Is there an optimal concentration of cotransplanted islets of Langerhans for stimulation of hepatocytes in three dimensional matrices?

Hepatocyte and Islet Cell Cotransplantation on Poly-L-Lactide Matrix for the Treatment of Liver Cirrhosis

The human autologous hepatocyte matrix implant is a promising alternative procedure to counter liver damage. We assessed the outcome of human hepatocytes isolation from cirrhotic liver compared to the clinical and histological scores of disease severity. A total of 11 patients with various clinical scores (CTP and MELD) and histological score (Metavir, fibrosis) of liver cirrhosis were included in the hepatocyte matrix implant clinical phase I study. The liver segment and pancreatic tissue were harvested from each patient, and hepatocytes and cells of islets of Langerhans were isolated. The freshly isolated human hepatocytes were coseeded with the islet cells onto poly(l-lactic acid) (PLLA) scaffolds, cultured, and transplanted back into the patient. Human hepatocytes were isolated from 11 cirrhotic liver specimens with a resulting yield of 1.4 ± 0.5 × 106 cells per gram of the liver specimen and a viability rate of 52 ± 13%. It was found that the yield and viability of the liver cells were not correlated with the clinical and histological scores of the liver cirrhosis. A correlation was found between the hepatocyte yield obtained and the average number of hepatocytes counted in 10 microscopic fields of view. More viable cells were obtained from cirrhotic livers caused by chronic hepatitis B as compared to chronic hepatitis C in the same MELD score range. There was no correlation between the clinical and histological disease severity scores of liver cirrhosis and the outcome of hepatocytes isolation. It seems that the yield could depend on the type of hepatitis underlying the cirrhotic tissue. The study was registered at www.clinicaltrial.gov with the study identifier: NCT01335568.

3D co-culturing model of primary pancreatic islets and hepatocytes in hybrid spheroid to overcome pancreatic cell shortage

Here, a spheroidal 3D co-culture model of primary (rat) pancreatic islets and hepatocytes with uniform size and shape was developed using hemispheric concave microwell arrays. We conducted morphological and functional analyses of hybrid spheroids versus mono-cultures of islets or hepatocytes (controls). For the establishment of a 3D hybrid model, a broad range of cell ratios - 1:1, 1:3, 1:5, 1:7, 3:1, 5:1 and 7:1 mixture - of hepatocytes and pancreatic islets were used. As control, each hepatocyte and pancreatic islet were mono-cultured forming 3D spheroids. The transient morphology of spheroid formation in 9 culture models was observed using optical microscopy. Cell viability under these culture environments was assessed, and the morphologies of the outer and inner porous cell-spheroid structures were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and imaging of stained spheroid sections. The pancreatic islet-specific function of hybrid spheroids was evaluated by measuring insulin secretion and in vivo test by xenotransplantation of encapsulated spheroids in microfibers with a consistent maintenance of normal blood glucose levels over 4 weeks, while liver-specific functions were measured in terms of albumin secretion, urea secretion and cytochrome P450 activity. These diverse observations and evaluations validated the positive and bidirectional effects of co-cultured 3D spheroids. The proposed 3D co-culture model demonstrated that both cells appeared to support each other's functions strongly in spheroids, even though smaller proportions of each cell type was evaluated compared to mono-culture models, suggesting that the proposed model could help overcome the problem of cell shortages in clinical applications.

Hepatic tissue engineering: from transplantation to customized cell-based liver directed therapies from the laboratory

Today, liver transplantation is still the only curative treatment for liver failure due to end-stages liver diseases. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, e.g. liver tissue engineering, are under investigation with the aim, that in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients. Using cells instead of organs in this setting should permit (i) expansion of cells in an in vitro phase, (ii) genetic or immunological manipulation of cells for transplantation, (iii) tissue typing and cryopreservation in a cell bank, and (iv) the ex vivo genetic modification of patient's own cells prior re-implantation. Function and differentiation of liver cells are influenced by the three-dimensional organ architecture. The use of polymeric matrices permits the three dimensional formation of a neo-tissue and specific stimulation by adequate modification of the matrix-surface which might be essential for appropriate differentiation of transplanted cells. Additionally, culturing hepatocytes on three dimensional matrices permits culture in a flow bioreactor system with increased function and survival of the cultured cells. Based on bioreactor technology, bioartificial liver devices (BAL) are developed for extracorporeal liver support. Although BALs improved clinical and metabolic conditions, increased patient survival rates have not been proven yet. For intra-corporeal liver replacement, a concept which combines Tissue Engineering using three-dimensional, highly porous matrices with cell transplantation could be useful. In such a concept, whole liver mass transplantation, long term engraftment and function as well as correction of a metabolic defect in animal models could be achieved with a principally reversible procedure. Future studies have to investigate, which environmental conditions and transplantation system would be most suitable for the development of artificial functional liver tissue including blood supply for a potential use in a clinical setting.

Hepatic tissue engineering: from transplantation to customized cell-based liver directed therapies from the laboratory

Today, liver transplantation is still the only curative treatment for liver failure due to end-stages liver diseases. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, e.g. liver tissue engineering, are under investigation with the aim, that in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients. Using cells instead of organs in this setting should permit (i) expansion of cells in an in vitro phase, (ii) genetic or immunological manipulation of cells for transplantation, (iii) tissue typing and cryopreservation in a cell bank, and (iv) the ex vivo genetic modification of patient's own cells prior re-implantation. Function and differentiation of liver cells are influenced by the three-dimensional organ architecture. The use of polymeric matrices permits the three dimensional formation of a neo-tissue and specific stimulation by adequate modification of the matrix-surface which might be essential for appropriate differentiation of transplanted cells. Additionally, culturing hepatocytes on three dimensional matrices permits culture in a flow bioreactor system with increased function and survival of the cultured cells. Based on bioreactor technology, bioartificial liver devices (BAL) are developed for extracorporeal liver support. Although BALs improved clinical and metabolic conditions, increased patient survival rates have not been proven yet. For intra-corporeal liver replacement, a concept which combines Tissue Engineering using three-dimensional, highly porous matrices with cell transplantation could be useful. In such a concept, whole liver mass transplantation, long term engraftment and function as well as correction of a metabolic defect in animal models could be achieved with a principally reversible procedure. Future studies have to investigate, which environmental conditions and transplantation system would be most suitable for the development of artificial functional liver tissue including blood supply for a potential use in a clinical setting.

Liver-specific gene expression in mesenchymal stem cells is induced by liver cells

AIM: The origin of putative liver cells from distinct bone marrow stem cells, e.g. hematopoietic stem cells or multipotent adult progenitor cells was found in recent in vitro studies. Cell culture experiments revealed a key role of growth factors for the induction of liver-specific genes in stem cell cultures. We investigated the potential of rat mesenchymal stem cells (MSC) from bone marrow to differentiate into hepatocytic cells in vitro. Furthermore, we assessed the influence of cocultured liver cells on induction of liver-specific gene expression.

METHODS: Mesenchymal stem cells were marked with green fluorescent protein (GFP) by retroviral gene transduction. Clonal marked MSC were either cultured under liver stimulating conditions using fibronectin-coated culture dishes and medium supplemented with SCF, HGF, EGF, and FGF-4 alone, or in presence of freshly isolated rat liver cells. Cells in cocultures were harvested and GFP+ or GFP- cells were separated using fluorescence activated cell sorting. RT-PCR analysis for the stem cell marker Thy1 and the hepatocytic markers CK-18, albumin, CK-19, and AFP was performed in the different cell populations.

RESULTS: Under the specified culture conditions, rat MSC cocultured with liver cells expressed albumin-, CK-18, CK-19, and AFP-RNA over 3 weeks, whereas MSC cultured alone did not show liver specific gene expression.

CONCLUSION: The results indicate that (1) rat MSC from bone marrow can differentiate towards hepatocytic lineage in vitro, and (2) that the microenvironment plays a decisive role for the induction of hepatic differentiation of rMSC.

Influence of pancreatic islets on spheroid formation and functions of hepatocytes in hepatocyte-pancreatic islet spheroid culture

Hepatotrophic stimulation of hepatocytes is necessary to preserve long-term function of hepatocytes in hepatocyte transplantation and bioartificial liver system. The main source of hepatotrophic factors in portal venous blood seems to be the pancreatic islets. It was also reported that hepatocyte spheroids, tightly packed multicellular aggregates, showed enhanced liver-specific activities and a prolonged differentiated state compared with cells that were maintained as a monolayer. On the basis of these two facts, the authors tried to form hepatocyte-pancreatic islet spheroids and to evaluate the influence of pancreatic islets on spheroid formation and functions of hepatocytes in spheroid culture. Hepatocytes and pancreatic islet cells were harvested from adult male Sprague-Dawley rats weighing 200-250 g. Hepatocytes were cultured in spinner flasks with either basic nonstimulated medium (hepatocytes only [group BH] and cocultures with islet cells [group BI]) or hormone-stimulated medium (hepatocytes only [group HH] and cocultures with islet cells [group HI]). The size and morphology of spheroids, as determined by phase-contrast microscopy, and liver-specific functions, such as albumin secretion, urea synthesis, and ammonia removal, were compared among groups. The results were as follows: the size of spheroids, 66 +/- 53.4 microm, in group BH on day 2 was smaller than in group BI (179 +/- 66.2 microm on day 2, p < 0.05). In group BI, group HH, and group HI, smooth spheroids were observed on culture day 2. However, in group BH rugged incomplete aggregates were observed on the same day. In groups with basal medium, group BI showed better results in terms of hepatocyte-specific function such as albumin secretion, urea synthesis, and ammonia removal compared with group BH on days 2 and 3 (p < 0.05). In groups with hormone-defined medium, cocultures had no impact on albumin secretion rate, urea synthetic rate, and ammonia removal rate. In conclusion, we made a new type of hepatocyte-pancreatic islet spheroid, using a rotational culture method. Pancreatic islets in a spheroid culture system stimulated hepatocyte spheroid formation and some hepatocyte-specific functions in vitro.

Microencapsulated hepatocytes and islets as in vivo bioartificial liver support system

AIM: To confirm the xenotransplantation of microencapsulated hepatocytes and islets as a temporary bioartificial liver support system for mice with acute liver failure (ALF).

METHODS: Mice were rendered ALF by a single intra-peritoneal injection of D-galactosamine (D-gal) and their tail blood was sampled to examine differences in blood ALT, albumin (ALB), total bilirubin (TB) and glucose (GLU) between 4 experimental groups. Rat hepatocytes and islets were collected and microencapsulated referring to both Sun’s and Fritschy’s methods. Mice were grouped into control group (CG), free hepatocyte group (FHG), microencapsulated hepatocyte group (MHG) and microencapsulated hepatocyte plus islet group (HIG). Tissue samples were subjected to microscopic and electron microscopic (EM) examinations.

RESULTS: The highest survival was observed in HIG, surprisingly at 100% (16/16), while the lowest was in CG at 12.5% (2/16), with inter-group statistical difference P < 0.05. ALT levels revealed no statistical difference between groups but the ALB level of HIG descended by the slightest margin {q = (0.54, 0.24, 1.33), P < 0.05} at the time when it reached the lowest point in all groups. TB of HIG returned to normal reference range (NRR) statistically sooner than that of others after a fierce elevation. No statistical inter-group difference was observed in GLU levels. Fusion between hepatocytes and beta cells was demonstrated giving rise to theoretical assumptions.

CONCLUSION: Hepatocytes to be microencapsulated together with islets should be a preferred in vivo hepatic functional supporting system, which can dramatically prolong survival and improve living status.

Hepatocytes transplantation in rats with acute hepatic failure

AIM: To study the effect of allogeneic hepatocytes transplantation (HcT) intraperitoneally, intrasplenically or through vena portae in rats with acute hepatic failure (AHF) induced by D-galactosamine (D-gal).

METHODS: AHF rats were induced by D-gal. HcT was carried out 60h after intoxication, and all rats were divided into six groups: GroupⅠ received 2×10¹⁰/L hepatocytes 1 mL intraperitoneally with cyclosporin A (CsA) at 10 mg/kg simultaneously; Group Ⅱ received 1 mL normal saline (NS) intraperitoneally with CsA10 mg/kg; Group Ⅲ received 2×10¹⁰/L hepatocytes 1 mL through vena portae; Group Ⅳreceived 1mL NS through vena portae; Group Ⅴreceived 2×10¹⁰/L hepatocytes 1 mL intrasplenically; Group Ⅵ received 1 mL NS intrasplenically. After 1 wk the survival rates, liver function and liver histology of all rats were observed.

RESULTS: The survival rate of Group Ⅰ was higher than that of GroupⅡ (60 % vs 20%, P < 0.01), and their liver function and liver histology were obviously improved as compared with GroupⅡ. Similarly, the survival rate of Group Ⅴ was higher than that of Group Ⅵ (47% vs 20%, P < 0.05), and the liver function and liver histology were also improved in GroupⅤas compared with Group Ⅵ. On the other hand, the survival rate of Group Ⅲ was similar to that of GroupⅥ (20% vs 13.3%, P > 0.05), and their liver function and liver histology were also not improved significantly as compared with Group Ⅱ.

CONCLUSION: After HcT intraperitoneally or intrasplenically, the survival rates of AHF rats intoxicated with D-gal are increased, and the liver function and histology are also improved. On the contrary, the survival rate, liver function and liver histology of AHF rats through vena portae HcT are not improved.

Hepatocyte transplantation using biodegradable matrices in ascorbic acid-deficient rats: comparison with heterotopically transplanted liver grafts

BACKGROUND

Hepatocyte transplantation using polymeric matrices is under investigation as an alternative therapy for metabolic liver diseases. Long-term engraftment of hepatocytes in polymers has been demonstrated. However, the metabolic activity of hepatocytes in such devices has never been assessed in direct comparison with liver grafts.

METHODS

Hepatocyte and partial liver transplantation were evaluated in the scurvy-prone osteogenic disorder Shionogi rat model. Biodegradable poly glycolic acid matrices seeded with hepatocytes equivalent to 20% of the recipient's liver mass, or 20% liver grafts were heterotopically transplanted into ascorbic acid- (AsA) deficient recipients. Recipients of cell-free matrices or AsA-deficient liver grafts served as controls. Recipients were set on AsA-free diet after transplantation. Plasma AsA levels, AsA concentrations in liver and adrenal gland tissue, and body weight ratios were assessed and H&E histology was performed.

RESULTS

Recipients from the control groups showed symptoms of scurvy at 1 month after cessation of AsA supply. Hepatocyte transplantation and auxiliary liver transplantation prevented symptoms of scurvy and increased plasma and tissue AsA levels and body weight ratios. AsA levels in recipients of 20% liver grafts were comparable to normal control animals.

CONCLUSIONS

Hepatocytes transplanted in polymeric matrices are able to compensate for liver-based metabolic deficiencies. Hepatocyte transplantation improves plasma AsA levels in AsA-deficient recipients. However, auxiliary liver grafts are superior to hepatocyte grafts in improving metabolic parameters. Further research work is needed to increase the efficiency of liver cell transplantation with regard to a clinical application.