Orlando Castro e Silva

Cellular aspects of liver regeneration

This paper has the objective to analyze the cellular aspects of liver regeneration (LR). Upon damage in this organ, the regenerative capacity of hepatocyte is sufficiently able to reestablish the parenchyma as a whole. Taking into account the regenerative capacity of hepatocyte, the need of a progenitor or a liver trunk cell was not obvious. Nowadays it is well-established that precursor cells take part in the liver regenerative process. The liver trunk cell, oval cell, acts as a by-potential precursor, contributing for the liver restoration, mainly when the hepatocytes are unable to proliferate. Another precursor, trunk cell of hematopoetic origin (HSC), takes part in the regenerative process, originating cells of the hepatocytic lineage and colangiocytes, as well as the oval cell. The way the trans-differentiation takes place is not established yet. A number of studies must be undertaken in order to clarify questions, such as the possible occurrence of cellular fusion process between the HSC and the hepatic cells and the possibility of application as a new therapeutic procedure in the treatment of diseases associated with insufficiency of this noble organ.

A molecular view of liver regeneration

The purpose of this review was to carry out an analysis of the liver regenerative process focusing on the molecular interactions involved in this process. The authors undertook a review of scientific publications with a focus on the liver regeneration. The cellular processes involved in liver regeneration require multiple systematic actions related to cytokines and growth factors. These interactions result in the initiation of mitogenic potential of the hepatocytes. The action of these modulators in the regenerative process require a processing in the extra-cellular matrix. Serines and metal proteins are responsible for the bio availability of cytokines and growth factors so that they can interact as receptors in the cellular membrane generating signaling events for the beginning and end of the liver regenerative process. The exact mechanism of interaction between cells, cytokines and growth factors is not well established yet. A series of ordered events that result in the hepatic tissue regeneration has been described. The better understanding of these interactions should provide a new approach of the treatment for liver diseases, aiming at inducing the regenerative process.

Biochemical liver function after partial hepatic resection with or without partial hepatic vascular exclusion

PURPOSEnThe aim of the present study was to assess the advantages and disadvantages of liver vascular partial exclusion (LVPE) (liver dysfunction due to ischemia) during liver resection in patients submitted to partial hepatectomy.nnnMETHODSnA total of 114 patients were submitted to partial hepatectomy (minor versus major resections) with LPVE being used in 57 of them but not in the remaining 57. Patient age ranged from 35 to 73 years and 57 % were women. Mitochondrial function was assessed 30 minutes after liver resection in the remnant liver and serum aminotransferases were determined before surgery and for seven days postoperatively. LPVE time ranged from 30 to 60 minutes. Data were analyzed statistically by the Student T test (5 % level of significance).nnnRESULTSnMitochondrial function was similar in the minor and major liver resections. The maximum postoperative aminotransferase peak was similar in the groups with and without LPVE.nnnCONCLUSIONnLPVE did not induce mitochondrial changes in hepatic tissue in either type of surgery, and aminotransferase levels were similar for patients with and without LPVE. Thus, the results show that LPVE is a safe procedure that does not induce the significant changes typical of ischemia and reperfusion in the liver remnant.

Fluorescence spectroscopy to diagnose hepatic steatosis in a rat model of fatty liver

Background: Steatosis is diagnosed on the basis of the macroscopic aspect of the liver evaluated by the surgeon at the time of organ extraction or by means of a frozen biopsy.

Effects of hyperbaric oxygen (HBO), as pre-conditioning in liver of rats submitted to periodic liver ischemia/reperfusion

PURPOSEnto assess the effect of hyperbaric oxygen (HBO) as pre-conditioning on periodic liver ischemia/reperfusion injury.nnnMETHODSnThirty-six male Wistar rats were divided into 4 groups (SHAM, I/R , HBO-I/R and CONTROL). The surgical technique consisted of total clamping of the hepatic pedicle for 15 min followed by twice repeated reperfusion for 5 min (unclamping). HBO was applied in a collective chamber (simultaneous exposure of 4 rats) directly pressurized with oxygen at 2 ATA for 60 min. Hepatic mitochondrial function was determined using samples of the median lobe obtained after exactly 5 min of reperfusion for the analysis of mitochondrial respiration based on the determination of states 3 and 4, the respiratory control ratio and the transition of mitochondrial permeability (mitochondrial swelling).Data were analyzed by the Mann-Whitney test and the level of significance was set at p < 0.05.nnnRESULTSnThere was a statistically significant difference (p < 0.05) in state 3 between the CONTROL and I/R and HBO-I/R groups, in state 4 between the CONTROL and I/R and HBO-I/R groups; in respiratory control ratio (RCR) between the CONTROL and I/R and HBO-I/R groups and between the CONTROL and Sham groups, and in mitochondrial swelling between the CONTROL and I/R and HBO-/R groups and between the Sham and I/R and HBO-I/R groups.nnnCONCLUSIONnIn this process of periodic ischemia and reperfusion, hyperbaric pre-conditioning did not improve significantly hepatic mitochondrial function.

Brain metastasis of hepatocellular carcinoma detected after liver transplantation

AIMnWe report the case of a patient with hepatocellular carcinoma submitted to liver transplantation, who subsequently manifested tumor recurrence initially as brain metastasis.nnnCASE DESCRIPTIONnA 48-year-old male cirrhotic patient with hepatitis C infection, and two focal hepatic lesions, had a cytologic and histologic diagnosis of hepatocellular carcinoma. Before transplant, he was submitted to adjuvant treatment with a combination of arterial embolization and intratumoral ethanol injection. In the 3rd month post-liver transplantation, the patient developed headache, nausea and vomiting, without any neurological impairment. Brain computed tomography and magnetic resonance imaging identified an expansive hypervascular lesion with internal bleeding. Evaluation of the surgical explant revealed macroscopic invasion of portal vessels.nnnCONCLUSIONnBrain metastasis of a hepatocellular carcinoma after liver transplantation may occur. This metastasis may have occurred before or soon after the transplant. Patients with hepatocellular carcinoma, awaiting liver transplant, should be screened for cerebral metastasis. Vascular invasion may indicate hematogenic dissemination of the tumor.

Can joint analysis of postoperative MELD, base excess and blood lactate levels be used as an index of postoperative outcome for patients submitted to liver transplantation?

PURPOSEnThe objective of the present study was to evaluate the postoperative levels of classical or pure MELD and changes in lactate or base excess (BE) levels as possible predictive factors of the type of outcome of patients submitted to orthotopic liver transplantation (OLT).nnnMETHODSnThe study was conducted on 60 patients submitted to OLT at the University Hospital, Faculty of Medicine of Ribeirão Preto, USP, between October 2008 and March 2012. The 30 latest survivor (S) and non-survivor (NS) cases were selected. All liver transplants were performed using the piggy-back technique. ALT, AST, BE and blood lactate values were determined for each group at five time points (immediate preoperative period, end of hypothermal ischemia, 5 and 60 minutes after arterial revascularization and in the immediate postoperative period, when the postoperative MELD was also calculated.nnnRESULTSnThe aminotransferases reached a maximum increase 24 hours after surgery in both the S and NS groups. There was a significantly higher increase in BE and blood lactate in the NS group, especially after 5 minutes of afterial reperfusion of the graft, p<0.05. There was no significant difference in preoperative MELD between groups (p>0.05), while the postoperative MELD was higher in the NS than in the S group (p<0.05)nnnCONCLUSIONnJoint analysis of postoperative MELD, BE and blood lactate can be used as an index of severity of the postoperative course of patients submitted to liver transplantation.

Analysis of the Liver Effluent as a Marker of Preservation Injury and Early Graft Performance

In liver transplantation, the effluent solution, which represents the washout of residual preservation solution, can be collected before reperfusion to determine the release of the markers of endothelial cell injury and damage to the liver. The enzyme activities detected in the washout solution may allow the development of an index that could be clinically valuable for the prediction of early posttransplant graft function. In the present study, we collected liver effluents from 47 livers at the time of graft rinsing to measure liver enzymes (aminotransferases and lactate dehydrogenase) as well as the serum enzyme levels of the recipients for correlation with early postoperative graft viability (1-month survival). The patients were divided into two groups: death (D) and survival (S). Nonparametric statistical analysis was used with the level of significance set at P < .05. Aminotransferases and lactate dehydrogenase levels higher among the D group (P < .05 for all measurements), leading us to conclude that the effluent represents a good marker of preservation injury and early graft performance.

Effect of hyperbaric hepatic hyperoxia on the liver of rats submitted to intermittent ischemia/reperfusion injury

PURPOSEnTo determine the effect of hyperbaric hyperoxia as hepatic preconditioning on hepatocellular integrity in rats submitted to intermittent hepatic ischemia/reperfusion injury.nnnMETHODSnTwenty male Wistar rats were divided into 4 groups (SHAM, I/R, HBO-I/R and CONTROL). The surgical technique consisted of total clamping of the hepatic pedicle for 15 min, followed by reperfusion for 5 min, performed twice. The application of hyperbaric oxygen (HBO) was carried out in a collective chamber (simultaneous exposure of 4 rats) pressurized directly with oxygen at 2 ATA for 60 min. Tissue malondialdehyde (MDA) levels were determined and blood samples were collected for the determination of serum AST and ALT levels. Data were analyzed statistically by the Mann-Whitney test, with the level of significance set at p < 0.05.nnnRESULTSnA statistically significant difference in MDA (p< 0.05) was observed between control and HBO-I/R, but not between control and I/R. Regarding AST, there was a difference between control and I/R and HBO-I/R. Analysis of ALT revealed a significant difference between control and I/R (p<0.05) and between I/R and HBO-I/R, with no difference between control and HBO-IR.nnnCONCLUSIONnHyperoxic preconditioning proved to be favorable regarding alanine transaminase, but not aspartate aminotranserase or malondialdehyde levels.

The Influence of Hemorrhagic Shock on Rat Liver Regeneration after Partial Hepatectomy: Serum Aminotranspherases, Mitochondrial Function, and Hepatocellular Replication Studies

This study was designed to evaluate the influence of hemorrhagic shock on hepatic regeneration in rats submitted to partial hepatectomy. The experimental protocol included 26 male Wistar rats, randomly assigned to 4 groups: GI: simulated operation; GII: 30% hepatectomy without hemorrhagic shock; GIII: only hemorrhagic shock; GIV: 30% hepatectomy associated with hemorrhagic shock. The methodologies used were: determination of aminotranspherases plasma levels; analysis of mitochondrial respiration, membrane potential and osmotic swelling; and markers of hepatocellular replication. Aminotranspherases increased only in GIV. There were no differences in mitochondrial respiration. Mitochondrial membrane potential decreased only in the GIV. There were no differences in mitochondrial swelling among the groups; cellular replication markers increased significantly in the Groups II and IV but without difference between these two groups. Despite the conditions imposed on the organism by hemorrhagic shock, the hepatic regenerative capacity is preserved in animals submitted to partial hepatectomy.