绝经后骨质疏松症发病机制的表观遗传学研究进展

表观遗传学修饰是指在DNA序列未变化情况下发生可遗传的基因表达的变化,主要机制包括DNA甲基化、组蛋白修饰、非编码RNAs、染色质修饰等。绝经后骨质疏松症(postmenopausal osteoporosis,PMOP)属于原发性骨质疏松症的一种,主要是由于绝经后女性激素水平改变等原因致使骨代谢失衡,骨微结构破坏,骨量减少。近年来,大量研究证实了表观遗传学参与绝经后骨质疏松症的发生发展,本文将从DNA甲基化、组蛋白修饰和非编码RNAs这三个方面综述绝经后骨质疏松症在表观遗传学方面的发病机制。     

精子发生过程中的表观遗传学调控

精子发生是由精原细胞增殖、精母细胞减数分裂以及精子形成所组成的连续过程。精子发生也是染色质不断凝集的过程,最终在精子头部达到高度浓缩状态。近年来的研究表明,表观遗传调控在精子发生过程中发挥作用。我们将从三方面简要阐述精子发生过程中的表观遗传学调控机制:DNA甲基化,组蛋白修饰以及非编码RNA。这些表观因素之间也可以互相调控,通过调控基因表达、转座子活化、性染色体失活以及基因印记等,在精子发生,受精以及胚胎发育过程中扮演重要角色。     

Epigenetic regulation in the acute kidney injury to chronic kidney disease transition

Epigenetic modifications have emerged as a new, important contributor to gene expression regulation in both normal and pathophysiological conditions. Epigenetics have been studied in many diseases and conditions such as acute kidney injury (AKI), a syndrome with a high prevalence that carries a poor prognosis with increased morbidity and mortality. In addition, it has recently been shown that AKI increases the risk for the development of chronic kidney disease (CKD). The specific molecular mechanisms by which AKI increases the risk of CKD and end stage renal disease (ESRD) remain unknown, although there is new evidence supporting a role of epigenetic changes. The most studied epigenetic regulations in AKI are chromatin compaction, DNA methylation, and histone acetylation/deacetylation. These modifications predominantly increase the production of pro‐inflammatory and profibrotic cytokines such as: monocyte chemoattractant protein‐1 (MCP‐1), complement protein 3 (C3), transforming growth factor β (TGF‐β) that have been shown for perpetuating inflammation, promoting epithelial‐to‐mesenchymal transition (EMT) and ultimately causing renal fibrosis. A review of epigenetic mechanisms, the pathophysiology of AKI and recent studies that implicate epigenetic modifications in AKI and in the transition to CKD are discussed below.     

Oxygen species in the microvascular environment: regulation of vascular tone and the development of hypertension.

Derangements of the three endothelium-related vasodilator systems (prostaglandins, endothelium-derived hyperpolarizing factor(s) and nitric oxide) cause the endothelial dysfunction observed in hypertension. Free radical-induced nitric oxide degradation plays a crucial role in hypertension. An increase in superoxide producing enzymes such as NAD(P)H oxidase and xanthine oxidase has been demonstrated. Superoxide dismutase may correct endothelial dysfunction in vitro and superoxide dismutase mimetics can lower blood pressure in experimental animals. Antioxidant agents and xanthine oxidase-inhibiting compounds have been used in humans. In addition, the synthesis of vasoconstrictor peroxides derived from the activity of cyclooxygenase in the endothelium and the vascular smooth muscle is stimulated by the OH. radical. Hydrogen peroxide levels are augmented in hypertension, but its role is unclear because recent investigations have shown that this substance may act as a hyperpolarizing factor. It is thought that the therapeutic benefit of anti-hypertensive drugs, such as calcium antagonists and angiotensin-converting enzyme inhibitors, could be in part due to an inhibition of free radical production. A role of superoxide in the endothelial dysfunction and hypertension of chronic renal failure has also been suggested by recent animal experiments.     

How important is the duration of the brain death period for the outcome in kidney transplantation?

In kidney transplantation, graft survival using grafts from donation after brain death (DBD) donors is inferior to results after living donation. However, little is known about the effect of the duration of brain death (BDdur) on outcome after transplantation. This is a retrospective Organ Procurement and Transplant Network analysis using kidney donor and recipient data from 1994 to 2006. BDdur was calculated as the period between brain death declaration and aortic cross clamp. Effects of BDdur on delayed graft function (DGF), acute rejection and graft failure were calculated using binary logistic regression and Cox regression models. Median BDdur was 23.8 h. Longer BDdur decreased the risk for DGF and 1‐ and 3‐year graft failure slightly, but not for acute rejection. In multivariate analysis, donor age and acute rejection were confounders. However, in a multivariate subgroup analysis of donors aged ≤55 years BDdur independently predicted DGF; each hour of BDdur decreasing the risk of DGF with 0.4% (P = 0.008). Longer BDdur is not detrimental and in fact slightly beneficial in DBD donors ≤55 years of age, reducing the chance of DGF in the recipient. This finding may have an impact on organ retrieval procedures, as no rush but rather an improved donor management prior to retrieval will benefit donor kidney viability.     

Gene transfer to the rat kidney in vivo and ex vivo using an adenovirus vector: factors influencing transgene expression.

BACKGROUND: The characteristics of adenovirus-mediated gene transfer into the kidney are not well examined. We studied the effects of contact time and temperature on adenovirus-mediated transgene expression in rat kidneys, using catheter-based in vivo gene transfer and a rat renal transplant model ex vivo. METHODS: An adenovirus vector containing the luciferase (Ad-Luc) or beta-galactosidase (Ad-LacZ) gene was introduced in vivo into the kidney via a renal artery catheter. Various contact times and temperatures were evaluated. Ex vivo, the renal graft was injected with Ad-Luc through the renal artery, chilled for 60 min and then transplanted. Luciferase expression was evaluated periodically by a non-invasive bioimaging system or histology. Cells expressing the LacZ gene were identified by immunoelectron microscopy. RESULTS: In in vivo gene transfer, successful transgene expression was achieved; however, its efficiency was independent of contact time or temperature. In ex vivo gene transfer, transgene expression in the renal graft peaked early and gradually decreased. Strong gene expression was observed in the recipients' livers. LacZ expression was detected in fibroblasts, parietal epithelial cells of Bowman's capsule, mesangial cells, podocytes and tubular cells. CONCLUSIONS: This study generated new information about in vivo and ex vivo gene transfer into the kidney, which would be useful for renal gene therapy.     

Endemic rise in cases of acute kidney injury in children in Indonesia and Gambia: what is the likely culprit and why?

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大鼠腹部增压皮瓣模型中动、静脉增压作用的研究

目的 对大鼠腹部增压皮瓣模型中血流变化进行连续、动态观测,探索动脉增压、静脉增压分别在避免皮瓣远端坏死中的作用.方法 在SD大鼠腹部设计动静脉增压、动脉增压和静脉增压3种形式的增压皮瓣,采用近红外荧光血管造影技术对3种增压皮瓣模型中血流变化进行连续、动态的观测,对获得的血流变化影像视频进行比较和分析.同时另设计对照组皮瓣.结果 血管造影视频显示,静脉增压组和对照组皮瓣远端动脉灌注消失,术后出现了不同程度的远端皮瓣坏死,相对于对照组,静脉增压组皮瓣远端坏死面积明显减少.动静脉增压组和动脉增压组皮瓣远端动脉血流灌注充分,术后所有皮瓣完全成活.结论 皮瓣远端动脉灌注不足是造成皮瓣远端静脉瘀滞、坏死的主要原因,动脉增压确保皮瓣远端动脉血流的灌注,能够避免皮瓣远端坏死的发生.     

The antioxidant tempol ameliorates arterial medial calcification in uremic rats: important role of oxidative stress in the pathogenesis of vascular calcification in chronic kidney disease

Vascular calcification is closely related to cardiovascular morbidity and mortality. Accumulating data indicate that oxidative stress is associated with dysfunction of various organs, including cardiovascular diseases in chronic kidney disease (CKD). However, it remains undetermined if oxidative stress induced by uremia promotes arterial medial calcification. The present study investigated the role of oxidative stress in the pathogenesis of arterial medial calcification in uremic rats. Rats with uremia induced by adenine-rich diet progressively developed arterial medial calcification, which was accompanied by time-dependent increases in both aortic and systemic oxidative stress. Immunohistochemical and biochemical analyses showed that the arterial medial calcification progressed in a time-dependent manner that is parallel to the osteogenic transdifferentiation of vascular smooth muscle cells. Accumulation of oxidative stress was also identified in the calcified regions. Time-course studies indicated that both oxidative stress and hyperphosphatemia correlated with arterial medial calcification. Tempol, an antioxidant, ameliorated osteogenic transdifferentiation of vascular smooth muscle cells and arterial medial calcification in uremic rats, together with reduction in aortic and systemic oxidative stress levels, without affecting serum biochemical parameters. Our data suggest that oxidative stress induced by uremia can play a role in the pathogenesis of vascular calcification in CKD, and that antioxidants such as tempol are potentially useful in preventing the progression of vascular calcification in CKD.     

Functional changes in the ageing kidney: is there a role for asymmetric dimethylarginine?

Age-related changes of renal haemodynamics Normal human ageing occurs with morphological and functionalchanges in nearly all organ systems, and the kidney is no exceptionto this rule. Even in individuals without primary renal disease,kidney structure and function deteriorate with senescence tosome extent. Recent studies have revealed, however, that age-relatedrenal changes are accelerated by co-morbid conditions such ashypertension, atherosclerosis and heart failure [1–5]. Results from the seminal ‘Baltimore Longitudinal Studyon Aging’ and from several cross-sectional studies haveshown that the decrease of glomerular filtration rate (GFR)in healthy elderly subjects is less than was thought previously[1,3,6,7]. In some     

SHOX gene is expressed in vertebral body growth plates in idiopathic and congenital scoliosis: Implications for the etiology of scoliosis in turner syndrome

Reduced SHOX gene expression has been demonstrated to be associated with all skeletal abnormalities in Turner syndrome, other than scoliosis (and kyphosis). There is evidence to suggest that Turner syndrome scoliosis is clinically and radiologically similar to idiopathic scoliosis, although the phenotypes are dissimilar. This pilot gene expression study used relative quantitative real-time PCR (qRT-PCR) of the SHOX (short stature on X) gene to determine whether it is expressed in vertebral body growth plates in idiopathic and congenital scoliosis. After vertebral growth plate dissection, tissue was examined histologically and RNA was extracted and its integrity was assessed using a Bio-Spec Mini, NanoDrop ND-1000 spectrophotometer and standard denaturing gel electrophoresis. Following cDNA synthesis, gene-specific optimization in a Corbett RotorGene 6000 real-time cycler was followed by qRT-PCR of vertebral tissue. Histological examination of vertebral samples confirmed that only growth plate was analyzed for gene expression. Cycling and melt curves were resolved in triplicate for all samples. SHOX abundance was demonstrated in congenital and idiopathic scoliosis vertebral body growth plates. SHOX expression was 11-fold greater in idiopathic compared to congenital (n = 3) scoliosis (p = 0.027). This study confirmed that SHOX was expressed in vertebral body growth plates, which implies that its expression may also be associated with the scoliosis (and kyphosis) of Turner syndrome. SHOX expression is reduced in Turner syndrome (short stature). In this study, increased SHOX expression was demonstrated in idiopathic scoliosis (tall stature) and congenital scoliosis. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 807–813, 2009     

Cement volume is the most important modifiable predictor for pain relief in BKP: results from SWISSspine, a nationwide registry

Purpose

The effectiveness of vertebral augmentation techniques is a currently highly debated issue. The biomechanical literature suggests that cement filling volumes may play an important role in the “dosage” of vertebral augmentation and its pain alleviating effect. Good clinical data about filling volumes are scarce and most patient series are small. Therefore, we investigated the predictors of pain alleviation after balloon kyphoplasty in the nationwide SWISSspine registry where cement volumes are also recorded.

Methods

All single-level vertebral fractures with no additional fracture stabilization and availability of at least one follow-up within 6 months after surgery were included. The following potential predictors were assessed in a multivariate logistic regression model with the group’s average pain alleviation of 41 points on VAS as the desired outcome: patient age, patient sex, diagnosis, preoperative pain, level of fracture, type of fracture, age of fracture, segmental kyphotic deformity, cement volume, vertebral body filling volume, and cement extrusions.

Results

There were 194 female and 82 males with an average age of 70.4 and 65.3 years, respectively. Female patients were about twice as likely for achieving the average pain relief compared to males (p = 0.04). The preoperative pain level was the strongest predictor in that the likelihood for achieving an at least 41-point pain relief increased by about 8 % with each additional point of preoperative pain (p < 0.001). A thoraco-lumbar fracture had a three times higher odds for the average pain relief compared with a lumbar fracture (p = 0.03). An A.3.1 fracture only had about a third of the probability for average pain relief compared with an A.1.1 fracture (p = 0.004). Cement volumes up to 4.5 ml only had an approximately 40 % chance for a minimum 41-point pain alleviation as compared with cement volumes of at least 4.5 ml (p = 0.007). In addition, the relationship between cement volume and pain alleviation followed a dose-dependent pattern.

Conclusions

Cement volume was revealed as a significant predictor for pain relief in BKP. Cement volume was the third most important influential covariate and the most important modifiable and operator dependent one. The clear dose-outcome relationship between cement filling volumes and pain relief additionally supports these findings. Cement volumes of >4.5 ml seem to be recommendable for achieving relevant pain alleviation. Patient sex and fracture type and location were further significant predictors and all these covariates should be recorded and reported in future studies about the pain alleviating effectiveness of vertebral augmentation procedures.     

Angiotensin II facilitates autoregulation in the perfused mouse kidney: An optimized in vitro model for assessment of renal vascular and tubular function

BACKGROUND AND AIMS: We have optimized the isolated perfused mouse kidney (IPMK) model for studying renal vascular and tubular function in vitro using 24-28 g C57BL6J mice; the wild type controls for many transgenic mice. METHODS AND RESULTS: Buffer composition was optimized for bovine serum albumin concentration (BSA). The effect of adding erythrocytes on renal function and morphology was assessed. Autoregulation was investigated during stepped increases in perfusion pressure. Perfusion for 60 min at 90-110 mmHg with Krebs bicarbonate buffer containing 5.5% BSA, and amino acids produced functional parameters within the in vivo range. Erythrocytes increased renal vascular resistance (3.8 +/- 0.2 vs 2.4 +/- 0.1 mL/min.mmHg, P < 0.05), enhanced sodium reabsorption (FE(Na) = 0.3 +/- 0.08 vs 1.5 +/- 0.7%, P < 0.05), produced equivalent glomerular filtration rates (GFR; 364 +/- 38 vs 400 +/- 9 microL/min per gkw) and reduced distal tubular cell injury in the inner stripe (5.8 +/- 1.7 vs 23.7 +/- 3.1%, P < 0.001) compared to cell free perfusion. The IPMK was responsive to vasoconstrictor (angiotensin II, EC50 100 pM) and vasodilator (methacholine, EC50 75 nM) mediators and showed partial autoregulation of perfusate flow under control conditions over 65-85 mmHg; autoregulatory index (ARI) of 0.66 +/- 0.11. Angiotensin II (100 pM) extended this range (to 65-120 mmHg) and enhanced efficiency (ARI 0.21 +/- 0.02, P < 0.05). Angiotensin II facilitation was antagonized by methacholine (ARI 0.76 +/- 0.08) and papaverine (ARI 0.91 +/- 0.13). CONCLUSION: The IPMK model is useful for studying renal physiology and pathophysiology without systemic neurohormonal influences.     

Blood circulation in the fingers is aggravated after creating a vascular access for dialysis: assessment using skin perfusion pressure

Abstract

Internal vascular shunts for haemodialysis can cause different complications. One of the most serious complications is steal syndrome, which can result in disturbed peripheral circulation causing finger necrosis and lead to amputation. Thus, prevention of these complications is important. Measurement of skin perfusion pressure (SPP) has been used in various clinical settings, including wound-healing management, and its usefulness has been increasingly unveiled. The present study was undertaken to evaluate changes in haemodynamics after internal shunt creation by measuring SPP of the thumb and the little finger before and after surgery in five patients undergoing shunt surgery using the radial artery and the cephalic vein. The study revealed average changes of ?22.8 mmHg in thumb SPP. The change in the thumb was statistically significant (p < 0.05). If the effect of surgery and the threshold for wound healing are taken into account, the present results indicate the necessity to pay extra attention to fingers with extremely low preoperative SPP values. For the prevention of serious disturbances of peripheral circulation (e.g. steal syndrome), routine preoperative SPP measurement seems effective for screening of high-risk patients.     

Androgen receptor (AR) in osteocytes is important for the maintenance of male skeletal integrity: Evidence from targeted AR disruption in mouse osteocytes

Androgens play a key role in the maintenance of male skeletal integrity. The regulation of this integrity by androgen receptor (AR) signaling has been mainly attributed to osteoblasts. Although osteocytes have emerged as key regulators of bone remodeling, the influence of sex steroids on these cells has been poorly studied. We aimed to investigate the role of AR signaling, specifically in osteocytes using the Cre/LoxP system in male mice (driven by dentin matrix protein 1 [ocy‐ARKOs]). Osteocyte fractions of control (AR(ex2)/Y) and ocy‐ARKO (ARflox(ex2)/Y; DMP1‐cre) mice isolated through sequential collagenase digestion showed increasing AR expression toward the mature osteocyte fraction of control males compared with the more immature fractions, whereas this was reduced by >80% in ocy‐ARKO osteocytes. The skeletal phenotype of mutant mice was further assessed by histomorphometry and quantitative micro‐computed tomography at 12 and 32 weeks of age. Ocy‐ARKOs had significantly lower trabecular bone volume and number in femora and tibias at 32 weeks as well as decreased trabecular number in the L₅ vertebra at 12 weeks. Biomechanical testing showed that ocy‐ARKO femora were also stiffer and required a lower ultimate force to induce failure at 32 weeks. However, femoral cortical structure was not significantly different at any time point. The absence of AR in osteocyte also did not appear to affect trabecular bone formation nor its response to mechanical loading. In conclusion, selective inactivation of the AR in osteocytes of male mice accelerates age‐related deterioration of skeletal integrity. These findings provide evidence for a direct role of androgens in the maintenance of trabecular bone through actions of the AR in osteocytes. © 2012 American Society for Bone and Mineral Research.     

Progression of pulse pressure in kidney recipients durably exposed to CsA is a risk factor for epithelial phenotypic changes: an ancillary study of the CONCEPT trial

In this ancillary study of the CONCEPT trial, we studied the role of CsA withdrawal at 3 months (3M) post‐transplant on the intensity of epithelial phenotypic changes (EPC, an early marker for kidney fibrogenesis) on the 12M surveillance biopsy. Although conversion from CsA to sirolimus (SRL) at 3M was reported to have improved mean graft function at 12M, it did not reduce the score of EPC (1.73 ± 1.15 in the SRL group vs. 1.87 ± 1 in the CsA group, P = 0.61). Acute rejection, which had occurred twice more frequently in SRL‐converted patients included here, was associated with 12M EPC. Interestingly, we observed that the patients durably exposed to CsA and who developed 12M EPC had a significant progression of blood pulse pressure (pp) from 1 to 6M post‐transplantation (Δpp = +12.3 mmHg, P = 0.0035). Pulse pressure at 4, 6, and 9M and pp progression from 1 to 6M were significantly associated with the development of EPC at 12M in renal grafts. Logistic regression analysis revealed that a high 6M pp (≥60 mmHg) was an independent risk factor for 12M EPC with an odds ratio of 2.25 per additional 10 mmHg pp (95%CI: 1.14–4.4, P = 0.02) after adjustment with recipient's and donor's age, acute rejection incidence and immunosuppressive regimen. A post hoc analysis of the data collected in the whole population CONCEPT study revealed that pp was significantly higher at 6 months in patients maintained on CsA and that at this time point pp correlated negatively with GFR at 1 year.