Mesenchymal Stromal Cell-Derived Factors Promote Tissue Repair in a Small-for-Size Ischemic Liver Model but Do Not Protect against Early Effects of Ischemia and Reperfusion Injury.

UNLABELLED: Loss of liver mass and ischemia/reperfusion injury (IRI) are major contributors to postresectional liver failure and small-for-size syndrome. Mesenchymal stromal cell- (MSC-) secreted factors are described to stimulate regeneration after partial hepatectomy. This study investigates if liver-derived MSC-secreted factors also promote liver regeneration after resection in the presence of IRI. C57BL/6 mice underwent IRI of 70% of their liver mass, alone or combined with 50% partial hepatectomy (PH). Mice were treated with MSC-conditioned medium (MSC-CM) or unconditioned medium (UM) and sacrificed after 6 or 24 hours (IRI group) or after 48 hours (IRI + PH group). Blood and liver tissue were analyzed for tissue injury, hepatocyte proliferation, and gene expression. In the IRI alone model, serum ALT and AST levels, hepatic tissue damage, and inflammatory cytokine gene expression showed no significant differences between both treatment groups. In the IRI + PH model, significant reduction in hepatic tissue damage as well as a significant increase in hepatocyte proliferation was observed after MSC-CM treatment. CONCLUSION: Mesenchymal stromal cell-derived factors promote tissue regeneration of small-for-size livers exposed to ischemic conditions but do not protect against early ischemia and reperfusion injury itself. MSC-derived factors therefore represent a promising treatment strategy for small-for-size syndrome and postresectional liver failure.

Support of hepatic regeneration by trophic factors from liver-derived mesenchymal stromal/stem cells.

Mesenchymal stromal/stem cells (MSCs) have multilineage differentiation potential and as such are known to promote regeneration in response to tissue injury. However, accumulating evidence indicates that the regenerative capacity of MSCs is not via transdifferentiation but mediated by their production of trophic and other factors that promote endogenous regeneration pathways of the tissue cells. In this chapter, we provide a detailed description on how to obtain trophic factors secreted by cultured MSCs and how they can be used in small animal models. More specific, in vivo models to study the paracrine effects of MSCs on regeneration of the liver after surgical resection and/or ischemia and reperfusion injury are described.

Detection of spontaneous tumorigenic transformation during culture expansion of human mesenchymal stromal cells.

Human mesenchymal stem/stromal cells (MSCs) have been explored in a number of clinical trials as a possible method of treating various diseases. However, the effect of long-term cell expansion in vitro on physiological function and genetic stability is still poorly understood. In this study, MSC cultures derived from bone marrow and liver were evaluated for the presence of aberrant cells following long-term expansion. In 46 independent cultures, four batches of transformed MSCs (TMCs) were found, which were all beyond the culture period of five weeks. These aberrant cells were first identified based on the appearance of abnormal cytology and the acquirement of growth advantage. Despite common MSC markers being diminished or absent, TMCs remain highly susceptible to lysis by allogenic natural killer (NK) cells. When transplanted into immunodeficient mice, TMCs formed sarcoma-like tumors, whereas parental MSCs did not form tumors in mice. Using a combination of high-resolution genome-wide DNA array and short-tandem repeat profiling, we confirmed the origin of TMCs and excluded the possibility of human cell line contamination. Additional genomic duplication and deletions were observed in TMCs, which may be associated with the transformation event. Using gene and microRNA expression arrays, a number of genes were identified that were differentially expressed between TMCs and their normal parental counterparts, which may potentially serve as biomarkers to screen cultures for evidence of early transformation events. In conclusion, the spontaneous transformation of MSCs resulting in tumorigenesis is rare and occurs after relatively long-term (beyond five weeks) culture. However, as an added safety measure, cultures of MSCs can potentially be screened based on a novel gene expression signature.

Secreted factors of human liver-derived mesenchymal stem cells promote liver regeneration early after partial hepatectomy.

Rapid liver regeneration is required after living-donor liver transplantation and oncologic liver resections to warrant sufficient liver function and prevent small-for-size syndrome. Recent evidence highlights the therapeutic potential of mesenchymal stem cells (MSC) for treatment of toxic liver injury, but whether MSC and their secreted factors stimulate liver regeneration after surgical injury remains unknown. Therefore, the aim of this study is to investigate the effect of human liver-derived MSC-secreted factors in an experimental liver resection model. C57BL/6 mice were subjected to a 70% partial hepatectomy and treated with either concentrated MSC-conditioned culture medium (MSC-CM) or vehicle control. Animals were analyzed for liver and body weight, hepatocyte proliferation, and hepatic gene expression. Effects of MSC-CM on gene expression in a human hepatocyte-like cell line (Huh7 cells) were analyzed using genome-wide gene expression arrays. Liver regeneration was significantly stimulated by MSC-CM as shown by an increase in liver to body weight ratio and hepatocyte proliferation. MSC-CM upregulated hepatic gene expression of cytokines and growth factors relevant for cell proliferation, angiogenesis, and anti-inflammatory responses. In vitro, treatment of Huh7 cells with MSC-CM significantly altered expression levels of ~3,000 genes. Functional analysis revealed strong effects on networks associated with protein synthesis, cell survival, and cell proliferation. This study shows that treatment with MSC-derived factors can promote hepatocyte proliferation and regenerative responses in the early phase after surgical resection. MSC-CM may represent a feasible new strategy to promote liver regeneration in patients undergoing extensive liver resection or after transplantation of small liver grafts.

Mobilization of hepatic mesenchymal stem cells from human liver grafts.

Extensive studies have demonstrated the potential applications of bone marrow-derived mesenchymal stem cells (BM-MSCs) as regenerative or immunosuppressive treatments in the setting of organ transplantation. The aims of the present study were to explore the presence and mobilization of mesenchymal stem cells (MSCs) in adult human liver grafts and to compare their functional capacities to those of BM-MSCs. The culturing of liver graft preservation fluids (perfusates) or end-stage liver disease tissues resulted in the expansion of MSCs. Liver-derived mesenchymal stem cells (L-MSCs) were equivalent to BM-MSCs in adipogenic and osteogenic differentiation and in wingless-type-stimulated proliferative responses. Moreover, the genome-wide gene expression was very similar, with a 2-fold or greater difference found in only 82 of the 32,321 genes (0.25%). L-MSC differentiation into a hepatocyte lineage was demonstrated in immunodeficient mice and in vitro by the ability to support a hepatitis C virus infection. Furthermore, a subset of engrafted MSCs survived over the long term in vivo and maintained stem cell characteristics. Like BM-MSCs, L-MSCs were found to be immunosuppressive; this was shown by significant inhibition of T cell proliferation. In conclusion, the adult human liver contains an MSC population with a regenerative and immunoregulatory capacity that can potentially contribute to tissue repair and immunomodulation after liver transplantation.

Endothelial activation markers and their key regulators after restrictive bariatric surgery.

OBJECTIVE: Increased plasma levels of endothelial activation markers in obese subjects reflect the positive association between cardiovascular diseases and obesity. The pro-inflammatory state associated with obesity is thought to play a major role in endothelial cell activation in severely obese individuals. Previous studies demonstrated that long-term weight loss after bariatric surgery is accompanied by a decreased proinflammatory state. However, little is known about the long-term effects of bariatric surgery on endothelial cell activation. RESEARCH METHODS AND PROCEDURES: Plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble endothelial selectin (sE-selectin), and soluble vascular cell adhesion molecule-1 (sVCAM-1), all markers of endothelial cell activation, and of their regulators adiponectin and resistin were measured at different time-points postoperatively in 26 consecutive patients who underwent restrictive surgery, with a follow-up of 2 years. RESULTS: During the first 6 months after bariatric surgery, sE-selectin levels decreased. Despite substantial weight loss, sICAM-1 and sVCAM-1 plasma levels did not decrease significantly. After 24 months, sICAM-1 levels were significantly decreased, whereas sE-selectin levels were further decreased. However, sVCAM-1 levels remained elevated. Adiponectin levels did not change significantly during the first 6 months after bariatric surgery, whereas resistin levels increased. After 24 months, adiponectin levels were similar to normal-weight controls, but resistin levels remained high. DISCUSSION: Reductions in plasma levels of different markers of endothelial activation after bariatric surgery show different temporal patterns, suggesting that distinct mechanisms are involved in their regulation. Although not all endothelial activation markers normalize after bariatric surgery, our findings suggest that bariatric surgery can reduce endothelial activation in the long term.