Arteriolar vascular smooth muscle cell differentiation in benign nephrosclerosis

Heterogeneous afferent arteriolopathy: a key concept for understanding blood pressure-dependent renal damage

Hypertension, aging, and other factors are associated with arteriosclerosis and arteriolosclerosis, primary morphological features of nephrosclerosis. Although such pathological changes are not invariably linked with renal decline but are prevalent across chronic kidney disease (CKD), understanding kidney damage progression is more pragmatic than precisely diagnosing nephrosclerosis itself. Hyalinosis and medial thickening of the afferent arteriole, along with intimal thickening of small arteries, can disrupt the autoregulatory system, jeopardizing glomerular perfusion pressure given systemic blood pressure (BP) fluctuations. Consequently, such vascular lesions cause glomerular damage by inducing glomerular hypertension and ischemia at the single nephron level. Thus, the interaction between systemic BP and afferent arteriolopathy markedly influences BP-dependent renal damage progression in nephrosclerosis. Both dilated and narrowed types of afferent arteriolopathy coexist throughout the kidney, with varying proportions among patients. Therefore, optimizing antihypertensive therapy to target either glomerular hypertension or ischemia is imperative. In recent years, clinical trials have indicated that combining renin-angiotensin system inhibitors (RASis) and sodium-glucose transporter 2 inhibitors (SGLT2is) is superior to using RASis alone in slowing renal function decline, despite comparable reductions in albuminuria. The superior efficacy of SGLT2is may arise from their beneficial effects on both glomerular hypertension and renal ischemia. A comprehensive understanding of the interaction between systemic BP and heterogeneous afferent arteriolopathy is pivotal for optimizing therapy and mitigating renal decline in patients with CKD of any etiology. Therefore, in this comprehensive review, we explore the role of afferent arteriolopathy in BP-dependent renal damage.

Potential Involvement of Complement Activation in Kidney Vascular Lesions of Arterionephrosclerosis

Background

Complement dysregulation has been implicated in the pathogenesis of malignant nephrosclerosis with typical pathological manifestation as thrombotic microangiopathy (TMA) in recent studies. The aim of the present study was to evaluate the potential role of complement activation in arterionephrosclerosis, the major pathological change in benign hypertensive nephrosclerosis.

Methods

Patients with biopsy-proven arterionephrosclerosis from 2010 to 2018 in our center were retrospectively enrolled in the present study. The clinical data were retrieved from the medical chart record. The pathological changes of renal biopsy were semiquantitatively evaluated. The ratio of inner-/outer-luminal diameter of the arterioles was calculated to evaluate the degree of arteriosclerosis. Immunohistochemical staining of CD34 and CD68 was adopted to evaluate peritubular capillary (PTC) density and macrophage infiltration, respectively. Complement components, including C3d, C4d, C1q, and C5b-9, were detected by immunohistochemical staining in paraffin-embedded sections. IgM and albumin were detected by immunofluorescence staining in frozen renal tissues.

Results

Fifty-two patients were enrolled. The mean age was 45.0 ± 12.7 years, with 39 (75%) males. The median duration of hypertension was 66 months (IQR: 24–138 months). A total of 950 arterioles were evaluated, with a mean ratio of the inner/outer luminal diameter of 0.43 ± 0.05. The ratio of the inner-/outer-luminal diameter correlated with eGFR (r = 0.341, p = 0.013), sclerotic/ischemic glomerular lesions (r = –0.364, p = 0.008) and PTC density (r = 0.426, p = 0.002). Seventy-four percent (703/950) of the evaluated arterioles had C3d deposition with various patterns and intensities. The percentage of C3d-positive arterioles ranged from 63.6 to 100.0% in each specimen. The ratio of the inner/outer luminal diameter of arterioles correlated with the intensity of C3d deposition (r = –0.174, p = 0.001). Infiltration of macrophages was observed around C3d-positive arterioles. The percentage of C3d-positive arterioles was correlated with macrophage infiltration in each specimen (r = 0.330, p = 0.018). Occasional C4d-positive staining on arterioles was observed with no deposition of C1q or C5b-9 in arterionephrosclerosis specimens.

Conclusion

Our findings provide evidence for potential complement activation in the pathogenesis of vascular lesions in arterionephrosclerosis.

Neutralization of S100A4 induces stabilization of atherosclerotic plaques: role of smooth muscle cells

AIMS

During atherosclerosis, smooth muscle cells (SMCs) accumulate in the intima where they switch from a contractile to a synthetic phenotype. From porcine coronary artery, we isolated spindle-shaped (S) SMCs exhibiting features of the contractile phenotype and rhomboid (R) SMCs typical of the synthetic phenotype. S100A4 was identified as a marker of R-SMCs in vitro and intimal SMCs, in pig and man. S100A4 exhibits intra- and extracellular functions. In this study, we investigated the role of extracellular S100A4 in SMC phenotypic transition.

METHODS AND RESULTS

S-SMCs were treated with oligomeric recombinant S100A4 (oS100A4), which induced nuclear factor (NF)-κB activation. Treatment of S-SMCs with oS100A4 in combination with platelet-derived growth factor (PDGF)-BB induced a complete SMC transition towards a pro-inflammatory R-phenotype associated with NF-κB activation, through toll-like receptor-4. RNA sequencing of cells treated with oS100A4/PDGF-BB revealed a strong up-regulation of pro-inflammatory genes and enrichment of transcription factor binding sites essential for SMC phenotypic transition. In a mouse model of established atherosclerosis, neutralization of extracellular S100A4 decreased area of atherosclerotic lesions, necrotic core, and CD68 expression and increased α-smooth muscle actin and smooth muscle myosin heavy chain expression.

CONCLUSION

We suggest that the neutralization of extracellular S100A4 promotes the stabilization of atherosclerotic plaques. Extracellular S100A4 could be a new target to influence the evolution of atherosclerotic plaques.

7-O-methylpunctatin, a Novel Homoisoflavonoid, Inhibits Phenotypic Switch of Human Arteriolar Smooth Muscle Cells

Remodeling of arterioles is a pivotal event in the manifestation of many inflammation-based cardio-vasculopathologies, such as hypertension. During these remodeling events, vascular smooth muscle cells (VSMCs) switch from a contractile to a synthetic phenotype. The latter is characterized by increased proliferation, migration, and invasion. Compounds with anti-inflammatory actions have been successful in attenuating this phenotypic switch. While the vast majority of studies investigating phenotypic modulation were undertaken in VSMCs isolated from large vessels, little is known about the effect of such compounds on phenotypic switch in VSMCs of microvessels (microVSMCs). We have recently characterized a novel homoisoflavonoid that we called 7-O-methylpunctatin (MP). In this study, we show that MP decreased FBS-induced cell proliferation, migration, invasion, and adhesion. MP also attenuated adhesion of THP-1 monocytes to microVSMCs, abolished FBS-induced expression of MMP-2, MMP-9, and NF-κB, as well as reduced activation of ERK1/2 and FAK. Furthermore, MP-treated VSMCs showed an increase in early (myocardin, SM-22α, SM-α) and mid-term (calponin and caldesmon) differentiation markers and a decrease in osteopontin, a protein highly expressed in synthetic VSMCs. MP also reduced transcription of cyclin D1, CDK4 but increased protein levels of p21 and p27. Taken together, these results corroborate an anti-inflammatory action of MP on human microVSMCs. Therefore, by inhibiting the synthetic phenotype of microVSMCs, MP may be a promising modulator for inflammation-induced arteriolar pathophysiology.

Association between serum uric acid level and renal arteriolar hyalinization in individuals without chronic kidney disease

BACKGROUND AND AIMS

Recent studies have reported an association between serum uric acid (SUA) and renal arteriolar changes in patients with chronic kidney disease (CKD). However, the association in individuals without CKD remains unclear. In this study, we investigated the relationship between SUA and renal arteriolar lesions in individuals without CKD from our living kidney donor cohort.

METHODS

Between January 2006 and May 2016, 393 living kidney donors underwent "time-zero" biopsy at Kyushu University Hospital. Patients were divided into sex-specific quartiles of SUA before donation: Q1, Q2, Q3, and Q4 (male: <5.2,5.2-5.8,5.9-6.4, and ≥6.5 mg/dL, female: <3.8,3.8-4.3,4.4-5.0, and ≥5.1 mg/dL). Renal arteriolar hyalinization and wall thickening were assessed using a semiquantitative grading system. Predictive performance was compared between models with and without SUA by calculating the net reclassification improvement (NRI).

RESULTS

In total, 158 (40.2%) patients had arteriolar hyalinization, and 148 (37.6%) had wall thickening. High SUA was significantly associated with arteriolar hyalinization in multivariable logistic analysis (odds ratio [OR] per 1-mg/dL increase in SUA, 1.24; 95% confidence interval [CI], 1.00-1.53; p = 0.048. OR for Q4 vs. Q2, 2.22; 95% CI, 1.17-4.21; p = 0.01). We found no association between SUA and wall thickening. When SUA was incorporated into a predictive model with conventional atherosclerotic factors, the NRI was 0.21 (p = 0.04).

CONCLUSIONS

High SUA was an independent risk factor for arteriolar hyalinization in individuals without CKD. SUA provided additional predictive value beyond conventional atherosclerotic factors in predicting arteriolar hyalinization.

Sox10+ adult stem cells contribute to biomaterial encapsulation and microvascularization

Implanted biomaterials and biomedical devices generally induce foreign body reaction and end up with encapsulation by a dense avascular fibrous layer enriched in extracellular matrix. Fibroblasts/myofibroblasts are thought to be the major cell type involved in encapsulation, but it is unclear whether and how stem cells contribute to this process. Here we show, for the first time, that Sox10⁺ adult stem cells contribute to both encapsulation and microvessel formation. Sox10⁺ adult stem cells were found sparsely in the stroma of subcutaneous loose connective tissues. Upon subcutaneous biomaterial implantation, Sox10⁺ stem cells were activated and recruited to the biomaterial scaffold, and differentiated into fibroblasts and then myofibroblasts. This differentiation process from Sox10⁺ stem cells to myofibroblasts could be recapitulated in vitro. On the other hand, Sox10⁺ stem cells could differentiate into perivascular cells to stabilize newly formed microvessels. Sox10⁺ stem cells and endothelial cells in three-dimensional co-culture self-assembled into microvessels, and platelet-derived growth factor had chemotactic effect on Sox10⁺ stem cells. Transplanted Sox10⁺ stem cells differentiated into smooth muscle cells to stabilize functional microvessels. These findings demonstrate the critical role of adult stem cells in tissue remodeling and unravel the complexity of stem cell fate determination.

ADAMTS13: more than a regulator of thrombosis

ADAMTS13, a plasma reprolysin-like metalloprotease, proteolyzes von Willebrand factor (VWF). ADAMTS13 is primarily synthesized by hepatic stellate cells (HSCs), and mainly regulates thrombogenesis by cleaving VWF. Recent studies demonstrate that ADAMTS13 also plays a role in the down-regulation of inflammation, regulation angiogenesis, and degradation of extracellular matrix. The purpose of this review is to introduce the state of progress with respect to some of the theorized roles of ADAMTS13.

Androgen receptor expression in satellite cells of the neonatal levator ani of the rat

Androgens are thought to mediate sexual differentiation of spinal nucleus of the bulbocavernosus (SNB) motoneurons via actions on androgen receptors (ARs) within their target muscles bulbocavernosus and levator ani (LA). However, the cells within these muscles which mediate masculinization of the SNB remain undefined. Until recently, myocytes were thought to be the most likely candidate cell type. However, genetic tests of AR function in myocytes have failed to support a sufficient role for these cells in producing masculine SNB morphology, suggesting the involvement of other cell types. To identify other candidate cell types in the LA, we evaluated whether satellite cells or fibroblasts express AR. Fluorescent immunohistochemistry and confocal microscopy were used to evaluate whether satellite cells and fibroblasts express AR in neonatal male and female rats in the LA and an adjacent sexually monomorphic control muscle (CM). We found that a small proportion of satellite cells in the LA express AR and that this proportion is significantly greater in the LA compared to the CM. No sex differences were found between the proportions of satellite cells expressing AR in either muscle. Less colocalization of satellite cells and AR was seen in postnatal day 3 muscle than in postnatal day 1 muscle. In contrast, only negligible amounts of fibroblasts labeled with S100A4 express AR in either the LA or the CM. Together, findings support satellite cells, but not fibroblasts, as a candidate cell type involved in the sexual differentiation of the SNB neuromuscular system.

Skeletal muscle pericyte subtypes differ in their differentiation potential

Neural progenitor cells have been proposed as a therapy for central nervous system disorders, including neurodegenerative diseases and trauma injuries, however their accessibility is a major limitation. We recently isolated Tuj1+ cells from skeletal muscle culture of Nestin-GFP transgenic mice however whether they form functional neurons in the brain is not yet known. Additionally, their isolation from nontransgenic species and identification of their ancestors is unknown. This gap of knowledge precludes us from studying their role as a valuable alternative to neural progenitors. Here, we identified two pericyte subtypes, type-1 and type-2, using a double transgenic Nestin-GFP/NG2-DsRed mouse and demonstrated that Nestin-GFP+/Tuj1+ cells derive from type-2 Nestin-GFP+/NG2-DsRed+/CD146+ pericytes located in the skeletal muscle interstitium. These cells are bipotential as they generate either Tuj1+ cells when cultured with muscle cells or become "classical" α-SMA+pericytes when cultured alone. In contrast, type-1 Nestin-GFP-/NG2-DsRed+/CD146+ pericytes generate α-SMA+pericytes but not Tuj1+ cells. Interestingly, type-2 pericyte derived Tuj1+ cells retain some pericytic markers (CD146+/PDGFRβ+/NG2+). Given the potential application of Nestin-GFP+/NG2-DsRed+/Tuj1+ cells for cell therapy, we found a surface marker, the nerve growth factor receptor, which is expressed exclusively in these cells and can be used to identify and isolate them from mixed cell populations in nontransgenic species for clinical purposes.