Liver pathology and cell proliferation after calcineurin inhibitors and antiproliferative drugs following partial hepatectomy in rats

Liver Regeneration after Hepatectomy and Partial Liver Transplantation

The liver is a unique organ with an abundant regenerative capacity. Therefore, partial hepatectomy (PHx) or partial liver transplantation (PLTx) can be safely performed. Liver regeneration involves a complex network of numerous hepatotropic factors, cytokines, pathways, and transcriptional factors. Compared with liver regeneration after a viral- or drug-induced liver injury, that of post-PHx or -PLTx has several distinct features, such as hemodynamic changes in portal venous flow or pressure, tissue ischemia/hypoxia, and hemostasis/platelet activation. Although some of these changes also occur during liver regeneration after a viral- or drug-induced liver injury, they are more abrupt and drastic following PHx or PLTx, and can thus be the main trigger and driving force of liver regeneration. In this review, we first provide an overview of the molecular biology of liver regeneration post-PHx and -PLTx. Subsequently, we summarize some clinical conditions that negatively, or sometimes positively, interfere with liver regeneration after PHx or PLTx, such as marginal livers including aged or fatty liver and the influence of immunosuppression.

Alloresponses of Mixed Lymphocyte Hepatocyte Culture to Immunosuppressive Drugs as an In-Vitro Model of Hepatocyte Transplantation

Background

Hepatocyte transplantation (HCTx) has the potential for the treatment of end-stage liver disease. However, failure of engraftment and the long-term acceptance of cellular allografts remain significant challenges for its clinical application. The aim of this study was to investigate the efficacy of the immunosuppressive agents, Cyclosporine, Everolimus, and Belatacept to suppress the alloresponse of primary human hepatocytes in a mixed lymphocyte-hepatocyte culture (MLHC) and their potential hepatotoxicity in vitro.

Material/Methods

Primary human hepatocytes were co-cultured with allogeneic peripheral blood mononuclear cells (PBMCs) in an MLHC. Proliferative alloresponses were determined by flow cytometry, and cytokine secretion was measured using Luminex-based multiplex technology. Using an MLHC, the alloresponses of primary human hepatocytes were compared in the presence and absence of Cyclosporine, Everolimus, and Belatacept. Cultured primary human hepatocytes were assessed for the production of albumin, urea, aspartate transaminase (AST) and DNA content. Metabolic activity was determined with the MTT assay.

Results

Immune responses induced by primary human hepatocytes were effectively suppressed by Cyclosporine, Everolimus, and Belatacept. Everolimus significantly reduced the metabolic activity of primary human hepatocytes in vitro, suggesting impairment of cell viability. However, further functional analysis showed no significant differences between treated and untreated controls.

Conclusions

Cyclosporine, Everolimus, and Belatacept suppressed the alloresponse of primary human hepatocytes in an MLHC without significant cytotoxicity or functional cell impairment.

Immunological aspects of liver cell transplantation

Within the field of regenerative medicine, the liver is of major interest for adoption of regenerative strategies due to its well-known and unique regenerative capacity. Whereas therapeutic strategies such as liver resection and orthotopic liver transplantation (OLT) can be considered standards of care for the treatment of a variety of liver diseases, the concept of liver cell transplantation (LCTx) still awaits clinical breakthrough. Success of LCTx is hampered by insufficient engraftment/long-term acceptance of cellular allografts mainly due to rejection of transplanted cells. This is in contrast to the results achieved for OLT where long-term graft survival is observed on a regular basis and, hence, the liver has been deemed an immune-privileged organ. Immune responses induced by isolated hepatocytes apparently differ considerably from those observed following transplantation of solid organs and, thus, LCTx requires refined immunological strategies to improve its clinical outcome. In addition, clinical usage of LCTx but also related basic research efforts are hindered by the limited availability of high quality liver cells, strongly emphasizing the need for alternative cell sources. This review focuses on the various immunological aspects of LCTx summarizing data available not only for hepatocyte transplantation but also for transplantation of non-parenchymal liver cells and liver stem cells.

Sirolimus influence on hepatectomy-induced liver regeneration in rats

OBJECTIVE: To evaluate the influence of sirolimus on liver regeneration triggered by resection of 70% of the liver of adult rats. METHODS: we used 40 Wistar rats randomly divided into two groups (study and control), each group was divided into two equal subgroups according to the day of death (24 hours and seven days). Sirolimus was administered at a dose of 1mg/kg in the study group and the control group was given 1 ml of saline. The solutions were administered daily since three days before hepatectomy till the rats death to removal of the regenerated liver, conducted in 24 hours or 7 days after hepatectomy. Liver regeneration was measured by the KWON formula, by thenumber of mitotic figures (hematoxylin-eosin staining) and by the immunohistochemical markers PCNA and Ki-67. RESULTS: there was a statistically significant difference between the 24h and the 7d groups. When comparing the study and control groups in the same period, there was a statistically significant variation only for Ki-67, in which there were increased numbers of hepatocytes in cell multiplication in the 7d study group compared with the 7d control group (p = 0.04). CONCLUSION: there was no negative influence of sirolimus in liver regeneration and there was a positive partial effect at immunohistochemistry with Ki-67.

The effects of anesthetic regimen in 90% hepatectomy in rats

PURPOSE: To evaluate the influence of the anesthetic regimen on anesthetic recovery, survival, and blood glucose levels following a 90% partial hepatectomy in rats. METHODS: Thirty adult male Wistar rats were divided into two groups according to their anesthetic regimens: intraperitoneal ketamine and xylazine or inhaled isoflurane. In order to prevent hypoglycemia, glucose was administered intraperitoneally and glucose (20%) was added to the drinking water. RESULTS: Anesthetic recovery time was longer in the ketamine and xylazine group. The survival rate after 72 hours was lower (log rank=0.0001) in the ketamine and xylazine group (0.0%) than in the isoflurane group (26.7%). The blood glucose after six hours was lower (p=0.017) in the ketamine and xylazine group (63±31.7 mg/dL) than in the isoflurane group (98±21.2 mg/dL). The prolonged anesthesia recovery time associated with ketamine and xylazine decreased the survival rate and blood glucose levels after 90% hepatectomy. CONCLUSION: Isoflurane anesthesia reduced the recovery time and incidence of hypoglycemia and increased the survival rate in the early hours, providing a therapeutic window that is suitable for experimental studies.

The impact of sirolimus on hepatocyte proliferation after living donor liver transplantation

BACKGROUND

There is a lack of data on the use of sirolimus after partial liver transplantation, especially regarding its impact on post-transplant regeneration.

METHODS

We reviewed adult living donor transplantations, with de novo sirolimus (n = 7) and without sirolimus (n = 21). Liver biopsies were stained for KI-67, a proliferation marker. Controls included specimens with normal liver parenchyma (n = 13).

RESULTS

Both groups had similar demographics, graft and patient survival and complication rates. During the first six wk and over the whole first year post-transplant, the use of sirolimus was associated with lower levels of hepatocyte proliferation compared to sirolimus-free patients, (overall, 0.3 [0-7.2] vs. 3 [0-49] KI-67 positive hepatocytes per high power field, p ≤ 0.05). The levels observed in the sirolimus group were similar to those seen in non-transplanted control patients with normal parenchyma (0.2 [0-1.3], p = NS). Post-transplant hepatocyte proliferation correlated with the serum levels of sirolimus (p ≤ 0.05), but not with those of tacrolimus or with the dose of mycophenolate mofetil (p = 0.9 and 0.3, respectively).

CONCLUSIONS

These data suggest that sirolimus is associated with decreased post-transplant hepatocyte proliferation. The clinical significance of this observation remains to be fully determined.

Rapamycin inhibits hepatectomy-induced stimulation of metastatic tumor growth by reduction of angiogenesis, microvascular blood perfusion, and tumor cell proliferation

BACKGROUND

Liver regeneration after hepatectomy stimulates metastatic tumor growth through the release of potent growth factors. In the signaling cascades of several growth factors, mTOR is a downstream mediator, triggering cell survival and cell cycle progression. The mTOR inhibitor rapamycin (RAPA) has been shown to exhibit potent antitumor activities. However, it is unknown whether RAPA is capable of exerting these effects under the conditions of hepatectomy-associated liver regeneration. We therefore analyzed the effect of RAPA and cyclosporine A (CyA) on tumor growth characteristics after major hepatectomy using a mouse model of colorectal metastasis.

METHODS

Tumor growth was studied by using GFP-transfected CT26.WT colorectal cancer cells, which were implanted into the dorsal skinfold chambers of BALB/c-mice after 70% hepatectomy. The animals were treated daily with RAPA (1.5 mg/kg) or CyA (10 mg/kg). Tumors were analyzed for angiogenesis, microvascular blood perfusion, cell proliferation, apoptotic cell death, and tumor growth.

RESULTS

RAPA significantly inhibited tumor growth compared with CyA and sham treatment. This was associated with a decreased microvascular density within the tumors and a markedly reduced microvascular blood perfusion. CyA only slightly reduced angiogenesis and tumor growth. The effects of RAPA were associated with a significant reduction of tumor cell proliferation, whereas manifestation of apoptotic cell death was not affected by the immunosuppressive treatment regimen.

CONCLUSIONS

RAPA is capable of inhibiting angiogenesis, microvascular blood perfusion, and tumor growth of colorectal metastasis during hepatectomy-associated liver regeneration. Thus, targeting mTOR might represent an interesting strategy to prevent tumor recurrence after hepatectomy for colorectal metastasis.

Survivin is upregulated during liver regeneration in rats and humans and is associated with hepatocyte proliferation

BACKGROUND

Survivin regulates cell division and inhibits apoptosis. Liver regeneration is a complex process involving both proliferation and apoptosis. The role of survivin is not well elucidated and no data exist in humans.

METHODS

Seventy per cent liver resection was used to investigate liver regeneration in rats. Survivin was identified by means of reverse transcriptase polymerase chain reaction, Western blotting and immunohistochemistry. Proliferation and apoptosis were quantified. Liver biopsies from 33 patients who underwent living donor liver transplantation were used to study survivin immuno-expression, proliferation and apoptosis within the first 17 days after transplantation. Seven healthy donors served as controls.

RESULTS

Survivin transcript and protein were significantly upregulated in rat hepatocytes after 24-72 h during regeneration and showed a significant correlation with proliferation but not with apoptosis. In humans, survivin was nearly absent in donor and reperfused liver tissue but increased significantly 5-7 days after transplantation and correlated with proliferation but not with apoptosis.

CONCLUSIONS

Survivin is upregulated in human and rodent liver regeneration and correlates with proliferation, suggesting an association of survivin and cell division.

Effect of the immunosuppressants on hepatocyte proliferation and apoptosis in a young animal model of liver regeneration: an immunohistochemical study using tissue microarrays

Hepatocyte proliferation and apoptosis (programmed cell death) occur during the liver parenchyma regeneration and the liver size modeling is mainly controlled by hepatocyte apoptosis. The purpose of the present study was to verify the influence of immunosuppressant drugs on these phenomena by utilizing tissue microarray techniques. Thirty-six weaning rats (age 21-23 days, weight 30-50 g) were divided into six groups: control, sham, hepatectomy, hepatectomy plus solumedrol, hepatectomy plus CsA, and hepatectomy plus Tac. The animals were killed one day after hepatectomy, and the remnant livers were weighed and harvested for tissue microarray sections. Liver cell proliferation was evaluated by staining for PCNA and apoptosis was detected by the TUNEL method. It was verified that CsA promoted a decrease in the liver weight, Tac and CsA decreased the proliferation index of hepatocytes, and glucocorticoid had no significant effects. The apoptosis index was not altered by hepatectomy or immunosuppressants. Our data indicate that, in the growing rat, CsA and Tac have negative effects on hepatocyte proliferation and have no effect on the hepatocyte apoptosis.

Effect of the immunosuppressants on hepatocyte cells proliferation and apoptosis during liver regeneration after hepatectomy - molecular studies

The regeneration and remodeling of the transplanted liver is the result of hepatocyte proliferation and apoptosis (programmed cell death). The purpose of this study was to verify the influence of immunosuppressants on the expression levels of genes: IL-6 (regulator of hepatocyte proliferation), pro-apoptotic (Bak and Bax) and anti-apoptotic (Bcl-Xl and Bcl-2). 36 newborn suckling rats (age 5-7 days, weight 6-10 g) were divided into four groups: hepatectomy, hepatectomy plus methylprednisolone, hepatectomy plus CsA and hepatectomy plus Tac. The same experiments were performed in 24 weaning rats (age 21-23 days, weight 30-50 g). The animals were killed one day after the hepatectomy and the remnant livers were analyzed. The livers of all animals exhibited histological changes of liver regeneration. The immunosuppressants did not promote any alteration on IL-6 gene expression levels. Methylprednisolone and CsA increased the expression levels of Bak gene in newborn rats. However, methylprednisolone and Tac promoted increased expression levels of Bcl-2 in all groups. We hypothesize that these effects explain the efficacy of these drugs on the treatment of acute and chronic liver rejection as the expression of Bcl-2 in cholangiocytes is decreased as a consequence of bile duct lesions

Effects of immunosuppressive drugs on in vitro neogenesis of human islets: mycophenolate mofetil inhibits the proliferation of ductal cells

Assuming that neogenesis contributes to long-term function of islet grafts, it is important to study the effects of immunosuppressive drugs on precursor cell proliferation and differentiation. We examined the effects of low-dose immunosuppressive drugs on these processes in vitro. Immunosuppressive drugs, including sirolimus, tacrolimus, mycophenolate mofetil (MMF), daclizumab and their combinations were tested in parallel culture wells through either the expansion phase (5-7 days) or the entire culture period (4-5 weeks). MMF, alone or in combination with sirolimus or tacrolimus, severely hampered duct-cell proliferation by 8-fold during the expansion period, and significantly reduced the total DNA content by about 40% after 5-week culture. After 4-5 week exposure to different drugs, only sirolimus and daclizumab showed no adverse effects on insulin content, whereas significant reductions of 30-60% in insulin content were seen in all other experimental groups. Only tacrolimus decreased the insulin content per DNA, as well as the proportion of insulin-positive cells. In conclusion, MMF has a potent inhibitory effect on neogenesis primarily through an antiproliferative effect on the precursors, whereas tacrolimus mainly affects beta-cell differentiation. Sirolimus and daclizumab have no adverse effects on these parameters. The immunosuppressive protocol may be an important determinant of long-term clinical islet graft function.

Beneficial effects of FK506 for experimental temporal lobe epilepsy

FK506, originally classified as an immunosuppressant, may also be implicated in some events in the central nervous system. FK506 elicits both neuroprotective and neurotrophic effects in vitro. FK506 is neuroprotective for focal cerebral ischemia, but it is not clear whether FK506 has neuroprotective effects for other brain diseases. In this study, we investigated possible neuroprotective effects of FK506 in experimental temporal lobe epilepsy (TLE) induced by kainic acid (KA) or trimethyltin (TMT). In rat models, we observed marked protection against seizures, abnormal behaviors, and accompanying delayed neuronal damage in the hippocampus by the systemic injection of FK506.