Demonstration of the proliferation marker Ki-67 in renal biopsies: correlation to clinical findings

A bioinspired carbon monoxide delivery system prevents acute kidney injury and the progression to chronic kidney disease

Renal ischemia-reperfusion (IR)-induced tissue hypoxia causes impaired energy metabolism and oxidative stress. These conditions lead to tubular cell damage, which is a cause of acute kidney injury (AKI) and AKI to chronic kidney disease (CKD). Three key molecules, i.e., hypoxia-inducible factor-1α (HIF-1α), AMP-activated protein kinase (AMPK), and nuclear factor E2-related factor 2 (Nrf2), have the potential to protect tubular cells from these disorders. Although carbon monoxide (CO) can comprehensively induce these three molecules via the action of mitochondrial reactive oxygen species (mtROS), the issue of whether CO induces these molecules in tubular cells remains unclear. Herein, we report that CO-enriched red blood cells (CO-RBC) cell therapy, the inspiration for which is the in vivo CO delivery system, exerts a renoprotective effect on hypoxia-induced tubular cell damage via the upregulation of the above molecules. Experiments using a mitochondria-specific antioxidant provide evidence to show that CO-driven mtROS partially contributes to the upregulation of the aforementioned molecules in tubular cells. CO-RBC ameliorates the pathological conditions of IR-induced AKI model mice via activation of these molecules. CO-RBC also prevents renal fibrosis via the suppression of epithelial mesenchymal transition and transforming growth factor-β1 secretion in an IR-induced AKI to CKD model mice. In conclusion, our results confirm that the bioinspired CO delivery system prevents the pathological conditions of both AKI and AKI to CKD via the amelioration of hypoxia inducible tubular cell damage, thereby making it an effective cell therapy for treating the progression to CKD.

Differential effects of sodium chloride and monosodium glutamate on kidney of adult and aging mice

Monosodium Glutamate (MSG) is used as flavour enhancer, with potential beneficial effects due to its nutritional value. Given the decline in kidney functions during aging, we investigated the impact of MSG voluntary intake on the kidney of male mice, aged 6 or 18 months. For 2 months, they freely consumed water (control group), sodium chloride (0.3% NaCl) or MSG (1% MSG) in addition to standard diet. Young animals consuming sodium chloride presented signs of proteinuria, hyperfiltration, enhanced expression and excretion of Aquaporin 2 and initial degenerative reactions suggestive of fibrosis, while MSG-consuming mice were similar to controls. In old mice, aging-related effects including proteinuria and increased renal corpuscle volume were observed in all groups. At an advanced age, MSG caused no adverse effects on the kidney compared to controls, despite the presence of a sodium moiety, similar to sodium chloride. These data show that prolonged MSG intake in mice has less impact on kidney compared to sodium chloride, that already in young animals induced some effects on kidney, possibly related to hypertension.

Renal interstitial fibrosis and Angiotensin inhibition

Tubulointerstitial (TI) fibrosis is a final common pathway to progressive renal injury of all forms of renal disease. However, once renal damage reaches a certain threshold, progression of renal disease is consistent, irreversible, and largely independent of the initial injury. Angiotensin (AT) II is the main effector of the renin angiotensin system (RAS) and effects that may contribute to the onset and progression of renal damage. AT II may also directly contribute to accelerate renal damage by sustaining cell growth, inflammation, and fibrosis. Interventions that inhibit the activity of the RAS are renoprotective and may retard or even halt the progression of chronic nephropathies. Unilateral ureteral obstruction suggested as a well-established experimental model of progressive interstitial expansion and fibrosis. Although technically challenging, some investigators have successfully relieved the obstruction and reported significant reduction in interstitial fibrosis severity. Drugs that modulate the RAS, such as ACE inhibitors and angiotensin type 1 (AT1) receptor antagonists, have demonstrated protective renal effects and can ameliorate fibrosis. However, neither ACE inhibitor nor AT1 receptor blockade completely suppresses progression of renal disease. Dual blockade of the RAS with ACE inhibitors and AT1 receptor blockers may provide renal benefit beyond therapy with either drug alone, due to their potential additive beneficial effect.

Lack of type VIII collagen in mice ameliorates diabetic nephropathy

OBJECTIVE

Key features of diabetic nephropathy include the accumulation of extracellular matrix proteins. In recent studies, increased expression of type VIII collagen in the glomeruli and tubulointerstitium of diabetic kidneys has been noted. The objectives of this study were to assess whether type VIII collagen affects the development of diabetic nephropathy and to determine type VIII collagen-dependent pathways in diabetic nephropathy in the mouse model of streptozotocin (STZ)-induced diabetes.

RESEARCH DESIGN AND METHODS

Diabetes was induced by STZ injections in collagen VIII-deficient or wild-type mice. Functional and histological analyses were performed 40 days after induction of diabetes. Type VIII collagen expression was assessed by Northern blots, immunohistochemistry, and real-time PCR. Proliferation of primary mesangial cells was measured by thymidine incorporation and direct cell counting. Expression of phosphorylated extracellular signal-regulated kinase (ERK1/2) and p27(Kip1) was assessed by Western blots. Finally, Col8a1 was stably overexpressed in mesangial cells.

RESULTS

Diabetic wild-type mice showed a strong renal induction of type VIII collagen. Diabetic Col8a1(-)/Col8a2(-) animals revealed reduced mesangial expansion and cellularity and extracellular matrix expansion compared with the wild type. These were associated with less albuminuria. High-glucose medium as well as various cytokines induced Col8a1 in cultured mesangial cells. Col8a1(-)/Col8a2(-) mesangial cells revealed decreased proliferation, less phosphorylation of Erk1/2, and increased p27(Kip1) expression. Overexpression of Col8a1 in mesangial cells induced proliferation.

CONCLUSIONS

Lack of type VIII collagen confers renoprotection in diabetic nephropathy. One possible mechanism is that type VIII collagen permits and/or fosters mesangial cell proliferation in early diabetic nephropathy.

Lymphoid cell proliferation in renal transplants: biologic and diagnostic implications

It is unclear whether alloreaction develops in peripheral lymphoid organs and effector cells being recruited to the target organs, or the entire process of alloreaction can happen within the transplanted kidneys. Interstitial inflammatory cell (IIC) proliferation was evaluated by MIB-1 antigen immunostain and the rate expressed as positive cells/1000 cells. This rate was higher in acute cell-mediated rejection (ACR) (25.7, n = 14) compared with normal kidney (0.4, n = 8), acute tubular necrosis (1.2, n = 8), chronic allograft nephropathy (CAN, 2.4, n = 20), and native kidneys with diverse diseases (9.2, n = 63); but was comparable to that in CAN with significant IIC (20.6, n = 16). 10.1% and 8.3% of T lymphocytes underwent proliferation in ACR with or without CAN, whereas only rare B lymphocytes or macrophages showed this change (<1.2%), regardless of diagnostic categories. All biopsies diagnosed as ACR in conjunction with a high rate of MIB-1 + IIC and 9/12 biopsies with CAN and significant IIC in which ACR was diagnosed due to a high rate of MIB-1 + IIC, responded to anti-rejection therapy. Proliferation of IIC involves predominantly T lymphocytes. These observations provide support for the concept of in situ alloimmunization, and facilitate the diagnosis of ACR.

Remodeling of renal interstitial and tubular lesions in pancreas transplant recipients

Tubular atrophy and interstitial fibrosis, important in progression of renal diseases, including diabetic (D) and cyclosporine-induced (CSA) nephropathy, have been considered irreversible. Normoglycemia for 10 years following pancreas transplantation alone (PTA) reversed D glomerulopathy lesions. This study quantified tubular, interstitial, and arteriolar parameters in PTA recipients. Kidney function studies and biopsies were performed in eight non-uremic type I D patients (pts) at 5 and 10 years after PTA. Renal biopsies were analyzed by morphometric analysis. All pts were normoglycemic and insulin independent and received CSA during the study. Cortical interstitial volume fraction was increased at 5 years (0.31+/-0.07 vs normal 0.15+/-0.02, P<0.01) and decreased at 10 years post-PTA (0.23+/-0.03, P<0.02 vs 5 years). There was a reduction in the volume fraction of interstitial collagen and cells per cortical tissue, measured using electron microscopy, from 5 (0.126+/-0.061 and 0.103+/-0.026, respectively) to 10 years (0.079+/-0.031, P<0.05, and 0.074+/-0.018, P<0.05, respectively). The volume fraction of tubules which were atrophic (AT) was abnormal at 5 years (0.160+/-0.090) and decreased from 5 to 10 years (0.044+/-0.034, P<0.02), apparently due to AT reabsorption. The index of arteriolar hyalinosis did not change during the study (1.30+/-0.22 and 1.34+/-0.33 at 5 and 10 years, respectively, nonsignificant). This study demonstrates, for the first time in humans, that interstitial expansion is reversible and that atrophic tubules can be reabsorbed. In contrast, there was no improvement in the arteriolar lesions. Whether this is due to long-term normoglycemia, reduction of CSA dose or other mechanisms is unclear.

Imatinib Attenuates Diabetic Nephropathy in Apolipoprotein E-Knockout Mice

In the diabetic kidney, clinical as well as experimental observations have shown an upregulation of growth factors such as PDGF. These studies, however, were not designed to address whether upregulation of PDGF is merely a manifestation of diabetic renal injury or whether PDGF plays an active role in the pathophysiology of diabetic nephropathy. The objectives of this study were first to assess whether PDGF-dependent pathways are involved in the development of diabetic nephropathy and second to determine the effects of PDGF receptor antagonism on this disorder and associated molecular and cellular processes. This study used the diabetic apolipoprotein E-knockout (apoE-KO) mouse, a recently described model of accelerated diabetic nephropathy. Diabetes was induced by injection of streptozotocin in 6-wk-old apoE-KO mice. Diabetic animals received treatment with a tyrosine kinase inhibitor that inhibits PDGF action, imatinib (STI-571, 10 mg/kg per d orally) or no treatment for 20 wk. Nondiabetic apoE-KO mice served as controls. This model of accelerated renal disease with albuminuria as well as glomerular and tubulointerstitial injury was associated with increased renal expression of PDGF-B, proliferating cells, and alpha-smooth muscle actin-positive cells. Furthermore, there was increased accumulation of type I and type IV collagen as well as macrophage infiltration. Imatinib treatment ameliorated both renal functional and structural parameters of diabetes as well as overexpression of a number of growth factors, collagens, proliferating cells, alpha-smooth muscle actin-positive cells, and macrophage infiltration within the kidney. Tyrosine kinase inhibition with imatinib seems to retard the development of experimental diabetic nephropathy.

An increase in the cell component of the cortical interstitium antedates interstitial fibrosis in type 1 diabetic patients

BACKGROUND

Interstitial expansion is important in the progression of a variety of kidney diseases, including diabetic nephropathy (DN). However, the interstitial elements that constitute interstitial expansion in DN are unknown and are the subject of this report.

METHODS

Interstitial composition was analyzed in 15 long-standing type 1 diabetic patients, 8 with mild ( congruent with 1.5 x normal) and 7 with moderate ( congruent with 2 x normal) increases in cortical interstitial fractional volume [Vv(Int/cortex]. The mild group was 29 +/- 5 (mean +/- SD) years old with diabetes duration of 17 +/- 5 years. The moderate group was older (41 +/- 7 years; P < 0.03), had longer diabetes duration (28 +/- 7 years; P = 0.002), lower creatinine clearance (90 +/- 14 mL/min/1.73 m2 vs. 109 +/- 18 mL/min/1.73 m2; P = 0.05) and used antihypertensive medications more frequently (0/8 vs. 4/7; P < 0.03) compared to the mild group. Age- and gender-matched normal controls (N = 9) also were studied. Interstitial composition was evaluated by morphometric analysis of electron microscopic (EM) micrographs systematically obtained without bias at high (x 7500) and low (x 1500) magnification.

RESULTS

Mild interstitial expansion was associated with an congruent with 50% increase in fractional volume of interstitial cells (P < 0.001) and congruent with 70% increase in fractional volume of interstitial nuclei (P < 0.01). Numerical density of interstitial nuclei was normal in these patients, suggesting that the interstitial cells might be larger rather than simply more numerous. An increase over normal in the interstitial fractional volume of fibrillary collagen of congruent with 50% was seen only with moderate expansion (P < 0.001), when creatinine clearance was already decreased. Interstitial expansion was associated with a decrease in volume and surface of peritubular capillaries as well as with a reduction in surface ratio of capillaries to tubules.

CONCLUSIONS

In contrast to early mesangial expansion where matrix accumulation plays a dominant role, mild interstitial expansion in long-standing type 1 diabetic patients is largely due to an increase in the cell component of the interstitium. Increased fractional volume of interstitial fibrillary collagen is only seen at later stages of the disease, when the glomerular filtration rate is already reduced. Different pathogenetic processes may be operative in early diabetic glomerular and interstitial diseases.

Proteinuria and tubulointerstitial lesions in lupus nephritis

BACKGROUND

Response of the renal tubules to proteinuria is implicated in progression of renal disease. Experimentally, proteinuria causes increased tubular synthesis of macrophagic and other chemokines, with increased tubular cellular proliferation and apoptosis, leading to interstitial inflammation and fibrosis. Clinically, diminution of proteinuria leads to the slowing of progression, but whether this leads to reduction in tubular lesions has not been directly demonstrated in humans.

METHODS

Initial (Bx1) and systematic six-month biopsies (Bx2) from 71 patients with lupus nephritis were studied, with a subset of 34 biopsies also stained for proliferating cell nuclear antigen (PCNA), the macrophage marker PGM1, and cytokeratins (AE1/AE3), and morphometric cell and tubular profile counts performed.

RESULTS

Positive correlations were found between increasing levels of proteinuria and the following light microscopic parameters: tubular epithelial pyknosis, tubular epithelial nuclear "activation," tubular lumenal macrophages, interstitial inflammation and fibrosis, but not with tubulointerstitial immunofluorescence. Significant positive correlations also were found with the following immunohistochemical parameters: PCNA in epithelial cells (r = 0.74) and tubular luminal cells (r = 0.47); tubular lumenal macrophages (r = 0.63) and tubular epithelial cells with acquired PGM1 staining (r = 0.36); and pyknotic tubular epithelial cells (r = 0.47). All showed strong correlations with serum creatinine (S(Cr)) as well. All were reduced at Bx2, generally in parallel to the reduction in proteinuria. Tubulointerstitial immune deposits appear to play only a minor role in the development of tubular epithelial lesions and the progression of renal disease in lupus. They show only limited correlation with SCr and no correlation with proteinuria. By multiple regression, they are not associated with tubular epithelial lesions, interstitial inflammation or interstitial fibrosis at either biopsy, whereas tubular epithelial lesions are strongly associated with interstitial inflammation at Bx1 and with interstitial fibrosis at Bx2. Cytokeratin correlated strongly with S(Cr) (r = 0.53, P = 0.002) but not with proteinuria (r = 0.27, NS), and was the sole immunohistochemical parameter to increase at Bx2. It appears to be a sensitive marker for tubular atrophy.

CONCLUSIONS

In this study both proteinuria and SCr showed a hierarchy of correlations with morphologic variables: Tubular epithelial cell changes> tubular macrophages> interstitial inflammation> interstitial fibrosis, corresponding to current experimental models, but not previously demonstrated in humans.

Correlation between the expression of DNA topoisomerases I and IIalpha and clinical parameters in kidney disease

Multiple factors interact during the evolution of renal diseases. In the present study, we examined the expression of DNA topoisomerases type I and IIalpha, which reflect gene transcription and DNA replication, respectively. Enzyme content was assessed by immunohistochemistry using two specific monoclonal antibodies, C21 and Ki-S4, on 81 archival punch-biopsy specimens from patients with renal diseases, including minimal change disease (MCD; n = 10), focal segmental glomerular sclerosis (FSGS; n = 6), mesangial proliferative glomerulonephritis (MPGN; n = 11), membranous glomerulonephritis (MGN; n = 10), mesangial capillary glomerulonephritis (MCGN; n = 7), rapidly progressive glomerulonephritis (RPGN; n = 12), lupus nephritis (LN; n = 15), and tubulointerstitial nephritis (TIN; n = 10). Both enzymes were strongly expressed in diseases tending to rapid progression, notably RPGN and LN, whereas MCD and MGN showed low protein levels in both the glomerular and tubular compartments. Moreover, topoisomerase expression was significantly associated with the density of monocytogenic infiltrates (monitored by means of the monoclonal antibody Ki-M1p), such pathogenesis-associated factors as antinuclear antibodies and paranuclear antineutrophilic antibodies, and serum immunoglobulin levels. There also was a positive correlation with serum creatinine levels and an inverse association with proteinuria and nephrotic syndrome. We conclude that the expression of DNA topoisomerases may be linked to pathogenetic mechanisms and may provide prognostic information. Because of their comparatively low nephrotoxicity, topoisomerase inhibitors might prove to be useful therapeutic agents in the treatment of renal diseases.

Expression of DNA topoisomerases in chronic proliferative kidney disease

BACKGROUND

Circulating autoantibodies to human topoisomerases have been reported in glomerular kidney disease associated with scleroderma and systemic lupus erythematosus. However, limited information is available about the expression of topoisomerases in the kidney under normal and pathological conditions.

METHODS

The expression of DNA topoisomerases I and IIalpha was studied by immunohistochemistry on archival biopsies from 70 patients with chronic renal diseases. Normal kidney tissue was examined for comparison. Topoisomerase I was detected by means of monoclonal antibody (mAb) C21, and topoisomerase IIalpha was detected by means of mAb Ki-S4. In addition, mAb Ki-M1p was used to assess the density of monocytic infiltrates. All parameters were assessed in a semiquantitative manner.

RESULTS

Glomerular topoisomerase IIalpha levels were increased in mesangial proliferative glomerulonephritis (MPGN), rapidly progressive glomerulonephritis (RPGN), and lupus nephritis (LN) and were reduced in membranous glomerulonephritis (MGN), chronic transplant nephropathy (CTN), and tubulointerstitial nephritis (TIN). Tubular epithelia displayed high topoisomerase IIalpha levels in mesangiocapillary glomerulonephritis (MCGN), RPGN, TIN, miscellaneous entities (MISC) and LN, and displayed low levels in MPGN and CTN. Topoisomerase I expression was high in the glomeruli of focal segmental glomerulosclerosis (FSGS), MCGN, and RPGN and was extreme in LN, whereas it was strikingly diminished in the glomeruli of MGN, CTN, and TIN. Almost all conditions displayed lower tubular topoisomerase I levels than normal kidney, except for LN, in which the enzyme content was markedly increased. Increased glomerular monocytic infiltrates were found in FSGS, MCGN, RPGN, TIN, and LN, and tubulointerstitial Ki-M1p+ cells were seen at high numbers in MCGN, RPGN, TIN, MISC, and LN. The expression of the topoisomerases I and IIalpha was significantly correlated; also, topoisomerases showed a positive association with the density of monocytic infiltrates. The parameter profiles exhibited significant differences between distinct types of chronic renal disease.

CONCLUSION

Topoisomerase IIalpha expression is tightly linked to cell cycling, and topoisomerase I is likely a reflection of gene transcription. Rapidly progressing glomerular disease therefore appears to be accompanied by active mesangial cell proliferation and increased metabolic activity in glomerular cells. The correlation with inflammatory infiltrates is likely to reflect a positive feedback mechanism involving cytokines, growth factors, and adhesion molecules. Assessment of topoisomerases may therefore be of diagnostic help and might allow prognostic predictions. Provided that our observations are supported by clinicopathological follow-up studies, one might envisage the use of topoisomerase inhibitors in the therapy of chronic proliferative renal disease refractory to current treatment protocols.

The evolving contribution of renal pathology to understanding interstitial nephritis

One hundred years of progress in the study of interstitial nephritis has expanded our diagnostic entities, resulted in identification of numerous pathogenic events, and defined the nature of the inflammatory infiltrate in ways that are useful both for general understanding and for diagnostic classification. We stand poised to enter the next hundred years with new techniques applicable to renal biopsies that detect specific biologic activities in situ in tissue sections. In the future, the information gained from these techniques is likely to result in refined and more accurate assessments of prognosis in patients with kidney disease, and to guide therapeutic interventions designed to interrupt specific sequences of active renal injury.

Expression of the cyclin kinase inhibitor, p27kip1, in developing and mature human kidney

It has been shown that glomerular visceral epithelial cells (VEC) proliferate during glomerulogenesis, but differentiated VEC of the fetal kidney do not. It is also recognized that the proliferative capacity of the VEC in mature kidneys is very limited, and according to some investigators, may be completely absent. The basis for this remains unknown. Cell proliferation is controlled by cell cycle-related proteins, of which one class, the cyclin kinase inhibitors (CKI), cause cell cycle arrest and inhibit proliferation. A role for CKI in kidney development is not known. Accordingly, we examined the expression of the CKI p27kip1 (p27) in developing and mature human kidney tissue. Concomitant expression of markers of cell proliferation, Ki-67-related antigen (Ki-67) and proliferating cell nuclear antigen (PCNA), also were examined in fetal and mature human kidney tissue by immunocytochemical techniques. In developing kidney, Ki-67 and PCNA expression are most pronounced in the nephrogenic zone where expression correlates inversely with increasing glomerular maturation. In well-differentiated glomeruli, Ki-67 and PCNA expression is present in some parietal epithelial cells but is absent in the VEC. In contrast, p27 staining exhibits a reverse gradient of expression. p27 is absent in the proliferating tissue exhibiting the earliest stages of differentiation, whereas expression is widespread in the differentiated epithelial cells of more mature glomeruli, in which detectable cell proliferation has ceased. Expression of p27 was not identified in fetal mesangial or glomerular endothelial cells. In the mature human kidney, the pattern of p27 expression identified in differentiated fetal glomeruli persists and appears to be constitutive and specific for glomerular VEC. This pattern of p27 expression in terminally differentiated VEC may explain their limited proliferative capacity in response to injury. This is the first demonstration of a potential role for p27 in human renal development.