Bone marrow mesenchymal stem cells ameliorate hepatic ischemia/reperfusion injuries via inactivation of the MEK/ERK signaling pathway in rats

In situ transverse rectus abdominis myocutaneous flap: a rat model of myocutaneous ischemia reperfusion injury

Free tissue transfer is the gold standard of reconstructive surgery to repair complex defects not amenable to local options or those requiring composite tissue. Ischemia reperfusion injury (IRI) is a known cause of partial free flap failure and has no effective treatment. Establishing a laboratory model of this injury can prove costly both financially as larger mammals are conventionally used and in the expertise required by the technical difficulty of these procedures typically requires employing an experienced microsurgeon. This publication and video demonstrate the effective use of a model of IRI in rats which does not require microsurgical expertise. This procedure is an in situ model of a transverse abdominis myocutaneous (TRAM) flap where atraumatic clamps are utilized to reproduce the ischemia-reperfusion injury associated with this surgery. A laser Doppler Imaging (LDI) scanner is employed to assess flap perfusion and the image processing software, Image J to assess percentage area skin survival as a primary outcome measure of injury.

Machine perfusion in organ transplantation: a tool for ex-vivo graft conditioning with mesenchymal stem cells?

PURPOSE OF REVIEW

Machine perfusion has emerged as a tool to evaluate pretransplant graft function more objectively during preservation. Machine perfusion also offers the possibility to recondition questionable organs and to 'immunomodulate' allografts ex vivo. This article aims to review the current knowledge on machine perfusion of the various solid thoracic and abdominal organs, and to discuss the new possibility of conditioning and treating grafts with mesenchymal stem cells (MSCs) during machine perfusion.

RECENT FINDINGS

Different methods of machine perfusion have been described varying among organs in temperature and composition of perfusate. Commercial devices have recently become available for machine perfusion of all organs, with the largest clinical experience acquired in kidney and lung transplantation. Clinical studies are ongoing for liver, heart, and pancreas. MSC therapy in organ transplantation is now emerging with clinical studies set up to investigate its potential to attenuate ischemia/reperfusion injury (innate immunity) and to downregulate the alloimmune response (adaptive immunity) and promote engraftment after transplantation. We hypothesize that delivery of MSCs directly into the machine perfusion circuit may provide a unique opportunity to treat and immunomodulate organs prior to transplantation. To our knowledge, no study on ex-vivo delivery of MSCs during machine perfusion has been reported.

SUMMARY

Machine perfusion of solid organs has regained much attention during the last decade. It provides a new promising tool that may allow pretransplant ex-vivo assessment, preservation, repair, and conditioning of grafts. Experimental research and clinical trials testing the administration of MSCs during machine perfusion are warranted to explore the potential benefit and mechanisms of this approach.

Mesenchymal stem cell-conditioned medium reduces liver injury and enhances regeneration in reduced-size rat liver transplantation

BACKGROUND

Mesenchymal stem cell (MSC) therapy can prevent parenchymal cell loss and promotes tissue repair through the action of trophic, secreted molecules. In this study, we investigated whether MSC-conditioned medium (MSC-CM) could protect hepatocytes and sinusoidal endothelial cells (SECs) and stimulate their regeneration in 50% reduced-size liver transplantation (RSLT).

MATERIALS AND METHODS

Rats were randomly divided into three groups: sham-operated group, MSC-CM group (rats with 50% RSLT receiving MSC-CM infusion), and medium group (rats with 50% RSLT receiving medium therapy). Graft function, proinflammatory cytokines, incidence of apoptosis, proliferation of hepatocytes and SECs, and the expression of vascular endothelial growth factor and matrix metallopeptidase 9 were assessed in this study.

RESULTS

Systemic infusion of MSC-CM prevented the release of liver injury biomarkers and provided a significant survival benefit. Furthermore, MSC-CM therapy resulted in reduction of apoptosis of hepatocytes and SECs. The number of proliferating hepatocytes and SECs increased 1.2- and 1.6-fold, respectively, accompanied by a decrease in the expression levels of several proinflammatory cytokines and a noticeable decrease in infiltration of neutrophils and activation of Kupffer cells. Also, increased expression of vascular endothelial growth factor and matrix metallopeptidase 9 in the grafts was observed after MSC-CM therapy.

CONCLUSIONS

These data suggest that MSC-CM therapy in RSLT provides trophic support to the injured liver by inhibiting SEC and hepatocellular death and stimulating their regeneration.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

Mesenchymal stem cells overexpressing C-X-C chemokine receptor type 4 improve early liver regeneration of small-for-size liver grafts

Mesenchymal stem cell (MSC) therapy can prevent hepatic parenchymal cell loss and promote tissue repair. However, poor MSC engraftment is one of the primary barriers to the effectiveness of cell therapy because culture-expanded MSCs progressively down-regulate C-X-C chemokine receptor type 4 (CXCR4) expression and lose their ability to migrate toward a concentration gradient of stromal cell-derived factor 1a (SDF1a). In this study, we investigated whether a CXCR4-MSC infusion could protect hepatocytes and stimulate regeneration in 50% reduced size liver transplantation (RSLT). Rats that underwent 50% RSLT were randomly divided into 3 groups: a phosphate-buffered solution group (PBS), a green fluorescent protein (GFP)-MSC group, and a CXCR4-MSC group. Rats received 1 mL of PBS with or without a resuspension of GFP-MSCs or CXCR4-MSCs. The factors secreted by MSCs, the graft function, the apoptosis and proliferation of hepatocytes, the efficacy of MSC engraftment, and the expression of SDF1α, albumin (Alb), and cytokeratin 18 (CK18) in engrafted GFP-positive MSCs were assessed. A systemic infusion of GFP-MSCs led to a reduction of the release of liver injury biomarkers and apoptosis of hepatocytes; CXCR4 overexpression did not further reduce the liver injury. However, CXCR4 overexpression enhanced MSC engraftment in liver grafts, improved the effect on the proliferation of hepatocytes, and thus provided a significant 1-week survival benefit. SDF1α expression in grafts was elevated after transplanted CXCR4-MSCs were recruited to the remnant liver. However, engrafted MSCs did not express the markers of hepatocytes, including Alb and CK18, in vivo 168 hours after transplantation. CXCR4 overexpression enhanced the mobilization and engraftment of MSCs into small-for-size liver grafts, in which these cells promoted the early regeneration of the remnant liver not by direct differentiation but perhaps by a paracrine mechanism.