevance in clinical and public health practice as well as in health education, health promotion, and disease- and risk-factor prevention strategies. It also presents a plausible unifying hypothesis for the burden of CVD seen globally and in sub-Saharan Africa. Importantly, the heterogeneity in individual responses to metabolic, behavioural, and social drivers of CVD may stem from a complex interplay of these drivers with genomic, epigenetic and environmental factors that underpin eNOS uncoupling. Therefore, further biomedical research into the underlying genetic and other mechanisms of eNOS uncoupling may enlighten and shape strategies for addressing the burden of CVD in sub-Saharan Africa and other regions of the world.

Mitigation of diabetes-related complications in implanted collagen and elastin scaffolds using matrix-binding polyphenol

There is a major need for scaffold-based tissue engineered vascular grafts and heart valves with long-term patency and durability to be used in diabetic cardiovascular patients. We hypothesized that diabetes, by virtue of glycoxidation reactions, can directly crosslink implanted scaffolds, drastically altering their properties. In order to investigate the fate of tissue engineered scaffolds in diabetic conditions, we prepared valvular collagen scaffolds and arterial elastin scaffolds by decellularization and implanted them subdermally in diabetic rats. Both types of scaffolds exhibited significant levels of advanced glycation end products (AGEs), chemical crosslinking and stiffening -alterations which are not favorable for cardiovascular tissue engineering. Pre-implantation treatment of collagen and elastin scaffolds with penta-galloyl glucose (PGG), an antioxidant and matrix-binding polyphenol, chemically stabilized the scaffolds, reduced their enzymatic degradation, and protected them from diabetes-related complications by reduction of scaffold-bound AGE levels. PGG-treated scaffolds resisted diabetes-induced crosslinking and stiffening, were protected from calcification, and exhibited controlled remodeling in vivo, thereby supporting future use of diabetes-resistant scaffolds for cardiovascular tissue engineering in patients with diabetes.

A factorial randomized controlled trial to evaluate the effect of micronutrients supplementation and regular aerobic exercise on maternal endothelium-dependent vasodilatation and oxidative stress of the newborn

Background

Many studies have suggested a relationship between metabolic abnormalities and impaired fetal growth with the development of non-transmissible chronic diseases in the adulthood. Moreover, it has been proposed that maternal factors such as endothelial function and oxidative stress are key mechanisms of both fetal metabolic alterations and subsequent development of non-transmissible chronic diseases. The objective of this project is to evaluate the effect of micronutrient supplementation and regular aerobic exercise on endothelium-dependent vasodilation maternal and stress oxidative of the newborn.

Methods and design

320 pregnant women attending to usual prenatal care in Cali, Colombia will be included in a factorial randomized controlled trial. Women will be assigned to the following intervention groups: 1. Control group: usual prenatal care (PC) and placebo (maltodextrine). 2. Exercise group: PC, placebo and aerobic physical exercise. 3. Micronutrients group: PC and a micronutrients capsule consisting of zinc (30 mg), selenium (70 μg), vitamin A (400 μg), alphatocopherol (30 mg), vitamin C (200 mg), and niacin (100 mg). 4. Combined interventions Group: PC, supplementation of micronutrients, and aerobic physical exercise. Anthropometric measures will be taken at the start and at the end of the interventions.

Discussion

Since in previous studies has been showed that the maternal endothelial function and oxidative stress are related to oxidative stress of the newborn, this study proposes that complementation with micronutrients during pregnancy and/or regular physical exercise can be an early and innovative alternative to strengthen the prevention of chronic diseases in the population.

Trial registration

NCT00872365.