Bone marrow mononuclear cell transplantation improves survival and induces hepatocyte proliferation in rats after CCl(4) acute liver damage

Elucidating the Mechanisms of Dynamic and Robust Control of the Liver Homeostatic Renewal Process: Cell Network Modeling and Analysis

Recent experimental investigations of liver homeostatic renewal have identified high replication capacity hepatocyte populations as the primary maintainers of liver mass. However, the molecular and cellular processes controlling liver homeostatic renewal remain unknown. To address this problem, we developed and analyzed a mathematical model describing cellular network interactions underlying liver homeostatic renewal. Model simulation results demonstrate that without feedback control, basic homeostatic renewal is not robust to disruptions, leading to tissue loss under persistent/repetitive insults. Consequently, we extended our basic model to incorporate putative regulatory interactions and investigated how such interactions may confer robustness on the homeostatic renewal process. We utilized a Design of Experiments approach to identify the combination of feedback interactions that yields a cell network model of homeostatic renewal capable of maintaining liver mass robustly during persistent/repetitive injury. Simulations of this robust model indicate that repeated injury destabilizes liver homeostasis within several months, which differs from epidemiological observations of a much slower decay of liver function occurring over several years. To address this discrepancy, we extended the model to include feedback control by liver nonparenchymal cells. Simulations and analysis of the final multicellular feedback control network suggest that achieving robust liver homeostatic renewal requires intrinsic stability in a hepatocellular network combined with feedback control by nonparenchymal cells.

Paracrine Effects of Bone Marrow Mononuclear Cells in Survival and Cytokine Expression after 90% Partial Hepatectomy

Acute liver failure is a complex and fatal disease. Cell-based therapies are a promising alternative therapeutic approach for liver failure due to relatively simple technique and lower cost. The use of semipermeable microcapsules has become an interesting tool for evaluating paracrine effects in vivo. In this study, we aimed to assess the paracrine effects of bone marrow mononuclear cells (BMMC) encapsulated in sodium alginate to treat acute liver failure in an animal model of 90% partial hepatectomy (90% PH). Encapsulated BMMC were able to increase 10-day survival without enhancing liver regeneration markers. Gene expression of Il-6 and Il-10 in the remnant liver was markedly reduced at 6 h after 90% PH in animals receiving encapsulated BMMC compared to controls. This difference, however, was neither reflected by changes in the number of CD68+ cells nor by serum levels of IL6. On the other hand, treated animals presented increased caspase activity and gene expression in the liver. Taken together, these results suggest that BMMC regulate immune response and promote apoptosis in the liver after 90% PH by paracrine factors. These changes ultimately may be related to the higher survival observed in treated animals, suggesting that BMMC may be a promising alternative to treat acute liver failure.

Encapsulated Whole Bone Marrow Cells Improve Survival in Wistar Rats after 90% Partial Hepatectomy

Background and Aims. The use of bone marrow cells has been suggested as an alternative treatment for acute liver failure. In this study, we investigate the effect of encapsulated whole bone marrow cells in a liver failure model. Methods. Encapsulated cells or empty capsules were implanted in rats submitted to 90% partial hepatectomy. The survival rate was assessed. Another group was euthanized at 6, 12, 24, 48, and 72 hours after hepatectomy to study expression of cytokines and growth factors. Results. Whole bone marrow group showed a higher than 10 days survival rate compared to empty capsules group. Gene expression related to early phase of liver regeneration at 6 hours after hepatectomy was decreased in encapsulated cells group, whereas genes related to regeneration were increased at 12, 24, and 48 hours. Whole bone marrow group showed lower regeneration rate at 72 hours and higher expression and activity of caspase 3. In contrast, lysosomal-β-glucuronidase activity was elevated in empty capsules group. Conclusions. The results show that encapsulated whole bone marrow cells reduce the expression of genes involved in liver regeneration and increase those responsible for ending hepatocyte division. In addition, these cells favor apoptotic cell death and decrease necrosis, thus increasing survival.

Injured hepatocyte-released microvesicles induce bone marrow-derived mononuclear cells differentiation

The ability of bone marrow-derived mononuclear cells (BMMCs) to differentiate into hepatocyte-like cells under different conditions has been demonstrated previously. In the present study, we investigated the effect of CCl4-injured hepatocytes on the differentiation of the non-adherent (NAD) fraction of BMMCs. Differentiation (cell fate) was analyzed after 2, 6 and 24h of co-culture by gene and protein expression and by urea production. We also evaluated the presence of microvesicles (MVs) in the supernatant of differentiated cells, their content and the ability of these cells to absorb them. Hepatocyte-like characteristics were observed in the NAD cells after 24h of co-culture with injured hepatocytes. Cells that were co-cultured with healthy hepatocytes did not present signs of differentiation at any analyzed time point. Analysis of the supernatant from differentiated cells revealed the presence of MVs carrying hepatocyte-specific mRNAs, including Albumin, Coagulation factor V, Alpha-fetoprotein, and Cytokeratin 18. The incorporation of injured hepatocyte-derived MVs by NAD cells was shown at 24h, suggesting a possible role for MVs in the induction of cell plasticity.

Platelet increases survival in a model of 90% hepatectomy in rats

BACKGROUND & AIMS

Ninety per cent hepatectomy in rodents is a model for acute liver failure. It has been reported that platelets have a strong effect enhancing liver regeneration, because of the production of several growth factors such as serotonin. The aim of this study was to investigate the role of microencapsulated platelets on 90% hepatectomy in rats.

METHODS

Platelets (PLT) were microencapsulated in sodium alginate and implanted in the peritoneum of rats after 90% partial hepatectomy (PH). Control group received empty capsules (EC). Animals were euthanized at 6, 12, 24, 48 and 72 h post PH (n=9-12/group/time) to evaluate liver regeneration rate, mitotic index, liver content, serum and tissue levels of Interleukin 6 (IL-6) and serotonin and its receptor 5-hydroxytryptamine type 2B (5Ht2b). Survival rate in 10 days was evaluated in a different set of animals (n=20/group).

RESULTS

Platelets group showed the highest survival rate despite the lowest liver regeneration rate at any time point. Mitotic and BrdU index showed no difference between groups. However, the number of hepatocytes was higher and the internuclear distance was shorter for PLT group. Liver dry weight was similar in both groups indicating that water was the main responsible factor for the weight difference. Gene expression of IL-6 in the liver was significantly higher in EC group 6 h after PH, whereas 5Ht2b was up-regulated at 72 h in PLT group.

CONCLUSIONS

Platelets enhance survival of animals with 90% PH, probably by an early protective effect on hepatocytes and the increase in growth factor receptors.

Freshly isolated hepatocyte transplantation in acetaminophen-induced hepatotoxicity model in rats

CONTEXT: Hepatocyte transplantation is an attractive therapeutic modality for liver disease as an alternative for orthotopic liver transplantation. OBJECTIVE: The aim of the current study was to investigate the feasibility of freshly isolated rat hepatocyte transplantation in acetaminophen-induced hepatotoxicity model. METHODS: Hepatocytes were isolated from male Wistar rats and transplanted 24 hours after acetaminophen administration in female recipients. Female rats received either 1x10(7) hepatocytes or phosphate buffered saline through the portal vein or into the spleen and were sacrificed after 48 hours. RESULTS: Alanine aminotransferase levels measured within the experiment did not differ between groups at any time point. Molecular analysis and histology showed presence of hepatocytes in liver of transplanted animals injected either through portal vein or spleen. CONCLUSION: These data demonstrate the feasibility and efficacy of hepatocyte transplantation in the liver or spleen in a mild acetaminophen-induced hepatotoxicity model.

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.

From hepatocytes to stem and progenitor cells for liver regenerative medicine: advances and clinical perspectives

The parenchymal liver cell is a unique fully functional metabolic unit that can be used for liver regenerative medicine to restore function of the diseased organ; the aim of the procedure is to prevent progression of end-stage disease. The alternative, orthotopic liver transplantation, is highly intrusive, irreversible and limited by general organ shortage. Mature liver cell - hepatocyte - transplantation has been shown to have short- to medium-term efficacy for correction of miscellaneous inborn errors of metabolism. However, although proof of concept has been established, the procedure has not yet achieved full success, due to limited durability of functional benefit. Hepatocyte procurement is also restricted by organ shortage, and their storage is difficult due to poor tolerance of cryopreservation. Alternative cell sources are therefore needed for development and wider accessibility of cell-based liver regenerative medicine. Besides safety, the main challenge for these alternative cells is to acquire similar levels of functionality once implanted into the target organ. In this respect, liver derived progenitor cells may have some advantages over stem cells derived from other tissues.