Propagation and functional characterization of serum-free cultured porcine hepatocytes for downstream applications

Mesenchymal stromal cells mitigate liver damage after extended resection in the pig by modulating thrombospondin-1/TGF-β

Post-surgery liver failure is a serious complication for patients after extended partial hepatectomies (ePHx). Previously, we demonstrated in the pig model that transplantation of mesenchymal stromal cells (MSC) improved circulatory maintenance and supported multi-organ functions after 70% liver resection. Mechanisms behind the beneficial MSC effects remained unknown. Here we performed 70% liver resection in pigs with and without MSC treatment, and animals were monitored for 24 h post surgery. Gene expression profiles were determined in the lung and liver. Bioinformatics analysis predicted organ-independent MSC targets, importantly a role for thrombospondin-1 linked to transforming growth factor-β (TGF-β) and downstream signaling towards providing epithelial plasticity and epithelial-mesenchymal transition (EMT). This prediction was supported histologically and mechanistically, the latter with primary hepatocyte cell cultures. MSC attenuated the surgery-induced increase of tissue damage, of thrombospondin-1 and TGF-β, as well as of epithelial plasticity in both the liver and lung. This suggests that MSC ameliorated surgery-induced hepatocellular stress and EMT, thus supporting epithelial integrity and facilitating regeneration. MSC-derived soluble factor(s) did not directly interfere with intracellular TGF-β signaling, but inhibited thrombospondin-1 secretion from thrombocytes and non-parenchymal liver cells, therewith obviously reducing the availability of active TGF-β.

Mitochondrial Transfer by Human Mesenchymal Stromal Cells Ameliorates Hepatocyte Lipid Load in a Mouse Model of NASH

Mesenchymal stromal cell (MSC) transplantation ameliorated hepatic lipid load; tissue inflammation; and fibrosis in rodent animal models of non-alcoholic steatohepatitis (NASH) by as yet largely unknown mechanism(s). In a mouse model of NASH; we transplanted bone marrow-derived MSCs into the livers; which were analyzed one week thereafter. Combined metabolomic and proteomic data were applied to weighted gene correlation network analysis (WGCNA) and subsequent identification of key drivers. Livers were analyzed histologically and biochemically. The mechanisms of MSC action on hepatocyte lipid accumulation were studied in co-cultures of hepatocytes and MSCs by quantitative image analysis and immunocytochemistry. WGCNA and key driver analysis revealed that NASH caused the impairment of central carbon; amino acid; and lipid metabolism associated with mitochondrial and peroxisomal dysfunction; which was reversed by MSC treatment. MSC improved hepatic lipid metabolism and tissue homeostasis. In co-cultures of hepatocytes and MSCs; the decrease of lipid load was associated with the transfer of mitochondria from the MSCs to the hepatocytes via tunneling nanotubes (TNTs). Hence; MSCs may ameliorate lipid load and tissue perturbance by the donation of mitochondria to the hepatocytes. Thereby; they may provide oxidative capacity for lipid breakdown and thus promote recovery from NASH-induced metabolic impairment and tissue injury.

A fat option for the pig: hepatocytic differentiated mesenchymal stem cells for translational research

STUDY BACKGROUND

Extended liver resection is the only curative treatment option of liver cancer. Yet, the residual liver may not accomplish the high metabolic and regenerative capacity needed, which frequently leads to acute liver failure. Because of their anti-inflammatory and -apoptotic as well as pro-proliferative features, mesenchymal stem cells differentiated into hepatocyte-like cells might provide functional and regenerative compensation. Clinical translation of basic research requires pre-clinical approval in large animals. Therefore, we characterized porcine mesenchymal stem cells (MSC) from adipose tissue and bone marrow and their hepatocyte differentiation potential for future assessment of functional liver support after surgical intervention in the pig model.

METHODS

Mesenchymal surface antigens and multi-lineage differentiation potential of porcine MSC isolated by collagenase digestion either from bone marrow or adipose tissue (subcutaneous/visceral) were assessed by flow cytometry. Morphology and functional properties (urea-, glycogen synthesis and cytochrome P450 activity) were determined during culture under differentiation conditions and compared with primary porcine hepatocytes.

RESULTS

MSC from porcine adipose tissue and from bone marrow express the typical mesenchymal markers CD44, CD29, CD90 and CD105 but not haematopoietic markers. MSC from both sources displayed differentiation into the osteogenic as well as adipogenic lineage. After hepatocyte differentiation, expression of CD105 decreased significantly and cells adopted the typical polygonal morphology of hepatocytes. Glycogen storage was comparable in adipose tissue- and bone marrow-derived cells. Urea synthesis was about 35% lower in visceral than in subcutaneous adipose tissue-derived MSC. Cytochrome P450 activity increased significantly during differentiation and was twice as high in hepatocyte-like cells generated from bone marrow as from adipose tissue.

CONCLUSION

The hepatocyte differentiation of porcine adipose tissue-derived MSC was shown for the first time yielding hepatocyte-like cells with specific functions similar in bone marrow and subcutaneous adipose tissue-derived MSC. That makes them good pre-clinical candidates for supportive approaches after liver resection in the pig.

Profiling the impact of medium formulation on morphology and functionality of primary hepatocytes in vitro

The characterization of fully-defined in vitro hepatic culture systems requires testing of functional and morphological variables to obtain the optimal trophic support, particularly for cell therapeutics including bioartificial liver systems (BALs). Using serum-free fully-defined culture medium formulations, we measured synthetic, detoxification and metabolic variables of primary porcine hepatocytes (PPHs)--integrated these datasets using a defined scoring system and correlated this hepatocyte biological activity index (HBAI) with morphological parameters. Hepatic-specific functions exceeded those of both primary human hepatocytes (PHHs) and HepaRG cells, whilst retaining biotransformation potential and in vivo-like ultrastructural morphology, suggesting PPHs as a potential surrogate for PHHs in various biotech applications. The HBAI permits assessment of global functional capacity allowing the rational choice of optimal trophic support for a defined operational task (including BALs, hepatocellular transplantation, and cytochrome P450 (CYP450) drug metabolism studies), mitigates risk associated with sub-optimal culture systems, and reduces time and cost of research and therapeutic applications.

Effects of time culture and prototypical cytochrome P450 3A (CYP3A) inducers on CYP2B22, CYP2C, CYP3A and nuclear receptor (NR) mRNAs in long-term cryopreserved pig hepatocytes (CPHs)

In the present study, transcriptional and post-translational effects of culturing time and prototypical cytochrome P450 3A (CYP3A) inducers on principal nuclear receptors (NRs), CYP2B22, 2C and 3A were investigated in long-term stored (~10 years) cryopreserved pig hepatocytes (CPHs). In the time-course study, a crush and rise effect was observed for pregnane X receptor (NR1I2) and constitutive androstane receptor (NR1I3) mRNAs, while a time-dependent increase of retinoid X receptor alpha (NR2B1) was noticed. Cytochrome P450 gene expression profiles were down-regulated as a function of time. In the induction study, an increase of NR1I2, NR1I3 and NR2B1 mRNAs was observed in dexamethasone-exposed CPHs. About CYPs, an overall up-regulation was seen in CPHs exposed to phenobarbital, while dexamethasone and rifampicin up-regulated only CYP3A. In both studies, transcriptional CYP results were confirmed at the post-translational level (immunoblotting and enzyme activities), except for CYP2B immunoblotting in the induction study. The present data demonstrate that long-term stored CPHs may be used to investigate mechanisms involved in CYPs regulation, expression and function; provide further info about NR regulation of CYPs, and confirm species-differences in these mechanisms of regulation; finally, they suggest the usefulness and relevance of gene expression profiling to early detect any modulation of CYP expression and bioactivity.

Isolation of primary human hepatocytes after partial hepatectomy: criteria for identification of the most promising liver specimen

Demands for primary human hepatocytes are continuously increasing, while supply is insufficient due to limited cell sources. To improve cell availability, the present study investigates the influence of donor liver characteristics on the outcome of hepatocyte isolation from surgically removed liver tissue (n = 50). Hepatocytes were isolated from liver specimens using a standardized two-step collagenase perfusion technique. The patient's sex, previous chemotherapy, or histopathology have shown no influence. Donor age significantly affected the isolation outcome, but was not found suitable for predicting cell yields. Preoperative blood parameters did not correlate with cell yield, although cell function was affected: total protein, albumin synthesis, and cell viability were significantly decreased for serum gamma-glutamyl-transferase (GGT) levels >60 U/L. Specimens from patients with benign diseases gave significantly higher cell yields than tissue removed due to secondary and primary tumors, respectively. The indication for surgery is a valuable basis for identifying the most yielding specimens. Hepatocytes from donors with high GGT levels appear to show reduced functional properties.