Transplantation of human fetal mesenchymal stem cells improves glomerulopathy in a collagen type I alpha 2-deficient mouse

Mesenchymal Stem Cell Therapy for Osteogenesis Imperfecta

The aim of this study was to provide a brief overview on the background and rationale on treating fetuses and children suffering from osteogenesis imperfecta (OI) with mesenchymal stem cells (MSCs). MSCs ability to migrate, engraft, and differentiate into bone cells and to act via paracrine effects on the recipient's tissues makes these cells promising candidates as a clinical therapy for OI. Animal work and limited clinical studies in humans support the use of MSC in treating OI. Off-the-shelf MSC have a good safety profile and exhibit multilineage differentiation potential and a low immunogenic profile and thereby may enable this potential therapy to become widely available. MSC transplantation before and after birth to treat OI is an experimental therapy that is currently tested in the international multicentre phase I/II clinical trial BOOSTB4 that aims to assess the safety and efficacy of fetal MSC transplantation for the treatment of severe types of OI.

Modification of COL1A1 in Autologous Adipose Tissue-Derived Progenitor Cells Rescues the Bone Phenotype in a Mouse Model of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a congenital genetic disorder mainly manifested as bone fragility and recurrent fracture. Mutation of COL1A1/COL1A2 genes encoding the type I collagen are most responsible for the clinical patients. Allogenic mesenchymal stem cells (MSCs) provide the potential to treat OI through differentiation into osteoblasts. Autologous defective MSCs have not been utilized in OI treatment mainly because of their impaired osteogenesis, but the latent mechanism has not been well understood. Here, the relative signaling abnormality of adipose-derived mesenchymal stem cells (ADSCs) isolated from OI type I mice (Col1a1^+/-365 mice) was explored. Autologous ADSCs transfected by retrovirus carrying human COL1A1 gene was first utilized in OI therapy. The results showed that decreased activity of Yes-associated protein (YAP) due to hyperactive upstream Hippo kinases greatly contributed to the weakened bone-forming capacity of defective ADSCs. Recovered collagen synthesis of autologous ADSCs by COL1A1 gene modification normalized Hippo/YAP signaling and effectively rescued YAP-mediated osteogenesis. And the COL1A1 gene engineered autologous ADSCs efficaciously improved the microstructure, enhanced the mechanical properties and promoted bone formation of Col1a1^+/-365 mice after femoral bone marrow cavity delivery and might serve as an alternative source of stem cells in OI treatment. © 2021 American Society for Bone and Mineral Research (ASBMR).

Stem Cell Therapy as a Treatment for Osteogenesis Imperfecta

PURPOSE OF REVIEW

Osteogenesis imperfecta (OI) is a chronic disease with few treatment options available. The purpose of this review is to provide an overview on treating OI with mesenchymal stem cells (MSC).

RECENT FINDINGS

Off-the-shelf MSC have a good safety profile and exhibit multilineage differentiation potential and a low immunogenic profile and are easy to manufacture. Their ability to migrate, engraft, and differentiate into bone cells, and also to act via paracrine effects on the recipient's tissues, makes MSC candidates as a clinical therapy for OI. Due to their high osteogenic potency, fetal MSC offer an even higher therapeutic potential in OI compared with MSC derived from adult sources. Preclinical and initial clinical data support the use of MSC in treating OI. The characteristics of MSC make them of great interest in treating OI. MSC may be safely transplanted via intravenous administration and show potential positive clinical effects.

Mesenchymal Stem Cells in Kidney Repair

Every year 13.3 million people suffer acute kidney injury (AKI), which is associated with a high risk of death or development of long-term chronic kidney disease (CKD) in a substantial percentage of patients besides other organ dysfunctions. To date, the mortality rate per year for AKI exceeds 50 % at least in patients requiring early renal replacement therapy and is higher than the mortality for breast and prostate cancer, heart failure and diabetes combined.Until now, no effective treatments able to accelerate renal recovery and improve survival post AKI have been developed. In search of innovative and effective strategies to foster the limited regeneration capacity of the kidney, several studies have evaluated the ability of mesenchymal stem cells (MSCs) of different origin as an attractive therapeutic tool. The results obtained in several models of AKI and CKD document that MSCs have therapeutic potential in repair of renal injury, preserving renal function and structure thus prolonging animal survival through differentiation-independent pathways. In this chapter, we have summarized the mechanisms underlying the regenerative processes triggered by MSC treatment, essentially due to their paracrine activity. The capacity of MSC to migrate to the site of injury and to secrete a pool of growth factors and cytokines with anti-inflammatory, mitogenic, and immunomodulatory effects is described. New modalities of cell-to-cell communication via the release of microvesicles and exosomes by MSCs to injured renal cells will also be discussed. The translation of basic experimental data on MSC biology into effective care is still limited to preliminary phase I clinical trials and further studies are needed to definitively assess the efficacy of MSC-based therapy in humans.

Intracellular trafficking and endocytosis of CXCR4 in fetal mesenchymal stem/stromal cells

Background

Fetal mesenchymal stem/stromal cells (MSC) represent a developmentally-advantageous cell type with translational potential.

To enhance adult MSC migration, studies have focussed on the role of the chemokine receptor CXCR4 and its ligand SDF-1 (CXCL12), but more recent work implicates an intricate system of CXCR4 receptor dimerization, intracellular localization, multiple ligands, splice variants and nuclear accumulation. We investigated the intracellular localization of CXCR4 in fetal bone marrow-derived MSC and role of intracellular trafficking in CXCR4 surface expression and function.

Results

We found that up to 4% of human fetal MSC have detectable surface-localized CXCR4. In the majority of cells, CXCR4 is located not at the cell surface, as would be required for ‘sensing’ migratory cues, but intracellularly. CXCR4 was identified in early endosomes, recycling endosomes, and lysosomes, indicating only a small percentage of CXCR4 travelling to the plasma membrane. Notably CXCR4 was also found in and around the nucleus, as detected with an anti-CXCR4 antibody directed specifically against CXCR4 isoform 2 differing only in N-terminal sequence. After demonstrating that endocytosis of CXCR4 is largely independent of endogenously-produced SDF-1, we next applied the cytoskeletal inhibitors blebbistatin and dynasore to inhibit endocytotic recycling. These increased the number of cells expressing surface CXCR4 by 10 and 5 fold respectively, and enhanced the number of cells migrating to SDF1 in vitro (up to 2.6 fold). These molecules had a transient effect on cell morphology and adhesion, which abated after the removal of the inhibitors, and did not alter functional stem cell properties.

Conclusions

We conclude that constitutive endocytosis is implicated in the regulation of CXCR4 membrane expression, and suggest a novel pharmacological strategy to enhance migration of systemically-transplanted cells.

Molecular imaging of urogenital diseases

There is an expanding and exciting repertoire of PET imaging radiotracers for urogenital diseases, particularly in prostate cancer, renal cell cancer, and renal function. Prostate cancer is the most commonly diagnosed cancer in men. With growing therapeutic options for the treatment of metastatic and advanced prostate cancer, improved functional imaging of prostate cancer beyond the limitations of conventional CT and bone scan is becoming increasingly important for both clinical management and drug development. PET radiotracers, apart from ¹⁸F-FDG, for prostate cancer are ¹⁸F-sodium fluoride, ¹¹C-choline, and ¹⁸F-fluorocholine, and (¹¹C-acetate. Other emerging and promising PET radiotracers include a synthetic l-leucine amino acid analogue (anti-¹⁸F-fluorocyclobutane-1-carboxylic acid), dihydrotestosterone analogue (¹⁸F-fluoro-5α-dihydrotestosterone), and prostate-specific membrane antigen-based PET radiotracers (eg, N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-¹⁸F-fluorobenzyl-l-cysteine, ⁸⁹Zr-DFO-J591, and ⁶⁸Ga [HBED-CC]). Larger prospective and comparison trials of these PET radiotracers are needed to establish the role of PET/CT in prostate cancer. Although renal cell cancer imaging with FDG-PET/CT is available, it can be limited, especially for detection of the primary tumor. Improved renal cell cancer detection with carbonic anhydrase IX (CAIX)-based antibody (¹²⁴I-girentuximab) and radioimmunotherapy targeting with ¹⁷⁷Lu-cG250 appear promising. Evaluation of renal injury by imaging renal perfusion and function with novel PET radiotracers include p-¹⁸F-fluorohippurate, hippurate m-cyano-p-¹⁸F-fluorohippurate, and rubidium-82 chloride (typically used for myocardial perfusion imaging). Renal receptor imaging of the renal renin-angiotensin system with a variety of selective PET radioligands is also becoming available for clinical translation.

Human unrestricted somatic stem cell administration fails to protect nude mice from cisplatin-induced acute kidney injury

BACKGROUND

Kidney failure is a debilitating disorder with limited treatment options. The kidney-protective effects of stem cells have been vastly investigated and promising results have been achieved with various sources of stem cells. However, in spite of beneficial effects on other disease models, the renoprotective potential of human cord blood-derived unrestricted somatic stem cells (USSC) has not been examined so far.

METHODS

In the present study, acute kidney failure was induced in female nude mice and the effect of USSC transplantation on kidney function and structure was assessed. Furthermore, the expression of some cytokine genes was examined by real-time PCR. Homing of the transplanted cells into kidneys was assessed by flow cytometry, immunohistochemistry, and real-time PCR.

RESULTS

USSC-conditioned medium did not attenuate the in vitro nephrotoxic effects of cisplatin. Transplantation of USSC to nude mice did not protect kidney function and was associated with worsened kidney structural damage. USSC transplantation was also associated with a decline in the renal expression of VEGF-A gene. In spite of these effects, the transplanted cells could not be detected in the kidneys by any of the exploited methods and they were mainly entrapped in the lungs.

CONCLUSION

These data indicate that USSC are not suitable for cell therapy in the setting of acute kidney injury. Also, this study shows that these stem cells are able to affect damaged kidneys even if they are not homed there.

Cloning and expression of feline colony stimulating factor receptor (CSF-1R) and analysis of the species specificity of stimulation by colony stimulating factor-1 (CSF-1) and interleukin-34 (IL-34)

Colony stimulating factor (CSF-1) and its receptor, CSF-1R, have been previously well studied in humans and rodents to dissect the role they play in development of cells of the mononuclear phagocyte system. A second ligand for the CSF-1R, IL-34 has been described in several species. In this study, we have cloned and expressed the feline CSF-1R and examined the responsiveness to CSF-1 and IL-34 from a range of species. The results indicate that pig and human CSF-1 and human IL-34 are equally effective in cats, where both mouse CSF-1 and IL-34 are significantly less active. Recombinant human CSF-1 can be used to generate populations of feline bone marrow and monocyte derived macrophages that can be used to further dissect macrophage-specific gene expression in this species, and to compare it to data derived from mouse, human and pig. These results set the scene for therapeutic use of CSF-1 and IL-34 in cats.

Ontological differences in first compared to third trimester human fetal placental chorionic stem cells

Human mesenchymal stromal/stem cells (MSC) isolated from fetal tissues hold promise for use in tissue engineering applications and cell-based therapies, but their collection is restricted ethically and technically. In contrast, the placenta is a potential source of readily-obtainable stem cells throughout pregnancy. In fetal tissues, early gestational stem cells are known to have advantageous characteristics over neonatal and adult stem cells. Accordingly, we investigated whether early fetal placental chorionic stem cells (e-CSC) were physiologically superior to their late gestation fetal chorionic counterparts (l-CSC). We showed that e-CSC shared a common phenotype with l-CSC, differentiating down the osteogenic, adipogenic and neurogenic pathways, and containing a subset of cells endogenously expressing NANOG, SOX2, c-MYC, and KLF4, as well as an array of genes expressed in pluripotent stem cells and primordial germ cells, including CD24, NANOG, SSEA4, SSEA3, TRA-1-60, TRA-1-81, STELLA, FRAGILIS, NANOS3, DAZL and SSEA1. However, we showed that e-CSC have characteristics of an earlier state of stemness compared to l-CSC, such as smaller size, faster kinetics, uniquely expressing OCT4A variant 1 and showing higher levels of expression of NANOG, SOX2, c-MYC and KLF4 than l-CSC. Furthermore e-CSC, but not l-CSC, formed embryoid bodies containing cells from the three germ layer lineages. Finally, we showed that e-CSC demonstrate higher tissue repair in vivo; when transplanted in the osteogenesis imperfecta mice, e-CSC, but not l-CSC increased bone quality and plasticity; and when applied to a skin wound, e-CSC, but not l-CSC, accelerated healing compared to controls. Our results provide insight into the ontogeny of the stemness phenotype during fetal development and suggest that the more primitive characteristics of early compared to late gestation fetal chorionic stem cells may be translationally advantageous.

Recent advances in fetal gene therapy

Over the first decade of this new millennium gene therapy has demonstrated clear clinical benefits in several diseases for which conventional medicine offers no treatment. Clinical trials of gene therapy for single gene disorders have recruited predominantly young patients since older subjects may have suffered irrevocablepathological changes or may not be available because the disease is lethal relatively early in life. The concept of fetal gene therapy is an extension of this principle in that diseases in which irreversible changes occur at or beforebirth can be prevented by gene supplementation or repair in the fetus or associated maternal tissues. This article ccnsiders the enthusiasm and skepticism held for fetal gene therapy and its potential for clinical application. It coversa spectrum of candidate diseases for fetal gene therapy including Pompe disease, Gaucher disease, thalassemia, congenital protein C deficiency and cystic fibrosis. It outlines successful and not-so-successful examples of fetal gene therapy in animal models. Finally the application and potential of fetal gene transfer as a fundamental research tool for developmental biology and generation of somatic transgenic animals is surveyed.

Genetic modification of mesenchymal stem cells to overexpress CXCR4 and CXCR7 does not improve the homing and therapeutic potentials of these cells in experimental acute kidney injury

The therapeutic potential of bone marrow mesenchymal stem cells (MSCs) in kidney failure has been examined in some studies. However, recent findings indicate that after transplantation, these cells home to kidneys at very low levels. Interaction of stromal derived factor-1 (SDF-1) with its receptor, CXCR4, is of pivotal importance in migration and homing. Recently, CXCR7 has also been recognized as another SDF-1 receptor that interacts with CXCR4 and modulates its functions. In this study, CXCR4 and CXCR7 were separately and simultaneously overexpressed in BALB/c bone marrow MSCs by using a lentiviral vector system and the homing and renoprotective potentials of these cells were evaluated in a mouse model of cisplatin-induced acute kidney injury. Using flow cytometry, immunohistochemistry, and real-time PCR methods for detection of GFP-labeled MSCs, we found that although considerably entrapped in lungs, native MSCs home very rarely to kidneys and bone marrow and this rate cannot be significantly affected by CXCR4 and/or CXCR7 upregulation. Transplantation of neither native nor genetically engineered MSCs ameliorated kidney failure. We concluded that overexpression of CXCR4 and CXCR7 receptors in murine MSCs cannot improve the homing and therapeutic potentials of these cells and it can be due to severe chromosomal abnormalities that these cells bear during ex vivo expansion.

Upregulating CXCR4 in human fetal mesenchymal stem cells enhances engraftment and bone mechanics in a mouse model of osteogenesis imperfecta

Stem cells have considerable potential to repair damaged organs and tissues. We previously showed that prenatal transplantation of human first trimester fetal blood mesenchymal stem cells (hfMSCs) in a mouse model of osteogenesis imperfecta (oim mice) led to a phenotypic improvement, with a marked decrease in fracture rate. Donor cells differentiated into mature osteoblasts, producing bone proteins and minerals, including collagen type Iα2, which is absent in nontransplanted mice. This led to modifications of the bone matrix and subsequent decrease of bone brittleness, indicating that grafted cells directly contribute to improvement of bone mechanical properties. Nevertheless, the therapeutic effect was incomplete, attributing to the limited level of engraftment in bone. In this study, we show that although migration of hfMSCs to bone and bone marrow is CXCR4-SDF1 (SDF1 is stromal-derived factor) dependent, only a small number of cells present CXCR4 on the cell surface despite high levels of internal CXCR4. Priming with SDF1, however, upregulates CXCR4 to increase the CXCR4(+) cell fraction, improving chemotaxis in vitro and enhancing engraftment in vivo at least threefold in both oim and wild-type bone and bone marrow. Higher engraftment in oim bones was associated with decreased bone brittleness. This strategy represents a step to improve the therapeutic benefits of fetal cell therapy toward being curative.

Integration potential of mouse and human bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a multipotent cell population which has been described to exert renoprotective and regenerative effects in experimental models of kidney injury. Several lines of evidence indicate that MSCs also have the ability to contribute to nephrogenesis, suggesting that the cells can be employed in stem cell-based applications aimed at de novo renal tissue generation. In this study we re-evaluate the capacity of mouse and human bone marrow-derived MSCs to contribute to the development of renal tissue using a novel method of embryonic kidney culture. Although MSCs show expression of some genes involved in renal development, their contribution to nephrogenesis is very limited in comparison to other stem cell types tested. Furthermore, we found that both mouse and human MSCs have a detrimental effect on the ex vivo development of mouse embryonic kidney, this effect being mediated through a paracrine action. Stimulation with conditioned medium from a mouse renal progenitor population increases the ability of mouse MSCs to integrate into developing renal tissue and prevents the negative effects on kidney development, but does not appear to enhance their ability to undergo nephrogenesis.

Mesenchymal stromal cell-conditioned medium prevents radiation-induced small intestine injury in mice

BACKGROUND AIMS

Effective therapy for radiation-induced intestinal injury is currently unavailable. Mesenchymal stromal cells (MSC) are expected to be useful in repairing intestinal damage caused by irradiation. We determined whether the MSC-derived bioactive components could protect radiation-induced small intestine injury in mice.

METHODS

Human umbilical cord (UC)-derived MSC were isolated, expanded and exposed to hypoxic conditions in vitro. The hypoxia-conditioned medium was ultrafiltrated with a 3-kDa molecular weight cut-off to prepare the high molecular weight fraction (HMWF). The effect of HMWF on the viability of irradiated rat intestinal epithelial cells (IEC-6) was examined by MTT(methyl thiazolyl tetrazolium) assay. HMWF was also delivered to BALB/C male mice by tail intravenous injection immediately after receiving local abdominal irradiation at a selected dose of 10 Gy. Animal body weight, survival and diarrhea were monitored for 30 days. The improvement of mice intestine structure, including epithelium thickness and villus height, was examined by histology.

RESULTS

HMWF enhanced the viability of irradiated IEC-6 cells in vitro. Repeated infusion of HMWF for 7 days immediately after abdominal irradiation of 10 Gy ((60)Coγ-ray) increased the survival rate, decreased diarrhea occurrence and improved the small intestinal structural integrity of irradiated mice.

CONCLUSIONS

MSC-derived bioactive components could be a novel therapeutic approach for the treatment of radiation-induced injury.

Mesenchymal stem cells as a therapeutic approach to glomerular diseases: benefits and risks

Most studies using adult stem cells (ASCs) and progenitor cells as potential therapeutics for kidney disorders have been conducted in models of acute kidney injury, where the damage mainly affects the tubulointerstitium. The results are promising, whereas the underlying mechanisms are still being discussed controversially. Glomerular diseases have not received as much attention. Likely reasons include the often insidious onset, rendering the choice of optimal treatment timing difficult, and the fact that chronic diseases may require long-term therapy. In this mini review, we summarize current strategies in adult stem cell-based therapies for glomerular diseases. In addition, we focus on possible side effects of stem cell administration that have been reported recently, that is, profibrotic actions and maldifferentiation of mesenchymal stem cells.

Evaluation of intrarenal mesenchymal stem cell injection for treatment of chronic kidney disease in cats: a pilot study

The feasibility of autologous intrarenal mesenchymal stem cell (MSC) therapy in cats with chronic kidney disease (CKD) was investigated. Six cats (two healthy, four with CKD) received a single unilateral intrarenal injection of autologous bone marrow-derived or adipose tissue-derived MSC (bmMSC or aMSC) via ultrasound guidance. Minimum database and glomerular filtration rate (GFR) via nuclear scintigraphy were determined pre-injection, at 7 days and at 30 days post-injection. Intrarenal injection did not induce immediate or long-term adverse effects. Two cats with CKD that received aMSC experienced modest improvement in GFR and a mild decrease in serum creatinine concentration. Despite the possible benefits of intrarenal MSC injections for CKD cats, the number of sedations and interventions required to implement this approach would likely preclude widespread clinical application. We concluded that MSC could be transferred safely by ultrasound-guided intrarenal injection in cats, but that alternative sources and routes of MSC therapy should be investigated.

Activated invariant NKT cells regulate osteoclast development and function

Invariant NKT (iNKT) cells modulate innate and adaptive immune responses through activation of myeloid dendritic cells and macrophages and via enhanced clonogenicity, differentiation, and egress of their shared myeloid progenitors. Because these same progenitors give rise to osteoclasts (OCs), which also mediate the egress of hematopoietic progenitors and orchestrate bone remodeling, we hypothesized that iNKT cells would extend their myeloid cell regulatory role to the development and function of OCs. In this study, we report that selective activation of iNKT cells by α-galactosylceramide causes myeloid cell egress, enhances OC progenitor and precursor development, modifies the intramedullary kinetics of mature OCs, and enhances their resorptive activity. OC progenitor activity is positively regulated by TNF-α and negatively regulated by IFN-γ, but is IL-4 and IL-17 independent. These data demonstrate a novel role of iNKT cells that couples osteoclastogenesis with myeloid cell egress in conditions of immune activation.

Biological characteristics of stem cells from foetal, cord blood and extraembryonic tissues

Foetal stem cells (FSCs) can be isolated during gestation from many different tissues such as blood, liver and bone marrow as well as from a variety of extraembryonic tissues such as amniotic fluid and placenta. Strong evidence suggests that these cells differ on many biological aspects such as growth kinetics, morphology, immunophenotype, differentiation potential and engraftment capacity in vivo. Despite these differences, FSCs appear to be more primitive and have greater multi-potentiality than their adult counterparts. For example, foetal blood haemopoietic stem cells proliferate more rapidly than those found in cord blood or adult bone marrow. These features have led to FSCs being investigated for pre- and post-natal cell therapy and regenerative medicine applications. The cells have been used in pre-clinical studies to treat a wide range of diseases such as skeletal dysplasia, diaphragmatic hernia and respiratory failure, white matter damage, renal pathologies as well as cancers. Their intermediate state between adult and embryonic stem cells also makes them an ideal candidate for reprogramming to the pluripotent status.

Review article: Potential cellular therapies for renal disease: can we translate results from animal studies to the human condition?

The incidence of chronic kidney disease is increasing worldwide, prompting considerable research into potential regenerative therapies. These have included studies to determine whether an endogenous renal stem cell exists in the postnatal kidney and whether non-renal adult stem cells, such as mesenchymal stem cell, can ameliorate renal damage. Such stem cells will either need to be recruited to the damaged kidney to repair the damage in situ or be differentiated into the desired cell type and delivered into the damaged kidney to subsequently elicit repair without maldifferentiation. To date, these studies have largely been performed using experimental and genetic models of renal damage in rodents. The translation of such research into a therapy applicable to human disease faces many challenges. In this review, we examine which animal models have been used to evaluate potential cellular therapies and how valid these are to human chronic kidney disease.

Multipotent mesenchymal stromal cell therapy in renal disease and kidney transplantation

Cell therapies aim at differentiation of stem cells into the specific cell type required to repair damaged or destroyed cells or tissues. Over recent years, cell therapy has been introduced in a variety of application areas, including cardiovascular repair, diabetes, musculoskeletal disorders and renal repair. Multipotent mesenchymal stromal cells (MSCs), often referred to as mesenchymal stem cells, are of particular interest as a cell therapy model, as this is one of the few cell types that are on the brink of entering the clinical arena in different areas of application. MSCs can be differentiated in vitro and in vivo into various cell types of mesenchymal origin such as bone, fat and cartilage. They have important effects on the innate and adaptive immune system and possess striking anti-inflammatory properties that make them attractive for potential use in diseases characterized by autoimmunity and inflammation. In addition, MSCs have been shown to migrate to sites of tissue injury and to enhance repair by secreting anti-fibrotic and pro-angiogenic factors. In this review, evidence for the renoprotective mechanisms of MSCs as well as their therapeutic possibilities and potential hazards in acute and chronic renal disease and allograft rejection is summarized.

Is there such a thing as a renal stem cell?

Increasing interest in the potential of adult stem cells in regenerative medicine has led to numerous studies focused on the identification of endogenous renal stem cells within the mature mammalian kidney. A variety of approaches have been taken to identify such cells, including physical location, cell surface marker expression, and functional properties. Proof of clonogenicity or renal potential remains questionable, and few such populations have been characterized in humans; however, recent evidence that even podocytes, a cell type with limited proliferative capacity under normal conditions, are constantly regenerated from a population within the Bowman's capsule has breathed new life into the quest for a renal stem cell. Here we examine whether current evidence is sufficient to conclude such a population does indeed exist or whether the jury is still out. We also ask which properties we would wish such a cell to possess to allow for repair of the diseased kidney.

Mesenchymal stem cells enhance the viability and proliferation of human fetal intestinal epithelial cells following hypoxic injury via paracrine mechanisms

BACKGROUND

Mesenchymal stem cells (MSCs) may be used to treat injured tissues. The ability of MSCs to treat injured fetal intestinal epithelial cells (FIEs), similar to those in infants with necrotizing enterocolitis, has not been elucidated. We hypothesized that MSCs would enhance FIE viability and proliferation after hypoxic injury via paracrine mechanisms.

METHODS

LLC-PK1 cells (differentiated control [DC]) and human MSCs were exposed to 1 hour of hypoxia. Cells were reoxygenated for 24 hours and cell-free conditioned media were collected. Human FIEs were exposed to 1 hour of hypoxia and plated for experiments. FIEs were reoxygenated in nonconditioned media, DC-conditioned media, or MSC-conditioned media. Supernatants were analyzed for interleukin-6 (IL-6), hepatocyte growth factor (HGF), fibroblast growth factor (FGF), and vascular endothelial growth factor (VEGF) via enzyme-linked immunosorbent assay. Cell viability was assessed by trypan blue exclusion and cell counting. Proliferation was determined via 5-bromo-2'-deoxyuridine (BrdU). Expression of caspases-3 and -8 was determined via Western blot.

RESULTS

FIEs reoxygenated in MSC-conditioned media demonstrated enhanced viability and increased proliferation after hypoxic injury. Enhanced FIE viability and proliferation were associated with increased IL-6, HGF, and VEGF, as well as decreased expression of caspase-3.

CONCLUSION

MSCs may increase the viability and proliferative capacity of FIEs after hypoxic injury via the paracrine release of IL-6, HGF, and VEGF, as well as downregulation of apoptotic signaling.

Stem cell options for kidney disease

Chronic kidney disease (CKD) is increasing at the rate of 6-8% per annum in the US alone. At present, dialysis and transplantation remain the only treatment options. However, there is hope that stem cells and regenerative medicine may provide additional regenerative options for kidney disease. Such new treatments might involve induction of repair using endogenous or exogenous stem cells or the reprogramming of the organ to reinitiate development. This review addresses the current state of understanding with respect to the ability of non-renal stem cell sources to influence renal repair, the existence of endogenous renal stem cells and the biology of normal renal repair in response to damage. It also examines the remaining challenges and asks the question of whether there is one solution for all forms of renal disease.

Potential implications of cell therapy for osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a brittle-bone disease whose hallmark is bone fragility. Since the disease is genetic, there is currently no available cure. Several pharmacological agents have been tried with not much success, except the recent use of bisphosphonates. Stem cells have been suggested as an alternative OI treatment, but many hurdles remain before this technology can be applied for treating patients with OI. This review summarizes what is known at present regarding the application of stem cells to treat OI using animal models, clinical trials using mesenchymal stem cells to treat patients with OI and the knowledge gained from the clinical trials. Application of gene therapy in combination with stem cells is also discussed. The hurdles to be overcome to bring stem cells close to the clinic and future perspectives are discussed.

Imaging mesenchymal stem cell migration and the implications for stem cell-based cancer therapies

Mesenchymal stem cells are promising cellular vehicles for the delivery of therapeutic proteins to sites of cancer growth upon transplantation. To better understand the physiology and biology of the transplanted stem cells, it is necessary and desirable to track the fate of stem cells noninvasively and longitudinally. Reporter gene imaging is a powerful tool to monitor live stem cells in vivo. In this special report, we review currently investigated reporter genes used for tracking stem cells in vivo by optical, radionuclide, magnetic resonance and multimodality imaging techniques. We also discuss the possibility and feasibility of applying reporter gene imaging to monitor stem-cell-based therapeutic gene delivery efficiency and treatment efficacy.

Fetal cells in the maternal appendix: a marker of inflammation or fetal tissue repair?

BACKGROUND

Fetal microchimeric cells that have trafficked into the maternal circulation persist in maternal tissues for years after pregnancy, but their biological role is unclear. We investigated whether fetal cells participate in maternal tissue repair during human pregnancy.

METHODS

Appendix specimens were acquired from women undergoing appendicectomy during (n = 8) or after (n = 1) pregnancy. Fluorescence in situ hybridization (FISH) determined the presence of male presumed-fetal cells, and immunostaining indicated the fetal cell phenotype.

RESULTS

Male cells were identified in appendiceal tissues from all women with known present or past male pregnancies (n = 7) and from a woman with a previous spontaneous abortion of undetermined gender (n = 1), but not in one woman with three daughters. One woman was only 6 weeks pregnant at appendicectomy. Male cells were evenly distributed through appendix tissues, in larger numbers where there was a greater degree of inflammation and when the current pregnancy was male. Combined immunostaining and Y-FISH demonstrated male desmin+ muscle cells and CD3+ lymphocytes, suggesting fetal cells had differentiated.

CONCLUSIONS

Male-presumed fetal cells of haematopoietic and mesenchymal origin were identified in the appendix of all pregnant women who had sons. We suggest that fetal cells are present at sites of maternal tissue injury during pregnancy, and may participate in tissue repair.