De novo kidney regeneration with stem cells

Advances in the Knowledge about Kidney Decellularization and Repopulation

End-stage renal disease (ESRD) is characterized by the progressive deterioration of renal function that may compromise different tissues and organs. The major treatment indicated for patients with ESRD is kidney transplantation. However, the shortage of available organs, as well as the high rate of organ rejection, supports the need for new therapies. Thus, the implementation of tissue bioengineering to organ regeneration has emerged as an alternative to traditional organ transplantation. Decellularization of organs with chemical, physical, and/or biological agents generates natural scaffolds, which can serve as basis for tissue reconstruction. The recellularization of these scaffolds with different cell sources, such as stem cells or adult differentiated cells, can provide an organ with functionality and no immune response after in vivo transplantation on the host. Several studies have focused on improving these techniques, but until now, there is no optimal decellularization method for the kidney available yet. Herein, an overview of the current literature for kidney decellularization and whole-organ recellularization is presented, addressing the pros and cons of the actual techniques already developed, the methods adopted to evaluate the efficacy of the procedures, and the challenges to be overcome in order to achieve an optimal protocol.

Stem cell therapy: An emerging modality in glomerular diseases

The kidney has been considered a highly terminally differentiated organ with low proliferative potential and thus unlikely to undergo regeneration. Glomerular disease progresses to end-stage renal disease (ESRD), which requires dialysis or renal transplantation for better quality of life for patients with ESRD. Because of the shortage of implantable kidneys and complications such as immune rejection, septicemia and toxicity of immunosuppression, kidney transplantation remains a challenge. Therapeutic options available for glomerular disease include symptomatic treatment and strategies to delay progression. In an attempt to develop innovative treatments by promoting the limited capability of regeneration and repair after kidney injury and overcome the progressive pathological process that is uncontrolled with conventional treatment modalities, stem cell-based therapy has emerged as novel intervention due to its ability to inhibit inflammation and promote regeneration. Recent developments in cell therapy have demonstrated promising therapeutic outcomes in terms of restoration of renal structure and function. This review focuses on stem cell therapy approaches for the treatment of glomerular disease, including the various cell sources used and recent advances in preclinical and clinical studies.

De novo assembly of plant body plan: a step ahead of Deadpool

While in the movie Deadpool it is possible for a human to recreate an arm from scratch, in reality plants can even surpass that. Not only can they regenerate lost parts, but also the whole plant body can be reborn from a few existing cells. Despite the decades old realization that plant cells possess the ability to regenerate a complete shoot and root system, it is only now that the underlying mechanisms are being unraveled. De novo plant regeneration involves the initiation of regenerative mass, acquisition of the pluripotent state, reconstitution of stem cells and assembly of regulatory interactions. Recent studies have furthered our understanding on the making of a complete plant system in the absence of embryonic positional cues. We review the recent studies probing the molecular mechanisms of de novo plant regeneration in response to external inductive cues and our current knowledge of direct reprogramming of root to shoot and vice versa. We further discuss how de novo regeneration can be exploited to meet the demands of green culture industries and to serve as a general model to address the fundamental questions of regeneration across the plant kingdom.

Human embryonic mesenchymal stem cells participate in differentiation of renal tubular cells in newborn mice

Stem cells are used with increasing success in the treatment of renal tubular injury. However, whether mesenchymal stem cells (MSC) differentiate into renal tubular epithelial cells remains controversial. The aims of the present study were to observe the localization of human embryonic MSCs (hMSCs) in the kidneys of newborn mice, and to investigate hMSC differentiation into tubular epithelium. Primary culture hMSCs were derived from 4–7-week-old embryos and labeled with the cell membrane fluorescent dye PKH-26. The degree of apoptosis, cell growth, differentiation and localization of hMSCs with and without this label were then determined using immunohistochemical methods and flow cytometry. hMSCs and PKH26-labeled hMSCs were revealed to differentiate into chondrocytes and adipocytes, and were demonstrated to have similar proliferative capability. In the two cell types, the antigens CD34 and CD45, indicative of hematopoietic lineages, were not expressed; however, the expression of the mesenchymal markers CD29 and CD90 in MSCs, was significantly increased. During a 4-week culture period, laser confocal microscopy revealed that PKH26-labeled hMSCs in the kidneys of newborn mice gradually dispersed. Two weeks after the injection of the PKH26-labeled cells, the percentage of PKH26-labeled hMSCs localized to the renal tubules was 10±2.1%. In conclusion, PKH26 labeling has no effect on hMSC differentiation, proliferation and mesenchymal cell surface features, and hMSCs injected into the kidneys of newborn mice may transform to renal tubule epithelium.

Fetal Renal Stem Cell Transplant in Nephrotic and Nonnephrotic Glomerulonephritis with Stage 2-4 Chronic Kidney Disease: Potential Effect on Proteinuria and Glomerular Filtration Rate

OBJECTIVES

Proteinuria is a major cause of glomerulosclerosis progression in glomerular diseases, and the development of end-stage renal disease is more rapid in nephrotic patients than in nonnephrotic ones. The renal parenchyma is less regenerable because it is a tissue consisting of renal cells. Thus, stem cells obtained from fetal kidney tissue might be effective for reducing proteinuria and delaying glomerulosclerosis in these patients.

MATERIALS AND METHODS

This report presents preliminary data from a prospective cohort study that included 17 patients with chronic glomerulonephritis in stage 2 to 4 chronic kidney disease who completed 3 visits during 1 year of follow-up. Fetal renal stem cells (multiple cells in suspension) were injected into the patient every 6 months. Patients were divided into 2 groups according to their nephrotic status, and 24-hour maximal proteinuria was recorded for at least 6 months (first group with proteinuria < 3.5 g/24 h, and second group with proteinuria > 3.5 g/24 h).

RESULTS

During follow-up, group 1 was observed to have stable hemoglobin and total protein levels but significantly decreased albumin levels and glomerular filtration rates. In group 2, total protein with serum albumin significantly increased, and proteinuria and glomerular filtration rates significantly decreased. There was no significant difference in glomerular filtration rate decline between groups.

CONCLUSIONS

Treatment with fetal renal stem cells significantly decreased proteinuria in nephrotic patients. However, this outcome also might have resulted from a reduction in glomerular filtration rate. Further studies with a larger number of patients and a control group would help to achieve better results that measure the efficacy of this treatment.

Renal physiological regenerative medicine to prevent chronic renal failure: should we start at birth?

With the incidence of end-stage renal disease increasing dramatically during the last ten years, its prevalence rising about 8% per year, chronic kidney disease (CKD) represents one of the most problematic public health problems worldwide. CKD represents a growing clinical problem that, in its terminal stages, requires renal replacement therapy. Kidney transplant has been proposed as the definitive therapy able to address the growing clinical, social and economic problems related to the increasing prevalence of end-stage kidney disease (ESKD). Traditional stem cell-based regenerative medicine, when applied to kidneys disrupted by end-stage renal disease, has been shown to be unable to regenerate the damaged organ. The theme of this work is to hypothesize a new approach to the prevention of CKD, based on the management of the huge amount of stem/progenitor cells physiologically present in the kidney of preterm babies at birth. Here a new concept of primary prevention of renal disease is suggested: a true primary prevention, starting in the perinatal period aimed at increasing the number of functioning glomeruli. This approach has been defined as "physiological regenerative medicine", in order to underline the use of physiological tools, including endogenous renal stem cells and stem cell stimulators physiologically expressed in our cells.

Chromatin dynamics in kidney development and function

Epigenetic mechanisms are fundamental key features of developing cells connecting developmental regulatory factors to chromatin modification. Changes in the environment during renal development can have long-lasting effects on the permanent tissue structure and the level of expression of important functional genes. These changes are believed to contribute to kidney disease occurrence and progression. Although the mechanisms of early patterning and cell fate have been well described for renal development, little is known about associated epigenetic modifications and their impact on how genes interact to specify the renal epithelial cells of nephrons and how this specification is relevant to maintaining normal renal function. A better understanding of the renal cell-specific epigenetic modifications and the interaction of different cell types to form this highly complex organ will not only help to better understand developmental defects and early loss of kidney function in children, but also help to understand and improve chronic disease progression, cell regeneration and renal aging.

Differentiation of human pluripotent stem cells into nephron progenitor cells in a serum and feeder free system

Objectives

Kidney disease is emerging as a critical medical problem worldwide. Because of limited treatment options for the damaged kidney, stem cell treatment is becoming an alternative therapeutic approach. Of many possible human stem cell sources, pluripotent stem cells are most attractive due to their self-renewal and pluripotent capacity. However, little is known about the derivation of renal lineage cells from human pluripotent stem cells (hPSCs). In this study, we developed a novel protocol for differentiation of nephron progenitor cells (NPCs) from hPSCs in a serum- and feeder-free system.

Materials and Methods

We designed step-wise protocols for differentiation of human pluripotent stem cells toward primitive streak, intermediate mesoderm and NPCs by recapitulating normal nephrogenesis. Expression of key marker genes was examined by RT-PCR, real time RT-PCR and immunocytochemistry. Each experiment was independently performed three times to confirm its reproducibility.

Results

After modification of culture period and concentration of exogenous factors, hPSCs can differentiate into NPCs that markedly express specific marker genes such as SIX2, GDNF, HOXD11, WT1 and CITED1 in addition to OSR1, PAX2, SALL1 and EYA1. Moreover, NPCs possess the potential of bidirectional differentiation into both renal tubular epithelial cells and glomerular podocytes in defined culture conditions. In particular, approximately 70% of SYN-positive cells were obtained from hPSC-derived NPCs after podocytes induction. NPCs can also form in vitro tubule-like structures in three dimensional culture systems.

Conclusions

Our novel protocol for hPSCs differentiation into NPCs can be useful for producing alternative sources of cell replacement therapy and disease modeling for human kidney diseases.