Capillary Rarefaction Research Articles

Statins Reverse Postpartum Cardiovascular Dysfunction in a Rat Model of Preeclampsia.

Preeclampsia is associated with increased cardiovascular long-term risk; however, the underlying functional and structural mechanisms are unknown. We investigated maternal cardiac alterations after preeclampsia. Female rats harboring the human angiotensinogen gene [TGR(hAogen)L1623] develop a preeclamptic phenotype with hypertension and albuminuria during pregnancy when mated with male rats bearing the human renin gene [TGR(hRen)L10J] but behave physiologically normal before and after pregnancy. Furthermore, rats were treated with pravastatin. We tested the hypothesis that statins are a potential therapeutic intervention to reduce cardiovascular alterations due to simulated preeclamptic pregnancy. Although hypertension persists for only 8 days in pregnancy, former preeclampsia rats exhibit significant cardiac hypertrophy 28 days after pregnancy observed in both speckle tracking echocardiography and histological staining. In addition, fibrosis and capillary rarefaction was evident. Pravastatin treatment ameliorated the remodeling and improved cardiac output postpartum. Preeclamptic pregnancy induces irreversible structural changes of cardiac hypertrophy and fibrosis, which can be moderated by pravastatin treatment. This pathological cardiac remodeling might be involved in increased cardiovascular risk in later life.

Swept-source Optical Coherence Tomography Angiography Findings in Uveitic Cystoid Macular Edema

ABSTRACTPurpose: To describe swept-source optical coherence tomography angiography (OCTA) findings in uveitic cystoid macular edema (CME).Methods: Prospective study of 36 eyes.Results: Cystoid black spaces were shown in the deep capillary plexus (DCP) in 36 eyes (100%) and in the superficial capillary plexus (SCP) in 6 eyes (16.7%). Grayish areas of capillary non perfusion/hypoperfusion were seen in 69.4% of eyes in the DCP (vs 25% in the SCP, p < .001). The foveal avascular zone was larger than in the control healthy eyes in the DCP (p < .001). Capillary density was lower than in the control group in the SCP (p = .001) and the DCP (p < .001). Of 11 eyes with resolved CME on OCT, 4 eyes showed complete recovery of both plexuses on OCTA. There was a persistence of areas of capillary rarefaction in 4 eyes, and of hypoperfusion/nonperfusion in 3 eyes.Conclusion: OCTA visualizes perifoveal microvascular changes in uveitic CME.

Oxygen therapy, capillary rarefaction and blood pressure rise in premature low birth weight infants: is there a link?

Oxygen therapy, capillary rarefaction and blood pressure rise in premature low birth weight infants: is there a link?

Tyrosine Kinase Inhibitor-Induced Hypertension: Role of Hypertension as a Biomarker in Cancer Treatment.

Cancer treatment is an area of continuous improvement. Therapy is becoming more targeted and the use of anti-angiogenic agents in multiple cancers, specifically tyrosine kinase inhibitors (TKIs), has demonstrated prolonged survival outcomes compared with previous drugs. Therefore, they have become a well-established part of the treatment. Despite good results, there is a broad range of moderate to severe adverse effects associated with treatment. Hypertension (HTN) is one of the most frequent adverse effects and has been associated with favourable outcomes (in terms of cancer treatment) of TKI treatment. High blood pressure is considered a class effect of TKI treatment, although the mechanisms have not been fully described. Three current hypotheses of TKI-associated HTN are highlighted in this narrative review. These include nitric oxide decrease, a change in endothelin-1 levels and capillary rarefaction. Several studies have investigated HTN as a potential biomarker of TKI efficacy. HTN is easy to measure and adding this factor to prognostic models has been shown to improve specificity. HTN may become a potential biomarker in clinical practice involving treating advanced cancers. However, data are currently limited by the number of studies and knowledge of the mechanism of action.

P1246Myocardial transit time (MTT) - a novel and easy-to-perform CMR parameter to assess microvascular disease

Abstract Background Myocardial microvascular disease is primarily characterized by arteriolar obliteration and capillary rarefaction, and may occur during the disease course of different disorders. With the present study, we introduce a novel and easy-to-perform cardiovascular magnetic resonance (CMR) parameter named “myocardial transit time” (MTT). Methods N=20 patients with known hypertrophic cardiomyopathy (HCM) and N=20 control patients without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner (Ingenia, Philips, Best, The Netherlands). The CMR protocol comprised cine and late-gadolinium-enhancement (LGE) imaging and first-pass perfusion acquisitions at rest for MTT measurement: an imaging plane covering both the aortic bulbus and the coronary sinus was planned in order to track the flooding of gadolinium. MTT was defined as the time interval between first appearance of gadolinium in the aortic bulbus and the subsequent appearance of gadolinium in the coronary sinus reflecting the transit time of gadolinium in the myocardial microvasculature (in the absence of epicardial coronary artery disease). Results There was no significant difference in left ventricular ejection fraction (LV-EF) between both groups: 61% (55–68%) in HCM patients vs. 60% (58–67%) in controls (p=ns) whereas LV mass was significantly higher in HCM patients (79g/m2 (63–98g/m2) vs. 50g/m2 (45–56g/m2) in controls, p&lt;0.001). The extent of LGE was 17% (6–22%) in HCM patients while there was no LGE at all in the control group (p&lt;0.001). MTT at rest was substantially longer in HCM patients: 11.0sec (9.1–14.5sec) vs. 6.5sec (4.8–8.4sec) in controls (p&lt;0.001). Correlation analyses revealed a significant relationship between LV mass and MTT (r = +0.64, p&lt;0.001) as well as between LGE extent and MTT (r=0.75, p&lt;0.001). ROC analysis resulted in an area-under-curve (AUC) of 0.90 for MTT and showed an optimal sensitivity/specificity cut-off of 7.85sec to differentiate HCM from controls. Patient characteristics HNCM patients (N=20) Control group (N=20) p-value Absolute MTT, sec 11.0 (9.1–14.5) 6.5 (4.8–8.4) &lt;0.001 MTT indexed to heart rate 0.159 (0.100–0.198) 0.081 (0.063–0.106) &lt;0.001 No. of patients with MTT &lt;7.85 sec, n (%) 2 (10) 15 (75) &lt;0.001 MTT = Myocardial Transit Time, HNCM = Hypertrophic Non obstructive Cardiomyopathy. Multiple images illustrating MTT method Conclusion “Myocardial transit time” (MTT) is a novel and easy-to-perform CMR parameter that allows a quick assessment of the extent of myocardial microvascular disease. This novel CMR parameter may open new vistas in the assessment of microvascular disease - not only in HCM patients. Future studies will show the usefulness and clinical relevance of this novel CMR parameter.

Capillary rarefaction is more closely associated with CKD progression after cisplatin, rhabdomyolysis, and ischemia-reperfusion-induced AKI than renal fibrosis.

Acute kidney injury (AKI) is a strong independent predictor of mortality and often results in incomplete recovery of renal function, leading to progressive chronic kidney disease (CKD). Many clinical trials have been conducted on the basis of promising preclinical data, but no therapeutic interventions have been shown to improve long-term outcomes after AKI. This is partly due to the failure of preclinical studies to accurately model clinically relevant injury and long-term outcomes on CKD progression. Here, we evaluated the long-term effects of AKI on CKD progression in three animal models reflecting diverse etiologies of AKI: repeat-dose cisplatin, rhabdomyolysis, and ischemia-reperfusion injury. Using transdermal measurement of glomerular filtration rate as a clinically relevant measure of kidney function and quantification of peritubular capillary density to measure capillary rarefaction, we showed that repeat-dose cisplatin caused capillary rarefaction and decreased renal function in mice without a significant increase in interstitial fibrosis, whereas rhabdomyolysis-induced AKI led to severe interstitial fibrosis, but renal function and peritubular capillary density were preserved. Furthermore, long-term experiments in mice with unilateral ischemia-reperfusion injury showed that restoration of renal function 12 wk after a contralateral nephrectomy was associated with increasing fibrosis, but a reversal of capillary rarefaction was seen at 4 wk. These data demonstrate that clear dissociation between kidney function and fibrosis in these models of AKI to CKD progression and suggest that peritubular capillary rarefaction is more strongly associated with CKD progression than renal fibrosis.

Abstract P126: Statines Reduce Cardiac Dysfunction After Preeclamptic Pregnancy

Introduction: Former preeclamptic women have an increased risk of cardiovascular disease in later life. However, the underlying functional and structural mechanisms are still unknown. Objective: We tested the hypothesis that pravastatin has a beneficial effect on the remodeling of the maternal heart after preeclamptic pregnancy and thus reduces the long-term cardiovascular risk. Methods: Female rats harboring the human angiotensinogen gene [TGR(hAogen)L1623] developed a preeclamptic phenotype during pregnancy when mated with male rats carrying the human renin gene [TGR(hRen)L10J], but behaved physiologically normal postpartum. To investigate a possible intervention, we treated preeclamptic dams with pravastatin for four weeks after birth, which was started already during pregnancy. Cardiac structure and function was compared by speckle tracking echocardiography, gene expression analysis, and immune staining of the maternal heart. Results: Due to pravastatin treatment, former preeclamptic rats reduced signs of cardiac hypertrophy (perimeter cardiomyocytes 65.3±0.3 vs. 60.5±0.5 μm), fibrosis (fibronectin 3.9±0.3 vs. 1.8±0.2 %) and improved cardiac microcirculation (CD31+ cells 219.0±4.7 vs. 269.1±8.6). In addition, cardiac output was increased postpartum by statin treatment (ejection fraction 57.2±1.2 vs. 61.0±1.9; global longitudinal strain -14.5±0.6 vs. -19.8±1.0 %; heartrate 355.0±8.7 vs. 328.6±8.3 bpm). Analysis of maternal blood serum showed a reduction of brain natriuretic peptide (BNP 0.39±0.05 vs. 0.33±0.01 ng/ml) and soluble fms-like tyrosine kinase 1 (sFlt1 0.69±0.02 vs. 0.51±0.02 ng/ml) even four weeks after birth. Fetuses at the time of birth also benefited from treatment (brain liver ratio 0.93±0.03 vs. 0.82±0.01; heart body ratio 7.14±0.09 vs. 6.80±0.12). Discussion: Former preeclamptic rats showed significant cardiac hypertrophy in combination with fibrosis and capillary rarefaction. These irreversible structural changes can be reduced by pravastatin treatment. We could not detect any harmful influence of statins on the fetus. Values mean±SEM, PE vs. PE+pravastatin

CAPILLARY NETWORK ALTERATIONS IN X-LINKED RETINOSCHISIS IMAGED ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

To assess foveal and parafoveal vasculature at the superficial capillary plexus, deep capillary plexus, and choriocapillaris of patients with X-linked retinoschisis by means of optical coherence tomography angiography. Six patients with X-linked retinoschisis (12 eyes) and seven healthy controls (14 eyes) were recruited and underwent complete ophthalmologic examination, including best-corrected visual acuity, dilated fundoscopy, and 3 × 3-mm optical coherence tomography angiography macular scans (DRI OCT Triton; Topcon Corp). After segmentation and quality review, optical coherence tomography angiography slabs were imported into ImageJ 1.50 (NIH; Bethesda) and digitally binarized. Quantification of vessel density was performed after foveal avascular zone area measurement and exclusion. Patients were additionally divided into "responders" and "nonresponders" to dorzolamide therapy. Foveal avascular zone area resulted markedly enlarged at the deep capillary plexus (P < 0.001), particularly in nonresponders. Moreover, patients disclosed a significant deep capillary plexus rarefaction, when compared with controls (P: 0.04); however, a subanalysis revealed that this damage was limited to the fovea (P: 0.006). Finally, the enlargement of foveal avascular zone area positively correlated with a decline in best-corrected visual acuity (P: 0.01). Prominent foveal vascular impairment is detectable in the deep capillary plexus of patients with X-linked retinoschisis. Our results correlate with functional outcomes, suggesting a possible vascular role in X-linked retinoschisis clinical manifestations.

Chronic exposure to hypoxia attenuates renal injury and innate immunity activation in the remnant kidney model.

Hypoxia is thought to influence the pathogenesis of chronic kidney disease, but direct evidence that prolonged exposure to tissue hypoxia initiates or aggravates chronic kidney disease is lacking. We tested this hypothesis by chronically exposing normal rats and rats with 5/6 nephrectomy (Nx) to hypoxia. In addition, we investigated whether such effect of hypoxia would involve activation of innate immunity. Adult male Munich-Wistar rats underwent Nx (n = 54) or sham surgery (sham; n = 52). Twenty-six sham rats and 26 Nx rats remained in normoxia, whereas 26 sham rats and 28 Nx rats were kept in a normobaric hypoxia chamber (12% O2) for 8 wk. Hypoxia was confirmed by immunohistochemistry for pimonidazole. Hypoxia was confined to the medullary area in sham + normoxia rats and spread to the cortical area in sham + hypoxia rats, without changing the peritubular capillary density. Exposure to hypoxia promoted no renal injury or elevation of the content of IL-1β or Toll-like receptor 4 in sham rats. In Nx, hypoxia also extended to the cortical area without ameliorating the peritubular capillary rarefaction but, unexpectedly, attenuated hypertension, inflammation, innate immunity activation, renal injury, and oxidative stress. The present study, in disagreement with current concepts, shows evidence that hypoxia exerts a renoprotective effect in the Nx model instead of acting as a factor of renal injury. The mechanisms for this unexpected beneficial effect are unclear and may involve NF-κB inhibition, amelioration of oxidative stress, and limitation of angiotensin II production by the renal tissue.

Complement C3 exacerbates renal interstitial fibrosis by facilitating the M1 macrophage phenotype in a mouse model of unilateral ureteral obstruction.

The impact of the renal microenvironment on macrophage phenotype determination can contribute to the progression or resolution of renal fibrosis. Although the complement proteins affect macrophage polarization, whether complement component 3 (C3) can induce macrophage polarization and regulate renal interstitial fibrosis remains undetermined. In the present study, we investigated the contribution of C3 on macrophage polarization and renal fibrosis in C3-deficient mice with unilateral ureteral obstruction and bone marrow-derived macrophages. C3-deficient mice exhibited attenuated renal fibrosis and ameliorated peritubular capillary rarefaction. Lack of C3 contributed to M2 macrophage polarization, increased IL-10 and VEGF164, and decreased TNF-α and soluble VEGF receptor 1 expression in the obstructed kidneys at the early stages of unilateral ureteral obstruction. C3a facilitated LPS-induced M1 polarization and inflammatory factor production in bone marrow-derived macrophages in vitro, accompanied by increased ERK, NF-κB, and STAT1 phosphorylation. The ERK-specific inhibitor PD98059 inhibited the phosphorylation of ERK, NF-κB, and STAT1 and attenuated M1 polarization-related inflammatory factor production. Furthermore, the culture supernatant from M1 macrophages and C3a-treated M2 macrophages were more detrimental to angiogenesis compared with M2 macrophage supernatants. Thus, complement C3 exacerbates renal interstitial fibrosis by facilitating macrophage M1 polarization, promoting proinflammatory cytokine expression, and deteriorating peritubular capillary rarefaction in the kidney.

Imbalance of Pro- and Anti-Angiogenic Factors Due to Maternal Vitamin D Deficiency Causes Renal Microvasculature Alterations Affecting the Adult Kidney Function.

Vitamin D (Vit.D) is involved in cellular proliferation and differentiation and regulation of the renin gene, which are important aspects of nephrogenesis and quiescence of renal health in adulthood. This study evaluated the angiogenic mechanisms involved in long term renal disturbances induced by Vit.D deficiency persistent in adulthood in rats. First-generation male Hannover offspring from mothers fed either a control diet (control group, CG) or Vit.D-deficient diet (Vit.D- group) were evaluated. Systolic blood pressure (SBP) was measured monthly during the first 6 months after birth, and blood and urine samples were collected to evaluate renal function. Nitric oxide (NO), angiotensin II (ANGII), parathyroid hormone (PTH), calcium, and Vit.D were measured. The kidneys were then removed for morphometric, NO, immunohistochemical, and Western blot studies. We evaluated the expression of vascular growth factor (VEGF) and angiopoietins 1 and 2 and their receptors since this intrinsic renal axis is responsible for endothelial quiescence. Compared to CG, the Vit.D- group presented higher SBP, ANG II plasma levels, renin expression, and AT1 receptor expression levels. Capillary rarefaction was observed, as well as an imbalance between pro- and anti-angiogenic factors. Collectively, the present findings support the role of Vit.D for maintaining the integrity of renal microcirculation.

Morphological alterations of mouse skeletal muscles during early ageing are muscle specific.

One of the hallmarks of ageing is muscle wasting that may be preceded by morphological changes, such as capillary rarefaction. Muscle-specific changes in morphology in early ageing may differ between locomotor and respiratory muscles. To investigate this, we compared capillarization, fiber type composition, fiber cross-sectional area (FCSA) and oxidative capacity of individual fibers of the soleus (n = 6/5 for 20- and 79 weeks, respectively), extensor digitorum longus (EDL: n = 3/3) and diaphragm (n = 7/5) muscles in 20- (mature) and 79-week-old (early ageing) CD-1 female mice. There was no significant loss of soleus and EDL mass. The FCSA was larger and the capillary density lower at 79 than 20 weeks in the diaphragm, while in the EDL the opposite was found (both p ≤ 0.002) with no significant ageing-related differences in the soleus. The heterogeneity in capillary spacing, which may negatively impact on muscle oxygenation, was highest in muscles from 20-week-old mice, irrespective of muscle (p ≤ 0.011). Succinate dehydrogenase activity, indicative of oxidative capacity, and capillary to fiber ratio did not significantly change with age in any muscle. At all ages, the capillary supply to a fiber was positively related to FCSA in each muscle. We conclude that despite previously reported early age-related reductions in specific tension in both locomotor and respiratory muscles, morphological changes show a muscle-specific pattern in early ageing CD-1 mice. Specifically, early ageing was associated with 1) diaphragm hypertrophy 2) and fiber atrophy in the EDL that was not accompanied by angiogenesis, capillary rarefaction or reductions in oxidative capacity.

Abstract 731: Sorafenib Induces Cardiotoxicity via Damage to Cardiac Endothelial Cells

Aim: Sorafenib (Nexavar) is a multitargeted tyrosine kinase inhibitor that is used for treatment of hepatocellular carcinoma and renal cell carcinoma. Cancer treatment with sorafenib has been reported to be associated with cardiotoxic side effects such as hypertension, myocardial ischemia, thrombosis and pulmonary embolism, whereas incidence of LV dysfunction is rare. Aim of the current study was to identify the mechanism of sorafenib cardiotoxicity. Results: Healthy mice were treated with sorafenib (50 mg/kg/d) for 4 weeks. Echocardiography analysis revealed no difference in LV systolic function, but LV posterior wall thickness and relative wall thickness were significantly increased, and LV volume decreased in sorafenib treated mice. Hearts of sorafenib treated mice showed a 10-fold increase in expression of heart failure marker gene ANP and a 3-fold increase in the number of apoptotic cells. Electron microscopy analysis indicated damage to cardiac endothelial cells with no evidence of cardiomyocyte loss and co-staining of cardiac sections with endothelial marker CD31 revealed that ~80% of apoptotic cells in sorafenib treated hearts were endothelial cells (ECs). To assess for the time course for EC damage, we treated mice with sorafenib for 8h, 24h, 48h and 72h. The increase in EC death was already detected after 8h treatment and peaking at 24h-48h. RNA profiling analysis showed that expression of angiopoietin-1 (Angpt1) was reduced, whereas expression of Angpt2 was induced in hearts of mice treated with sorafenib for 4 weeks and in EC fractions from hearts of mice treated with sorafenib for 72h. Angpt-1 overexpression induced protective signaling pathways in hearts of mice treated with sorafenib for 48h, but did not rescue from acute EC injury. Treatment of Angpt1 overexpressing mice with sorafenib for 4 weeks resulted in capillary rarefaction and heart failure, evidenced by a decrease in LV systolic function and a 40-fold increase in ANP expression. Conclusion: our data shows that sorafenib cardiotoxicity is due to endothelial cell damage in the heart and results in heart failure with preserved ejection fraction. Furthermore, antagonizing the function of Angpt2 by overexpression of Angpt1 is detrimental during sorafenib treatment.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FINDINGS IN PATIENTS WITH NONOCULAR BEHÇET DISEASE.

To describe the optical coherence tomography angiography findings in nonocular Behçet disease. The superficial capillary plexus (SCP) and deep capillary plexus (DCP) and outer retinal and choroidal flow were evaluated using optical coherence tomography angiography. Perimetry was performed to correlate any microvascular and functional changes. Capillary nonperfusion areas were found in the superficial capillary plexus in 16/20 eyes (80%) and in the DCP in 17/20 eyes (85%). Perifoveal capillary arcade disruption and vessel rarefaction were present in both plexuses in all cases. Capillary telangiectasia was present in the superficial capillary plexus in five eyes (25%) and in the DCP in all eyes. Telangiectasia of the parafoveal capillaries was present in the DCP in all eyes. The mean area of the foveal avascular zone was not significantly different from that in 20 normal eyes (P = 0.68). However, mean and central subfield capillary density values were significantly lower (P < 0.001 and P < 0.005, respectively) in the Behçet disease group. Perimetry revealed central scotomata on the pattern deviation plot in 12 eyes (60%). Telangiectasia of the parafoveal capillaries was detected in the DCP in all cases. Microvascular changes in the superficial capillary plexus and DCP in nonocular Behçet disease can be detected by optical coherence tomography angiography.

Altered ellipsoid zone reflectivity and deep capillary plexus rarefaction correlate with progression in Best disease

AimsTo evaluate the effects of neurovascular damage in patients with the typical vitelliform lesion of Best vitelliform macular dystrophy (BVMD) in the attempt to identify different progression patterns.MethodsProspective, observational case...

Nox2 contributes to age-related oxidative damage to neurons and the cerebral vasculature.

Oxidative stress plays an important role in aging-related neurodegeneration. This study used littermates of WT and Nox2-knockout (Nox2KO) mice plus endothelial cell–specific human Nox2 overexpression–transgenic (HuNox2Tg) mice to investigate Nox2-derived ROS in brain aging. Compared with young WT mice (3–4 months), aging WT mice (20–22 months) had obvious metabolic disorders and loss of locomotor activity. Aging WT brains had high levels of angiotensin II (Ang II) and ROS production; activation of ERK1/2, p53, and γH2AX; and losses of capillaries and neurons. However, these abnormalities were markedly reduced in aging Nox2KO brains. HuNox2Tg brains at middle age (11–12 months) already had high levels of ROS production and activation of stress signaling pathways similar to those found in aging WT brains. The mechanism of Ang II–induced endothelial Nox2 activation in capillary damage was examined using primary brain microvascular endothelial cells. The clinical significance of Nox2-derived ROS in aging-related loss of cerebral capillaries and neurons was investigated using postmortem midbrain tissues of young (25–38 years) and elderly (61–85 years) adults. In conclusion, Nox2 activation is an important mechanism in aging-related cerebral capillary rarefaction and reduced brain function, with the possibility of a key role for endothelial cells.

Reduced vessel density in the superficial and deep plexuses in diabetic retinopathy is associated with structural changes in corresponding retinal layers.

PurposeTo explore the relationships between vessel density (VD) in the retinal vascular plexuses with the thickness and structural changes of their corresponding retinal layers in patients with diabetic retinopathy (DR).MethodsRetrospective analysis of 17 eyes of 17 Type 1 diabetes (T1D) patients with severe non-proliferative or proliferative DR and no current or past macular edema. Seventeen age- and sex-matched healthy subjects were included as controls. Using optical coherence tomography (OCT) and OCT-angiography (OCTA), VD was measured in the superficial vascular plexus (SVP) and deep vascular complex (DVC) that includes the intermediate (ICP) and deep capillary plexuses (DCP), and compared to the retinal thickness (RT) of the inner (from the inner limiting membrane to the inner plexiform layer) and intermediate (inner nuclear and outer plexiform layer) retinal layers. The correlation between the inner and intermediate RT and the VD of the corresponding vascular networks (SVP and DVC, respectively) was assessed. All OCT and OCTA examinations were performed using the RTVue XR Avanti (Optovue, Fremont, CA).ResultsThe inner RT and VD in all plexuses were significantly reduced in T1D patients compared to healthy subjects. The capillary drop-out patterns were polygonal and well-defined in the SVP while the ICP and DCP showed a more diffuse capillary rarefaction and a VD that varied in the same proportion. The inner RT significantly correlated with VD in the SVP (r = 0.71 in healthy subjects and r = 0.62 in T1D patients, p <0.01). The intermediate RT did not significantly correlate with VD in the DVC.ConclusionsIn T1D subjects, OCTA allowed observing different capillary drop-out patterns in the SVP and in the ICP-DCP, with different structural changes in the corresponding retinal layers, suggesting that they should be considered as distinct anatomical and functional entities.

Glomerular Function and Structural Integrity Depend on Hyaluronan Synthesis by Glomerular Endothelium.

A glycocalyx envelope consisting of proteoglycans and adhering proteins covers endothelial cells, both the luminal and abluminal surface. We previously demonstrated that short-term loss of integrity of the luminal glycocalyx layer resulted in perturbed glomerular filtration barrier function. To explore the role of the glycocalyx layer of the endothelial extracellular matrix in renal function, we generated mice with an endothelium-specific and inducible deletion of hyaluronan synthase 2 (Has2), the enzyme that produces hyaluronan, the main structural component of the endothelial glycocalyx layer. We also investigated the presence of endothelial hyaluronan in human kidney tissue from patients with varying degrees of diabetic nephropathy. Endothelial deletion of Has2 in adult mice led to substantial loss of the glycocalyx structure, and analysis of their kidneys and kidney function showed vascular destabilization, characterized by mesangiolysis, capillary ballooning, and albuminuria. This process develops over time into glomerular capillary rarefaction and glomerulosclerosis, recapitulating the phenotype of progressive human diabetic nephropathy. Using a hyaluronan-specific probe, we found loss of glomerular endothelial hyaluronan in association with lesion formation in tissue from patients with diabetic nephropathy. We also demonstrated that loss of hyaluronan, which harbors a specific binding site for angiopoietin and a key regulator of endothelial quiescence and maintenance of EC barrier function results in disturbed angiopoietin 1 Tie2. Endothelial loss of hyaluronan results in disturbed glomerular endothelial stabilization. Glomerular endothelial hyaluronan is a previously unrecognized key component of the extracelluar matrix that is required for glomerular structure and function and lost in diabetic nephropathy.

Skeletal muscle-derived exosomes regulate endothelial cell functions via reactive oxygen species-activated nuclear factor-κB signalling.

What is the central question of this study? Capillary rarefaction is found in diabetic and aged muscle, whereas exercise increases skeletal muscle angiogenesis. The association implies a crosstalk between muscle cells and endothelial cells. The underlying mechanisms mediating the crosstalk between these cells remains to be elucidated fully. What is the main finding and its importance? Endothelial cell functions are regulated by skeletal muscle cell-derived exosomes via a vascular endothelial growth factor-independent pathway. This study reveals a new mechanism mediating the crosstalk between skeletal muscle cells and endothelial cells. Loss of skeletal muscle capillarization, known as capillary rarefaction, is found in type2 diabetes, chronic heart failure and healthy ageing and is associated with impaired delivery of substrates to the muscle. However, the interaction and communication of skeletal muscle with endothelial cells in the regulation of capillaries surrounding the muscle remains elusive. Exosomes are a type of secreted extracellular vesicle containing mRNAs, proteins and, especially, microRNAs that exert paracrine and endocrine effects. In this study, we investigated whether skeletal muscle-derived exosomes (SkM-Exo) regulate the endothelial cell functions of angiogenesis. We demonstrated that C2C12 myotube-derived exosomes improved endothelial cell functions, assessed by the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs), which were increased by 20, 23 and 40%, respectively, after SkM-Exo exposure. The SkM-Exo failed to activate HUVEC vascular endothelial growth factor (VEGF) signalling. The SkM-Exo increased HUVEC reactive oxygen species and activated the nuclear factor-κB pathway, suggesting that SkM-Exo-induced angiogenesis was mediated by a VEGF-independent pathway. In addition, several angiogenic microRNAs were packaged in SkM-Exo, with miR-130a being particularly enriched and successfully transferred from SkM-Exo to HUVECs. Delivery of miRNAs into endothelial cells might explain the enhancement of reactive oxygen species production and angiogenesis by SkM-Exo. The potential angiogenic effect of SkM-Exo could provide an effective therapy for promoting skeletal muscle angiogenesis in diseases characterized by capillary rarefaction or inadequate angiogenesis.

Estrogen Contributions to Microvascular Dysfunction Evolving to Heart Failure With Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is a syndrome involving microvascular dysfunction. No treatment is available yet and as the HFpEF patient group is expanding due to the aging population, more knowledge on dysfunction of the cardiac microvasculature is required. Endothelial dysfunction, impaired angiogenesis, (perivascular) fibrosis and the pruning of capillaries (rarefaction) may all contribute to microvascular dysfunction in the heart and other organs, e.g., the kidneys. The HFpEF patient group consists mainly of post-menopausal women and female sex itself is a risk factor for this syndrome. This may point toward a role of estrogen depletion after menopause in the development of HFpEF. Estrogens favor the ratio of vasodilating over vasoconstricting factors, which results in an overall lower blood pressure in women than in men. Furthermore, estrogens improve angiogenic capacity and attenuate (perivascular) fibrosis formation. Therefore, we hypothesize that the drop of estrogen levels after menopause contributes to myocardial microvascular dysfunction and renders post-menopausal women more vulnerable for heart diseases that involve the microvasculature. This review provides a detailed summary of molecular targets of estrogen, which might guide future research and treatment options.