Transdifferentiation Of Bone Marrow Cells Research Articles

Regenerating the field of cardiovascular cell therapy.

The retraction of >30 falsified studies by Anversa et al. has had a disheartening impact on the cardiac cell therapeutics field. The premise of heart muscle regeneration by the transdifferentiation of bone marrow cells or putative adult resident cardiac progenitors has been largely disproven. Over the past 18 years, a generation of physicians and scientists has lost years chasing these studies, and patients have been placed at risk with little scientific grounding. Funding agencies invested hundreds of millions of dollars in irreproducible work, and both academic institutions and the scientific community ignored troubling signals over a decade of questionable work. Our collective retrospective analysis identifies preventable problems at the level of the editorial and peer-review process, funding agencies and academic institutions. This Perspective provides a chronology of the forces that led to this scientific debacle, integrating direct knowledge of the process. We suggest a science-driven path forward that includes multiple novel approaches to the problem of heart muscle regeneration.

The therapeutic effect of bone marrow–derived liver cells in the phenotypic correction of murine hemophilia A

AbstractThe transdifferentiation of bone marrow cells (BMCs) into hepatocytes has created enormous interest in applying this process to the development of cellular medicine for degenerative and genetic diseases. Because the liver is the primary site of factor VIII (FVIII) synthesis, we hypothesized that the partial replacement of mutated liver cells by healthy cells in hemophilia A mice could manage the severity of the bleeding disorder. We perturbed the host liver with acetaminophen to facilitate the engraftment and hepatic differentiation of lineage-depleted enhanced green fluorescent protein-expressing BMCs. Immunohistochemistry experiments with the liver tissue showed that the donor-derived cells expressed the markers of both hepatocytes (albumin and cytokeratin-18) and endothelial cells (von Willebrand factor). The results of fluorescent in situ hybridization and immunocytochemistry experiments suggested that differentiation was direct in this model. The BMC-recipient mice expressed FVIII protein and survived in a tail clip challenge experiment. Furthermore, a coagulation assay confirmed that the plasma FVIII activity was maintained at 20.4% (± 3.6%) of normal pooled plasma activity for more than a year without forming its inhibitor. Overall, this report demonstrated that BMCs rescued the bleeding phenotype in hemophilia A mice, suggesting a potential therapy for this and other related disorders.

Challenging the Cardiac Differentiation of Bone Marrow Cells: A Clinical Perspective

The plasticity of adult bone marrow cells remains a controversial topic. The initial enthusiastic claims that these cells could “regenerate” the infarcted myocardium by converting into new cardiomyocytes1 have subsequently been dampened by reports that such an outcome was unlikely.2,3,4 Indeed, the purported transdifferentiation of bone marrow cells has most often been based on immunohistochemical data, which are known to be potentially misleading because of the autofluorescence of infarcted tissue. More reliable cell-tracking methods, based on genetic tags, have led to the opposite conclusion—that bone marrow cells are in fact lineage-restricted.2,3,4 Scherschel et al.,5 using two-photon laser scanning microscopy (TPLSM), provide compelling evidence in this issue of Molecular Therapy that bone marrow cells actually lack a fundamentally important attribute of cardiomyocytes: the ability to develop cytosolic calcium transients in response to membrane depolarization.

Cytokine mobilization of bone marrow cells and pancreatic lesion do not improve streptozotocin-induced diabetes in mice by transdifferentiation of bone marrow cells into insulin-producing cells

Objective Transdifferentiation of bone marrow cells (BMC) into insulin-producing cells might provide a new cellular therapy for type I diabetes, but its existence is controversial. Our aim was to determine if those cells could transdifferentiate, even at low frequency, into insulin-producing cells, in testing optimized experimental conditions. Methods We grafted mice with total BMC, genetically labeled either ubiquitarily, or with a marker conditionally expressed under the control of the insulin β-cell specific promoter. We treated some of the recipients with an agent toxic to β-cells (streptozotocin) and with cytokines stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF). Results The contribution of grafted cells could be detected neither for natural turnover ( n = 6), nor for β-cell regeneration after pancreatic lesion ( n = 7), 90 days post-transplantation. Cytokine mobilization of BMC in the blood stream, reported to favor their transdifferentiation into cardiac and neural cells, had never been tested before for β-cell generation. Here, we showed that injection of SCF and G-CSF did not lead to a detectable level of transdifferentiation ( n = 7). Conclusions We conclude that BMC cannot spontaneously transdifferentiate into insulin-producing cells in vivo, even after β-cell lesion and mobilization induced by cytokines. Interestingly, however, treatment by cytokines may have beneficial indirect effects on STZ-induced hyperglycaemia.

Origin of hepatocellular carcinoma: Role of stem cells

The question of whether hepatocellular carcinoma (HCC) arises from the differentiation block of stem cells or dedifferentiation of mature cells remains controversial. Recently, researchers suggested that HCC may originate from the transdifferentiation of bone marrow cells. Interestingly, there are four levels of cells in the hepatic stem cell lineage: bone marrow cells, hepato-pancreas stem cells, oval cells and hepatocytes. Hematopoietic stem cells and the liver are known to have a close relationship in early development. Bone marrow stem cells could differentiate into oval cells, which could differentiate into hepatocytes and duct cells. The development of pancreatic and liver buds in embryogenesis suggests the existence of a common progenitor cell to both the pancreas and liver. Cellular events during hepatocarcinogenesis illustrate that HCC may arise from cells at various stages of differentiation in the hepatic stem cell lineage.

Liver Stem Cells

The concept of a liver stem cell or progenitor cell has not been widely accepted until the last decade. Studies investigating liver regeneration under conditions which totally or substantially preclude hepatocyte proliferation report the proliferation of a subpopulation of small, oval-shaped cells, which are first observed in the portal triad, adjacent to the terminal ducts. These cells, termed liver progenitor oval cells (LPCs) are shown to participate in liver regeneration in a variety of rodent models of chronic liver damage. They express markers common to hepatocytes and cholangiocytes suggesting they are a common precursor of both liver cell lineages. Supporting evidence for liver stem cells has also come from cell tracing studies which show transdifferentiation of bone marrow cells into hepatocytes in both human and animal models. Another important issue is the link between LPCs and hepatocellular carcinoma (HCC). The widening liver donor-recipient gap; a consequence of poor donation rates coupled with increasing incidence of liver disease highlights the importance of establishing the utility of cell transplant as an alternative to treat liver disease. In this regard, liver stem cells and progenitor cells may have a significant role to play. To successfully utilize liver stem cells or LPCs for cell therapy, we have to first develop methods for maintaining and differentiating them in culture. This technology must be based on a thorough understanding of conditions which regulate their behaviour in vitro. In particular, we need to know which growth factors and cytokines affect them and their mechanism of action. Since they are a potential source of HCC, it is also necessary to understand the mechanisms which underlie their transformation to cancer.

Human mesenchymal stem cells xenografted directly to rat liver are differentiated into human hepatocytes without fusion

AbstractHepatic transdifferentiation of bone marrow cells has been previously demonstrated by intravenous administration of donor cells, which may recirculate to the liver after undergoing proliferation and differentiation in the recipient's bone marrow. In the present study, to elucidate which cellular components of human bone marrow more potently differentiate into hepatocytes, we fractionated human bone marrow cells into mesenchymal stem cells (MSCs), CD34+ cells, and non-MSCs/CD34- cells and examined them by directly xenografting to allylalcohol (AA)-treated rat liver. Hepatocyte-like cells, as revealed by positive immunostaining for human-specific alpha-fetoprotein (AFP), albumin (Alb), cytokeratin 19 (CK19), cytokeratin 18 (CK18), and asialoglycoprotein receptor (AGPR), and by reverse transcription-polymerase chain reaction (RT-PCR) for expression of AFP and Alb mRNA, were observed only in recipient livers with MSC fractions. Cell fusion was not likely involved since both human and rat chromosomes were independently identified by fluorescence in situ hybridization (FISH). The differentiation appeared to follow the process of hepatic ontogeny, reprogramming of gene expression in the genome of MSCs, as evidenced by expression of the AFP gene at an early stage and the albumin gene at a later stage. In conclusion, we have demonstrated that MSCs are the most potent component in hepatic differentiation, as revealed by directly xenografting into rat livers. (Blood. 2005;106:756-763)

Can a bone marrow cell contribute to organ regeneration? In vivo analysis using transgenic rats with reporter genes

Although implantation of multipotent bone marrow–derived stem cells represents an attractive new cell therapy to repair damaged tissues, recent reports have raised serious concerns over the feasibility of using stem cells deriving from the bone marrow to promote cell transdifferentiation. We established transgenic (Tg) rats with reporter genes as specific molecular tags to examine the effect of bone marrow cells (BMCs) on transdifferentiation into tissues/organs. To monitor transdifferentiation events of locally transplanted BMCs into hepatocytes or capillary endothelial cells, a liver injury model and an ischemic hind-limb model were developed in rats. To test the ability of circulating bone marrow–derived cells to give rise to myocytes after skeletal muscle injury, we used a bone marrow cell transplantation model from Tg rats, which showed ubiquitous expression of β-galactosidase (lacZ), into lethally irradiated non-Tg rats. Our results show that there was little transdifferentiation of BMCs into the targeted cells in these tissue injury models. However, in the ischemic hind-limb model, laser Doppler imaging and histologic analysis showed that both implantation of BMCs and treatment with microspheres incorporating basic fibroblast-like growth factor (bFGF), which enables the release of bFGF at the site of action over a period of time, effectively induced angiogenesis. In conclusion, rat BMCs with specific marker genes could be a useful tool for detecting transdifferentiation events in vivo.

Basic fibroblast growth factor promotes the trans-differentiation of mouse bone marrow cells into hepatic lineage cells via multiple liver-enriched transcription factors

Evidence that bone marrow cells have trans-differentiating potential to hepatocytes has been described in recent reports. However, the molecular mechanism underlying this phenomenon is unclear. To address this issue, we investigated the parameters involved in the trans-differentiation of bone marrow cells into a hepatic lineage. Mouse BM cells were cultured in a collagen gel without or with growth factors including basic fibroblast growth factor. The expression of hepatocyte-specific markers, cholangiocyte-specific marker and liver-enriched transcription factors was identified by RT-PCR and immunohistochemistry. Basic fibroblast growth factor was found to be the most effective for inducing albumin in cultured BM cells. Furthermore, on stimulation of basic fibroblast growth factor, BM cells were found to express other hepatocyte-specific markers and a cholangiocyte-specific marker. This conversion was found to be associated with the induction of transcription factors including hepatocyte nuclear factors and GATA family proteins. We established an in vitro culture system in which mouse bone marrow cells could trans-differentiate to hepatic lineage cells in response to growth factors, without cell fusion. In particular, basic fibroblast growth factor has the ability to induce the trans-differentiation into hepatic lineage cells from BM cells.

Establishment of Alb-DsRed2 transgenic rat for liver regeneration research

Because serum albumin is specifically produced by mature hepatocytes, detection system of albumin producing cells could be a valuable tool to visualize liver regeneration or development. We have developed here an albumin enhancer/promoter-driven Alb-DsRed2 Tg rat that expresses DsRed2, having liver-specific reporter gene expression of red fluorescent protein. To study the transdifferentiation of bone marrow cells (BMCs) into albumin producing cells, BMCs from the Alb-DsRed2 Tg rat were injected into rats having acute liver damage caused by 2-acetylaminofluorene plus carbon tetrachloride and chronic liver damage by repeated administration of CCl 4. DsRed2-positive cells were generated in the recipient liver after BMC injection. The number of transdifferentiated DsRed2-positive cells in chronic liver injury model was increased comparing with that in acute injury model. We propose that the Alb-DsRed2 Tg rat is well suited to studying in vivo liver regeneration.

Establishment of Alb-DsRed2 transgenic rat for liver regeneration research

Because serum albumin is specifically produced by mature hepatocytes, detection system of albumin producing cells could be a valuable tool to visualize liver regeneration or development. We have developed here an albumin enhancer/promoter-driven Alb-DsRed2 Tg rat that expresses DsRed2, having liver-specific reporter gene expression of red fluorescent protein. To study the transdifferentiation of bone marrow cells (BMCs) into albumin producing cells, BMCs from the Alb-DsRed2 Tg rat were injected into rats having acute liver damage caused by 2-acetylaminofluorene plus carbon tetrachloride and chronic liver damage by repeated administration of CCl4. DsRed2-positive cells were generated in the recipient liver after BMC injection. The number of transdifferentiated DsRed2-positive cells in chronic liver injury model was increased comparing with that in acute injury model. We propose that the Alb-DsRed2 Tg rat is well suited to studying in vivo liver regeneration.

An in vivo model for monitoring trans-differentiation of bone marrow cells into functional hepatocytes.

The plasticity of bone marrow cells (BMCs) remains controversial. The present study found that persistent injury induces efficient trans-differentiation of BMCs into functional hepatocytes. Mice with liver cirrhosis induced by carbon tetrachloride were injected with 1 x 10(5) non-treated green fluorescent protein (GFP)-positive BMCs via the tail vein. In these mice, transplanted GFP-positive BMCs efficiently migrated into the peri-portal area of liver lobules after one day, repopulating 25% of the recipient liver by 4 weeks. In contrast, no GFP-positive BMCs were detected following transplantation into control mice with undamaged livers. BMCs trans-differentiated into functional mature hepatocytes via immature hepatoblasts. Serum albumin levels were significantly elevated to compensate for chronic liver failure in BMC transplantation. These results reveal that recipient conditions and microenvironments represent key factors for successful cell therapy using BMCs.

Sera from liver failure patients and a demethylating agent stimulate transdifferentiation of murine bone marrow cells into hepatocytes in coculture with nonparenchymal liver cells

Background/Aims: The plasticity of bone marrow cells (BMCs) is shown by their ability to differentiate into mesenchymal as well as endodermal and ectodermal lineages. Transdifferentiation of BMCs into hepatocytes has also been demonstrated, both in vitro and in vivo. In the present study we investigated the effects of liver nonparenchymal cells (NPCs) and sera from liver failure patients (HSLF) on the in vitro transdifferentiation of murine BMCs into hepatocytes. Methods: Liver NPCs from wild-type mice, and 5-azacytidine-treated BMCs from green fluorescence protein transgenic mice, were cocultured in medium containing HSLF in combination with several cytokines. Hepatocyte-specific gene expression in BMCs was identified by immunocytochemistry and reverse transcription–polymerase chain reaction. Results: Bone marrow cell-derived hepatocyte-like colonies appeared after several days of coculture in medium containing HSLF, oncostatin M (OSM) and hepatocyte growth factor (HGF). These colonies expressed hepatocyte-specific genes. Transdifferentiation was enhanced by 5-azacytidine treatment, and by HSLF, OSM and HGF. It did not take place when the BMCs were separated from the NPCs in a dual chamber dish, or cultured with other mesenchymal cells. Conclusions: Direct interaction of murine BMCs with liver NPCs, as well as soluble factors in the HSLF and a demethylating agent, strongly stimulate transdifferentiation into hepatocytes.

Liver nonparenchymal cells and sera from liver failure patients stimulate transdifferentiation of bone marrow cells into hepatocytes

Liver nonparenchymal cells and sera from liver failure patients stimulate transdifferentiation of bone marrow cells into hepatocytes

Preservation of hematopoietic properties in transplanted bone marrow cells in the brain.

Recent studies have described the possible transdifferentiation of bone marrow cells (BMC) into neurons and glia when they migrate to the brain. However, we have reported that some immature BMC migrating into the brain parenchyma after bone marrow transplantation express early hematopoietic markers but not neural or glial markers. The present study further characterizes transplanted BMC that migrate to the brain. Double immunolabeling confirmed that BMC migrating to the brain expressed hematopoietic but not neural markers, such as nestin, microtubule-associated protein-2 and glial fibrillary acidic protein, even 4 and 18 weeks after bone marrow transplantation. BMC that expressed green fluorescent protein also expressed hematopoietic but not neural markers when cultured with mixed brain cells according to double immunolabeling and single-cell dissection using a laser. Analysis of the DNA content indicated that most of the migrated BMC were arrested at the G0/G1 phase, and aneuploidy or tetraploidy was undetectable. Thus, BMC that migrate to the brain probably have preserved hematopoietic properties under physiological conditions.

Bone Marrow-Derived Hepatocytes: Rare but Promising

Bone Marrow-Derived Hepatocytes: Rare but Promising