Hepatocyte growth factor gene therapy enhances infiltration of macrophages and may induce kidney repair in db/db mice as a model of diabetes.

AIMS/HYPOTHESIS: We previously demonstrated hepatocyte growth factor (HGF) gene therapy was able to induce regression of glomerulosclerosis in diabetic nephropathy through local reparative mechanisms. The aim of this study was to test whether bone-marrow-derived cells are also involved in this HGF-induced reparative process. METHODS: We have created chimeric db/db mice as a model of diabetes that produce enhanced green fluorescent protein (EGFP) in bone marrow cells. We performed treatment with HGF gene therapy either alone or in combination with granulocyte-colony stimulating factor, in order to induce mobilisation of haematopoietic stem cells in these diabetic and chimeric animals. RESULTS: We find HGF gene therapy enhances renal expression of stromal-cell-derived factor-1 and is subsequently associated with an increased number of bone-marrow-derived cells getting into the injured kidneys. These cells are mainly monocyte-derived macrophages, which may contribute to the renal tissue repair and regeneration consistently observed in our model. Finally, HGF gene therapy is associated with the presence of a small number of Bowman's capsule parietal epithelial cells producing EGFP, suggesting they are fused with bone-marrow-derived cells and are contributing to podocyte repopulation. CONCLUSIONS/INTERPRETATION: Altogether, our findings provide new evidence about the therapeutic role of HGF and open new opportunities for inducing renal regeneration in diabetic nephropathy.

Factores de crecimiento y regeneración renal / Growth factors and renal regeneration

Cuando se produce un daño en un tejido adulto, el proceso de renovación celular continuada es crítico y crucial para la reparación del mismo y, en determinados órganos, se facilita por la presencia de células madre o progenitoras. El riñón, a diferencia de otros órganos como el hígado, es de regeneración lenta. Incluso ha sido considerado durante años como incapaz de regenerarse. Sin embargo, varios estudios han demostrado que existen posibles nichos de células madre renales en la papila renal, progenitores tubulares o progenitores renales CD24+CD133+ localizados en el polo urinario de la cápsula de Bowman. Estas células podrían participar teóricamente en la reparación de la lesión renal. Sin embargo, todavía no se ha demostrado de forma precisa cuál sería su papel ni cómo actuarían después del daño. Aún así, estas células madre renales podrían ser dianas terapéuticas para el remodelado del tejido renal dañado. Por otro lado, se ha postulado que las células madre derivadas de la médula ósea podrían participar en la regeneración renal, especialmente las de estirpe mesenquimal. Sin embargo, tampoco se conoce con exactitud el modo en que actuarían. Hay estudios que sugieren la existencia de fusión celular entre estas células y células residentes, otros apuntan a su diferenciación en células renales, mientras que otros sugieren una acción paracrina responsable del efecto reparador a través de la secreción de factores de crecimiento como HGF, VEGF y IGF-1. Todas estas moléculas secretadas proporcionarían un entorno regenerativo que limitaría el área del daño y que facilitaría la migración de las células madre (AU)

Cell replenishment is critical for adult tissue repair after damage. In some organs this process is facilitated by stem cells. In contrast to the liver, the kidney has limited capacity for regeneration. Nevertheless, there are several recent studies suggesting the presence of stem cells in the adult kidney. Stem cell renal niches have been identified in the renal papilla in animals as well as in the urinary pole of the Bowman capsule in humans (CD24 + CD133 + stem cells).Although these cells may contribute to organ regeneration, how these cells exert this effect and their role after kidney damage is not known. Nevertheless, renal stem cells maybe therapeutic targets for treatment of renal diseases. On the other hand, bone marrow derived stem cells may also contribute in renal repair, particularly mesenchymal stem cells. However, the mechanism for producing such effect has not been elucidated. Some studies suggest there is cell fusion between bone marrow and resident tubular cells; others suggest bone marrow cells are able to differentiate in resident cells, while some authors propose bone marrow cells facilitate organ regeneration by a paracrine action; that is by secreting growth factors as hepatocyte growth factor, vascular endothelial growth factor and insulin growth factor 1. All these secreted molecules would provide a regenerative milieu able to constrain renal damage and to amplify migration of stem cells to the damaged organ (AU)

[Growth factors and renal regeneration]. / Factores de crecimiento y regeneración renal.

Cell replenishment is critical for adult tissue repair after damage. In some organs this process is facilitated by stem cells. In contrast to the liver, the kidney has limited regeneration capacity and has even been considered over several years as not being able to regenerate itself. Nevertheless, there are several recent studies suggesting the presence of stem cells in the adult kidney. Stem cell renal niches have been identified in the renal papillae in animals as well as in the urinary pole of the Bowman's capsule in humans (CD24+CD133+ stem cells). Although these cells may contribute to organ regeneration, how these cells exert this effect and their role after kidney injury is not known. Nevertheless, renal stem cells may be therapeutic targets for treatment of renal diseases. On the other hand, bone-marrow-derived stem cells may also contribute to renal repair, particularly mesenchymal stem cells. However, the mechanism for producing such effect has not been elucidated. Some studies suggest there is cell fusion between bone marrow and resident tubular cells; others suggest that bone marrow cells are able to differentiate in resident cells, while some authors propose bone marrow cells facilitate organ regeneration by a paracrine action; that is by secreting growth factors such as HGF, VEGF and IGF1. All these secreted molecules would provide a regenerative milieu able to constrain renal damage and to amplify stem cells migration to the damaged organ.

Bone marrow transplantation induces normoglycemia in a type 2 diabetes mellitus murine model.

OBJECTIVE: To study the cellular mechanisms involved in the regression of diabetic nephropathy, bone marrow-derived cells must be identified. The aim of this study was to obtain a diabetic chimeric model with bone marrow cells expressing enhanced green fluorecence protein (EGFP), without modifying the course of diabetic nephropathy. MATERIALS AND METHODS: Bone marrow transplantation (BMT) was performed in an obese type 2 diabetic murine model (db/db) owing to a mutation in the leptin receptor gene. Whole bone marrow from female donor C57BL/6 EGFP+ mice was transplanted into 8-week-old C57BL/6 mice and into 8- and 24-week-old female C57BLKS (db/db) EGFP- mice. Recipient mice received total body irradiation (TBI) followed by bone marrow (BM) cell infusion. We tested various irradiation doses (Gy) and numbers of BM cells. RESULTS: When a low TBI dose and a small number of BM cells were administered, only syngeneic C57BL/6 mice became chimeric, whereas allogeneic db/db mice showed rejection. When Gy dose and BM cells were increased, db/db mice became chimeric. However, 8-week-old db/db mice lost the obese phenotype and became normoglycemic, probably due to peripheral BM cell infiltration. Conversely, 24-week-old db/db mice remained obese showing similar blood glucose values, body weights, albuminuria, and glomerular lesions at nontransplanted db/db mice. CONCLUSIONS: Recipient age greatly influenced the peripheral repopulation after BMT in db/db mice. Only the adult chimeric db/db mice seemed to be a good model to study the cellular mechanisms involved in the regression of diabetic nephropathy.