Parietal damage in intestinal infarction. Clinical and anatomo-pathological considerations

The physiopathology of parietal damage due to acute ischaemia is reviewed on the basis of a personal series of more than 70 cases. The reported data (not particularly abundant) is examined and an attempt made to draw conclusions that, free from mere theoretical and abstract value, may materially help the surgeon in his by no means easy decision to revascularize or resect an intestinal segment.     

Recruitment of Podocytes from Glomerular Parietal Epithelial Cells

Loss of a critical number of podocytes from the glomerular tuft leads to glomerulosclerosis. Even in health, some podocytes are lost into the urine. Because podocytes themselves cannot regenerate, we postulated that glomerular parietal epithelial cells (PECs), which proliferate throughout life and adjoin podocytes, may migrate to the glomerular tuft and differentiate into podocytes. Here, we describe transitional cells at the glomerular vascular stalk that exhibit features of both PECs and podocytes. Metabolic labeling in juvenile rats suggested that PECs migrate to become podocytes. To prove this, we generated triple-transgenic mice that allowed specific and irreversible labeling of PECs upon administration of doxycycline. PECs were followed in juvenile mice beginning from either postnatal day 5 or after nephrogenesis had ceased at postnatal day 10. In both cases, the number of genetically labeled cells increased over time. All genetically labeled cells coexpressed podocyte marker proteins. In conclusion, we demonstrate for the first time recruitment of podocytes from PECs in juvenile mice. Unraveling the mechanisms of PEC recruitment onto the glomerular tuft may lead to novel therapeutic approaches to renal injury.Chronic kidney disease, resulting in renal failure and the need for lifelong renal replacement therapy, has become a significant problem worldwide. In the United States, approximately 7% of the total Medicare budget is spent on the treatment of ESRD, and projections suggest that the amount spent will increase by another 50% by 2020.¹Most renal pathologies that ultimately lead to ESRD originate within the glomerulus. It has now been established that a depletion of podocytes, the visceral epithelium of the capillary convolute (Figure 1), is central in this process. As soon as damage to the glomerular podocytes exceeds a certain threshold (approximately 30%), glomerulosclerosis ensues.² Indeed, in patients with a surgical reduction of ≥75% of renal mass, a relative lack of podocytes (podocytopenia) and subsequent FSGS in the originally healthy remnant kidney can lead to renal failure.³ Glomerulosclerosis is also the common final pathway of all glomerular diseases leading to ESRD.⁴ In glomerular diseases such as diabetic nephropathy, glomerulonephritides, or preeclampsia, significant numbers of podocytes are lost as a result of apoptosis, necrosis or excretion of living cells into the urine. Even in normal individuals, low numbers of living podocytes are continuously shed into the urine.^5–7 These numbers are too high to be compatible with renal survival for 80 yr, suggesting the existence of a regenerative mechanism. Also, the reversal of early glomerular damage in animal models and humans^8–10 argues for the existence of such a mechanism; however, podocytes are postmitotic cells that cannot undergo complete cell divisions and are therefore unable to regenerate themselves.^8–10 A potential mechanism for podocyte replacement from bone marrow–derived stem cells has been described in the Alport mouse model as well as in kidney transplants.^11–13 Nevertheless, most studies concluded that regeneration occurs predominantly from an as-yet-unknown source of resident renal cells.^12,14–16Open in a separate windowFigure 1.Renal glomerulus. The glomerular epithelium consists of PECs (red) and podocytes (Pod; blue), which reside on the capillary convolute. Both epithelia adjoin directly at the vascular pole (VP; arrow). At the tubular pole (TP), the parietal epithelium is connected to the epithelium of the proximal tubule. In male mice, this transition from PECs to proximal tubular cells often occurs within the glomerulus. The glomerular basement membrane (black) forms a continuous barrier between the glomerular epithelium and the endocapillary compartment that contains mesangial cells (shaded) and endothelial cells of the glomerular capillaries (*). Primary urine is filtered across the three-layered filtration barrier (endothelial cells, glomerular basement membrane, and Pod) into Bowman''s space (BS).In this study, we tested the hypothesis that glomerular parietal epithelial cells (PECs) lining the inner aspect of Bowman''s capsule migrate onto the glomerular tuft and differentiate into podocytes. Several arguments support this hypothesis. PECs are present in all species whose kidneys contain glomeruli. They are located within the same compartment and are in direct continuity with podocytes at the glomerular vascular stalk, so PECs do not have to cross an anatomic barrier such as the glomerular basement membrane, as was suggested for bone marrow–derived stem cells.^11–13 PECs proliferate lifelong at a relatively low frequency,¹⁷ express several stem cell marker proteins, and could be transdifferentiated in vitro into other cell types such as adipocytes or neuronal cells, suggesting that these cells retain multipotency.^9,18,19 In rodents, PECs do not express any known specific marker protein, which has so far precluded a detailed analysis of the function of these cells.In this work, we provide the first evidence that PECs possess the capability to migrate onto the glomerular tuft via the vascular stalk, where they differentiate into podocytes. This establishes that PECs represent an intrinsic cell population from which podocytes can be recruited.     

Tracing the Origin of Glomerular Extracapillary Lesions from Parietal Epithelial Cells

Cellular lesions form in Bowman''s space in both crescentic glomerulonephritis and collapsing glomerulopathy. The pathomechanism and origin of the proliferating cells in these lesions are unknown. In this study, we examined proliferating cells by lineage tracing of either podocytes or parietal epithelial cells (PECs) in the nephrotoxic nephritis model of inflammatory crescentic glomerulonephritis. In addition, we traced the fate of genetically labeled PECs in the Thy-1.1 transgenic mouse model of collapsing glomerulopathy. In both models, cellular bridges composed of PECs were observed between Bowman''s capsule and the glomerular tuft. Genetically labeled PECs also populated larger, more advanced cellular lesions. In these lesions, we detected de novo expression of CD44 in activated PECs. In contrast, we rarely identified genetically labeled podocytes within the cellular lesions of crescentic glomerulonephritis. In conclusion, PECs constitute the majority of cells that compose early extracapillary proliferative lesions in both crescentic glomerulonephritis and collapsing glomerulopathy, suggesting similar pathomechanisms in both diseases.Glomerular epithelial hyperplasia is an important characteristic of crescentic glomerulonephritis (CrGN), also known as rapidly progressive glomerulonephritis. Despite a wide variety of underlying causes, CrGN is characterized commonly by the development of cellular crescents (multilayered accumulation of cells in Bowman''s space) and necrosis of glomerular capillaries.¹ Loss of renal function occurs as a consequence of the obstruction of the tubular outlet by cellular crescents, so the proliferating cells present an important target for therapeutic interventions.²Collapsing glomerulopathy (CG) is characterized by massive proteinuria and rapid progressive renal insufficiency and histologically by segmental to global collapse of the capillary tuft and pronounced epithelial cell hyperplasia.³ This pattern has been described in HIV-associated nephropathy,⁴ parvovirus B19 infection,⁵ and pamidronate toxicity⁶ and also as an idiopathic form.³The pathomechanism of the development of cellular lesions remains to be established, and in both CrGN and CG the origin of the hyperplastic cells within cellular lesions has been a matter of debate. In CrGN, the cellular composition of crescents appears to change over time, with predominantly epithelial cells of unknown origin proliferating in early stages and increasing numbers of infiltrating macrophages, lymphocytes, and myofibroblasts in later stages, especially when Bowman''s capsule is ruptured.^7–9 Recent studies also pointed to a contribution of podocytes in the development of crescentic lesions.^10–13 Collapsing glomerulopathy lesions in turn often are associated with hyperplasia of epithelial cells covering the glomerular tuft, although connections to Bowman''s capsule appeared to be lacking. The visceral localization and the finding that these proliferating cells lacked expression of podocyte markers led to the concept of dysregulated podocytes, which are no longer growth restricted, causing epithelial hyperplasia.¹⁴ However, from the findings that these cells expressed markers normally expressed by PECs¹⁵ and the finding in serial sections that the cells on the tuft were connected to the PECs on Bowman''s capsule,¹⁶ we and others suggested that these cells may originate from parietal epithelial cells (PECs) rather than from podocytes.^16–20In the studies described above, the origin of the proliferating cells was identified based on the expression or loss of specific markers. This approach may be misleading, given that, first, PECs and podocytes share a common embryonic origin. Only during the last stages of nephrogenesis the phenotypes of both cells diverge. Second, PECs lack specific differentiation markers, and third, proliferating cells may possibly transdifferentiate into cells with a different phenotype. Genetic cell lineage tracing is a technique that has been established recently and enables one to trace cells over prolonged times, even when the cells switch to a different phenotype due to de- or transdifferentiation.^19,21 In the present study, we therefore used this technique to trace the relative contributions of PECs and podocytes in the development of cellular glomerular lesions in two murine models of CrGN, namely, nephrotoxic nephritis, and CG, namely, Thy-1.1 transgenic mice. These established murine models were chosen because both characteristically develop proliferative extracapillary lesions.     

Nephrin dissociates from actin, and its expression is reduced in early experimental membranous nephropathy

These studies examined the expression of the podocyte slit diaphragm protein nephrin and its association with actin at the onset of proteinuria in passive Heymann nephritis (PHN), a rat model of human membranous nephropathy. Four days after immunization, 58% of PHN rats had mild proteinuria. At that time, most slit diaphragms were still visible on electron microscopy; however, in those locations where the deposits encroached on the filtration slits, the slit diaphragms were either displaced or absent. On day 7, the PHN rats were severely proteinuric, and most slit diaphragms were either absent, displaced, or replaced by occluding-type junctions. Immunofluorescence microscopy with antibodies to the external and cytoplasmic domains of nephrin showed a progressive loss of staining and a change in the distribution of nephrin from an interrupted linear pattern in normal controls to a more dispersed and clustered pattern in PHN. In contrast, the intensity of staining for ZO-1 and CD2-associated protein (CD2AP), two other proteins that are located on the cytoplasmic face of the slit diaphragm, was undiminished. Immunogold electron microscopy confirmed the progressive disappearance of nephrin from podocyte foot processes and retention of CD2AP. Glomeruli and glomerular cell membranes were extracted sequentially with Triton X-100, followed by DNase I or potassium iodide to depolymerize actin. Western blot analysis of the extracts showed a progressive decline of total nephrin on days 4 and 7 of PHN as well as a reduction in the actin-associated fraction. These findings show that nephrin partly dissociates from actin at the onset of podocyte injury in PHN. This is accompanied by a progressive loss of nephrin from the podocyte foot processes and prominent changes in the morphology of the slit diaphragms. These events may underlie the loss of podocyte barrier function in membranous nephropathy.     

Studies on renal damage from percutaneous nephrolitholapaxy

To study in detail the effects of percutaneous nephrolitholapaxy on renal function, a consecutive series of 11 patients were investigated preoperatively by excretory urography, gamma camera renography for determination of individual renal function and computerized tomography of the kidneys. Postoperatively, gamma camera examination, computerized tomography, antegrade nephrostography, renal angiography and excretory urography were performed. With 2 exceptions, percutaneous nephrostomy, dilation of the tract and stone removal were done in 1 stage with the patient under continuous epidural anesthesia. Nephrostomy tract dilation was done with an Olbert type balloon catheter or Alken metallic dilators. Thickening of Gerota's fascia was demonstrated by computerized tomography in most cases, and small to moderate perirenal hematomas were found in several. At gamma camera examination decrease of renal function was noted regularly on postoperative day 1 and returned to near initial levels 2 weeks postoperatively in most cases. Angiography in 10 patients showed discrete parenchymal scarring in some and a peripheral arteriovenous fistula in 1. We conclude that percutaneous renal stone surgery usually is tolerated well by the kidney.     

Gastric damage from ingested acid in children

Acid ingestion occurs relatively rarely and produces a spectrum of injury that is markedly different from the more commonly encountered alkaline burns of the oropharynx and esophagus. Gastric damage results from pylorospasm with pooling of the ingested caustic in a dependent location. Symptoms may be delayed for days or weeks. Perforation and/or strictures may require extensive gastric surgery. Early fiberoptic endoscopy is essential.     

褪黑素保护卵母细胞应对热应激损伤的研究

目的探讨褪黑素对热激条件下小鼠卵母细胞体外成熟的潜在影响。方法采用小鼠卵母细胞成熟的热激模型,将卵母细胞随机分成3组,分别是对照组、热激组和热激+褪黑素组,测定1×10-9 mol/L褪黑素对热激后卵母细胞质量的改善作用。结果与对照组相比,热激组小鼠卵母细胞成熟率显著下降[(33.00±0.07)%vs.(85.00±0.03)%,P0.01],纺锤体组装异常,早期凋亡比率显著增加[(59.7±4.5)%vs.(22.0±3.5)%,P0.01];热激+褪黑素组与热激组相比,卵母细胞成熟率显著上升[(70.00±0.05)%vs.(33.00±0.07)%,P0.01],纺锤体异常比率显著下降,发生早期凋亡的卵母细胞比率亦显著下降[(37.3±6.1)%vs.(59.7±4.5)%,P0.01]。热激+褪黑素组热休克蛋白70的表达水平与对照组和热激组相比显著上调(P0.01)。结论褪黑素能通过调节热激后热休克蛋白70过表达来改善热激对卵母细胞造成的成熟率下降、纺锤体组装异常和早期凋亡比率的增加。     

Sperm DNA damage in men from infertile couples

Aim： To investigate the prevalence of high levels of sperm DNA damage among men from infertile couples with both normal and abnormal standard semen parameters. Methods： A total of 350 men from infertile couples were assessed. Standard semen analysis and sperm chromatin structure assay （SCSA） were carried out. Results： Ninety-seven men （28% of the whole study group） had a DNA fragmentation index （DFI） 〉 20%, and 43 men （12%） had a DFI 〉 30%. In the group of men with abnormal semen parameters （n = 224）, 35% had a DFI 〉 20%, and 16% had a DFI 〉 30%, whereas these numbers were 15% and 5%, respectively, in the group of men with normal semen parameters （n = 126）. Men with low sperm motility and abnormal morphology had significantly higher odds ratios （ORs） for having a DFI 〉 20% （4.0 for motility and 1.9 for morphology） and DFI 〉 30% （6.2 for motility and 2.8 for morphology） compared with men with normal sperm motility and morphology. Conclusion： In almost one-third of unselected men from infertile couples, the DFI exceeded the level of 20% above which, according to previous studies, the in vivo fertility is reduced. A significant proportion of men with otherwise normal semen parameters also had high sperm DNA damage levels. Thus, the SCSA test could add to explaining causes of infertility in cases where semen analysis has not shown any deviation from the norm. We also recommend running the SCSA test to choose the appropriate assisted reproductive technique （ART）.     

Oxidant conditioning protects cartilage from mechanically induced damage

Articular cartilage degeneration in osteoarthritis has been linked to abnormal mechanical stresses that are known to cause chondrocyte apoptosis and metabolic derangement in in vitro models. Evidence implicating oxidative damage as the immediate cause of these harmful effects suggests that the antioxidant defenses of chondrocytes might influence their tolerance for mechanical injury. Based on evidence that antioxidant defenses in many cell types are stimulated by moderate oxidant exposure, we hypothesized that oxidant preconditioning would reduce acute chondrocyte death and proteoglycan depletion in cartilage explants after exposure to abnormal mechanical stresses. Porcine cartilage explants were treated every 48 h with tert‐butyl hydrogen peroxide (tBHP) at nonlethal concentrations (25, 100, 250, and 500 µM) for a varying number of times (one, two, or four) prior to a bout of unconfined axial compression (5 MPa, 1 Hz, 1800 cycles). When compared with untreated controls, tBHP had significant positive effects on post‐compression viability, lactate production, and proteoglycan losses. Overall, the most effective regime was 100 µM tBHP applied four times. RNA analysis revealed significant effects of 100 µM tBHP on gene expression. Catalase, hypoxia‐inducible factor‐1alpha (HIF‐1α), and glyceraldehyde 6‐phosphate dehydrogenase (GAPDH) were significantly increased relative to untreated controls in explants treated four times with 100 µM tBHP, a regime that also resulted in a significant decrease in matrix metalloproteinase‐3 (MMP‐3) expression. These findings demonstrate that repeated exposure of cartilage to sublethal concentrations of peroxide can moderate the acute effects of mechanical stress, a conclusion supported by evidence of peroxide‐induced changes in gene expression that could render chondrocytes more resistant to oxidative damage. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:914–920, 2010     

二氢欧山芹通过调节自噬保护高糖诱导的足细胞损伤

目的 探讨二氢欧山芹(columbianetin,CBT)对高糖诱导的足细胞损伤保护作用及其机制研究.方法 体外培养永生化小鼠足细胞系MPC-5,给予高浓度的葡萄糖刺激,观察CBT对高糖诱导的足细胞损伤及自噬的影响;采用蛋白质印迹法检测足细胞自噬相关蛋白;荧光显微镜观察GFP-LC3-Ⅱ转染后足细胞绿色荧光颗粒.结果 ...     

Failure of verapamil to protect from ischaemic renal damage

To reassess the reported protective effects of verapamil in renal ischaemia, we perfused the left kidney of uninephrectomized female Wistar rats with verapamil (0.1 and 1.0 mg/kg) immediately prior to clamping the renal artery for 60 min. When compared to controls, both doses of verapamil failed to afford protection with respect to urine flow, plasma creatinine, creatinine clearance or histology 24 and 48 h after ischaemia, whereas the purine nucleotide inosine (200 mg/kg) was partially protective: mean plasma creatinine 48 h after ischaemia (+/- SEM) was 547 +/- 54 mumol/l in controls, 686 +/- 38 mumol/l with 0.1 mg/kg verapamil, 491 +/- 68 mumol/l with 1.0 mg/kg verapamil and 374 +/- 45 mumol/l with inosine (p less than 0.05 vs. controls). Using the same model, the effect of verapamil 1.0 mg/kg on renal blood flow, creatinine clearance, urine flow and arterial pressure was studied in the first 2 h after ischaemia. Although significant amounts of verapamil were present in the kidney during ischaemia as evidenced by decreases in systemic blood pressure and in renal vascular resistance after unclamping the renal artery, the early course of renal failure was not altered when compared to controls. In conclusion, we have been unable to confirm earlier reports of a protective effect of verapamil in this rat model of ischaemic renal failure. If there is such an effect, its demonstration appears to depend on very specific experimental circumstances. Based on the results of this and other studies, verapamil is unlikely to afford an impressive overall benefit in the clinical setting of ischaemic renal failure.