Innate Sleep Apnea in Spontaneously Hypertensive Rats Is Associated With Microvascular Rarefaction and Neuronal Loss in the preBötzinger Complex.

BACKGROUND: Sleep apnea (SA) is a major threat to physical health and carries a significant economic burden. These impacts are worsened by its interaction with, and induction of, its comorbidities. SA holds a bidirectional relationship with hypertension, which drives atherosclerosis/arteriolosclerosis, ultimately culminating in vascular dementia. METHODS: To enable a better understanding of these sequelae of events, we investigated innate SA and its effects on cognition in adult-aged spontaneously hypertensive rats, which have a range of cardiovascular disorders: plethysmography and electroencephalographic/electromyographic recordings were used to assess sleep-wake state, breathing parameters, and sleep-disordered breathing; immunocytochemistry was used to assess vascular and neural health; the forced alteration Y maze and Barnes maze were used to assess short- and long-term memories, respectively; and an anesthetized preparation was used to assess baroreflex sensitivity. RESULTS: Spontaneously hypertensive rats displayed a higher degree of sleep-disordered breathing, which emanates from poor vascular health leading to a loss of preBötzinger Complex neurons. These rats also display small vessel white matter disease, a form of vascular dementia, which may be exacerbated by the SA-induced neuroinflammation in the hippocampus to worsen the related deficits in both long- and short-term memories. CONCLUSIONS: Therefore, we postulate that hypertension induces SA through vascular damage in the respiratory column, culminating in neuronal loss in the inspiratory oscillator. This induction of SA, which, in turn, will independently exacerbate hypertension and neural inflammation, increases the rate of vascular dementia.

Assessment of peritubular capillary rarefaction in kidneys of cats with chronic kidney disease.

BACKGROUND: Hypoxia is a key driver of fibrosis and is associated with capillary rarefaction in humans. OBJECTIVES: Characterize capillary rarefaction in cats with chronic kidney disease (CKD). ANIMALS: Archival kidney tissue from 58 cats with CKD, 20 unaffected cats. METHODS: Cross-sectional study of paraffin-embedded kidney tissue utilizing CD31 immunohistochemistry to highlight vascular structures. Consecutive high-power fields from the cortex (10) and corticomedullary junction (5) were digitally photographed. An observer counted and colored the capillary area. Image analysis was used to determine the capillary number, average capillary size, and average percent capillary area in the cortex and corticomedullary junction. Histologic scoring was performed by a pathologist masked to clinical data. RESULTS: Percent capillary area (cortex) was significantly lower in CKD (median 3.2, range, 0.8-5.6) compared to unaffected cats (4.4, 1.8-7.0; P = <.001) and was negatively correlated with serum creatinine concentrations (r = -.36, P = .0013), glomerulosclerosis (r = -0.39, P = <.001), inflammation (r = -.30, P = .009), and fibrosis (r = -.30, P = .007). Capillary size (cortex) was significantly lower in CKD cats (2591 pixels, 1184-7289) compared to unaffected cats (4523 pixels, 1801-7618; P = <.001) and was negatively correlated with serum creatinine concentrations (r = -.40, P = <.001), glomerulosclerosis (r = -.44, P < .001), inflammation (r = -.42, P = <.001), and fibrosis (r = -.38, P = <.001). CONCLUSIONS AND CLINICAL IMPORTANCE: Capillary rarefaction (decrease in capillary size and percent capillary area) is present in kidneys of cats with CKD and is positively correlated with renal dysfunction and histopathologic lesions.

VEGF (Vascular Endothelial Growth Factor) Inhibition and Hypertension: Does Microvascular Rarefaction Play a Role?

Drugs acting by inhibition of the angiogenic action of VEGF (vascular endothelial growth factor) have become major instruments in the treatment of cancer. The downside of their favorable effects in cancer treatment is their frequent cardiovascular side effects. The most consistent finding thus far on the cardiovascular side effects of VEGF inhibitors is the high incidence of hypertension. In this short review, we discuss the evidence that hypertension occurring during VEGF inhibitor treatment is caused by microvascular rarefaction. After a review of the role of VEGF in microvascular growth and differentiation, we present evidence from studies in experimental models of hypertension as well as clinical studies on the microvascular network changes during and after VEGF inhibitor treatment.

Cardiac epigenetic changes in VEGF signaling genes associate with myocardial microvascular rarefaction in experimental chronic kidney disease.

Chronic kidney disease (CKD) is common in patients with heart failure and often results in left ventricular diastolic dysfunction (LVDD). However, the mechanisms responsible for cardiac damage in CKD-LVDD remain to be elucidated. Epigenetic alterations may impose long-lasting effects on cellular transcription and function, but their exact role in CKD-LVDD is unknown. We investigate whether changes in cardiac site-specific DNA methylation profiles might be implicated in cardiac abnormalities in CKD-LVDD. CKD-LVDD and normal control pigs (n = 6 each) were studied for 14 wk. Renal and cardiac hemodynamics were quantified by multidetector CT and echocardiography. In randomly selected pigs (n = 3/group), cardiac site-specific 5-methylcytosine (5mC) immunoprecipitation (MeDIP)- and mRNA-sequencing (seq) were performed, followed by integrated (MeDiP-seq/mRNA-seq analysis), and confirmatory ex vivo studies. MeDIP-seq analysis revealed 261 genes with higher (fold change > 1.4; P < 0.05) and 162 genes with lower (fold change < 0.7; P < 0.05) 5mC levels in CKD-LVDD versus normal pigs, which were primarily implicated in vascular endothelial growth factor (VEGF)-related signaling and angiogenesis. Integrated MeDiP-seq/mRNA-seq analysis identified a select group of VEGF-related genes in which 5mC levels were higher, but mRNA expression was lower in CKD-LVDD versus normal pigs. Cardiac VEGF signaling gene and VEGF protein expression were blunted in CKD-LVDD compared with controls and were associated with decreased subendocardial microvascular density. Cardiac epigenetic changes in VEGF-related genes are associated with impaired angiogenesis and cardiac microvascular rarefaction in swine CKD-LVDD. These observations may assist in developing novel therapies to ameliorate cardiac damage in CKD-LVDD.NEW & NOTEWORTHY Chronic kidney disease (CKD) often leads to left ventricular diastolic dysfunction (LVDD) and heart failure. Using a novel translational swine model of CKD-LVDD, we characterize the cardiac epigenetic landscape, identifying site-specific 5-methylcytosine changes in vascular endothelial growth factor (VEGF)-related genes associated with impaired angiogenesis and cardiac microvascular rarefaction. These observations shed light on the mechanisms of cardiac microvascular damage in CKD-LVDD and may assist in developing novel therapies for these patients.

Systemic microvascular rarefaction is correlated with dysfunction of late endothelial progenitor cells in mild hypertension: a substudy of EXCAVATION-CHN1.

BACKGROUND: Hypertension often presents with microvascular rarefaction (MVR), which is closely associated with impaired angiogenesis. Early detection of MVR is essential for systemic assessment in patient with hypertension. We aimed to determine the systemic MVR through both optical coherence tomography angiography (OCTA) and intravital capillaroscopy, and to investigate their respective efficacies and related mechanisms associated with late endothelial progenitor cells (LEPCs) dysfunction. METHODS: Seventy-one hypertensive and sixty-nine age-match normotensive subjects were included in this study. All subjects received intravital capillaroscopy for skin capillary density (SCD) and OCTA for retinal capillary density (RCD) and non-perfused areas (R-NPA). Subsequently, correlation of LEPCs activities and microvascular rarefaction were examined. RESULTS: Compared with normotensive subjects, hypertensive patients had significantly lower RCD [(52.9 ± 2.9)% vs. (57.8 ± 1.6)%, P < 0.01] and higher R-NPA [(0.12 ± 0.07) mm2 vs. (0.053 ± 0.020) mm2, P < 0.01]. SCD correlated positively with RCD but negatively with R-NPA [(RCD: OR = 0.40, 95% CI 0.25-0.67, P < 0.01); (R-NPA: OR = 0.39, 95% CI - 0.0029 to 0.0011, P < 0.01)]. The discriminative powers of RCD performed best (AUC 0.79 versus SCD AUC 0.59, P < 0.001) followed by R-NPA (AUC 0.73 versus SCD AUC 0.59, P < 0.001) for systolic blood pressure. Similar pattern is also found for diastolic blood pressure (RCD AUC 0.80 versus SCD AUC 0.54, P < 0.001; R-NPA AUC 0.77 versus SCD AUC 0.54, P < 0.001). Furthermore, LEPCs tube formation was impaired in hypertensive patients (36.8 ± 2.3 vs. 28 ± 3.7, P < 0.01). After multivariate adjustments, positive correlation existed between RCD or R-NPA with LEPCs tube formation (RCD: ß = 0.64, 95% CI 0.34-0.91, P < 0.01; R-NPA: ß = - 24.67, 95% CI - 43.14 to - 4.63, P < 0.05) but not with SCD (ß = 0.082, 95% CI 0.01-0.18, P = 0.085). CONCLUSION: Compared to intravital capillaroscopy, OCTA is a more precise technique for early detection of hypertensive microvascular rarefaction, which is associated with the fall in LEPC-mediated angiogenesis. Both of OCTA and LEPCs function can help identify hypertension-related capillary abnormality. Trail Registration The trial is a substudy of EXCAVATION-CHN1, registered at clinicaltrials.gov as NCT02817204 (June 26, 2016).