Molecular pathogenesis of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the commonest inherited human disorders yet remains relatively unknown to the wider medical, scientific and public audience. ADPKD is characterised by the development of bilateral enlarged kidneys containing multiple fluid-filled cysts and is a leading cause of end-stage renal failure (ESRF). ADPKD is caused by mutations in two genes: PKD1 and PKD2. The protein products of the PKD genes, polycystin-1 and polycystin-2, form a calcium-regulated, calcium-permeable ion channel. The polycystin complex is implicated in regulation of the cell cycle via multiple signal transduction pathways as well as the mechanosensory function of the renal primary cilium, an enigmatic cellular organelle whose role in normal physiology is still poorly understood. Defects in cilial function are now documented in several other human diseases including autosomal recessive polycystic kidney disease, nephronophthisis, Bardet-Biedl syndrome and many animal models of polycystic kidney disease. Therapeutic trials in these animal models of polycystic kidney disease have identified several promising drugs that ameliorate disease severity. However, elucidation of the function of the polycystins and the primary cilium will have a major impact on our understanding of renal cystic diseases and will create exciting new opportunities for the design of disease-specific therapies.     

Regulation of production and secretion of adrenomedullin in the cardiovascular system

Adrenomedullin (AM) has multi-functional properties, of which the vasodilatory hypotensive effect is the most characteristic. AM and its gene are ubiquitous in a variety of tissues and organs, in the cardiovascular system, as well as the adrenal medulla. AM secretion, especially in cardiovascular tissues, is regulated mainly by mechanical stressors such as shear stress, inflammatory cytokines such as interleukin (IL)-1, tumor necrosis factor (TNF), and lipopolysaccharide (LPS), hormones such as angiotensin (Ang) II and endothelin (ET)-1, and metabolic factors such as hypoxia, ischemia, or hyperglycemia. Elevation of plasma AM due to overproduction in response to one or more of these stimuli in pathological conditions may explain the raised plasma AM levels present in cardiovascular and renal diseases such as congestive heart failure, myocardial infarction, hypertension, chronic renal failure, stroke, diabetes mellitus, and septic shock. In addition to shear stress, stretching of cardiomyocytes may be another mechanical stimulus for AM synthesis and secretion. Our recent studies have shown the importance of aldosterone and additional hormonal factor on AM secretion in vascular wall.     

Exploring the association between extra-cardiac troponin elevations and risk of future mortality

Although the measurement of cardiac troponin I (cTnI) and T (cTnT) has now become the cornerstone for diagnosing cardiac injury, both ischemic and non-ischemic, recent evidence has become available that many patients display extra-cardiac causes of cTn elevations and carry a considerably enhanced risk of future mortality. The current literature data suggests that cTn elevations may be equally common in patients with cardiac and extra-cardiac diseases. Among the latter cohort of patients, the leading extra-cardiac diseases which may be responsible for either cTnI or cTnT elevations include infectious diseases/sepsis, pulmonary disorders, renal failure, malignancy, as well as gastrointestinal, neurological and musculoskeletal diseases. What also emerges rather clearly from the current literature data, is that the risk of dying for extra-cardiac diseases is higher (i.e., between two to three-fold) in patients with extra-cardiac cTn elevations than in those with cardiac pathologies, and that the most frequent cause of death would then be infections/sepsis, followed by malignancy, respiratory disorders, myocardial infarction, gastrointestinal and neurological diseases, heart failure, stroke, cardiac arrhythmias, renal failure, psychiatric, metabolic, urogenital and musculoskeletal disorders. These figures would lead to conclude that there is a considerable risk that the underlying pathology causing cardiac injury and cTn elevation would then become the cause of death in these patients. This important evidence shall lead the way to defining appropriate and effective strategies for managing patients with extra-cardiac cTn elevations, so that their risk of future death could be prevented or limited.     

Role of HRTPT in kidney proximal epithelial cell regeneration: Integrative differential expression and pathway analyses using microarray and scRNA-seq

Damage to proximal tubules due to exposure to toxicants can lead to conditions such as acute kidney injury (AKI), chronic kidney disease (CKD) and ultimately end-stage renal failure (ESRF). Studies have shown that kidney proximal epithelial cells can regenerate particularly after acute injury. In the previous study, we utilized an immortalized in vitro model of human renal proximal tubule epithelial cells, RPTEC/TERT1, to isolate HRTPT cell line that co-expresses stem cell markers CD133 and CD24, and HREC24T cell line that expresses only CD24. HRTPT cells showed most of the key characteristics of stem/progenitor cells; however, HREC24T cells did not show any of these characteristics. The goal of this study was to further characterize and understand the global gene expression differences, upregulated pathways and gene interaction using scRNA-seq in HRTPT cells. Affymetrix microarray analysis identified common gene sets and pathways specific to HRTPT and HREC24T cells analysed using DAVID, Reactome and Ingenuity software. Gene sets of HRTPT cells, in comparison with publicly available data set for CD133+ infant kidney, urine-derived renal progenitor cells and human kidney-derived epithelial proximal tubule cells showed substantial similarity in organization and interactions of the apical membrane. Single-cell analysis of HRTPT cells identified unique gene clusters associated with CD133 and the 92 common gene sets from three data sets. In conclusion, the gene expression analysis identified a unique gene set for HRTPT cells and narrowed the co-expressed gene set compared with other human renal–derived cell lines expressing CD133, which may provide deeper understanding in their role as progenitor/stem cells that participate in renal repair.     

Immunoglobulin-free light chains elicit immediate hypersensitivity-like responses

Immunoglobulin (Ig)-free light chains IgLC are present in serum and their production is augmented under pathological conditions such as multiple sclerosis, rheumatoid arthritis and neurological disorders. Until now, no (patho)physiological function has been ascribed to circulating Ig light chains. Here we show that IgLCs can confer mast cell dependent hypersensitivity in mice. Antigenic stimulation results in plasma extravasation, cutaneous swelling and mast-cell degranulation. We show that IgLCs have a crucial role in development of contact sensitivity, which could be completely prevented by a novel IgLC antagonist. Although IgE and IgG(1) are central to the induction of immediate hypersensitivity reactions, our results show that IgLCs have similar activity. IgLCs may therefore be a novel factor in the humoral immune response to antigen exposure. Our findings open new avenues in investigating the pathogenesis of autoimmune diseases and their treatments.     

动脉钙化发生机制研究进展

动脉钙化是指钙盐沉积在动脉壁组织的一种病理改变,会减少主动脉和支动脉的弹性,改变心血管系统的血液流动力学,导致高血压、主动脉瓣狭窄、心脏肥厚、心肌和下肢缺血、充血性心力衰竭等严重心脑血管疾病发生。动脉钙化在老年人群中是一种常见的疾病。早期研究发现尿毒症患者体内磷酸钙沉积的抑制剂——焦磷酸盐水平升高,故有学者认为钙磷被动地沉积于血管壁是引起血管钙化的主要原因。近年来的研究发现,血管钙化并非简单地由于磷酸钙晶体被动地沉积于血管壁,而是一个与骨发育相似的主动的、可预防和可逆转的高度可调控的生物学过程。动脉钙化的发生受多因素共同调控,但其确切机制尚不清楚,最近发现炎症小体也以某种未知的机制参与钙化调控过程。     

An alternative origin for nanobacteria in kidney stones

Small (50–200 nm), calcium phosphate (apatite)-covered organic particles called nanobacteria or calcifying nanoparticles (CNP) seem to be ubiquitous in kidney stones and are thought to be involved in stone formation. Although initial claims that these particles are the smallest known life forms have been somewhat softened, much controversy remains as to their involvement in kidney stone formation as well as in other pathological calcifications. I suggest that such particles are non-living and may be formed during the normal living activities of bona-fide bacteria which inhabit the kidneys. This hypothesis is based on previous observations that bacteria immersed in a supersaturated fluid produce organic globules which calcify when released to the surrounding fluid, forming CNP-like particles. The possibility that this process is responsible for the formation of CNP associated with pathological calcifications deserves greater scrutiny.     

金属硫蛋白与医学

金属硫蛋白是一类富含巯基与金属的内源性蛋白,化学结构极为特殊,该蛋白的为具有很强的诱导性,金属,糖皮质激素,某些化的和应激状态均可诱导其生成,在炎症等应激过程中ＩＬ－６可能为诱导者。在不降低疗效的情况下该蛋白可解除抗肿瘤药物ＣＤＤＰ的抗药性密切有关,金属硫蛋白与炎性肠病,妊娠中毒症,肝脏疾患等多种疾病密切相关。     

The role of microvesicles in tissue repair

Microvesicles (MVs) are released by almost all cells in resting and activated conditions. First described several years ago, it is only recently that their mechanisms of action are being elucidated, and their potential role in health and disease is drawing increasing attention. The main function of MVs is signaling through specific interactions with target cells and the transferring of gene products. Gaining further insights into the molecular specificity of MVs has allowed identification of the cellular source and may provide new diagnostic tools in the future. Indeed, an increasing body of evidence indicates that MVs are capable of mediating tissue repair in models of acute kidney and liver injury. In this review, we will discuss the mechanisms through which MVs from stem cells may act on target cells and may modify the response to injury. Furthermore, MVs from inflammatory cells are suspected to be involved in various diseases, such as cardiovascular and renal diseases, pathological pregnancy, tumors and sepsis. MVs are no doubt also involved in modulating immunity, and future studies will clarify their functional role in negatively modulating the cell response. Their role in physiological and pathological processes is increasingly appreciated. Depending on the cell source and the condition, MVs may be either beneficial or detrimental to the host. The recognition of their pathogenetic role may suggest new approaches to future therapies.     

The role of microvesicles in tissue repair

Microvesicles (MVs) are released by almost all cells in resting and activated conditions. First described several years ago, it is only recently that their mechanisms of action are being elucidated, and their potential role in health and disease is drawing increasing attention. The main function of MVs is signaling through specific interactions with target cells and the transferring of gene products. Gaining further insights into the molecular specificity of MVs has allowed identification of the cellular source and may provide new diagnostic tools in the future. Indeed, an increasing body of evidence indicates that MVs are capable of mediating tissue repair in models of acute kidney and liver injury. In this review, we will discuss the mechanisms through which MVs from stem cells may act on target cells and may modify the response to injury. Furthermore, MVs from inflammatory cells are suspected to be involved in various diseases, such as cardiovascular and renal diseases, pathological pregnancy, tumors and sepsis. MVs are no doubt also involved in modulating immunity, and future studies will clarify their functional role in negatively modulating the cell response. Their role in physiological and pathological processes is increasingly appreciated. Depending on the cell source and the condition, MVs may be either beneficial or detrimental to the host. The recognition of their pathogenetic role may suggest new approaches to future therapies.     

Tackling the effects of extracellular vesicles in fibrosis

Fibrosis is a physiological process of tissue repair that turns into pathological when becomes chronic, damaging the functional structure of the tissue. In this review we outline the current status of extracellular vesicles as modulators of the fibrotic process at different levels. In adipose tissue, extracellular vesicles mediate the intercellular communication not only between adipocytes, but also between adipocytes and other cells of the stromal vascular fraction. Thus, they could be altering essential processes for the functionality of adipose tissue, such as adipocyte hypertrophy/hyperplasia, tissue plasticity, adipogenesis and/or inflammation, and ultimately trigger fibrosis. This process is particularly important in obesity, and may eventually, influence the development of obesity-associated alterations. In this regard, obesity is now recognized as an independent risk factor for the development of chronic kidney disease, although the role of extracellular vesicles in this connection has not been explored so far. Nonetheless, the role of extracellular vesicles in the onset and progression of renal fibrosis has been highlighted due to the critical role of fibrosis as a common feature of kidney diseases. In fact, the content of extracellular vesicles disturbs cellular signaling cascades involved in fibrosis in virtually all types of renal cells. What is certain is that the study of extracellular vesicles is complex, as their isolation and manipulation is still difficult to reproduce, which complicates the overview of their physiopathological effects. Nevertheless, new strategies have been developed to exploit the potential of extracellular vesicles and their cargo, both as biomarkers and as therapeutic tools to prevent the progression of fibrosis towards an irreversible event.     

Options in uraemia therapy for diabetics with end-stage renal disease

In many countries, diabetic renal disease has become, or will soon become, the single most common cause of end-stage renal disease (ESRD). End-stage renal failure (ESRF) in type-2 diabetic patients is increasing worldwide. Incidence of ESRF caused by diabetic nephropathy (DN) in 1996 in the USA was 41.7% and prevalence was 32.4%. ESRD and ESRF caused by DN was 10%, 5-15% in different haemodialysis centres in adults in the year 2000 in the Republic of Macedonia. In this review article we discuss options in uraemia therapy for diabetics with ESRD. Assessment and treatment of a diabetic with ESRD must be highly individualized. Haemodialysis (HD) has emerged as the most common treatment for all forms of renal failure including diabetic nephropathy. In diabetics patients with ESRD, dialysis is started early at creatinine clearance as high as 15-20 ml/min, at serum creatinin levels as low as 3-5 mg/dl. The first choice of HD access in diabetics is an autologous a-v fistula of the Cimino-Brescia type. The A-V fistula should be created several months before starting HD when creatinine clearance is above 20-25 ml/min. When peritoneal dialysis (PD) is selected, advance planning should ensure that a suitable peritoneal catheter is in situ 2-4 weeks before starting dialysis. HD procedures should be with low ultrafiltration rates and prolonged duration of dialysis sessions. The ultrafiltration in diabetics should not exceed more than 500-600 ml/h on HD. This means dialysis sessions of more than 4h and, in larger patients, of more than 5h HD three times per week. Renal transplantation (RT) is a safe and effective treatment modality for diabetic subjects with ESRD. Cardiovascular disease and serious infections are the major causes of death in haemodialysed and transplanted diabetics. Despite recent improvement, rehabilitation of HD diabetics continues to be inferior to that of non-diabetics. Improvement of survival is a matter of reduction of cardiovascular death and infection.     

Understanding ageing.

A broad biological approach makes it possible to understand why ageing exists and also why different mammalian species have very different maximum longevities. The adult organism is maintained in a functional state by at least ten major mechanisms, which together comprise a substantial proportion of all biological processes. These maintenance mechanisms eventually fail, because the evolved physiological and anatomical design of higher animals is incompatible with continual survival. The lifespan of each mammalian species depends on the efficiency of maintenance of their cells, tissues and organisms, and there is much evidence that such maintenance is more effective in long-lived species, such as man, than in short-lived small mammals. It is also evident that there is an inverse relationship between reproductive potential and longevity, which would be expected if total metabolic resources are shared between investment in reproduction, and investment in the preservation of the adult body. It is proposed that the eventual failure of maintenance leads to the pathological changes seen in age-associated disease. Although we now have a biological understanding of the ageing process, much future research will be needed to uncover the cellular and molecular changes which give rise to age-associated diseases. The major aim of such research is to devise procedures to delay or prevent the onset of these diseases.     

Developement and quality control of a radioimmunoassay for measurement of endogenous digoxin

It has been suggested that sodium renal excretion is regulated, at least partially, by a factor with natriuretic properties called digoxin-like factor (DLF). As this substance crossreacts with digoxin antibodies, it was measured with a radioimmunoassay used to determine exogenous digoxin. Methodological conditions and quality control to determine DLF in plasma and urine have been established. Good correlation coefficients in specificity as well as dilution studies were obtained. Within--and between--assay coefficients of variations indicate good reproducibility. Moreover, changes in plasma DLF levels were detected in patients with cirrhosis or with renal failure, diseases which thrive on alterations in salt and water metabolism. In conclusion, this radioimmunoassay method for measuring DLF may be useful to investigate the role of this factor in several physiological and pathological conditions.     

ICAM-1 interactions in the renal interstitium: a novel activator of fibroblasts during nephritis.

Chronic renal diseases often degenerate towards end-stage failure, requiring replacement renal therapy. The progressive decline of such diseases is a highly complex, multi-factorial process, which is poorly understood. Indeed, not all chronic conditions take on a progressive course, some may recover to regain normal function, while others may remain functionally impaired yet stable. The structural features of progressive decline, however, show common histological features, despite the diverse nature of the primary injury. These aberrant structural alterations are characterised essentially by a dramatic expansion of the tubulointerstitium, with accompanying tubular atrophy, resulting from interstitial fibrosis. These changes are thought to be a uniform response to prolonged inflammation which may originate in the glomerulus, the vasculature or the interstitial space (Strutz et al., 1995). A histomorphometric analysis of renal diseases, initially performed by Risdon et al. (1968), and supported by Bohle et al. (1987) and others (Eknoyan et al., 1990), revealed that the severity of abnormal glomerular pathology did not always correlate directly with impaired renal function. The extent of interstitial inflammation and the degree of interstitial fibrosis, however, were both shown to be more accurate predictors of renal function (Bohle et al., 1992). Furthermore there was a high probability of irreversible functional decline, in the presence of interstitial fibrotic lesions and tubular atrophy. Interstitial fibrosis is therefore considered an important histological marker for end stage renal failure, and is believed to be functionally more significant than primary changes within the glomerulus. In most tissues, resident fibroblasts are believed to be the cells principally responsible for the synthesis and breakdown of extracellular matrix (ECM) within connective tissues. Indeed in fibrotic diseases of lung and skin, the resident fibroblast has been identified as the most important cell responsible for the abnormal deposition of ECM components during the disease process (Phan et al., 1985). In the kidney, there are probably several sources of matrix components during fibrosis including tubular epithelial cells, inflammatory macrophages (Vaage and Linbland, 1990) as well as interstitial fibroblasts. Although the precise cellular source of the bulk of this matrix requires clarification, there is mounting evidence supporting a significant contribution from resident or infiltrating fibroblasts (Rodemann and Muller, 1990, 1991a,b; Strutz and Muller, 1995).     

Molecular biology of hypophosphataemic rickets and oncogenic osteomalacia

Phosphate plays a centrol role in many of the basic processes essential to the cell and organism. In particular, skeletal mineralisation is dependent on the appropriate regulation of phosphate in the body, and any disturbances in phosphate homeostasis can have severe repercussions on the integrity of bone. The kidney regulates the serum levels of phosphate by tubular mechanisms which are not fully understood. Furthermore, the processes involved in regulating renal tubular phosphate reabsorption are complex, and involve a large number of factors. It is not surprising therefore that defects in renal phosphate handling result in a failure of bone mineralisation. There are three well characterised conditions which are associated with renal tubulopathies resulting in a phosphate leak, with consequent bone disease. Two are familial, hypophosphataemic rickets (HYP), and hereditary hypophosphataemic rickets with hypercalciuria (HHRH). The third is acquired via a tumour, oncogenic hypophosphataemic osteomalacia (OHO), and may well have relevance to the inherited hypophosphataemias. Recent advances in molecular genetics are permitting the identification of genes involved in human diseases from their chromosomal location. These approaches are now being applied to the analysis of the hypophosphataemias. The isolation of the genes responsible for the renal tubulopathies will be an important achievement. Ultimately this will help to increase our understanding of the mechanisms involved in the control of phosphate handling in the body.     

Lack of association of ACE/angiotensinogen genotype with renal function in autosomal dominant polycystic kidney disease

ACE polymorphisms have recently been shown to associate with worse renal and or cardiovascular outcome, with the D allele widely reported as a risk factor for cardiovascular disease. In autosomal dominant polycystic kidney disease (ADPKD), there are conflicting reports of an association between ACE polymorphisms and disease phenotype. There are no previous reports of any association between angiotensinogen polymorphisms and clinical phenotype in ADPKD. We examined the ACE I/D and angiotensinogen M235T polymorphisms in 176 patients with ADPKD. Patients are categorized into three groups according to the reason for initial investigation. Clinical history and examination findings were recorded at the time of first referral. A cohort of 17 patients had progressive renal impairment observed after 3 or more years of follow-up. Reciprocal creatinine against time was plotted in this group. From the patient population of 176, a total of 33 patients reached end-stage renal failure (ESRF) or a serum creatinine greater than 500 microm/liter. ACE genotype and M235T polymorphism frequencies were compared across groups. Serum creatinine and presence of hypertension and onset of ESRF were taken as outcome variables; age and source of referral were taken as confounding variables. There was no association of any genotype or allele with either creatinine, inverse creatinine, hypertension, or age at end-stage renal failure. These findings do not support the proposition that ACE genotype or angiotensinogen polymorphisms are associated with a worse prognosis in patients with ADPKD.     

Inhibition of TLR2 promotes graft function in a murine model of renal transplant ischemia-reperfusion injury

Toll-like receptors (TLRs) are important molecules involved in the activation of innate and subsequent development of adaptive immunity. TLRs are ligated by exogenous ligands from pathogens and by endogenous ligands released in inflammatory diseases. Activation of TLR leads to activation of NF-κB and release of proinflammatory cytokines, such as IL-6 and TNF-α. TLRs play an important role in the pathogenesis of renal diseases. Increased expression of TLRs have been associated with ischemic kidney damage, acute kidney injury, end-stage renal failure, acute renal transplant rejection, and delayed allograft function. OPN301 is a mouse anti-human TLR2 antibody that cross-reacts with mouse TLR2. We show that inhibition of TLR2 promotes graft function in an isograft model of renal transplantation. Recipient mice were treated intravenously with OPN301 before reperfusion of the transplanted kidney that had been subjected to 30 min of cold ischemia. After 5 d, the residual native kidney was removed, and renal transplant function was assessed 24 h later by measurement of blood urea nitrogen. Renal function in both saline- and isotype-treated mice was similar, with significant improvement in OPN301-treated mice (isotype-treated vs. OPN301-treated: 33.9±3.2 vs. 19.8±1.9 μM; P<0.01). The histopathological appearance corresponded with renal functional results. In OPN301-treated recipients, renal structure was well preserved, whereas in the saline-treated group, tubular injury was severe, with marked tubular thinning, epithelial shedding, cast formation and necrosis. Inhibition of TLR2 also leads to a decrease in C3d deposition, although it is unclear whether this is due directly to TLR2 inhibition or a decrease in renal inflammation. This study shows that inhibition of TLR2 with a therapeutic agent (OPN301) provides significant protection from ischemia/reperfusion injury in a model of kidney transplantation.