An unanticipated role for survivin in organ transplant damage

Ischemia/reperfusion (I/R) injury is a major determinant of graft survival in kidney transplantation. Survivin, an inhibitor of apoptosis that participates in the control of mitosis and cell cycle progression, has been implicated in renal protection and repair after I/R injury; however, no study has been performed in the transplant setting. We investigated the role of survivin in modulating posttransplant I/R injury in syngeneic and allogeneic kidney grafts, and studied whether protection from I/R injury impacted on the recipient immune system, on chronic allograft nephropathy and rejection. We used genetically engineered mice with survivin haploinsufficiency and WT mice in which survivin over-expression was induced by gene-delivery. Survivin haploinsufficiency in syngeneic grafts was associated with exuberant I/R tissue injury, which triggered inflammation eventually resulting in graft loss. Conversely, survivin over-expression in the grafts minimized I/R injury and dysfunction in syngeneic grafts and in a clinically relevant fully MHC-mismatched allogeneic combination. In the latter, survivin over-expression translated into limited anti-donor adaptive immune response and less long-term allograft injury with protection from renal parenchymal damage. Our data support survivin over-expression in the graft as a novel target for protocols aimed at limiting tissue damage at the time of transplant ultimately modulating the recipient immune system.

A novel strategy to enhance mesenchymal stem cell migration capacity and promote tissue repair in an injury specific fashion

Mesenchymal stem cells (MSCs) of bone marrow origin appear to be an attractive candidate for cell-based therapies. However, the major barrier to the effective implementation of MSC-based therapies is the lack of specific homing of exogenously infused cells and overall the inability to drive them to the diseased or damaged tissue. In order to circumvent these limitations, we developed a preconditioning strategy to optimize MSC migration efficiency and potentiate their beneficial effect at the site of injury. Initially, we screened different molecules by using an in vitro injury-migration setting, and subsequently, we evaluated the effectiveness of the different strategies in mice with acute kidney injury (AKI). Our results showed that preconditioning of MSCs with IGF-1 before infusion improved cell migration capacity and restored normal renal function after AKI. The present study demonstrates that promoting migration of MSCs could increase their therapeutic potential and indicates a new therapeutic paradigm for organ repair.

ACE inhibition reduces glomerulosclerosis and regenerates glomerular tissue in a model of progressive renal disease

Today angiotensin II inhibition is primarily used to slow the rate of progression of kidney diseases. There is evidence that these therapies can induce a partial regression of glomerular lesions. However, we do not know yet the extent of sclerotic lesion regression and whether new glomerular tissue is formed to help support the renal function. We used male Munich Wistar Fromter (MWF) rats, an experimental model for progressive kidney disease, to quantify kidney structural lesions upon angiotensin-converting enzyme (ACE) inhibition therapy. Animals were studied at 50 weeks of age, when renal function and structure are severely altered, and after a 10-week observation period, without or with treatment with lisinopril (80 mg/l in drinking water). A group of untreated Wistar rats was used as controls. With age, proteinuria, and serum creatinine worsen, but lisinopril almost normalized proteinuria and stabilized serum creatinine. Serial section analysis of whole glomerular tufts showed that at baseline, glomerulosclerosis affected the entire glomerular population, and that these changes further increased with age. Lisinopril significantly reduced incidence and extent of glomerulosclerosis, with the presence of glomerular tufts not affected by sclerosis (23% of glomeruli). Glomerular volume was not significantly affected by treatment, and glomerular mass spared from sclerosis increased from 46.9 to 65.5% upon treatment, indicating consistent regeneration of glomerular tissue. Lisinopril normalized baseline glomerular transforming growth factor-beta and alpha-smooth muscle actin overexpression, and prevented worsening of interstitial changes. Hence, ACE inhibition, which is widely used in human kidney disease, may not only halt the progression of renal failure, but also actually induce the regeneration of new renal tissue.

Angiotensin-converting enzyme inhibition prevents glomerular-tubule disconnection and atrophy in passive Heymann nephritis, an effect not observed with a calcium antagonist

In proteinuric nephropathies tubular atrophy leads to glomerular-tubule disconnection through an unknown mechanism. Here we studied whether proteinuria promoted glomerular-tubule disconnection in individual nephrons and whether this phenomenon was prevented by an angiotensin-converting enzyme (ACE) inhibitor. Passive Heymann nephritis (PHN) and control rats were studied at 4 and 8 months. Two additional groups of PHN rats received lisinopril (40 mg/L) or a calcium channel blocker (lacidipine, 3 mg/kg) from day 7 after surgery to 8 months. At sacrifice, kidneys were serially sectioned to identify glomerular- tubule abnormalities in individual nephrons and changes in interstitial volume. In PHN rats, the time-dependent increase in proteinuria was paralleled by tubular atrophy leading to glomerular-tubule disconnection and interstitial volume enlargement. Marked apoptosis was invariably found in atrophic tubules in contrast to the absent or very mild terminal dUTP nick-end labeling staining in tubules normally connected to glomeruli in PHN animals. Treatment with an ACE inhibitor prevented hypertension, proteinuria, the formation of atrophic tubuli, glomerular-tubule disconnection and limited the fractional interstitial volume expansion. Although lacidipine limited hypertension, it did not reduce proteinuria or prevent tubular atrophy and disconnection. Multivariate analysis showed that the appearance of atubular glomeruli and the increase in interstitial volume were better predicted by proteinuria than blood pressure. This study suggests that ACE inhibitors effectively prevent glomerular-tubule disconnection possibly by their ability of reducing proteinuria, which in turn favors proximal tubular cell apoptosis. Agents that only reduced hypertension but not proteinuria do not affect tubular behavior.

Combining an antiproteinuric approach with mycophenolate mofetil fully suppresses progressive nephropathy of experimental animals

Chronic renal diseases progress to organ insufficiency, which may require replacement therapy within one to three decades even independently of the type of initial insults. In the majority of cases, the degrees of proteinuria and interstitial leukocyte infiltration and scarring are strictly correlated with the rate of disease progression. This study tests the hypothesis that excess intrarenal protein traffic may cause lymphocyte-dependent interstitial injury that, while not fully controlled by antiproteinuric therapy, can be further inhibited by concomitant immunosuppression. A primarily nonimmune model was used to reproduce progressive renal disease due to a critical loss of nephron mass. Angiotensin-converting enzyme (ACE) inhibitor limited proteinuria, interstitial inflammation, MHC class II antigen expression, and severe lesions. Combined treatment with ACE inhibitor and a specific antilymphocyte agent, mycophenolate mofetil, dramatically attenuated macrophage and T cell infiltration, MHC-class II overexpression, dendritic cells, and all manifestations of the disease. Evidence of lymphocyte-mediated renal injury in the setting of excess protein traffic provides the basis for combining ACE inhibition and immunosuppression to halt progression of proteinuric kidney disease and minimize the need for dialysis or transplantation.