Apoptosis and Regeneration of Sinusoidal Endothelial Cells After Extended Cold Preservation and Transplantation of Rat Liver

Partial Inhibition of HO-1 Attenuates HMP-Induced Hepatic Regeneration against Liver Injury in Rats

We found better liver graft regeneration with hypothermic machine perfusion (HMP) compared with static cold storage (SCS) for the first time in our pilot study, but the underlying mechanisms are unknown. Upregulated heme oxygenase- (HO-) 1 expression has been reported to play a pivotal role in promoting hepatocyte proliferation. Here, we evaluated the novel role of HO-1 in liver graft protection by HMP. Rats with a heterozygous knockout of HO-1 (HO-1^+/-) were generated and subjected to 3 h of SCS or HMP pre-half-size liver transplantation (HSLT) in vivo or 6 h of SCS or HMP in vitro; control rats were subjected to the same conditions (HO-1^+/+). We found that HSLT induced significant elevation of the HO-1 protein level in the regenerated liver and that HO-1 haplodeficiency resulted in decreased proliferation post-HSLT. Compared with SCS, HMP induced significant elevation of the HO-1 protein level along with better liver recovery, both of which were reduced by HO-1 haplodeficiency. HO-1 haplodeficiency-induced decreased proliferation was responsible for the attenuated regenerative ability of HMP. Mechanistically, HO-1 haploinsufficiency resulted in suppression of hepatocyte growth factor (HGF)/Akt activity. Our results suggest that inhibition of HO-1 mitigates HMP-induced liver recovery effects related to proliferation, in part, by downregulating the HGF-Akt axis.

Angiotensin IV improves subnormothermic machine perfusion preservation of rat liver graft

This study aims to determine whether Angiotensin IV (Ang IV) addition to Celsior preservation solution could improve hepatic endothelium function and provide better liver protection during subnormothermic machine preservation (SMP). Two experimental models were used: In the first part of the study, rings isolated from rat hepatic artery were preserved in Celsior solution (6 h, 20 °C) with and without Ang IV (10^-9 M), then, endothelium-dependent relaxation (EDR) and the concentration of acetylcholine inducing half-maximal relaxation of pre-contracted rings (EC50) were measured. Also, in order to investigate the implication of nitric oxide (NO) on EDR, the rings of hepatic artery were incubated with L-NG-nitroarginine metyl ester (L-NAME). In the second part of the study, rat livers were subjected to SMP with oxygenated Celsior solution (6 h, 20 °C), supplemented or not with Ang IV (10^-9 M) and then perfused (2 h, 37 °C) with Krebs Henseleit solution. We found that Ang IV supplementation to Celsior solution decreased EC50 value and improved EDR of hepatic artery rings, 6h after sub-normothermic preservation. Interestingly, Ang IV amplified the vessel relaxation in a NO-dependent manner. Moreover, liver SMP with Ang IV reduced oxidative stress and cell injury and improved organ function. Ang IV activated pAkt, increased eNOS protein level and decreased apoptosis in the preserved liver grafts. In conclusion, we showed that the use of Ang IV in Celsior solution for sub-normothermic graft preservation insured a better NO-dependent relaxation and improved liver functional recovery.

Heterotopic ovarian transplantation results in less apoptosis than orthotopic transplantation in a minipig model

Background

Ovarian autotransplantation has shown increasing promise as a clinical method for the preservation of fertility and hormonal function. However, information regarding the success rate of this type of transplantation is limited. We hypothesized that results vary according to the site of the ovarian transplantation. To test this hypothesis, fresh or cryopreserved ovarian strips were autotransplanted to orthotopic or heterotopic sites. The strips were later collected, and the morphology and expression of selected markers of apoptosis were evaluated. We compared the Bax, Bcl-2 and cleaved caspase-3 staining levels and the morphometric aspects of autotransplanted fresh and cryopreserved ovarian strips placed at orthotopic and heterotopic sites in minipigs.

Methods

Forty female minipigs were allocated to the following five groups: group 1 (control), ovarian tissue removed during oophorectomy; group 2, transplantation of fresh ovarian strips to a heterotopic site; group 3, transplantation of fresh ovarian strips to an orthotopic site; group 4, transplantation of cryopreserved ovarian strips to a heterotopic site; and group 5, transplantation of ovarian trips to an orthotopic site. On day 7 after transplantation, ovarian strips were collected, and the morphology and expression of apoptosis markers were evaluated.

Results

In all groups, follicles across all stages of development were detected. The numbers of primordial, primary and secondary follicles were similar in all groups, but the numbers of antral follicles were lower in the cryopreserved groups in comparison with freshly derived ovarian tissue, with no significant differences observed between fresh and cryopreserved transplants. In all transplanted groups, Bcl-2 expression was lower and Bax expression was higher than in the control group. Furthermore, increased expression of apoptosis markers was detected in fresh intraperitoneal transplants. Lastly, the expression of cleaved caspase-3 was higher in the cryopreserved orthotopic group compared with the heterotopic group.

Conclusions

Orthotopic and heterotopic ovarian strip transplantations are feasible options using these techniques. Importantly, we found that heterotopic transplantation preserves ovarian follicle integrity to a greater degree (i.e., lower expression of apoptosis markers) than orthotopic transplantation, and cryopreservation does not exacerbate expression of apoptosis’s markers. These findings have major clinical applications and enhance the discussion regarding the heterotopic transplantation of ovarian tissue.

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.

Decreased apoptosis in fatty livers submitted to subnormothermic machine-perfusion respect to cold storage

Machine perfusion at subnormothermic temperature (20°C), MP20, was developed by Vairetti et al. and showed to afford a better preservation of fatty livers respect to traditional cold storage (CS) in terms of enzyme release into the perfusate and bile, glycogen stores, energy charge and oxidative stress. Here we investigated whether it also caused decreased cell death by apoptosis. Fatty and lean Zucker rats were submitted to MP20 or CS for 6 h and reperfused normothermically for 2 h. Apoptotic cells were revealed by immunohistochemistry of activated caspase-3 and M30 (new epitope on CK18 degraded by caspase-3) and by the TUNEL assay. Portal pressure was also determined. A statistically significant reduction of hepatocyte apoptosis, but especially of sinusoidal cells was determined for fatty livers submitted to MP20 respect to CS. Portal pressure was significantly lower after MP20 respect to CS. The reduction of sinusoidal cell death by apoptosis without need for anti-apoptotic therapies appears particularly positive since apoptotic sinusoidal cells hinder microcirculation in the sinusoids and are thrombogenic. These results further confirm the potential of MP20 for preserving fatty livers that would be otherwise discarded as grafts, and thus for increasing the donor pool for liver transplantation.

Induction of podocyte-derived VEGF ameliorates podocyte injury and subsequent abnormal glomerular development caused by puromycin aminonucleoside

Our previous studies using puromycin aminonucleoside (PAN) established that podocyte damage leads to glomerular growth arrest during development and glomerulosclerosis later in life. This study examined the potential benefit of maintaining podocyte-derived VEGF in podocyte defense and survival after PAN injury using conditional transgenic podocytes and mice, in which human VEGF-A (hVEGF) transgene expression is controlled by tetracycline responsive element (TRE) promoter and reverse tetracycline transactivator (rtTA) in podocytes. In vitro experiments used primary cultured podocytes harvested from mice carrying podocin-rtTA and TRE-hVEGF transgenes, in which hVEGF can be induced selectively. Induction of VEGF in PAN-exposed podocytes resulted in preservation of intrinsic VEGF, α-actinin-4 and synaptopodin, antiapoptotic marker Bcl-xL/Bax, as well as attenuation in apoptotic marker cleaved/total caspase-3. In vivo, compared with genotype controls, PAN-sensitive neonatal mice with physiologically relevant levels of podocyte-derived VEGF showed significantly larger glomeruli. Furthermore, PAN-induced up-regulation of desmin, down-regulation of synaptopodin and nephrin, and disruption of glomerular morphology were significantly attenuated in VEGF-induced transgenic mice. Our data indicate that podocyte-derived VEGF provides self-preservation functions, which can rescue the cell after injury and preempt subsequent deterioration of the glomerulus in developing mice.

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury associated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is endothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-protective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature evaluating the potential applications of regulating and promoting e-NOS activity in liver preservation and transplantation, showing the most current evidence to support the concept that enhanced bioavailability of NO derived from e-NOS is detrimental to ameliorate graft liver preservation, as well as preventing subsequent graft reperfusion injury. This review deals mainly with the beneficial effects of promoting “endogenous” pathways for NO generation, via e-NOS inducer drugs in cold preservation solution, surgical strategies such as ischemic preconditioning, and alternative “exogenous” pathways that focus on the enrichment of cold storage liquid with NO donors. Finally, we also provide a basic bench-to-bed side summary of the liver physiology and cell signalling mechanisms that account for explaining the e-NOS protective effects in liver preservation and transplantation.

Pharmacological strategies against cold ischemia reperfusion injury

IMPORTANCE OF THE FIELD

Good organ preservation is a determinant of graft outcome after revascularization. The necessity of increasing the quality of organ preservation, as well as of extending cold storage time, has made it necessary to consider the use of pharmacological additives.

AREAS COVERED IN THIS REVIEW

The complex physiopathology of cold-ischemia-reperfusion (I/R) injury--and in particular cell death, mitochondrial injury and endoplasmic reticulum stress--are reviewed. Basic principles of the formulation of the different preservation solutions are discussed.

WHAT THE READER WILL GAIN

Current strategies and new trends in static organ preservation using additives such as trimetazidine, polyethylene glycols, melatonin, trophic factors and endothelin antagonists in solution are presented and discussed. The benefits and mechanisms responsible for enhancing organ protection against I/R injury are also discussed. Graft preservation was substantially improved when additives were added to the preservation solutions.

TAKE HOME MESSAGE

Enrichment of preservation solutions by additives is clinically useful only for short periods. For longer periods of cold ischemia, the use of such additives becomes insufficient because graft function deteriorates as a result of ischemia. In such conditions, the preservation strategy should be changed by the use of machine perfusion in normothermic conditions.

Cytoprotective effects of human interleukin-10 gene transfer against necrosis and apoptosis induced by hepatic cold ischemia/reperfusion injury

BACKGROUND

Apoptosis as well as necrosis may play an important role in hepatic ischemia/reperfusion (I/R) injury. Interleukin 10 (IL-10), a Th2 type cytokine, modulates inflammatory responses by inhibiting the production of proinflammatory cytokines. The study focused on cytoprotective and antiapoptotic pathways to assess mechanisms by which gene transduction of human IL-10 (hIL-10) may renders grafts resistant to the cold I/R injury.

MATERIALS AND METHODS

Adenoviruses encoding hIL-10 or beta-galactosidase (LacZ) were injected via the superior mesenteric vein into prospective donor animals. The donor liver was harvested 48h after transduction, and stored for 12h at 4 degrees C lactated Ringer's solution prior to being transplanted. Graft survival, liver function, the degree of necrosis and apoptosis, and the molecules of apoptotic networks were assessed.

RESULTS

Ad-hIL-10 pretreatment significantly prolonged the survival of liver grafts by improving liver function, preserving hepatocyte integrity and architecture, and depressing intrahepatic apoptosis and necrosis. In addition, Ad-hIL-10 pretreatment diminished the release of cytochrome c from mitochondria into cytoplasm and caspase-3 activity, with simultaneous up-regulated of antioxidant HO-1 and anti-antiapoptotic Bcl-2 molecules.

CONCLUSION

Adenoviral gene transfer of hIL-10 ameliorated cold I/R injury by decreasing hepatic necrosis and apoptosis. The underlying mechanism of cytoprotective effects may at least be involved with the inhibition of caspase-3 activity and mitochondrial cytochrome c release, and the up-regulation of antiapoptotic (Bcl-2) and antioxidant (HO-1) molecules.