Stromal cell derived factor-1 enhances bone marrow mononuclear cell migration in mice with acute liver failure

Single-cell transcriptomics reveal the microenvironment landscape of perfluorooctane sulfonate-induced liver injury in female mice

Epidemic and animal studies have reported that perfluoroalkyl and polyfluoroalkyl substances (PFASs) are strongly associated with liver injury; however, to date, the effects of PFASs on the hepatic microenvironment remain largely unknown. In this study, we established perfluorooctane sulfonic acid (PFOS)-induced liver injury models by providing male and female C57BL/6 mice with water containing PFOS at varying doses for 4 weeks. Hematoxylin and eosin staining revealed that PFOS induced liver injury in both sexes. Elevated levels of serum aminotransferases including those of alanine aminotransferase and aspartate transaminase were detected in the serum of mice treated with PFOS. Female mice exhibited more severe liver injury than male mice. We collected the livers from female mice and performed single-cell RNA sequencing. In total, 36,529 cells were included and grouped into 10 major cell types: B cells, granulocytes, T cells, NK cells, monocytes, dendritic cells, macrophages, endothelial cells, fibroblasts, and hepatocytes. Osteoclast differentiation was upregulated and the T cell receptor signaling pathway was significantly downregulated in PFOS-treated livers. Further analyses revealed that among immune cell clusters in PFOS-treated livers, Tcf7+CD4+T cells were predominantly downregulated, whereas conventional dendritic cells and macrophages were upregulated. Among the fibroblast subpopulations, hepatic stellate cells were significantly enriched in PFOS-treated female mice. CellphoneDB analysis suggested that fibroblasts interact closely with endothelial cells. The major ligand-receptor pairs between fibroblasts and endothelial cells in PFOS-treated livers were Dpp4_Cxcl12, Ackr3_Cxcl12, and Flt1_complex_Vegfa. These genes are associated with directing cell migration and angiogenesis. Our study provides a general framework for understanding the microenvironment in the livers of female mice exposed to PFOS at the single-cell level.

CCR9 axis inhibition enhances hepatic migration of plasmacytoid dendritic cells and protects against liver injury

Plasmacytoid dendritic cells (pDCs) perform dual proinflammatory and immunosuppressive roles. We recently reported the potential of pDC therapy for treatment of intractable acute liver failure. However, establishment of efficient methods to deliver pDCs to the liver is essential for future clinical therapeutic applications. The present study demonstrates a higher abundance of liver and peripheral blood pDCs in mice lacking the C-C motif chemokine receptor 9 (CCR9), a pDC gut-homing receptor, than that in wild-type (WT) mice. Adoptive pDC transfer resulted in a higher efficiency of Ccr9-/- pDC migration to the liver than that to the original target organ, the small intestine, compared with that of WT pDCs. Further, Ccr9-/- pDCs consistently migrated efficiently to the concanavalin A-induced inflamed liver, and exerted a more effective immunosuppressive effect, resulting in better protection against acute liver inflammation than that demonstrated by WT pDCs. These findings highlight the therapeutic potential of the manipulation of CCR9 axis as a novel approach to improve migration of immunosuppressive pDCs to the liver in order to exploit their beneficial effects in acute liver disease.

Bone marrow mononuclear cells for joint therapy: The role of macrophages in inflammation resolution and tissue repair

Osteoarthritis (OA) is the most prevalent joint disease causing major disability and medical expenditures. Synovitis is a central feature of OA and is primarily driven by macrophages. Synovial macrophages not only drive inflammation but also its resolution, through a coordinated, simultaneous expression of pro- and anti-inflammatory mechanisms that are essential to counteract damage and recover homeostasis. Current OA therapies are largely based on anti-inflammatory principles and therefore block pro-inflammatory mechanisms such as prostaglandin E₂ and Nuclear factor-kappa B signaling pathways. However, such mechanisms are also innately required for mounting a pro-resolving response, and their blockage often results in chronic low-grade inflammation. Following minor injury, macrophages shield the damaged area and drive tissue repair. If the damage is more extensive, macrophages incite inflammation recruiting more macrophages from the bone marrow to maximize tissue repair and ultimately resolve inflammation. However, sustained damage and inflammation often overwhelms pro-resolving mechanisms of synovial macrophages leading to the chronic inflammation and related tissue degeneration observed in OA. Recently, experimental and clinical studies have shown that joint injection with autologous bone marrow mononuclear cells replenishes inflamed joints with macrophage and hematopoietic progenitors, enhancing mechanisms of inflammation resolution, providing remarkable and long-lasting effects. Besides creating an ideal environment for resolution with high concentrations of interleukin-10 and anabolic growth factors, macrophage progenitors also have a direct role in tissue repair. Macrophages constitute a large part of the early granulation tissue, and further transdifferentiate from myeloid into a mesenchymal phenotype. These cells, characterized as fibrocytes, are essential for repairing osteochondral defects. Ongoing “omics” studies focused on identifying key drivers of macrophage-mediated resolution of joint inflammation and those required for efficient osteochondral repair, have the potential to uncover ways for developing engineered macrophages or off-the-shelf pro-resolving therapies that can benefit patients suffering from many types of arthropaties, not only OA.

Progress in mesenchymal stem cell-based therapy for acute liver failure

Acute liver failure is a life-threatening clinical syndrome characterized by rapid development of hepatocellular necrosis leading to high mortality and resource costs. Numerous treatment strategies for acute liver failure simply prevent complications and decelerate disease progression. The only curative treatment for acute liver failure is liver transplantation, but there are many restrictions on the application of liver transplantation. In recent years, a growing number of studies have shown that stem cells can effectively treat acute liver failure. Several types of stem cells have been used to study liver diseases; mesenchymal stem cells are most commonly used because they are easy to obtain and present no ethical problems. The aims of this article are to review the current knowledge regarding therapeutic mechanisms of mesenchymal stem cells in acute liver failure, to discuss recent advancements in preclinical and clinical studies in the treatment of mesenchymal stem cells, and to summarize the methodological improvement of mesenchymal stem cell transplantation in treating liver failure.

Resveratrol pretreatment enhanced homing of SDF-1α-preconditioned bone marrow-derived mesenchymal stem cells in a rat model of liver cirrhosis

Stromal cell-derived factor-1α (SDF-1α) has been known to implicate in homing of MSCs, and resveratrol has been reported to have a positive influence on SDF-1 level in the site of injury. In this study, a combined strategy was applied to evaluate bone marrow-derived MSCs (BMSCs) homing to the rat model of liver cirrhosis induced by common bile duct ligation (CBDL): (1) pretreatment delivery of resveratrol into the cirrhotic liver, and (2) transplantation of ex vivo BMSC preconditioning with SDF-1α. BMSCs were preconditioned with 10 ng/µL SDF-1α for 1 h and then labeled with the CM-Dil. Cirrhosis was induced by CBDL. Animals received intraperitoneal injection of resveratrol for 7 days, started on day 28 of CBDL post-operative. On day 36 post-operative, 1 × 10⁶ of SDF-1α-preconditioned BMSCs was injected via caudal vein. Animals were sacrificed at 72 h post-cell transplantation. Immunofluorescence and flow cytometry assessments showed that the BMSC+SDF+RV group had an increased rate of homing into the liver, but it had a decreased rate of homing into the lung and spleen, as compared with the other groups (P < 0.05). The BMSC+SDF+RV group showed high protein expression of SIRT1, but low protein expression of p53 in the liver (P < 0.05 vs other groups). CXCR4 and matrix metalloproteinase (MMP)-9 highly expressed in SDF-1α-preconditioned BMSCs in vitro, and that AKTs and CXCL12 expressed in injured liver undergoing resveratrol injection. Our findings suggest that reseveratrol pretreatment prior to SDF-1α preconditioning could be a promising strategy for designing cell-based therapies for liver cirrhosis.

Adipose-derived stem cells: A candidate for liver regeneration

The scarcity of donor livers and the impracticality of hepatocyte transplantation represent the biggest obstacles for the treatment of liver failure. Adipose-derived stem cells, with their ability to differentiate into the hepatic lineage, provide a reliable alternative cell source with clear ethical and practical advantages. Moreover, adipose-derived stem cells can effectively repair liver damage by the dominant indirect pattern and increase the number of hepatocytes by the secondary direct pattern. In recent years, the development of the indirect pattern, which mainly includes immunomodulatory and trophic effects, has become a hot topic in the field of cell engineering. Therefore, adipose-derived stem cells are considered to be ideal therapeutic stem cells for human liver regeneration. In this article, we reviewed the advantages of adipose-derived stem cells in liver regeneration, and explore their underlying mechanisms.

Autologous mobilized peripheral blood CD34+ cell infusion in non-viral decompensated liver cirrhosis

AIM: To study the effect of mobilized peripheral blood autologous CD34 positive (CD34⁺) cell infusion in patients with non-viral decompensated cirrhosis.

METHODS: Cirrhotic patients of non-viral etiology were divided into 2 groups based on their willingness to be listed for deceased donor liver transplant (DDLT) (control, n = 23) or to receive autologous CD34⁺ cell infusion through the hepatic artery (study group, n = 22). Patients in the study group were admitted to hospital and received granulocyte colony stimulating factor injections 520 μg/d for 3 consecutive days to mobilize CD34⁺ cells from the bone marrow. On day 4, leukapheresis was done and CD34⁺ cells were isolated using CliniMAC magnetic cell sorter. The isolated CD34⁺ cells were infused into the hepatic artery under radiological guidance. The patients were discharged within 48 h. The control group received standard of care treatment for liver cirrhosis and were worked up for DDLT as per protocol of the institute. Both groups were followed up every week for 4 wk and then every month for 3 mo.

RESULTS: In the control and the study group, the cause of cirrhosis was cryptogenic in 18 (78.2%) and 16 (72.72%) and alcohol related in 5 (21.7%) and 6 (27.27%), respectively. The mean day 3 cell count (cells/μL) was 27.00 ± 20.43 with a viability of 81.84 ± 11.99%. and purity of 80%-90%. Primary end point analysis revealed that at 4 wk, the mean serum albumin in the study group increased significantly (2.83 ± 0.36 vs 2.43 ± 0.42, P = 0.001) when compared with controls. This improvement in albumin was, however, not sustained at 3 mo. However, at the end of 3 mo there was a statistically significant improvement in serum creatinine in the study group (0.96 ± 0.33 vs 1.42 ± 0.70, P = 0.01) which translated into a significant improvement in the Model for End-Stage Liver Disease score (15.75 ± 5.13 vs 19.94 ± 6.68, P = 0.04). On statistical analysis of secondary end points, the transplant free survival at the end of 1 mo and 3 mo did not show any significant difference (P = 0.60) when compared to the control group. There was no improvement in aspartate transaminase, alanine transaminase, and bilirubin at any point in the study population. There was no mortality benefit in the study group. The procedure was safe with no procedural or treatment related complications.

CONCLUSION: Autologous CD 34⁺ cell infusion is safe and effectively improves liver function in the short term and may serve as a bridge to liver transplantation.

Bone mesenchymal stem cell transplantation via four routes for the treatment of acute liver failure in rats

In the present study, we assessed the efficiency of four BMSC transplantation methods as a therapy for liver failure. A rat model (80 Sprague-Dawley rats) of D-galactosamine (D-gal)/lipopolysaccharide (LPS)-induced acute liver failure (ALF) was established and the rats were divided into 5 groups: a hepatic artery injection group, a portal vein injection group, a vena caudalis injection group, an intraperitoneal injection group and a control group (16 per group). Following transplantation, the liver tissue and blood samples were collected on days 1, 3 and 7, we detected the EdU (5-ethynyl-2′-deoxyuridine)-labeled cells homing to the liver tissue and assessed the proliferating cell nuclear antigen (PCNA) and cysteine-containing aspartate-specific protease (caspase)-3 expression in the liver tissue and detected the levels of stromal cell-derived factor 1 (SDF-1) and hepatocyte growth factor (HGF) in the liver tissues. Compared with the control group, the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and damage to the liver tissue in the hepatic artery group, the portal vein group and the vena caudalis group improved in vivo. The expression of PCNA and HGF in the liver was higher and caspase-3 expression was lower in the hepatic artery injection group, the portal vein injection group and the vena caudalis injection group than that in the intraperitoneal injection and control groups. The EdU-labeled BMSCs were only observed homing to the liver tissue in these three groups. However, no significant differences were observed between these three groups. Liver function in the rats with ALF was improved following BMSC transplantation via 3 endovascular implantation methods (through the hepatic artery, portal vein and vena caudalis). These 3 methods were effective in transplanting BMSCs for the treatment of ALF. However, the selection of blood vessel in the implantation pathway does not affect the transplantation outcome. Transplantation via intraperitoneal injection showed no therapeutic effect in our animal experiments.

Human bone marrow mesenchymal stem cell-derived hepatocytes improve the mouse liver after acute acetaminophen intoxication by preventing progress of injury

Mesenchymal stem cells from human bone marrow (hMSC) have the potential to differentiate into hepatocyte-like cells in vitro and continue to maintain important hepatocyte functions in vivo after transplantation into host mouse livers. Here, hMSC were differentiated into hepatocyte-like cells in vitro (hMSC-HC) and transplanted into livers of immunodeficient Pfp/Rag2⁻/⁻ mice treated with a sublethal dose of acetaminophen (APAP) to induce acute liver injury. APAP induced a time- and dose-dependent damage of perivenous areas of the liver lobule. Serum levels of aspartate aminotransferase (AST) increased to similar levels irrespective of hMSC-HC transplantation. Yet, hMSC-HC resided in the damaged perivenous areas of the liver lobules short-term preventing apoptosis and thus progress of organ destruction. Disturbance of metabolic protein expression was lower in the livers receiving hMSC-HC. Seven weeks after APAP treatment, hepatic injury had completely recovered in groups both with and without hMSC-HC. Clusters of transplanted cells appeared predominantly in the periportal portion of the liver lobule and secreted human albumin featuring a prominent quality of differentiated hepatocytes. Thus, hMSC-HC attenuated the inflammatory response and supported liver regeneration after acute injury induced by acetaminophen. They hence may serve as a novel source of hepatocyte-like cells suitable for cell therapy of acute liver diseases.

Cellular therapy for liver disease

Regenerative medicine is energizing and empowering basic science and has the potential to dramatically transform health care in the future. Given the remarkable intrinsic regenerative properties of the liver, as well as widespread adoption of regenerative strategies for liver disease (eg, liver transplant, partial hepatectomy, living donor transplant), hepatology has always been at the forefront of clinical regenerative medicine. However, an expanding pool of patients awaiting liver transplant, a limited pool of donor organs, and finite applicability of the current surgical approaches have created a need for more refined and widely available regenerative medicine strategies. Although cell-based therapies have been used extensively for hematologic malignant diseases and other conditions, the potential application of cellular therapy for acute and chronic liver diseases has only more recently been explored. New understanding of the mechanisms of liver regeneration and repair, including activation of local stem/progenitor cells and contributions from circulating bone marrow-derived stem cells, provide the theoretical underpinnings for the rational use of cell-based therapies in clinical trials. In this review, we dissect the scientific rationale for various modalities of cell therapy for liver diseases being explored in animal models and review those tested in human clinical trials. We also attempt to clarify some of the important ongoing questions that need to be addressed in order to bring these powerful therapies to clinical translation. Discussions will cover transplant of hepatocytes and liver stem/progenitor cells as well as infusion or stimulation of bone marrow-derived stem cells. We also highlight tremendous scientific advances on the horizon, including the potential use of induced pluripotent stem cells and their derivatives as individualized regenerative therapy for liver disease.

The generation of hepatocytes from mesenchymal stem cells and engraftment into the liver

PURPOSE OF REVIEW

Liver transplantation is the ultimate therapeutic option for the treatment of end-stage liver diseases, which, however, is restricted by the shortage of donor organs. Instead hepatocyte transplantation seemed to be a way out, but again marginal donor livers for the isolation of primary human hepatocytes are scarce. The hepatocyte differentiation capacity of mesenchymal stem cells might open a new cell resource to generate hepatocyte-like cells for therapeutical use.

RECENT FINDINGS

Apart from their potency of hepatocyte differentiation mesenchymal stem cells display pleiotropic biological features including modulation of immunogenicity, anti-inflammatory and anti-apoptotic as well as pro-proliferative impact at the site of tissue or organ lesions. They are mobilized from the bone marrow and migrate to the liver along chemoattractive gradients thus contributing to the humoral and cellular response in tissue repair. The cause of different liver diseases is varying depending on, for example, viral, toxic, nutritional, neoplastic challenges. As known from animal studies mesenchymal stem cells seem to have a beneficial impact on liver regeneration and tissue repair under a variety of liver disease conditions.

SUMMARY

Their versatile biological features render mesenchymal stem cells an alternate cell resource for the treatment of liver diseases. It is important to know the mechanisms of integration of transplanted cells into the recipient tissue and to understand the communication between donor cells and the host tissue on the molecular level in order to support efficacy of cell transplantation and thus optimize the therapeutical outcome.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Identification of miR-27b as a novel signature from the mRNA profiles of adipose-derived mesenchymal stem cells involved in the tolerogenic response

Adipose-derived mesenchymal stem cells (adipose-derived MSCs, ASCs) possess the ability to differentiate into multiple tissue types and have immune-modulatory properties similar to those of MSCs from other origins. However, the regulation of the MSC-elicited immune-modulatory activity by specific microRNA (miRNA) mechanisms remains unexplored. Gene expression profiling with knowledge-based functional enrichment analysis is an appropriate approach for unraveling these mechanisms. This tool can be used to examine the transcripts and miRNA regulators that differentiate the rat tolerogenic orthotopic liver transplantation (OLT; DA liver into PVG) and rejection OLT (DA liver into LEW) models. In both models, the rejection reaction was observed on postoperative day 7∼14 (rejection phase) but was overcome only by the PVG recipients. Thus, the global gene expression patterns of ASCs from spontaneously tolerant (PVG) and acute rejecting (LEW) rats in response to LPS activation were compared. In this study, we performed miRNA enrichment analysis based on the analysis of pathway, gene ontology (GO) terms and transcription factor binding site (TFBS) motif annotations. We found that the top candidate, miR-27, was specifically enriched and had the highest predicted frequency. We also identified a greater than 3-fold increase of miR-27b expression in the ASCs of tolerant recipients (DA to PVG) compared to those of rejecting recipients (DA to LEW) during the rejection phase in the rat OLT model. Furthermore, our data showed that miR-27b knockdown has a positive influence on the allosuppressive activity that inhibits T-cell proliferation. We found that miR-27 knockdown significantly induced the expression of CXCL12 in cultured ASCs and the expression of CXCL12 was responsible for the miR-27b antagomir-mediated inhibition of T-cell proliferation. These results, which through a series of comprehensive miRNA enrichment analyses, might be relevant for stem cell-based therapeutic applications in immunosuppressive function using ASCs.

The role of chemokines in acute liver injury

Chemokines are small molecular weight proteins primarily known to drive migration of immune cell populations. In both acute and chronic liver injury, hepatic chemokine expression is induced resulting in inflammatory cell infiltration, angiogenesis, and cell activation and survival. During acute injury, massive parenchymal cell death due to apoptosis and/or necrosis leads to chemokine production by hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells, and sinusoidal endothelial cells. The specific chemokine profile expressed during injury is dependent on both the type and course of injury. Hepatotoxicity by acetaminophen for example leads to cellular necrosis and activation of Toll-like receptors while the inciting insult in ischemia reperfusion injury produces reactive oxygen species and subsequent production of pro-inflammatory chemokines. Chemokine expression by these cells generates a chemoattractant gradient promoting infiltration by monocytes/macrophages, NK cells, NKT cells, neutrophils, B cells, and T cells whose activity are highly regulated by the specific chemokine profiles within the liver. Additionally, resident hepatic cells express chemokine receptors both in the normal and injured liver. While the role of these receptors in normal liver has not been well described, during injury, receptor up-regulation, and chemokine engagement leads to cellular survival, proliferation, apoptosis, fibrogenesis, and expression of additional chemokines and growth factors. Hepatic-derived chemokines can therefore function in both paracrine and autocrine fashions further expanding their role in liver disease. More recently it has been appreciated that chemokines can have diverging effects depending on their temporal expression pattern and the type of injury. A better understanding of chemokine/chemokine receptor axes will therefore pave the way for development of novel targeted therapies for the treatment of liver disease.

Rodent animal models for surrogate analysis of cell therapy in acute liver failure

Without therapeutic intervention acute liver failure (ALF) is the consequence of a progredient destruction of the liver parenchyma due to metabolic exhaustion of the hepatocytes. Perivenous hepatocytes are responsible for the detoxification of noxious compounds via the cytochrome P450 enzyme system. Liver transplantation is the only remaining therapeutic option in the end-stage of the disease. Assuming that metabolic capacity could be provided by healthy hepatocytes and thus substitute for the genuine parenchymal cells hepatocyte transplantation since quite some time is considered to be an alternative to whole liver transplantation. While this hypothesis achieved proof-of-concept in animal trials clinical breakthrough is still awaiting success, the reasons of which are ongoing matter of debate. In recent times mesenchymal stem cells (MSC) came into focus as a transplantable cell source to treat ALF. Interestingly, as demonstrated in various rodent animal models their mode of action is rather based on trophic support of hepatocytes remaining in the damaged host parenchyma rather than substitution of tissue loss. Mechanistically, either direct or indirect paracrine effects from the transplanted cells acting pro-proliferative, anti-apoptotic, and anti-inflammatory seem to trigger the regenerative response of the residual healthy hepatocytes in the otherwise lethally injured liver parenchyma. Thus, allogeneic MSC may be the best choice for the treatment of ALF taking advantage of their short-term benefit to sustain the critical phase of the acute insult avoiding long-term immunosuppression.

Ex vivo-expanded bone marrow stem cells home to the liver and ameliorate functional recovery in a mouse model of acute hepatic injury

BACKGROUND

Stem cell transplantation provides a theoretical approach for liver regeneration medicine; it may promote liver regeneration and self-repair. However, the transplantation of bone marrow-mesenchymal stem cells expanded ex vivo as a therapy for liver disease has rarely been investigated. This study aimed to explore whether bone marrow stem cells expanded ex vivo home to the liver and foster hepatic recovery after CCl4 injury.

METHODS

Bone marrow cells from BALB/c mice were expanded ex vivo by multiple-passage cultivation, characterized by cytoflow immunofluorescence, and pre-labeled with PKH26 before intravenous infusion into animals treated with CCl4. The integration of bone marrow cells into the liver was examined microscopically, and plasma hepatic enzymes were determined biochemically.

RESULTS

Cultured bone marrow cells exhibited antigenic profiles comparable to those of primary medullary stem cells. Double immunofluorescence showed colocalization of these cells with proliferative activity and albumin expression in the liver of CCl4-treated mice. Densitometry showed increased in situ cell proliferation (50+/-14 vs 20+/-3 cells/high-power field, P<0.05) and albumin expression (149+/-25 vs 20+/-5 cells/high-power field, P<0.05) in the liver, as well as reduced serum aminotransferase levels (P<0.05) and better survival rates (P<0.05) in animals receiving cultured bone marrow cells relative to controls.

CONCLUSIONS

Ex vivo-expanded bone marrow cells are capable of relocating to and proliferating in the chemically-injured liver. Transplantation of these pluripotent stem cells appears to improve serum indices of liver function and survival rate in mice after CCl4-induced hepatic damage.

Stromal-derived factor-1 and its receptor, CXCR4, are constitutively expressed by mouse liver sinusoidal endothelial cells: implications for the regulation of hematopoietic cell migration to the liver during extramedullary hematopoiesis

Stromal-derived factor (SDF)-1 is the main regulating factor for trafficking/homing of hematopoietic stem cells (HSC) to the bone marrow (BM). It is possible that this chemokine may also play a fundamental role in regulating the migration of HSC to several organs during extramedullary hematopoiesis. Because liver sinusoidal endothelial cells (LSEC) constitute an extramedullary niche for HSC, it is possible that these cells represent one of the main cellular sources of SDF-1 at the liver. Here, we show that LSEC express SDF-1 at the mRNA and protein level. Biological assays showed that conditioned medium from LSEC (LSEC-CM) stimulated the migration of BM progenitor lineage-negative (BM/Lin⁻) cells. This effect was significantly reduced by AMD3100, indicating that the SDF-1/CXCR4 axis is involved in the stimulatory migrating effect induced by LSEC-CM. Early localization of HSC in SDF-1-expressing LSEC microenvironment together with increased levels of this chemokine in hepatic homogenates was found in an experimental model of liver extramedullary hematopoiesis. Flow cytometry studies showed that LSEC express the CXCR4 receptor. Functional assays showed that activation of this receptor by SDF-1 stimulated the migration of LSEC and increased the expression of PECAM-1. Our findings suggest that LSEC through the production of SDF-1 may constitute a fundamental niche for regulation of HSC migration to the liver. To our knowledge, this is the first report showing that LSEC not only express and secrete SDF-1, but also its receptor CXCR4.

Pathological and MR-DWI study of the acute hepatic injury model after stem cell transplantation

AIM: To investigate apparent diffusion coefficient (ADC) values as an indication of reconditioning of acute hepatic injury (AHI) after allogeneic mononuclear bone marrow cell (MBMC) transplantation.

METHODS: Three groups were used in our study: a cell transplantation group (n = 21), transplantation control group (n = 21) and normal control group (n = 10). AHI model rabbits in the cell transplantation group were injected with 5 mL of MBMC suspension at multiple sites in the liver and the transplantation controls were injected with 5 mL D-Hanks solution. At the end of the 1st, 2nd and 4th wk, 7 rabbits were randomly selected from the cell transplantation group and transplantation control group for magnetic resonance diffusion-weighted imaging (MR-DWI) and measurement of the mean ADC values of injured livers. After MR-DWI examination, the rabbits were sacrificed and the livers subjected to pathological examination. Ten healthy rabbits from the normal control group were used for MR-DWI examination and measurement of the mean ADC value of normal liver.

RESULTS: At all time points, the liver pathological scores from the cell transplantation group were significantly lower than those in the transplantation control group (27.14 ± 1.46 vs 69.29 ± 6.16, 22.29 ± 2.29 vs 57.00 ± 1.53, 19.00 ± 2.31 vs 51.86 ± 6.04, P = 0.000). The mean ADC values of the cell transplantation group were significantly higher than the transplantation control group ((1.07 ± 0.07) × 10^-3 mm²/s vs (0.69 ± 0.05) × 10^-3 mm²/s, (1.41 ± 0.04) × 10^-3 mm²/s vs (0.84 ± 0.06) × 10^-3 mm²/s, (1.68 ± 0.04) × 10^-3 mm²/s vs (0.86 ± 0.04) × 10^-3 mm²/s, P = 0.000). The pathological scores of the cell transplantation group and transplantation control group gradually decreased. However, their mean ADC values gradually increased to near that of the normal control. At the end of the 1st wk, the mean ADC values of the cell transplantation group and transplantation control group were significantly lower than those of the normal control group [(1.07 ± 0.07) × 10^-3 mm²/s vs (1.76 ± 0.03) × 10^-3 mm²/s, (0.69 ± 0.05) × 10^-3 mm²/s vs (1.76 ± 0.03) × 10^-3 mm²/s, P = 0.000]. At any 2 time points, the pathological scores and the mean ADC values of the cell transplantation group were significantly different (P = 0.000). At the end of the 1st wk, the pathological scores and the mean ADC values of the transplantation control group were significantly different from those at the end of the 2nd and 4th wk (P = 0.000). However, there was no significant difference between the 2nd and 4th wk (P = 0.073 and 0.473, respectively). The coefficient of correlation between the pathological score and the mean ADC value in the cell transplantation group was -0.883 (P = 0.000) and -0.762 (P = 0.000) in the transplantation control group.

CONCLUSION: Tracking the longitudinally dynamic change in the mean ADC value of the AHI liver may reflect hepatic injury reconditioning after allogeneic MBMC transplantation.

Transplanted bone marrow stem cells relocate to infarct penumbra and co-express endogenous proliferative and immature neuronal markers in a mouse model of ischemic cerebral stroke

Background

Several studies demonstrate that neurogenesis may be induced or activated following vascular insults, which may be important for neuronal regeneration and functional recovery. Understanding the cellular mechanism underlying stroke-associated neurogenesis is of neurobiological as well as neurological/clinical relevance. The present study attempted to explore potential homing and early development of transplanted bone marrow stem cells in mouse forebrain after focal occlusion of the middle cerebral artery, an experimental model of ischemic stroke.

Results

Bone marrow stem cells isolated from donor mice were confirmed by analysis of surface antigen profile, and were pre-labeled with a lipophilic fluorescent dye PKH26, and subsequently transfused into recipient mice with middle cerebral artery coagulation. A large number of PKH26-labeled cells were detected surrounding the infarct site, most of which colocalized with immunolabelings for the proliferating cell nuclear antigen (PCNA) and some also colocalized with the immature neuronal marker doublecortin (DCX) during 1-2 weeks after the bone marrow cells transfusion.

Conclusions

The present study shows that transplanted bone morrow cells largely relocate to the infarct penumbra in ischemic mouse cerebrum. These transplanted bone marrow cells appear to undergo a process of in situ proliferation and develop into putative cortical interneurons during the early phase of experimental vascular injury.

Granulocyte colony-stimulating factor enhances bone marrow mononuclear cell homing to the liver in a mouse model of acute hepatic injury

BACKGROUND

Experiments have reported that granulocyte colony stimulating factor (G-CSF) can mobilize stem cells. However, few studies have examined the effect of G-CSF on bone marrow mononuclear cell (BMMC) mobilization, in particular regarding their capability to home to acutely injured liver.

AIMS

The aim of this study was to evaluate the effort of G-CSF on BMMC homing to the liver following chemically-induced hepatic failure.

METHODS

BMMC were isolated from mice, pre-labeled with PKH26 and infused into the mice in which hepatic injury had been induced followed by administration of G-CSF or vehicle. Livers were studied by fluorescent microscopy after transplantation of pre-labeled BMMC.

RESULTS

PKH26 labeled cells were found in liver tissue at 102 ± 10 cells/high power field in the BMMC+G-CSF group and 30 ± 5 cells/high power field in the BMMC group, but none in the G-CSF group and the control group (P < 0.05). In the former two groups the majority of PKH26 labeled cells colocalized with proliferative cell nuclear antigen (PCNA). The number of PCNA positive cells in the BMMC+G-CSF group was 20 ± 4 cells/high power field, while in the BMMC group it was 14 ± 2 cells/high power field, in the G-CSF group 12 ± 2 cells/high power field, and 8 ± 1 cells/high power field in the control group. Moreover, albumin expression was increased in the BMMC+G-CSF treated group (149 ± 7/high power field) relative to the BMMC group (48 ± 6/high power field), the G-CSF group (44 ± 5/high power field) and the vehicle group (30 ± 6/high power field), with the former three groups showing elevated levels as compared to vehicle control (30 ± 6) (P < 0.05).

CONCLUSION

Transplanted BMMC may home to injured liver, which appears to be enhanced by G-CSF administration.

Potential applications for cell regulatory factors in liver progenitor cell therapy

Orthotopic liver transplant represent the state of the art treatment for terminal liver pathologies such as cirrhosis in adults and hemochromatosis in neonates. A limited supply of transplantable organs in relationship to the demand means that many patients will succumb to disease before an organ becomes available. One promising alternative to liver transplant is therapy based on the transplant of liver progenitor cells. These cells may be derived from the patient, expanded in vitro, and transplanted back to the diseased liver. Inborn metabolic disorders represent the most attractive target for liver progenitor cell therapy, as many of these disorders may be corrected by repopulation of only a portion of the liver by healthy cells. Another potential application for liver progenitor cell therapy is the seeding of bio-artificial liver matrix. These ex vivo bioreactors may someday be used to bridge critically ill patients to other treatments. Conferring a selective growth advantage to the progenitor cell population remains an obstacle to therapy development. Understanding the molecular signaling mechanisms and micro-environmental cues that govern liver progenitor cell phenotype may someday lead to strategies for providing this selective growth advantage. The discovery of a population of cells within the bone marrow possessing the ability to differentiate into hepatocytes may provide an easily accessible source of cells for liver therapies.