Mesenchymal stromal cells for immunomodulatory cell therapy in liver transplantation: One step at a time

Induction of the differentiation of porcine bone marrow mesenchymal stem cells into premature hepatocyte-like cells in an indirect coculture system with primary hepatocytes

Liver transplantation is currently the only option for patients with end-stage liver disease. Thus, other alternate therapeutic strategies are needed. Bone marrow mesenchymal stem cells (BM-MSCs) are nonhematopoietic cells present in the bone marrow stroma that serve as precursors cells for various other cells. In this study, we evaluated the differentiation of porcine BM-MSCs into hepatocyte-like cells using three types of culture systems: hepatic induction medium (HIM), HIM/primary hepatocyte culture supernatant (HCS; 1:1 ratio), and a hepatocyte coculture system (HCCS; primary hepatocytes in the upper chamber, and BM-MSCs in the lower chamber). Primary hepatocytes were isolated from anesthetized healthy 1-month-old pigs by enzymatic digestion. Hepatic-specific marker expression (albumin [ALB], transferrin [TF], α-fetoprotein [AFP]), glycogen storage, low-density lipoprotein, and indocyanine green uptake were evaluated. Upregulation of hepatic-specific markers (ALB, TF, and AFP) was observed by real-time polymerase chain reaction in the HCCS group. Periodic acid-Schiff staining revealed enhanced glycogen storage in hepatocyte-like cells from the HCCS group compared with that from the HIM/HCS group. Furthermore, hepatocyte like-cells in the HCCS group showed improved LDL and ICG uptake than those in the other groups. Overall, our current study revealed that indirect coculture of primary hepatocytes and BM-MSCs enhanced the differentiation efficacy of BM-MSCs into hepatocyte-like cells by unknown useful soluble factors, including paracrine factors.

Generation of functional hepatocyte-like cells from human bone marrow mesenchymal stem cells by overexpression of transcription factor HNF4α and FOXA2

BACKGROUND

Our previous study showed that overexpression of hepatocyte nuclear factor 4α (HNF4α) could directly promote mesenchymal stem cells (MSCs) to differentiate into hepatocyte-like cells. However, the efficiency of hepatic differentiation remains low. The purpose of our study was to establish an MSC cell line that overexpressed HNF4α and FOXA2 genes to obtain an increased hepatic differentiation efficiency and hepatocyte-like cells with more mature hepatocyte functions.

METHODS

Successful establishment of high-level HNF4α and FOXA2 co-overexpression in human induced hepatocyte-like cells (hiHep cells) was verified by flow cytometry, immunofluorescence and RT-PCR. Measurements of albumin (ALB), urea, glucose, indocyanine green (ICG) uptake and release, cytochrome P450 (CYP) activity and gene expression were used to analyze mature hepatic functions of hiHep cells.

RESULTS

hiHep cells efficiently express HNF4α and FOXA2 genes and proteins, exhibit typical epithelial morphology and acquire mature hepatocyte-like cell functions, including ALB secretion, urea production, ICG uptake and release, and glycogen storage. hiHep cells can be activated by CYP inducers. The percentage of both ALB and α-1-antitrypsin (AAT)-positive cells was approximately 72.6%. The expression levels of hepatocyte-specific genes (ALB, AAT, and CYP1A1) and liver drug transport-related genes (ABCB1, ABCG2, and SLC22A18) in hiHep cells were significantly higher than those in MSCs-Vector cells. The hiHep cells did not form tumors after subcutaneous xenograft in BALB/c nude mice after 2 months.

CONCLUSION

This study provides an accessible, feasible and efficient strategy to generate hiHep cells from MSCs.

Bioluminescence Imaging of Transplanted Mesenchymal Stem Cells by Overexpression of Hepatocyte Nuclear Factor4α: Tracking Biodistribution and Survival

PURPOSE

The purposes of this study were to construct immortalized human bone marrow mesenchymal stem cells (UE7T-13) with overexpression of the hepatocyte nuclear factor4α (hHNF4α) and luciferase2-mKate2 dual-fusion reporter gene, further investigate their impact on treating acute liver injury (ALI) in rats, and track their biodistribution and survival by bioluminescence imaging (BLI).

PROCEDURES

The hHNF4α and luciferase2-mKate2 genes were transduced by a lentiviral vector into UE7T-13 cells (named E7-hHNF4α-R cells), and expression was verified by immunofluorescence, RT-PCR, and flow cytometry. E7-hGFP-R cells expressing the luciferase2-mKate2/hGFP gene served as a negative group. A correlation between the bioluminescence signal and cell number was detected by BLI. The ALI rats were established and divided into three groups: PBS, E7-hGFP-R, and E7-hHNF4α-R. After transplantation of 2.0 × 10⁶ cells, BLI was used to dynamically track their biodistribution and survival. The restoration of biological functions was assessed by serum biochemical and histological analyses.

RESULTS

Stable high-level expression of hHNF4α and mKate2 protein was established in the E7-hHNF4α-R cells in vitro. The E7-hHNF4α-R cells strongly expressed hGFP, hHNF4α, and mKate2 proteins, and the hHNF4α gene. hGFP-mKate2 dual-positive cell expression reached approximately 93 %. BLI verified that a linear relationship existed between the cell number and bioluminescence signal (R² = 0.9991). The cells improved liver function in vivo after transplantation into the ALI rat liver, as evidenced by the fact that AST and ALT temporarily returned to normal levels in the recipient ALI rats. The presence of the transplanted E7-hGFP-R and E7-hHNF4α-R cells in recipient rat livers was confirmed by BLI and immunohistochemistry. However, the cells were cleared by the immune system a short time after transplantation into ALI rats with a normal immune system.

CONCLUSION

Our data revealed that the E7-hHNF4α-R cells can transiently improve damaged liver function and were rapidly cleared by the immune system. In addition, BLI is a useful tool to track transplanted cell biodistribution and survival.

Mesenchymal Stem Cells Ameliorate Hepatic Ischemia/Reperfusion Injury via Inhibition of Neutrophil Recruitment

Ischemia/reperfusion injury (IRI) remains a major problem in organ transplantation, which represents the main cause of graft dysfunction posttransplantation. Hepatic IRI is characterized by an excessive inflammatory response within the liver. Mesenchymal stem cells (MSCs) have been shown to be immunomodulatory cells and have the therapeutic action on IRI in several organs. However, the mechanism of regulatory effect of MSCs on IRI remains unclear. In the present study, we examined the impact of MSCs on hepatic inflammatory response such as neutrophil influx and liver damage in a rat model of 70% hepatic IRI. Treatment with MSCs protected rat against hepatic IRI, with significantly decreased serum levels of liver enzymes, attenuated hepatic neutrophil infiltration, reduced expression of apoptosis-associated proteins, and ameliorated liver pathological injury. MSCs also significantly enhanced the intracellular activation of p38 MAPK phosphorylation, which led to decreased expression of CXCR2 on the surface of neutrophils. In addition, MSCs significantly diminished neutrophil chemoattractant CXCL2 production by inhibiting NF-κB p65 phosphorylation in macrophages. These results demonstrate that MSCs significantly ameliorate hepatic IRI predominantly through its inhibitory effect on hepatic neutrophil migration and infiltration.

Stem cells in lung repair and regeneration: Current applications and future promise

Lung diseases are major cause of morbidity and mortality worldwide. The progress in regenerative medicine and stem cell research in the lung are currently a fast-growing research topic that can provide solutions to these major health problems. Under normal conditions, the rate of cellular proliferation is relatively low in the lung in vivo, compared to other major organ systems. Lung injury leads to the activation of stem/progenitor cell populations that re-enter the cell cycle. Yet, little is known about stem cells in the lung, despite common thoughts that these cells could play a critical role in the repair of lung injuries. Nor do we fully understand the cellular and architectural complexity of the respiratory tract, and the diverse stem/progenitor cells that are involved in the lung repair and regeneration. In this review, we discuss the conceptual framework of lung stem/progenitor cell biology, and describe lung diseases, in which stem cell manipulations may be physiologically significant. In addition, we highlight the challenges of lung stem cell-based therapy.