Understanding the structural features of symptomatic calcific aortic valve stenosis: A broad-spectrum clinico-pathologic study in 236 consecutive surgical cases

Neovascularization of native cardiac valves, and correlation with histopathologic, clinical, and radiologic features

Native cardiac valves in the setting of chronic injury undergo remodeling that includes fibrous thickening and dystrophic calcification, as well as neovascularization, that result in abnormal valve function. In order to characterize the presence of neovascularization in valves, a retrospective review of 1246 sequentially reviewed native cardiac valves of all types was performed, with correlation with other histopathologic features, and clinical and echocardiographic findings. Neovascularization was present in 55.5% of cases, with the greatest prevalence amongst aortic valves. While microvasculature (representing capillaries, venules, and/or lymphatics) was at least present in all cases of valves with neovascularization, arterial vessels were never identified in valves without also the finding of concomitant microvasculature present. Patients with neovascularization had a greater mean age and body mass index compared to those without, and the proportions of cases with significant coronary artery disease, dyslipidemia, diabetes mellitus, rheumatic fever, and malignancy were greater in the setting of valves with neovascularization compared to cases without. The rate of neovascularization increased with degree of valve thickening and/or calcification, and stenosis; in contrast, neovascularization was observed at a greater rate with decreasing degrees of regurgitation. The prevalence rates of hemosiderin-laden macrophages, osseous metaplasia, chondromatous metaplasia, smooth muscle, and chronic inflammation were greater in valves with neovascularization compared to valves without. Neovascularization within native cardiac valves is a frequent histopathologic alteration associated with chronic valve disease, likely representing a constituent of structural remodeling that mediates and reflects chronic injury.

Clinical and Experimental Study of High Mobility Group Box-2 and Valvular Calcification in Elderly Patients with Degenerative Heart Valve Disease

INTRODUCTION

The aim of this study was to investigate the relationship between the high mobility group box-2 (HMGB2) and valve calcification in senile degenerative heart valve disease (SDHVD).

METHODS

According to the echocardiographic results, patients with calcified heart valves were used as the experimental group and patients without calcified heart valves were used as the control group; blood was drawn for testing, and serum levels of HMGB2 were measured by an enzyme-linked immunosorbent assay. Human heart valve interstitial cells (hVICs) cultured in vitro were randomly divided into two groups. The calcification group was cultured with a medium containing calcification induction solution and cells were induced on days 1, 3, and 5, and the control group was cultured with a standard medium. Expression of bone morphogenetic protein 4 (BMP-4) and HMGB2 in both groups was detected by Western blot. RT-PCR was performed to detect the expression of the HMGB2 gene during calcification. The hVICs were cultured in vitro for 4 days with different concentrations of exogenous HMGB2 (0.01 μg/mL, 0.1 μg/mL, 1 μg/mL, 2 μg/mL), while the control group was cultured with a standard medium and the expression of BMP-4 and NF-κB P65 was detected by Western blot.

RESULTS

The serum level of HMGB2 was 7.90 (5.92, 12.39) μg/L, higher than that of 7.06 (5.06, 9.73) μg/L in the valve calcification group in elderly patients with degenerative valve disease (p = 0.005); the differences were statistically significant. In in vitro experiments, the cellular calcification protein BMP-4 and the HMGB2 protein were higher in the calcification group compared to the control group (p < 0.05). Exogenous stimulation of hVICs with HMGB2 was able to upregulate the expression of BMP-4 and NF-κB P65 (p < 0.05).

CONCLUSIONS

HMGB2 is correlated with valvular calcification in senile degenerative heart valve disease. The HMGB2 protein may promote the process of SDHVD valve calcification by activating the NF-κB pathway and upregulating the expression of BMP-4.

A Straightforward Cytometry-Based Protocol for the Comprehensive Analysis of the Inflammatory Valve Infiltrate in Aortic Stenosis

Aortic stenosis (AS) is a frequent cardiac disease in old individuals, characterized by valvular calcification, fibrosis, and inflammation. Recent studies suggest that AS is an active inflammatory atherosclerotic-like process. Particularly, it has been suggested that several immune cell types, present in the valve infiltrate, contribute to its degeneration and to the progression toward stenosis. Furthermore, the infiltrating T cell subpopulations mainly consist of oligoclonal expansions, probably specific for persistent antigens. Thus, the characterization of the cells implicated in the aortic valve calcification and the analysis of the antigens to which those cells respond to is of utmost importance to develop new therapies alternative to the replacement of the valve itself. However, calcified aortic valves have been only studied so far by histological and immunohistochemical methods, unable to render an in-depth phenotypical and functional cell profiling. Here we present, for the first time, a simple and efficient cytometry-based protocol that allows the identification and quantification of infiltrating inflammatory leukocytes in aortic valve explants. Our cytometry protocol saves time and facilitates the simultaneous analysis of numerous surface and intracellular cell markers and may well be also applied to the study of other cardiac diseases with an inflammatory component.

Cardio-Oncology: A Myriad of Relationships Between Cardiovascular Disease and Cancer

Cardiovascular disease (CVD) and cancer are the leading causes of death worldwide. With an increasing number of the elderly population, and early cancer screening and treatment, the number of cancers cases are rising, while the mortality rate is decreasing. However, the number of cancer survivors is increasing yearly. With the prolonged life span of cancer patients, the adverse effects of anti-tumor therapy, especially CVD, have gained enormous attention. The incidence of cardiovascular events such as cardiac injury or cardiovascular toxicity is higher than malignant tumors' recurrence rate. Numerous clinical studies have also shifted their focus from the study of a single disease to the interdisciplinary study of oncology and cardiology. Previous studies have confirmed that anti-tumor therapy can cause CVD. Additionally, the treatment of CVD is also related to the tumors incidence. It is well established that the increased incidence of CVD in cancer patients is probably due to an unmodified unhealthy lifestyle among cancer survivors or cardiotoxicity caused by anti-cancer therapy. Nevertheless, some patients with CVD have a relatively increased cancer risk because CVD and malignant tumors are highly overlapping risk factors, including gender, age, hypertension, diabetes, hyperlipidemia, inflammation, and obesity. With advancements in the diagnosis and treatment, many patients simultaneously suffer from CVD and cancer, and most of them have a poor prognosis. Therefore, clinicians should understand the relationship between CVD and tumors, effectively identify the primary and secondary prevention for these diseases, and follow proper treatment methods.

Osseous metaplasia within native cardiac valves: clinicopathologic characterization of a histologic constituent with particular focus upon aortic valves

Native cardiac valves may undergo calcification in the setting of chronic injury, subsequently impeding normal valve structure and function. In the same setting, there may be evidence of metaplasia-specifically osseous metaplasia-with lamellar bone admixed with dystrophic calcification. In this study, the histologic features of 123 native aortic valves (identified from 1094 sequentially reviewed native valves of all types that included a total of 754 aortic valves) with osseous metaplasia are focused upon, as well as correlation with other histopathologic features, and clinical and echocardiographic findings. Osseous metaplasia was identified in aortic and significantly less frequently in mitral valves, and never in tricuspid or pulmonic valves. Notable observations included that osseous metaplasia in aortic valves were seen in patients with greater body mass index, and less commonly identified in patients with a history of autoimmune disease. Aortic valves with osseous metaplasia were more commonly tricuspid (as opposed to bicuspid), and with smaller aortic valve area and greater peak and mean gradients. The rate of osseous metaplasia in aortic valves increased with increasing degree of stenosis and decreasing degree of regurgitation. The rates of the presence of chondromatous metaplasia, smooth muscle, arterial vessels, capillary bed formation, chronic inflammation, and hemosiderin laden macrophages were greater in aortic valves with osseous metaplasia compared to valves without osseous metaplasia. Further investigation is required to determine potential physiologic and/or pathologic consequence of the presence of valvular osseous metaplasia.

A feedback loop: Interactions between Inflammatory Signals and Clonal Hematopoiesis in Cardiovascular Disease

Age and inflammation are powerful drivers of cardiovascular disease. With the growing recognition that traditional cardiovascular risk factors are not fully accurate predictors of cardiovascular disease, recent studies have revealed the prevalence of positive selection of somatic cell mutations in hematopoietic stem cells in the elderly population, which can cause clonal hematopoiesis. Interestingly, clonal hematopoiesis is not only associated with cancer and death, but also closely related to the risk of increased cardiovascular disease due to mutations in TET2, DNMT3A, ASXL1, and JAK2. However, the mechanism of the interaction of clonal hematopoiesis and cardiovascular disease is only partially understood. In mice, somatic mutations have led to significantly increased expression of inflammatory genes in innate immune cells, which may explain the relationship between mutations and cardiovascular disease. Here, we further discuss the association between inflammatory signaling, clonal hematopoiesis, and cardiovascular disease,and using two hypotheses to propose a feedback loop between inflammatory signaling and clonal hematopoiesis for getting insight into the pathogenesis of cardiovascular diseases in depth. Therapies targeting mutant clones or increased inflammatory mediators may be useful for ameliorating the risk of cardiovascular disease.

Elimination of macrophages reduces glutaraldehyde-fixed porcine heart valve degeneration in mice subdermal model

Glutaraldehyde-fixed porcine heart valve (GPHV) calcify and deteriorate over time. The aim of this study was to explore the roles macrophages play in mediating calcification and degeneration of the valve's connective tissue matrix. GPHV were implanted subcutaneously in the abdomens of C57BL/6 mice. The mice were equally divided into two study groups: (a) GPHV +phosphate buffered saline (PBS) liposomes, and (b) GPHV +clodronate liposomes. GPHV were collected for further analyses at 4 weeks post implant. Macrophages were almost depleted from the spleens of mice injected with clodronate liposomes as indicated by immunohistochemical staining. Furthermore, the expression of matrix metalloproteinase-2 (MMP-2), MMP-9, and proinflammatory cytokines like IL-1β, IL-6, MCP-1, MIP-1a, MIP-1b, were downregulated in the GPHV +Clodronate liposomal group compared with the GPHV+PBS liposomal group. Clodronate liposomal treatment led to significant decreases in the expression of RUNX2, ALP and OPN as well as less calcium deposits in GPHVs compared with PBS liposomal treatment. This finding indicated that infiltrating macrophages are critically involved in the development of calcification and deterioration in GPHVs. Macrophage depletion by clodronate liposomes decreased the extent of GPHV's calcification and deterioration.

Translating Evidence from Clonal Hematopoiesis to Cardiovascular Disease: A Systematic Review

Some random mutations can confer a selective advantage to a hematopoietic stem cell. As a result, mutated hematopoietic stem cells can give rise to a significant proportion of mutated clones of blood cells. This event is known as "clonal hematopoiesis." Clonal hematopoiesis is closely associated with age, and carriers show an increased risk of developing blood cancers. Clonal hematopoiesis of indeterminate potential is defined by the presence of clones carrying a mutation associated with a blood neoplasm without obvious hematological malignancies. Unexpectedly, in recent years, it has emerged that clonal hematopoiesis of indeterminate potential carriers also have an increased risk of developing cardiovascular disease. Mechanisms linking clonal hematopoiesis of indeterminate potential to cardiovascular disease are only partially known. Findings in animal models indicate that clonal hematopoiesis of indeterminate potential-related mutations amplify inflammatory responses. Consistently, clinical studies have revealed that clonal hematopoiesis of indeterminate potential carriers display increased levels of inflammatory markers. In this review, we describe progress in our understanding of clonal hematopoiesis in the context of cancer, and we discuss the most recent findings linking clonal hematopoiesis of indeterminate potential and cardiovascular diseases.

Non-pathological Chondrogenic Features of Valve Interstitial Cells in Normal Adult Zebrafish

In the heart, unidirectional blood flow depends on proper heart valve function. As, in mammals, regulatory mechanisms of early heart valve and bone development are shown to contribute to adult heart valve pathologies, we used the animal model zebrafish (ZF, Danio rerio) to investigate the microarchitecture and differentiation of cardiac valve interstitial cells in the transition from juvenile (35 days) to end of adult breeding (2.5 years) stages. Of note, light microscopy and immunohistochemistry revealed major differences in ZF heart valve microarchitecture when compared with adult mice. We demonstrate evidence for rather chondrogenic features of valvular interstitial cells by histological staining and immunodetection of SOX-9, aggrecan, and type 2a1 collagen. Collagen depositions are enriched in a thin layer at the atrial aspect of atrioventricular valves and the ventricular aspect of bulboventricular valves, respectively. At the ultrastructural level, the collagen fibrils are lacking obvious periodicity and orientation throughout the entire valve.

Increased Calcific Aortic Valve Disease in response to a diabetogenic, procalcific diet in the LDLr-/-ApoB100/100 mouse model

OBJECTIVE

Calcific aortic valve disease (CAVD) is a major cause of aortic stenosis (AS) and cardiac insufficiency. Patients with type II diabetes mellitus (T2DM) are at heightened risk for CAVD, and their valves have greater calcification than nondiabetic valves. No drugs to prevent or treat CAVD exist, and animal models that might help identify therapeutic targets are sorely lacking. To develop an animal model mimicking the structural and functional features of CAVD in people with T2DM, we tested a diabetogenic, procalcific diet and its effect on the incidence and severity of CAVD and AS in the, LDLr-/-ApoB100/100 mouse model.

RESULTS

LDLr-/-ApoB100/100 mice fed a customized diabetogenic, procalcific diet (DB diet) developed hyperglycemia, hyperlipidemia, increased atherosclerosis, and obesity when compared with normal chow fed LDLr-/-ApoB100/100 mice, indicating the development of T2DM and metabolic syndrome. Transthoracic echocardiography revealed that LDLr-/-ApoB100/100 mice fed the DB diet had 77% incidence of hemodynamically significant AS, and developed thickened aortic valve leaflets and calcification in both valve leaflets and hinge regions. In comparison, normal chow (NC) fed LDLr-/-ApoB100/100 mice had 38% incidence of AS, thinner valve leaflets and very little valve and hinge calcification. Further, the DB diet fed mice with AS showed significantly impaired cardiac function as determined by reduced ejection fraction and fractional shortening. In vitro mineralization experiments demonstrated that elevated glucose in culture medium enhanced valve interstitial cell (VIC) matrix calcium deposition.

CONCLUSIONS

By manipulating the diet we developed a new model of CAVD in T2DM, hyperlipidemic LDLr-/-ApoB100/100 that shows several important functional, and structural features similar to CAVD found in people with T2DM and atherosclerosis including AS, cardiac dysfunction, and inflamed and calcified thickened valve cusps. Importantly, the high AS incidence of this diabetic model may be useful for mechanistic and translational studies aimed at development of novel treatments for CAVD.