Infusing Mesenchymal Stromal Cells into Porcine Kidneys during Normothermic Machine Perfusion: Intact MSCs Can Be Traced and Localised to Glomeruli

Normothermic machine perfusion (NMP) of kidneys offers the opportunity to perform active interventions, such as the addition of mesenchymal stromal cells (MSCs), to an isolated organ prior to transplantation. The purpose of this study was to determine whether administering MSCs to kidneys during NMP is feasible, what the effect of NMP is on MSCs and whether intact MSCs are retained in the kidney and to which structures they home. Viable porcine kidneys were obtained from a slaughterhouse. Kidneys were machine perfused during 7 h at 37 °C. After 1 h of perfusion either 0, 10⁵, 10⁶ or 10⁷ human adipose tissue derived MSCs were added. Additional ex vivo perfusions were conducted with fluorescent pre-labelled bone-marrow derived MSCs to assess localisation and survival of MSCs during NMP. After NMP, intact MSCs were detected by immunohistochemistry in the lumen of glomerular capillaries, but only in the 10⁷ MSC group. The experiments with fluorescent pre-labelled MSCs showed that only a minority of glomeruli were positive for infused MSCs and most of these glomeruli contained multiple MSCs. Flow cytometry showed that the number of infused MSCs in the perfusion circuit steeply declined during NMP to approximately 10%. In conclusion, the number of circulating MSCs in the perfusate decreases rapidly in time and after NMP only a small portion of the MSCs are intact and these appear to be clustered in a minority of glomeruli.

The Application of Digital Pathology to Improve Accuracy in Glomerular Enumeration in Renal Biopsies

Background

In renal biopsy reporting, quantitative measurements, such as glomerular number and percentage of globally sclerotic glomeruli, is central to diagnostic accuracy and prognosis. The aim of this study is to determine the number of glomeruli and percent globally sclerotic in renal biopsies by means of registration of serial tissue sections and manual enumeration, compared to the numbers in pathology reports from routine light microscopic assessment.

Design

We reviewed 277 biopsies from the Nephrotic Syndrome Study Network (NEPTUNE) digital pathology repository, enumerating 9,379 glomeruli by means of whole slide imaging. Glomerular number and the percentage of globally sclerotic glomeruli are values routinely recorded in the official renal biopsy pathology report from the 25 participating centers. Two general trends in reporting were noted: total number per biopsy or average number per level/section. Both of these approaches were assessed for their accuracy in comparison to the analogous numbers of annotated glomeruli on WSI.

Results

The number of glomeruli annotated was consistently higher than those reported (p<0.001); this difference was proportional to the number of glomeruli. In contrast, percent globally sclerotic were similar when calculated on total glomeruli, but greater in FSGS when calculated on average number of glomeruli (p<0.01). The difference in percent globally sclerotic between annotated and those recorded in pathology reports was significant when global sclerosis is greater than 40%.

Conclusions

Although glass slides were not available for direct comparison to whole slide image annotation, this study indicates that routine manual light microscopy assessment of number of glomeruli is inaccurate, and the magnitude of this error is proportional to the total number of glomeruli.

Hepatitis C virus associated glomerulopathies

Hepatitis C virus (HCV) infection is a systemic disorder which is often associated with a number of extrahepatic manifestations including glomerulopathies. Patients with HCV infection were found to have a higher risk of end-stage renal disease. HCV positivity has also been linked to lower graft and patient survivals after kidney transplantation. Various histological types of renal diseases are reported in association with HCV infection including membranoproliferative glomerulonephritis (MPGN), membranous nephropathy, focal segmental glomerulosclerosis, fibrillary glomerulonephritis, immunotactoid glomerulopathy, IgA nephropathy, renal thrombotic microangiopathy, vasculitic renal involvement and interstitial nephritis. The most common type of HCV associated glomerulopathy is type I MPGN associated with type II mixed cryoglobulinemia. Clinically, typical renal manifestations in HCV-infected patients include proteinuria, microscopic hematuria, hypertension, acute nephritis and nephrotic syndrome. Three approaches may be suggested for the treatment of HCV-associated glomerulopathies and cryoglobulinemic renal disease: (1) antiviral therapy to prevent the further direct damage of HCV on kidneys and synthesis of immune-complexes; (2) B-cell depletion therapy to prevent formation of immune-complexes and cryoglobulins; and (3) nonspecific immunosuppressive therapy targeting inflammatory cells to prevent the synthesis of immune-complexes and to treat cryoglobulin associated vasculitis. In patients with moderate proteinuria and stable renal functions, anti-HCV therapy is advised to be started as pegylated interferon-α plus ribavirin. However in patients with nephrotic-range proteinuria and/or progressive kidney injury and other serious extra-renal manifestations, immunosuppressive therapy with cyclophosphamide, rituximab, steroid pulses and plasmapheresis should be administrated.

Suramin alleviates glomerular injury and inflammation in the remnant kidney

BACKGROUND

Recently, we demonstrated that suramin, a compound that inhibits the interaction of multiple cytokines/growth factors with their receptors, inhibits activation and proliferation of renal interstitial fibroblasts, and attenuates the development of renal interstitial fibrosis in the murine model of unilateral ureteral obstruction (UUO). However, it remains unclear whether suramin can alleviate glomerular and vascular lesions, which are not typical pathological changes in the UUO model. So we tested the efficacy of suramin in the remnant kidney after 5/6 nephrectomy, a model characterized by the slow development of glomerulosclerosis, vascular sclerosis, tubulointerstitial fibrosis and renal inflammation, mimicking human disease.

METHODS/FINDINGS

5/6 of normal renal mass was surgically ablated in male rats. On the second week after surgery, rats were randomly divided into suramin treatment and non-treatment groups. Suramin was given at 10 mg/kg once per week for two weeks. In the remnant kidney of mice receiving suramin, glomerulosclerosis and vascular sclerosis as well as inflammation were ameliorated. Suramin also attenuated tubular expression of two chemokines, monocyte chemoattractant protein-1 and regulated upon expression normal T cell expressed and secreted (RANTES). After renal mass ablation, several intracellular molecules associated with renal fibrosis, including NF-kappaB p65, Smad-3, signal transducer and activator of transcription-3 and extracellular regulated kinase 1/2, are phosphorylated; suramin treatment inhibited their phosphorylation. Futhermore, suramin abolished renal ablation-induced phosphorylation of epidermal growth factor receptor and platelet derived growth factor receptor, two receptors that mediate renal fibrosis.

CONCLUSIONS AND SIGNIFICANCE

These findings suggest that suramin attenuates glomerular and vascular injury and reduces inflammatory responses by suppression of multiple growth factor receptor-mediated profibrotic signaling pathways. Therefore, suramin may be a useful drug in preventing the fibrosis and sclerosis that characterizes progression of chronic kidney disease.

cDNA microarray analysis of adaptive changes after renal ablation in a sclerosis-resistant mouse strain

BACKGROUND

5/6 nephrectomy (Nx) in susceptible animals causes glomerular sclerosis and interstitial fibrosis in the remnant kidney. Oxidative stress, transforming growth factor-beta (TGF-beta), and the de novo synthesis of collagen seem to contribute to this process. However, these factors might also be required for tissue repair without fibrosis.

METHODS

We examined dynamic changes after nephron loss in a mouse strain capable of complete recovery. C57BL/6 mice underwent single-session Nx and were followed for 40 weeks. Gene expression was monitored over 20 days using 22,000 cDNA microarrays.

RESULTS

The mice developed transient hypertension and glomerular hypertrophy after Nx but failed to progress to glomerular sclerosis or renal failure. Gene expression profiles revealed three stages of recovery, an early phase of injury response, an intermediate phase of extracellular matrix (ECM) production and a later phase of reconstitution. Surprisingly, oxidative stress responses and collagen production were strongly upregulated soon after Nx. Furthermore, TGF-beta(1) and connective tissue growth factor were rapidly upregulated and remained elevated.

CONCLUSION

We suggest that oxidative stress, collagen production, profibrotic growth factors and ECM turnover are part of the comprehensive adaptation to nephron loss and not necessarily associated with progressive loss of renal function.

Glomerulotubular disconnection in neonatal mice after relief of partial ureteral obstruction

Ureteropelvic junction obstruction is a common cause of congenital obstructive nephropathy. To study the pathogenesis of nephropathy, a variable-partial, complete or a sham unilateral ureteral obstruction (UUO) was produced in mice within 2 days of birth. The obstruction was released in some animals at 7 days and kidneys harvested at 7-42 days of age for histologic and morphometric study. Renal parenchymal growth was stunted by partial UUO with the impairment proportional to the duration and severity of obstruction. Proximal tubule apoptosis and glomerulotubular disconnection led to nephron loss. Relief of partial UUO arrested glomerulotubular disconnection, resolved tubule atrophy, and interstitial fibrosis with remodeling of the renal architecture. Relief of severe UUO did not result in recovery. Compensatory growth of the contralateral kidney depended on the severity of obstruction. Our studies indicate that relief of moderate UUO will minimize nephron loss. Application of this technique to mutant mice will help develop future therapies to enhance nephron recovery.

Time course of the renal functional response to partial nephrectomy: measurements in conscious rats

Previous investigations into the functional responses of the surviving nephrons following reductions in renal mass have been performed largely in anaesthetized animals and have taken little account of how the compensatory changes develop with time. The present study has assessed a method for determining glomerular filtration rate (GFR) in unrestrained, uncatheterized, conscious rats (plasma disappearance of (99m)Tc-diethylenetriamene pentaacetic acid (DTPA)) and has used this method to document the time course of the changes in GFR over a 32 day period following uninephrectomy or 5/6 nephrectomy. Concurrent measurements of excretion rates and of the clearance of lithium (the latter being an index of end-proximal fluid delivery) provided information on changes in overall tubular function and segmental reabsorption. After uninephrectomy, the GFR of the remaining kidney (compared with that of a single kidney of sham-operated animals) increased maximally (by approximately 50%) within 8 days; after 5/6 nephrectomy, the increase in the GFR of the remnant kidney was maximal (at approximately 300%) within 16 days. Overall excretion rates of sodium and potassium were well maintained in partially nephrectomized animals throughout the period of study, while the excretion of water increased (by approximately 30% after uninephrectomy and by approximately 120% after 5/6 nephrectomy), partly as a result of the compensatory increases in GFR but mainly as a consequence of moderate (after uninephrectomy) or marked (after 5/6 nephrectomy) reductions in fractional reabsorption. During the early period after 5/6 nephrectomy, potassium excretion sometimes exceeded the filtered load, indicating net secretion. Lithium clearance data indicated that the changes in tubular function after 5/6 nephrectomy include a reduction in fractional reabsorption in the proximal tubule, whereas after uninephrectomy any such effect on the proximal tubule is minor and transient.

Computational simulation of renal biopsy accuracy in focal segmental glomerulosclerosis

The goal of this study was to estimate the diagnostic and prognostic accuracy of renal biopsies in focal segmental glomerulosclerosis (FSGS), accounting for the focal nature of affected glomeruli. Computational simulations were performed on a total of 138,600 virtual kidneys, across a range of FSGS involvement. Simulations were designed to address the diagnostic accuracy of renal biopsies, and the biopsy characteristics required to reflect accurately the true degree of involvement of FSGS in the entire kidney or just the juxtamedullary (JM) region. The diagnostic accuracy of renal biopsies for the detection of at least one FSGS glomerulus exceeded 80% when 10-20% of the kidney was affected by FSGS. Hundreds to thousands of biopsy glomeruli were required to characterize reliably the true extent of FSGS when fewer than 75% of the kidney's glomeruli were affected. Renal biopsies with an average of 20 glomeruli did not accurately reflect the extent of FSGS in kidneys until at least 80% of all glomeruli in the kidney were affected. Targeting JM glomeruli did not result in significant improvements in the prognostic performance characteristics of renal biopsies. These findings suggest that conventional renal biopsies might be inadequate for characterizing the extent of FSGS.

Reconstruction of renal glomerular tissue using collagen vitrigel scaffold

The construction of renal glomerular tissue has provided an important tool not only for the understanding of renal physiology and pathology in blood ultrafiltration and cell dysfunction, but also in the application of tissue engineering to glomeruli regeneration and nephritic therapy. In this study, a novel method to reconstruct glomerular tissue combining cultured cells on a collagen vitrigel scaffold is described. The method consists of two newly developed techniques, one to isolate glomerular epithelial and mesangial cells rapidly from kidney, which facilitates the prolongation of cell population doublings and allows a long-term cell culture without losing cellular features, and another to prepare a stable and thin transparent collagen gel membrane termed collagen vitrigel that can facilitate three-dimensional cultures for reconstructing an epithelial-mesenchymal model. By combining the two methods, we cocultured glomerular epithelial and mesangial cells on both surfaces of the collagen vitrigel by the manipulation of two-dimensional cultures, resulting in the successful reconstruction of a three-dimensional glomerular organoid. The coculture results showed that the collagen vitrigel maintains cell growth and cell viability for more than 1 month, and surprisingly, the epithelial layer demonstrated polarity formation, which usually appears in in vivo normal epithelial cells existing at the glomerular basement membrane, but seldom appears in epithelial cells cultured in vitro. Moreover, the coculture results showed that fibronectin, an extracellular matrix component, and integrin beta1, a receptor of fibronectin, were detected in high amounts on both cells, suggesting our collagen vitrigel can provide a suitable environment for cell-cell interactions that stabilize the cell structure and may contribute to the polarity formation of epithelial cells.

Characterization of heterogeneity in the molecular pathogenesis of lupus nephritis from transcriptional profiles of laser-captured glomeruli

The molecular pathogenesis of focal/diffuse proliferative lupus glomerulonephritis was studied by cDNA microarray analysis of gene expression in glomeruli from clinical biopsies. Transcriptional phenotyping of glomeruli isolated by laser-capture microscopy revealed considerable kidney-to-kidney heterogeneity in increased transcript expression, resulting in four main gene clusters that identified the presence of B cells, several myelomonocytic lineages, fibroblast and epithelial cell proliferation, matrix alterations, and expression of type I IFN-inducible genes. Glomerulus-to-glomerulus variation within a kidney was less marked. The myeloid lineage transcripts, characteristic of those found in isolated activated macrophages and myeloid dendritic cells, were widely distributed in all biopsy samples. One major subgroup of the samples expressed fibrosis-related genes that correlated with pathological evidence of glomerulosclerosis; however, decreased expression of TGF-beta1 argued against its role in lupus renal fibrosis. Expression of type I IFN-inducible transcripts by a second subset of samples was associated with reduced expression of fibrosis-related genes and milder pathological features. This pattern of gene expression resembled that exhibited by activated NK cells. A large gene cluster with decreased expression found in all samples included ion channels and transcription factors, indicating a loss-of-function response to the glomerular injury.

Remission of nephrotic syndrome due to AA amyloidosis and initiation of glomerular repair after surgical resection of localized Castleman's disease

To shed further light on the eventual destiny of amyloid kidney deposits after interruption of amylogenic stimulus, we report a case of a 47-year-old woman with nephrotic syndrome due to renal amyloidosis, complicating abdominal Castleman's disease. After 5 courses of therapy with melphalan and prednisolone which failed to improve the nephrotic syndrome or her general clinical condition, and 1 year after the diagnosis of renal amyloidosis, surgical excision of the abdominal mass was performed. Whereas her clinical symptoms and other laboratory findings rapidly improved, the proteinuria took 18 months to disappear. A second renal biopsy, performed 30 months after surgical resection, showed persistence of the amyloid deposits in the same extent. However, electron microscopy revealed subtle reparative phenomena at the epithelial site of the basement membrane. We conclude that proteinuria associated with amyloidosis does not only depend on structural damage and that the new synthesized segment of basement membrane observed by us probably represents a mechanism of repair and the start of a long healing process.

Prognostic value of plasminogen activator inhibitor type 1 mRNA in microdissected glomeruli from transplanted kidneys

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) exerts antifibrinolytic and profibrotic activities. Inside the glomerulus, PAI-1 is mainly synthesized by mesangial cells. We hypothesized that thrombin, via its receptor protease activated receptor type 1 (PAR-1), present on the membrane of glomerular cells, is an important mediator of PAI-1 synthesis.

METHODS

Using the technique of Peten et al., we microdissected the glomeruli of 23 kidney transplanted patients admitted in our department from 1993 to 1997, and we followed-up these patients for up to 5 years, with sometimes iterative renal biopsies. With this technique, we also microdissected the glomeruli of three patients who have had a nephrectomy for cancer (control patients). We investigated mRNA expression of the PAI-1, the thrombin receptor PAR-1, the alpha2 chain of type IV (alpha2 IV) collagen, and of a housekeeping gene (cyclophilin) by reverse transcription-polymerase chain reaction. The results were correlated with the renal function and the histological findings classified into acute rejection (9 biopsies), chronic rejection (22 biopsies), or normal (8 biopsies).

RESULTS

A significant up-regulation of PAI-1 and alpha2 IV collagen mRNA was observed in acute rejection (P<0.05) when compared to normal kidneys. A positive correlation exists between alpha2 IV collagen mRNA level and the degree of cellular infiltration. A negative correlation was found between the level of mRNA of PAR-1 and the degree of vascular thrombosis (P=0.005) and glomerulosclerosis (P=0.04). A positive correlation was found between the degradation of renal function and the mRNA level of PAI-1 at the time of the renal biopsy (P<0.05).

CONCLUSIONS

These results suggest that glomerular PAI-1 mRNA may be predictive of the long-term renal graft function.

Effects of maternal uninephrectomy on the development of fetal rat kidney: numerical and volumetric changes of the glomerulus and formation of the anionic site in the glomerular basement membrane

Developmental processes of the fetal rat kidney from uninephrectomized mothers were studied. The uninephrectomy was performed on day 5 of gestation. Glomerular number and volume in the fetal kidneys on days 18, 20, and 22 of gestation were morphometrically determined. To investigate the anionic site formation in the glomerular basement membrane, distribution of cationized ferritin (CF) in the fetal glomerulus was examined electron microscopically after CF injection. Blood urea nitrogen (BUN) concentration in the pregnant rats was also determined on various days after uninephrectomy. On fetal days 20 and 22, the glomerular volume was significantly larger in the fetuses from uninephrectomized mothers than in those from sham-operated ones. On fetal day 20, the CF particles were clustered in the laminae rarae interna and externa of the glomerular basement membrane in the fetuses from uninephrectomized mothers, while the clusters were arrayed in three to four layers in the glomerular basement membrane in the fetuses from sham-operated ones. On fetal day 22, the CF particles noted in the lamina rara externa in the fetuses from uninephrectomized mothers were slightly larger in number than such particles in the age-matched control fetuses. The BUN concentration of the uninephrectomized pregnant rats was significantly higher than that of the sham-operated pregnant ones on each postoperative day. These results suggest that the development of the fetal renal glomerulus is accelerated by the elevated BUN level following maternal uninephrectomy when the fetal kidney is functional in effective filtration in the rat.

Glomerular cell proliferation and apoptosis in uninephrectomized spontaneously hypertensive rats

We studied renal function, glomerular cell proliferation and apoptosis for three months after uninephrectomy (UNX) in young, male, spontaneously hypertensive rats (SHR). Apoptosis was assessed by in situ dUTP biotin nick-end labeling method (TUNEL) and by propidium iodide staining. Proliferation rate was determined by immunohistochemistry to proliferating cell nuclear antigen (PCNA). Glomerular bcl-2 expression was assessed by Northern blot analysis. Our results indicate a parallel increase in proliferation and in apoptotic rates in glomerular cells from the first to the second month after UNX. In the third month after UNX, PCNA-labeled cell number continues increasing, whereas TUNEL-labeled cells did not increase. Bcl-2 expression was negative in the first and second months and increased in the third month. Glomerular size and proteinuria increased progressively along the three months of follow-up. Our observations demonstrate a different profile of cell proliferation and apoptosis during the genesis of early glomerular damage in UNX-SHR.

Early increase in glomerular leucocyte number after a reduction in renal mass: implications for the pathogenesis of glomerulosclerosis

1. Adult female Wistar rats underwent uninephrectomy (n = 8) through a flank incision, or a sham operation (n = 7). One to two weeks later the kidney was perfused in situ and glomeruli were isolated from cortical tissue by sequential sieving, and partially digested. Glomerular leucocytes were labelled with a mouse monoclonal antibody against leucocyte common antigen followed by a fluorescein-labelled anti-mouse immunoglobulin to allow counting. 2. In a further group of animals 24 h albumin excretion and glomerular size were measured 2 weeks after either uninephrectomy (n = 6) or sham operation (n = 6). 3. Glomerular leucocyte number was significantly increased in uninephrectomized animals (15.7 +/- 0.9 versus 8.9 +/- 0.4, P < 0.001), with some glomeruli having leucocyte numbers comparable with those seen in glomerulonephritis. 4. Albuminuria was not increased 2 weeks after uninephrectomy (233 +/- 35 versus 170 +/- 42 micrograms/24 h, not significant), and glomerular size was unchanged. Light microscopical appearance was normal. 5. An increase in glomerular leucocyte number is an early response in what was previously considered a non-immunological lesion. It precedes the development of renal scarring and may be important in the pathogenesis of this process.

Canine renal glomerular ultrastructural changes after preservation and autotransplantation

Glomeruli of canine kidneys were studied by light and electron microscopy to determine whether significant structural alterations occur during 24 hr of hypothermic perfusion. The kidneys of eight dogs were preserved by continuous pulsatile perfusion with cold cryoprecipitated plasma; they were subsequently reimplanted as autographs and contralateral nephrectomy was performed at that time. Biopsies of the experimental kidneys were taken before nephrectomy, after 24 hr of perfusion, and at 1 hr postanastomosis. Tissue samples from two animals were studied at autopsy. Structural changes observed in the glomeruli after preservation were: margination of nuclear chromatin, nuclear pyknosis, and dilation of smooth and rough endoplasmic reticulum membranes. These changes were observed in all cell types, but were more severe in the endothelial cells. The basement membrane in four cases was edematous and thickened. At 1 hr postanastomosis the glomerular ultrastructural appearance was greatly improved. Blood urea nitrogen, serum creatinine, and the ability of the kidney to sustain the life of the recipient were used as criteria for determining the viability of the preserved kidneys. Blood urea nitrogen and serum creatinine returned to a normal range in five dogs. The physiologic tests and the length of survival attest to the functional capability of the preserved kidneys. Study of tissue samples at autopsy indicated that, although a number of the structural alterations observed after preservation were reversible, some changes persisted.