Versican undergoes speci?c alterations in the ?ne molecular structure and organization in human aneurysmal abdominal aortas

Is There Enough Evidence to Support the Role of Glycosaminoglycans and Proteoglycans in Thoracic Aortic Aneurysm and Dissection?—A Systematic Review

Altered proteoglycan (PG) and glycosaminoglycan (GAG) distribution within the aortic wall has been implicated in thoracic aortic aneurysm and dissection (TAAD). This review was conducted to identify literature reporting the presence, distribution and role of PGs and GAGs in the normal aorta and differences associated with sporadic TAAD to address the question; is there enough evidence to establish the role of GAGs/PGs in TAAD? 75 studies were included, divided into normal aorta (n = 51) and TAAD (n = 24). There is contradictory data regarding changes in GAGs upon ageing; most studies reported an increase in GAG sub-types, often followed by a decrease upon further ageing. Fourteen studies reported changes in PG/GAG or associated degradation enzyme levels in TAAD, with most increased in disease tissue or serum. We conclude that despite being present at relatively low abundance in the aortic wall, PGs and GAGs play an important role in extracellular matrix maintenance, with differences observed upon ageing and in association with TAAD. However, there is currently insufficient information to establish a cause-effect relationship with an underlying mechanistic understanding of these changes requiring further investigation. Increased PG presence in serum associated with aortic disease highlights the future potential of these biomolecules as diagnostic or prognostic biomarkers.

The Contribution of Glycosaminoglycans/Proteoglycans to Aortic Mechanics in Health and Disease: A Critical Review

While elastin and collagen have received a lot of attention as major contributors to aortic biomechanics, glycosaminoglycans (GAGs) and proteoglycans (PGs) recently emerged as additional key players whose roles must be better elucidated if one hopes to predict aortic ruptures caused by aneurysms and dissections more reliably. GAGs are highly negatively charged polysaccharide molecules that exist in the extracellular matrix (ECM) of the arterial wall. In this critical review, we summarize the current understanding of the contributions of GAGs/PGs to the biomechanics of the normal aortic wall, as well as in the case of aortic diseases such as aneurysms and dissections. Specifically, we describe the fundamental swelling behavior of GAGs/PGs and discuss their contributions to residual stresses and aortic stiffness, thereby highlighting the importance of taking these polyanionic molecules into account in mathematical and numerical models of the aorta. We suggest specific lines of investigation to further the acquisition of experimental data to complement simulations and solidify our current understanding. We underscore different potential roles of GAGs/PGs in thoracic aortic aneurysm (TAAD) and abdominal aortic aneurysm (AAA). Namely, we report findings according to which the accumulation of GAGs/PGs in TAAD causes stress concentrations which may be sufficient to initiate and propagate delamination. On the other hand, there seems to be no clear indication of a relationship between the marked reduction in GAG/PG content and the stiffening and weakening of the aortic wall in AAA.

A role for proteoglycans in vascular disease

The content of proteoglycans (PGs) is low in the extracellular matrix (ECM) of vascular tissue, but increases dramatically in all phases of vascular disease. Early studies demonstrated that glycosaminoglycans (GAGs) including chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS) and heparan sulfate (HS) accumulate in vascular lesions in both humans and in animal models in areas of the vasculature that are susceptible to disease initiation (such as at branch points) and are frequently coincident with lipid deposits. Later studies showed the GAGs were covalently attached to specific types of core proteins that accumulate in vascular lesions. These molecules include versican (CSPG), biglycan and decorin (DS/CSPGs), lumican and fibromodulin (KSPGs) and perlecan (HSPG), although other types of PGs are present, but in lesser quantities. While the overall molecular design of these macromolecules is similar, there is tremendous structural diversity among the different PG families creating multiple forms that have selective roles in critical events that form the basis of vascular disease. PGs interact with a variety of different molecules involved in disease pathogenesis. For example, PGs bind and trap serum components that accumulate in vascular lesions such as lipoproteins, amyloid, calcium, and clotting factors. PGs interact with other ECM components and regulate, in part, ECM assembly and turnover. PGs interact with cells within the lesion and alter the phenotypes of both resident cells and cells that invade the lesion from the circulation. A number of therapeutic strategies have been developed to target specific PGs involved in key pathways that promote vascular disease. This review will provide a historical perspective of this field of research and then highlight some of the evidence that defines the involvement of PGs and their roles in the pathogenesis of vascular disease.

The factors affecting lipid profile in adult patients with Mucopolysaccharidosis

Background

Mucopolysaccharidoses (MPS) are a group of rare inherited disorders characterized by abnormal accumulation of glycosaminoglycans (GAGs) within the myocytes and coronary arteries. Little is known about hyperlipidaemia as a potential cardiovascular risk factor in these patients. Baseline cholesterol data in adults are scarce. Therefore, the aim of this study was to analyse factors affecting lipid profile in different types of MPSs to determine if abnormalities in lipid profile contribute to the overall risk of cardiovascular disease.

Methods

Adult patients (above the age of 16) with MPS type I, II, III, IV and VI attending clinics in two Inherited Metabolic Disorders centres were included. Their lipid profile, lipoprotein (a), HbA1c, Glucose Tolerance Test (GTT), BMI and treatment type were extracted. Analysis included descriptive statistics and Student t-test.

Results

Eighty two patients with five MPS types (I, II, III, IV and VI) were included in the study; 29 were females (35%) and 53 were males (65%). BMI above 25 kg/m² in all MPS types indicated that some patients were overweight for their height. Only one patient post-HSCT had diabetes. In 3 cases insulin was analysed during GTT and showed no insulin resistance despite raised BMI. Mean total cholesterol and LDL-cholesterol were below 5 mmol/L and 3 mmol/L, respectively, in five individual MPS types. Lipoprotein (a) was available for 6 MPS IV patients and was not significantly raised.

Conclusions

MPS disorders are not associated with significant hypercholesterolaemia or diabetes mellitus despite increased BMI. Total cholesterol and LDL-cholesterol were within the targets for primary prevention for non-MPS population. Lipoprotein (a) is not a useful marker of cardiovascular disease in a small group of adult MPS IV patients irrespectively of treatment option. Whether long-term cardiovascular risk is dependent on lipid profile, diabetes, obesity or GAGs deposition within the organ system remains unanswered.

A disintegrin and metalloproteinase with thrombospondin motif 1 (ADAMTS1) expression increases in acute aortic dissection

Acute aortic dissection (AAD) is a life-threatening cardiovascular disease caused by progressive medial degeneration of the aortic wall. A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) is a recently identified extracellular metalloproteinase participating in the development of vascular disease, such as atherosclerosis. In the present study, we found that ADAMTS1 was significantly elevated in blood samples from AAD patients compared with patients with acute myocardial infarction and healthy volunteers. Based on these findings, we established an AAD model by infusing angiotensin II in older mice. AAD was successfully developed in aorta tissues, with an incidence of 42% after 14 days in the angiotensin II group. Macrophage and neutrophil infiltration was observed in the media of the aorta, and ADAMTS1 overexpression was found in the aorta by Western blot and immunohistochemistry. Double immunofluorescence staining showed the expression of ADAMTS1 in macrophages and neutrophils. Consistent with the upregulation of ADAMTS1 in aortic dissection tissues, versican (a proteoglycan substrate of ADAMTS1) was degraded significantly more in these tissues than in control aortic tissues. These data suggest that the increased expression of ADAMTS1 protein in macrophages and neutrophils that infiltrated aortic tissues may promote the progression of AAD by degrading versican.

ADAMTS-1 and ADAMTS-4 levels are elevated in thoracic aortic aneurysms and dissections

BACKGROUND

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) is a recently identified family of extracellular metalloproteinases that has been shown to participate in tissue destruction. We hypothesized that ADAMTS-1 and ADAMTS-4 expression is increased in aortic tissues from patients with thoracic aortic aneurysms and dissections.

METHODS

We examined ADAMTS-1 and ADAMTS-4 expression in human descending thoracic aortic aneurysms (n = 14), chronic descending thoracic aortic dissections (n = 16), and descending thoracic aortas from age-matched control organ donors (n = 12). In these tissues, we also evaluated the degradation of versican, a proteoglycan substrate of ADAMTS-1 and ADAMTS-4. In cultured macrophages, we examined whether ADAMTS-4 functions in macrophage infiltration by using a transwell assay.

RESULTS

ADAMTS-1 and ADAMTS-4 protein and mRNA expression was significantly higher in thoracic aortic aneurysm and dissection tissues than in control aortic tissues. Double immunofluorescence staining showed the expression of ADAMTS-1 and ADAMTS-4 in smooth muscle cells and macrophages. Consistent with the upregulation of ADAMTS-1 and ADAMTS-4 in thoracic aortic aneurysm and dissection tissues, versican was degraded significantly more in these tissues than in control aortic tissues. In cultured macrophages, transforming growth factor-β increased ADAMTS-4 protein levels and induced macrophage invasion, and the knockdown of ADAMTS-4 reduced cell invasion.

CONCLUSIONS

Increased expression of ADAMTS proteins may promote thoracic aortic aneurysm progression by degrading versican and facilitating macrophage invasion.

Cardiac disease in patients with mucopolysaccharidosis: presentation, diagnosis and management

The mucopolysaccharidoses (MPSs) are inherited lysosomal storage disorders caused by the absence of functional enzymes that contribute to the degradation of glycosaminoglycans (GAGs). The progressive systemic deposition of GAGs results in multi-organ system dysfunction that varies with the particular GAG deposited and the specific enzyme mutation(s) present. Cardiac involvement has been reported in all MPS syndromes and is a common and early feature, particularly for those with MPS I, II, and VI. Cardiac valve thickening, dysfunction (more severe for left-sided than for right-sided valves), and hypertrophy are commonly present; conduction abnormalities, coronary artery and other vascular involvement may also occur. Cardiac disease emerges silently and contributes significantly to early mortality.The clinical examination of individuals with MPS is often difficult due to physical and, sometimes, intellectual patient limitations. The absence of precordial murmurs does not exclude the presence of cardiac disease. Echocardiography and electrocardiography are key diagnostic techniques for evaluation of valves, ventricular dimensions and function, which are recommended on a regular basis. The optimal technique for evaluation of coronary artery involvement remains unsettled.Standard medical and surgical techniques can be modified for MPS patients, and systemic therapies such as hematopoietic stem cell transplantation and enzyme replacement therapy (ERT) may alter overall disease progression with regression of ventricular hypertrophy and maintenance of ventricular function. Cardiac valve disease is usually unresponsive or, at best, stabilized, although ERT within the first few months of life may prevent valve involvement, a fact that emphasizes the importance of early diagnosis and treatment in MPS.

Versican in health and disease

Versican is a component of the extracellular matrix, which interacts with several matrix and cell surface molecules. Versican plays central roles in tissue morphogenesis and homeostasis and is implicated in the development of numerous diseases. The expression of versican by multiple cell types is differentially regulated in a temporal and spatial manner in physiological and pathological processes. It participates in various biological events such as tissue organization, cell proliferation, adhesion, migration, and angiogenesis. The physiology of versican and its role in the progression of diseases such as atherosclerosis, cancer, and central nervous system injury are discussed.

Chondroitin sulfate proteoglycan 2 (CSPG2) gene polymorphisms rs173686 and rs251124 are not associated with intracranial aneurysms in Chinese Han nationality

BACKGROUND

There is evidence suggesting that genetic variants in the chondroitin sulfate proteoglycan2 (CSPG2, also known as versican) gene are involved in the pathogenesis of intracranial aneurysms (IAs). Some authors have demonstrated that single nucleotide polymorphisms (SNPs) rs173686 and rs251124 in the promoter region of the CSPG2 gene are associated with IAs. We performed a case-control study to investigate whether these SNPs might affect the development of IAs in Chinese Han nationality.

METHODS

The study group comprised 240 Chinese Han nationality patients with at least one intracranial aneurysm and 240 healthy Han nationality controls. Genomic DNA was isolated from blood leukocytes. The SNPs rs173686 and rs251124 were genotyped by PCR amplification and DNA sequencing. Differences in genotype and allele frequencies between patients and controls were tested by the chi-square method.

RESULTS

Genotype and allele frequencies of the SNPs rs173686 and rs251124 were both demonstrated to be in Hardy-Weinberg equilibrium. No significant difference in genotype or allele frequencies between case and control groups was detected at either of the two SNPs.

CONCLUSIONS

The data do not support the hypothesis that the two SNPs (rs173686 and rs251124) in the promoter region of the CSPG2 gene influence the development of intracranial aneurysms in Chinese Han nationality.

Versican degradation and vascular disease

Versican is an abundant proteoglycan in the blood vessel wall that is increased after vascular injury and accumulates in advanced atherosclerotic plaques. Versican is a large molecule with domains that mediate binding to cytokines, enzymes, lipoproteins, other extracellular matrix molecules, and signaling receptors. There is evidence that versican exists in the normal, as well as the diseased, vessel wall as discrete fragments, which represent these functional domains. We review the literature on versican degradation in vascular tissue and the function of versican domains, all of which suggest that proteolytic modification of versican may have physiologic as well as pathologic implications for the vascular system.