Onset of liver regeneration after subtotal resection is inhibited by the use of new immunosuppressive drugs

Deletion of mTOR in liver epithelial cells enhances hepatic metastasis of colon cancer

Activation of the mechanistic target of rapamycin (mTOR) pathway is frequently found in cancer, but mTOR inhibitors have thus far failed to demonstrate significant antiproliferative efficacy in the majority of cancer types. Besides cancer cell-intrinsic resistance mechanisms, it is conceivable that mTOR inhibitors impact on non-malignant host cells in a manner that ultimately supports resistance of cancer cells. Against this background, we sought to analyze the functional consequences of mTOR inhibition in hepatocytes for the growth of metastatic colon cancer. To this end, we established liver epithelial cell (LEC)-specific knockout (KO) of mTOR (mTOR^LEC ) mice. We used these mice to characterize the growth of colorectal liver metastases with or without partial hepatectomy to model different clinical settings. Although the LEC-specific loss of mTOR remained without effect on metastasis growth in intact liver, partial liver resection resulted in the formation of larger metastases in mTOR^LEC mice compared with wildtype controls. This was accompanied by significantly enhanced inflammatory activity in LEC-specific mTOR KO livers after partial liver resection. Analysis of NF-ĸB target gene expression and immunohistochemistry of p65 displayed a significant activation of NF-ĸB in mTOR^LEC mice, suggesting a functional importance of this pathway for the observed inflammatory phenotype. Taken together, we show an unexpected acceleration of liver metastases upon deletion of mTOR in LECs. Our results support the notion that non-malignant host cells can contribute to resistance against mTOR inhibitors and encourage testing whether anti-inflammatory drugs are able to improve the efficacy of mTOR inhibitors for cancer therapy. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

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.

mTOR signaling in liver regeneration: Rapamycin combined with growth factor treatment

AIM: To investigate the effects of mammalian target of rapamycin (mTOR) inhibition on liver regeneration and autophagy in a surgical resection model.

METHODS: C57BL/6 mice were subjected to a 70% partial hepatectomy (PH) and treated intraperitoneally every 24 h with a combination of the mTOR inhibitor rapamycin (2.5 mg/kg per day) and the steroid dexamethasone (2.0 mg/kg per day) in phosphate buffered saline (PBS) or with PBS alone as vehicle control. In the immunosuppressant group, part of the group was treated subcutaneously 4 h prior to and 24 h after PH with a combination of human recombinant interleukin 6 (IL-6; 500 μg/kg per day) and hepatocyte growth factor (HGF; 100 μg/kg per day) in PBS. Animals were sacrificed 2, 3 or 5 d after PH and liver tissue and blood were collected for further analysis. Immunohistochemical staining for 5-Bromo-2’-deoxyuridine (BrdU) was used to quantify hepatocyte proliferation. Western blotting was used to detect hepatic microtubule-associated protein 1 light chain 3 (LC3)-II protein expression as a marker for autophagy. Hepatic gene expression levels of proliferation-, inflammation- and angiogenesis-related genes were examined by real-time reverse transcription-polymerase chain reaction and serum bilirubin and transaminase levels were analyzed at the clinical chemical core facility of the Erasmus MC-University Medical Center.

RESULTS: mTOR inhibition significantly suppressed regeneration, shown by decreased hepatocyte proliferation (2% vs 12% BrdU positive hepatocyte nuclei at day 2, P < 0.01; 0.8% vs 1.4% at day 5, P = 0.02) and liver weight reconstitution (63% vs 76% of initial total liver weight at day 3, P = 0.04), and furthermore increased serum transaminase levels (aspartate aminotransferase 641 U/L vs 185 U/L at day 2, P = 0.02). Expression of the autophagy marker LC3-II, which was reduced during normal liver regeneration, increased after mTOR inhibition (46% increase at day 2, P = 0.04). Hepatic gene expression showed an increased inflammation-related response [tumor necrosis factor (TNF)-α 3.2-fold upregulation at day 2, P = 0.03; IL-1Ra 6.0-fold upregulation at day 2 and 42.3-fold upregulation at day 5, P < 0.01] and a reduced expression of cell cycle progression and angiogenesis-related factors (HGF 40% reduction at day 2; vascular endothelial growth factor receptor 2 50% reduction at days 2 and 5; angiopoietin 1 60% reduction at day 2, all P≤ 0.01). Treatment with the regeneration stimulating cytokine IL-6 and growth factor HGF could overcome the inhibitory effect on liver weight (75% of initial total liver weight at day 3, P = 0.02 vs immunosuppression alone and P = 0.90 vs controls) and partially reversed gene expression changes caused by rapamycin (TNF-α and IL-1Ra levels at day 2 were restored to control levels). However, no significant changes in hepatocyte proliferation, serum injury markers or autophagy were found.

CONCLUSION: mTOR inhibition severely impairs liver regeneration and increases autophagy after PH. These effects are partly reversed by stimulation of the IL-6 and HGF pathways.

Imunossupressão com tacrolimus favorece a regeneração hepática induzida por hepatectomia ampla em ratos

OBJETIVO: Avaliar em dois momentos distintos da regeneração hepática a influência do Tacrolimus sobre o fenômeno da regeneração hepática desencadeada pela ressecção de 70% do parênquima hepático em ratos plenamente desenvolvidos. MÉTODOS: Utilizaram-se 40 ratos Wistar com peso médio de 510,08 g ± 11.66 g distribuidos aleatoriamente em dois grupos de 20, cada grupo subdividido em dois subgrupos conforme o dia da morte após a hepatectomia. De acordo com o grupo os animais receberam por gavagem solução aquosa de Tacrolimus 0,1 mg/kg/dia ou solução salina no mesmo volume. Após três dias de pré-terapia todos foram submetidos à hepatectomia de 70% pela ressecção dos lobos hepáticos mediano e lateral esquerdo que foram pesados para posterior cálculo da regeneração hepática pela fórmula de Kwon. Vinte e quatro horas ou sete dias após a hepatectomia, 10 animais de cada grupo foram mortos, os fígados remanescentes (regenerados) foram pesados e amostrados para realização de índice mitótico por hematoxilina-eosina e estudo imunoistoquímico com os marcadores PCNA e Ki-67. RESULTADOS: Os animais que receberam tacrolimus mostraram índice maior de regeneração hepática, atingindo significância estatística quando comparado ao subgrupo de animais mantidos com placebo quando analisados pelos parâmetros: fórmula de Kwon, índice mitótico e marcador PCNA. A tendência para o marcador Ki-67 foi idêntica aos outros parâmetros mas não alcançou significância estatística. CONCLUSÃO: A imunossupressão com tacrolimus possui efeito estimulatório no processo de regeneração hepática desencadeado pela hepatectomia 70% em ratos Wistar adultos, plenamente desenvolvidos.

Imunossupressão com tacrolimus favorece a regeneração hepática induzida por hepatectomia extensa em ratos

RACIONAL: A regeneração hepática representa o resultado de respostas fisiológicas que ocorrem após perdas de parênquima, como consequência de agressões tóxico-medicamentosas, infecciosas, traumáticas ou cirúrgicas. OBJETIVO: Avaliar, em dois momentos distintos da regeneração hepática, a influência do tacrolimus sobre o fenômeno da regeneração hepática desencadeada pela ressecção de 70% do parênquima hepático em ratos plenamente desenvolvidos. MÉTODO: Utilizaram-se 40 ratos Wistar com peso médio de 510,08 g ± 11.66 g divididos aleatoriamente em dois grupos de 20 (Estudo e Controle), cada grupo subdividido em dois subgrupos conforme o dia da morte após a hepatectomia (24 horas e 7 dias). De acordo com o grupo os animais receberam por gavagem, diariamente, iniciando três dias antes da hepatectomia e prolongando-se por todo o período de observação, solução aquosa de tacrolimus 0,1 mg/kg/dia ou solução salina no mesmo volume. Após três dias de pré-terapia todos foram submetidos à hepatectomia de 70% pela ressecção dos lobos hepáticos mediano e lateral esquerdo que foram pesados para posterior cálculo da regeneração hepática pela fórmula de Kwon. Vinte e quatro horas ou sete dias após a hepatectomia, 10 animais de cada grupo foram mortos, os fígados remanescentes (regenerados) foram pesados e amostrados para realização de índice mitótico por hematoxilina-eosina e estudo imunoistoquímico com os marcadores PCNA e Ki-67. RESULTADOS: Os animais que receberam tacrolimus mostraram índice maior de regeneração hepática, atingindo significância estatística quando comparado ao subgrupo de animais mantidos com placebo quando analisados pelos parâmetros: fórmula de Kwon, índice mitótico e marcador PCNA. A tendência para o marcador Ki-67 foi idêntica aos outros parâmetros, mas não alcançou significância estatística. CONCLUSÕES: A imunossupressão com tacrolimus possui efeito estimulante no processo de regeneração hepática desencadeado pela hepatectomia 70% em ratos Wistar adultos, plenamente desenvolvidos.

Optimal administration of tacrolimus in reduced-size liver

The optimal administration of immunosuppressants such as tacrolimus (Tac) for small-for-size (SFS) grafts, where the functional liver mass is small and must regenerate, has not been reported so far. The aim of this study is to clarify the characteristics of Tac metabolism according to liver volume. Seven-week-old male Wistar rats were randomly divided into three groups: (1) Tac administrated and 70% Hx group (Tac 70% Hx group), (2) Tac administrated and 90% Hx group (Tac 90% Hx group), and (3) vehicle administrated and 90% Hx group (control 90% Hx group). In both the Tac groups, Tac (0.3 mg/kg) was given daily for 3 days before operation, and daily after surgery until sacrifice (each time point; n = 5). The plasma concentration of Tac (trough level), as well as liver toxicity, were measured. The plasma concentration of Tac in the Tac 90% Hx group was significantly higher than in the Tac 70% Hx group from 24 to 72 h after operation. Furthermore, expression of CYP3AII mRNA was significantly lower in the Tac 90% Hx group than in the Tac 70% Hx group. Regarding the liver toxicity, there was no significant difference in both the Tac 90% Hx and the control 90% Hx groups. In this experimental study, the plasma concentration of Tac was dependent on the remnant liver volume. Therefore, special attention in regard to Tac administration should also be taken for patients with SFS grafts in living-donor liver transplantation (LDLT).

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

Pharmacokinetics of cyclosporine A after massive hepatectomy: a hint for small-for-size graft in living donor liver transplantation

In living donor liver transplantation, graft size is very important, and various studies have been conducted regarding these problems in small-for-size (SFS) grafts. The administration of immunosuppressants for SFS graft, in which the functional liver mass is small and necessary for excessive liver regeneration, has not been reported so far. The aims of this study were to investigate the optimal administration of cyclosporine (CyA) and characteristics of metabolism of CyA, according to liver volume. Seven-week-old male Wister rats were randomly divided into four groups: two CyA-administered groups (CyA groups), 70% and 90% hepatectomy (Hx); and two control groups, 70% and 90% Hx. The 70% Hx and 90% Hx were used as the surrogate model of SFS for 30% and 10% graft models. In CyA groups, CyA (5 mg/kg/day) was given for 3 days before Hx and after surgery until sacrifice. Animals were sacrificed at 0, 12, 24, 48, and 72 hr after Hx. The blood concentration of CyA and the expression of the CYP3A2 gene were measured at each point in CyA groups, and liver regeneration was evaluated by measuring the ratio of remnant liver weight to body weight in each group. Regarding the blood concentration of CyA, no difference was recognized between 30% and 10% graft models except for 72 hr after Hx. As for liver regeneration, no significant difference was recognized. Regarding the expression of CYP3A2, no change was noted in the 30% graft model; on the other hand, CYP3A2 expression was reduced. Significant differences between the 30% and the 10% graft model were observed 48 and 72 hr after Hx. The blood concentration of CyA was not dependent on the volume of the liver graft.

Immunosuppression using the mTOR inhibition mechanism affects replacement of rat liver with transplanted cells

Successful grafting of tissues or cells from mismatched donors requires systemic immunosuppression. It is yet to be determined whether immunosuppressive manipulations perturb transplanted cell engraftment or proliferation. We used syngeneic and allogeneic cell transplantation assays based on F344 recipient rats lacking dipeptidyl peptidase IV enzyme activity to identify transplanted hepatocytes. Immunosuppressive drugs used were tacrolimus (a calcineurin inhibitor) and its synergistic partners, rapamycin (a regulator of the mammalian target of rapamycin [mTOR]) and mycophenolate mofetil (an inosine monophosphate dehydrogenase inhibitor). First, suitable drug doses capable of inducing long-term survival of allografted hepatocytes were identified. In pharmacologically effective doses, rapamycin enhanced cell engraftment by downregulating hepatic expression of selected inflammatory cytokines but profoundly impaired proliferation of transplanted cells, which was necessary for liver repopulation. In contrast, tacrolimus and/or mycophenolate mofetil perturbed neither transplanted cell engraftment nor their proliferation. Therefore, mTOR-dependent extracellular and intracellular mechanisms affected liver replacement with transplanted cells. In conclusion, insights into the biological effects of specific drugs on transplanted cells are critical in identifying suitable immunosuppressive strategies for cell therapy.

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

Immunosuppressants are the cornerstones of treatment after solid organ transplantation. This study investigated the pathology and cell proliferation following partial hepatectomy (PH) in rats undergoing immunosuppressive treatment. After 1 day, all rats were subjected to 70% PH. Groups A and B (n = 10) received calcineurin inhibitors subcutaneously: either FK506 or cyclosporine (CyA). Groups C and D (n = 10) received antiproliferative drugs: either mycophenolate mofetil (MMF) or sirolimus (SRL) by gavage. A control group (n = 5) received 1 mL of tap water daily. On postoperative day 2, all rats were sacrificed to obtain liver tissue for pathologic examination. Using immunohistochemistry we separately examined the hepatectomy surface and the liver parenchyma. In the parenchyma, the Ki-67 indices were higher in the CyA and FK506 groups and lower in the SRL and MMF groups compared with controls (P < .01). CyA had the highest and MMF the lowest values. On the hepatectomy surface, Ki-67 indices and TGF-alpha expressions were higher in the CyA group and lower in the SRL and MMF groups compared with the control group (P < .01). Slightly higher values in the FK506 group were not significantly different compared with the control group (P > .05). All groups other than FK506 showed prominent cholangiolar epithelial phenotypes compared with the control group. In the CyA and SRL groups, the number of cholangiolar cells was higher (P < .01), and in the MMF group lower than in the control group (P < .01). Among all groups, SRL had the highest values.