Glomerular fibrin deposition and removal

Donor kidney microthrombi and outcomes of kidney transplant: a single-center experience

The kidney wait list has outgrown the supply of available organs every year. Efforts are being made to minimize discard rate of organs. One such area is the use of kidneys with glomerular microthrombi (MT). We retrospectively examined graft/patient outcomes in 28 cases with MT in pre-implantation biopsies. All patients had follow-up of at least 36 months, or until graft loss or death. In total, 17 of the 18 patients who underwent follow-up biopsy within 90 days of transplantation had cleared all MT. Most patients had excellent long-term graft function. On a closer review of the biopsies included in our study, we found that even in the organs with the most widespread thrombosis, the median percentage of glomeruli with more than 50 percentage of the capillary loops occluded was 8% (range 0-17%). The current practice of mentioning the % of glomeruli with thrombi cannot adequately capture the extent of donor organ pathology, as the actual % glomerular area involved can vary greatly from case to case. Future studies should attempt to quantify donor thrombi by a more robust method and revisit the issue of using clinico-pathologic parameters to predict allograft function in the setting of MT.

Successful renal transplantation from a brain-dead deceased donor with head injury, disseminated intravascular coagulation and deranged renal functions

Deceased donors (DDs) with the brain death due to head injury are the major source of organs for transplantation. The incidence of post-head injury disseminated intravascular coagulation (DIC) ranges from 24% to 50%. Many centers do not accept organs from donors with DIC due to increased risk of primary graft non-function and/or high chances of morbidity/mortality. We performed two successful renal transplants from a DD with head injury with DIC and deranged renal function. One of the recipients developed transient thrombocytopenia, but there was no evidence of DIC or delayed graft functions in either of the recipients. Over a follow-up of 1 month, both are doing well with stable graft function and hematological profile. Thus, a carefully selected DD with severe DIC even with deranged renal function is not a contraindication for organ donation if other risk factors for primary non-function are excluded. This approach will also help in overcoming organ shortage.

Implications of donor disseminated intravascular coagulation on kidney allograft recipients

BACKGROUND AND OBJECTIVES

Disseminated intravascular coagulation (DIC) is common in deceased kidney donors and is considered a relative contraindication to donation. The significance of donor DIC on recipient kidney function is poorly understood. Additionally, the significance of thrombocytopenia in recipients of kidneys from DIC-positive donors is understudied.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a retrospective cohort of 162 kidney transplants, the presence of DIC in donors, the occurrence of thrombocytopenia in recipients, and risk factors for delayed or slow graft function (DGF/SGF) were assessed. The effects of DIC donor status on DGF/SGF in the study sample as a whole, and of thrombocytopenia on DGF/SGF in recipients of DIC-positive kidneys specifically, were examined using multiple logistic regression.

RESULTS

DIC donor status was not associated with occurrence of DGF/SGF, but thrombocytopenia was significantly associated with DIC-positive donor status (P=0.008). Thrombocytopenia was independently associated with DGF/SGF only in the recipients of DIC-positive kidneys (P=0.005). Patient and graft survival at 1 year were not affected by donor DIC status or by thrombocytopenia status.

CONCLUSIONS

Donor DIC was not associated with short-term suboptimal graft function, defined as DGF/SGF, nor with long-term patient or graft survival. However, thrombocytopenia appears to portend DGF/SGF in recipients of DIC-positive kidneys and may be a clinical sign on which the basis of therapeutic decisions could be undertaken.

Antithrombotic drug therapy for IgA nephropathy: a meta analysis of randomized controlled trials

BACKGROUND

Antithrombotic agents, including antiplatelet agents, anticoagulants and thrombolysis agents, have been widely used in the management of immunoglobulin A (IgA) nephropathy in Chinese and Japanese populations. To systematically evaluate the effects of antithrombotic agents for IgA nephropathy.

METHODS

Data sources consisted of MEDLINE, EMBASE, the Cochrane Library, Chinese Biomedical Literature Database (CBM), Chinese Science and Technology Periodicals Databases (CNKI) and Japana Centra Revuo Medicina (http://www.jamas.gr.jp) up to April 5, 2011. The quality of the studies was evaluated from the intention to treat analysis and allocation concealment, as well as by the Jadad method. Meta-analyses were performed on the outcomes of proteinuria and renal function.

RESULTS

Six articles met the predetermined inclusion criteria. Antithrombotic agents showed statistically significant effects on proteinuria (p<0.0001) but not on the protection of renal function (p=0.07). The pooled risk ratio for proteinuria was 0.53, [95% confidence intervals (CI): 0.41-0.68; I(2)=0%] and for renal function it was 0.42 (95% CI 0.17-1.06; I(2)=72%). Subgroup analysis showed that dipyridamole was beneficial for proteinuria (p=0.0003) but had no significant effects on protecting renal function. Urokinase had statistically significant effects both on the reduction of proteinuria (p=0.0005) and protecting renal function (p<0.00001) when compared with the control group.

CONCLUSION

Antithrombotic agents had statistically significant effects on the reduction of proteinuria but not on the protection of renal function in patients with IgAN. Urokinase had statistically significant effects both on the reduction of proteinuria and on protecting renal function. Urokinase was shown to be a promising medication and should be investigated further.

Glomerular capillary hemorrhage induced in rats by diagnostic ultrasound with gas-body contrast agent produces intratubular obstruction

Glomerular capillary hemorrhage (GCH) induced by ultrasonic cavitation during diagnostic imaging represents a unique contrast agent-related nephron injury. Consequences of GCH during 1.5-MHz diagnostic ultrasound with contrast agent were examined by histologic methods in rats. Definity was infused at 10 microl/kg/min for 5 min at the start of 8 min of intermittent image-exposure, with 2.3 MPa in situ peak rarefactional pressure amplitude. Kidney samples were taken for histology at 5 min, 30 min, 4 h, 2 d, 1 week and 4 weeks post exposure. In addition, samples were taken at 4 h from groups treated with heparin or aminocaproic acid. GCH was found in 61% of glomeruli in the center of the scan plane 5 min after exposure, which declined (p < 0.05) to 36.3% after 4 h. The width of Bowman's space was significantly increased for glomeruli with GCH relative to glomeruli without GCH (p < 0.05), consistent with tubular obstruction. Antibody staining revealed fibrin clotting in Bowman's space in 4-h samples and this persisted in the 2-d samples. Heparin reduced and aminocaproic acid increased the GCH seen in 4-h samples. Tubular dilation was evident with injury to the epithelium after 2 d. After one week, areas of inflammatory cell infiltration were present. After four weeks, areas of interstitial fibrosis were revealed by Masson's trichrome stain. The consequences of GCH induced by diagnostic ultrasound with contrast agents include rupture of glomerular capillaries, procoagulant activity resulting in intratubular obstruction, and the potential for progression of the resulting tubular injury toward interstitial fibrosis.

Role of mesangial fibrinogen deposition in the pathogenesis of crescentic Henoch-Schonlein nephritis in children

AIMS

To clarify the role of mesangial fibrinogen deposition in crescentic Henoch-Schönlein nephritis (HSN).

METHODS

A retrospective analysis of 21 children with HSN treated with immunosuppressants. Serial renal biopsies were performed before and after treatment. They were divided into two groups according to the immunofluorescent course of fibrinogen deposition: group I (n = 9), no or decreased deposition; group II (n = 12), persistent or increased deposition.

RESULTS

There were no differences between the two groups in renal manifestations or laboratory and histological findings at presentation. However, the activity index after immunosuppressive treatment was significantly decreased in group I (mean, 7.9 (SEM, 0.7) v 2.9 (0.4); p = 0.008) and unchanged in group II (mean, 6.8 (SEM, 0.3) v 6.0 (2.1)). The chronicity index was unchanged in group I, but increased in group II (mean, 0.8 (SEM, 0.3) v 1.8 (0.3); p = 0.02). Univariate analysis revealed that the only factor significantly related to persistent or increased fibrinogen deposition was age more than 9 years (p = 0.03). Furthermore, the intensity of fibrinogen deposition at the second biopsy correlated positively with the age at onset (R2= 0.306; p = 0.009) and changes in the percentage of crescents (post-treatment crescents (%) minus pretreatment crescents (%)) correlated positively with the intensity of fibrinogen deposition at the second biopsy (R2= 0.193; p = 0.046).

CONCLUSIONS

This study indicates that fibrinogen deposition has an important role to play in renal injury of crescentic HSN and reflects persistent severe histological activity.

Effects of co-administration of urokinase and benazepril on severe IgA nephropathy

BACKGROUND

The availability of treatment for IgA nephropathy (IgAN) is limited. Method. A prospective randomized controlled clinical trial was performed to evaluate the effects of therapy with urokinase (UK) and benazepril (BZ, an angiotensin-converting enzyme inhibitor) or BZ alone on severe IgAN. We divided 71 cases of IgAN, Lee's grade >/=III and with fibrinogen deposits, into two groups to be treated for 12 months with either UK + BZ or BZ alone.

RESULTS

There was no significant difference between the two groups in baseline clinical and histopathological data. After 12 months of treatment, 25 of 35 patients (71.4%) in the UK + BZ group and 16 of 36 (44.4%) in the BZ-alone group had a >/=50% decrease in 24-h urinary protein excretion compared with the baseline (chi(2) test, P<0.05). Proteinuria significantly decreased at 6 and 12 months of treatment in both groups compared with baseline (P<0.01 in the UK + BZ group, P<0.05 in the BZ group), and the therapeutic efficiency of UK + BZ was better than that of BZ alone (P<0.05 at 6 and 12 months). The endogenous creatinine clearance rate (Ccr) was stable in the UK + BZ group, while Ccr declined significantly at 6 and 12 months in the BZ-alone group compared with baseline (P<0.05, respectively). The Ccrs of the two groups at 12 months of treatment were statistically different (P<0.05).

CONCLUSIONS

Combined therapy with UK and BZ was more effective than with BZ alone in reducing proteinuria and protecting renal function in patients with severe IgAN.

Expression of glomerular plasminogen activator inhibitor type 1 in glomerulonephritis

Plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (tPA) are the major regulators of plasmin generation. Glomerular PAI-1/tPA balance is involved in extracellular matrix turnover, as well as fibrin deposition in glomeruli. Renal biopsy specimens were obtained from 80 patients with either primary or secondary glomerulonephritis (10 patients, minimal change nephrotic syndrome; 6 patients, focal segmental glomerulosclerosis [FSGS]; 10 patients, membranous nephropathy [MN]; 24 patients, mesangial proliferative glomerulonephritis; 15 patients, lupus nephritis; 14 patients, diabetic nephropathy; and 1 patient, membranoproliferative glomerulonephritis). We quantified glomerular PAI-1 and tPA messenger RNA (mRNA) by competitive polymerase chain reaction. We also determined PAI-1 mRNA localization by in situ hybridization. Glomerular PAI-1 mRNA levels in patients with FSGS and MN were significantly greater than those of controls. There was a sixfold increase in PAI-1-tPA mRNA ratio in patients with MN compared with the control group. In addition, glomerular PAI-1 mRNA level correlated with level of proteinuria. Conversely, there was no difference in tPA mRNA levels among types of glomerulonephritis. These results suggest that suppressed glomerular fibrinolytic and proteolytic activity may be associated with the pathogenesis of glomerulonephritis, especially in FSGS and MN.

Insertional mutation of the collagen genes Col4a3 and Col4a4 in a mouse model of Alport syndrome

Mice homozygous for the transgenic insertion in line OVE250 exhibit severe progressive glomerulonephritis. Ultrastructural changes in the glomerular basement membrane (GBM) at 2 weeks of age resemble those in Alport syndrome. The transgenic insertion site was mapped by FISH to mouse chromosome 1 close to Pax3. Genetic and molecular analyses identified a deletion of genomic DNA at the transgene insertion site. Exons 1 through 12 of the collagen IV gene Col4a4, exons 1 and 2 of the adjacent Col4a3 gene, and the intergenic promoter region are deleted. Transcripts of Col4a3 and Col4a4 are undetectable in mutant kidney, and both proteins are missing from the GBM. Persistent cellular proliferation in mutant kidneys suggests that interaction with the extracellular matrix may be important for cell maturation. Evolutionarily conserved sequence elements in the promoter regions of human and mouse Col4a3 and Col4a4 include a 19-bp element that was tandemly duplicated in the human lineage and a CTC box element common to several genes encoding extracellular matrix proteins. This new animal model of Alport syndrome, Col4Delta3-4, lacks both alpha3 and alpha4 chains of collagen IV and exhibits an earlier disease onset than mice lacking alpha3 only.

Expression of tissue type plasminogen activator and type 1 plasminogen activator inhibitor, and persistent fibrin deposition in chronic renal allograft failure

Persistent fibrin deposition has been observed in kidneys undergoing chronic rejection, and has been suggested to contribute to the obliteration of the vasculature in these grafts. The mechanisms leading to it are not clear. Fibrinolysis, the process to remove fibrin in tissues, is initiated by tissue type plasminogen activator (tPA) and suppressed by type 1 plasminogen activator inhibitor (PAI-1). To investigate their roles in chronic rejection and fibrin deposition, we serially examined the expression of tPA and PAI-1 in an unmodified chronic rejection model, using a Fisher 344 to Lewis rat renal transplant, at 0, 2, 4, 6, 10, 12, 16 and 20 weeks post-transplantation (N = 4 rats/time point in each group). We also analyzed fibrin deposition and the development of chronic changes in the grafts. Our results show that tPA was up-regulated only in the acute phase of rejection (P < 0.05), whereas PAI-1 was induced and persistently expressed during the progressive phase of chronic rejection, together with persistent fibrin deposition in the grafts. Immunohistochemistry showed PAI-1 was mainly localized to the damaged/proliferative vascular intima. The results suggest that persistent induction of PAI-1 may be responsible for the continuance of fibrin deposition, which is associated with irreversible damage and chronic graft loss.

Up-regulation of type 1 plasminogen activator inhibitor messenger RNA with thrombotic changes in renal grafts

Small vessel thrombosis is a prominent feature in kidneys undergoing vascular rejection. Type I and type 2 plasminogen activator inhibitors (PAI-1 and PAI-2, respectively) are known to mediate thrombosis. To examine the potential role of PAI-1 and PAI-2 in the mediation of vascular injury, the relationship and the time course of gene expression of PAI-1 and PAI-2 with the thrombotic changes in renal grafts were investigated in an unmodified rejection model in rats. Orthotopic renal transplantation was performed from Lewis to dark agouti (DA) rats and from DA to DA isografts; untreated normal rat kidneys were used as controls. The rats were killed on days 1-9 posttransplantation (n=18 in each allograft and isograft group). The grafts were analyzed by histopathology, in situ mRNA hybridization and Northern blot methods. The results show that PAM mRNA was first detected at day 4, when the thrombotic changes in the grafts were first seen, and that this relationship persisted during the time course observed to day 9. There was no detectable PAI-1 mRNA in the control groups and no PAI-2 in either group. In situ hybridization showed that PAI-1 positive cells were predominantly located in the cortical interstitium, consistent with the distribution of interstitial microthrombi. These results provide experimental evidence that the thrombotic changes in rejecting allografts are associated with the up-regulation of PAI-1 in the donor tissue, whereas PAI-2, from our results, does not seem to influence these changes. The data are consistent with a role for PAI-1 in the pathogenesis of vascular rejection.