Rapid growth of an intact human liver transplanted into a recipient larger than the donor

Volumetric graft changes after liver transplantation: evidence of adaptation to recipient body size

It is believed that whole liver grafts adjust their size to fit the body size of the recipient after transplantation, despite a lack of evidence. The aim of this study was to test this hypothesis. This was a retrospective cohort study of 113 liver transplantations performed at Karolinska University Hospital. The cohort was divided based on graft volume-to-standard liver volume ratio (GV/SLV) into quartiles of small, mid, and large grafts. Serial volumetric assessment was performed on the day of transplantation and at posttransplant check-ups early (<2 mo) and late (9-13 mo) after transplantation using computed tomography (CT) volumetry. Change in GV/SLV ratio over time was analyzed with ANOVA repeated measures. A multiple regression model was used to investigate the influence of intraoperative blood flow, recipient body size, age, and relative sickness on graft volume changes. Between the three time points, mean GV/SLV ratio adapted to 0.55-0.94-1.00 in small grafts (n = 29, P < 0.001); 0.87-1.18-1.13 in midgrafts (n = 56, P < 0.001); 1.11-1.51-1.18 in large grafts (n = 28, P < 0.001). Regression analysis showed a positive correlation between posttransplant graft growth and portal flow (β = 1.18, P = 0.005), arterial flow (β = 0.17, P = 0.001), and recipient body surface area (β = 59.85, P < 0.001). A negative correlation was observed for graft weight-to-recipient weight ratio (GRWR; β = -33.12, P < 0.001). Grafts with initial GV/SLV-ratio < 0.6 adapt toward the ideal volume for recipient body size 1 year after transplantation. The disparity between graft size relative to recipient body size, and the portal and arterial perfusion, influence volumetric graft changes.NEW & NOTEWORTHY This is the first and largest human study to verify the hypothesis that whole liver grafts adjust their size to match recipient body size 1 year after transplantation-a phenomenon that has previously only been observed in experimental animal studies and human case reports. The direction of volumetric changes is driven by the disparity between graft size relative to recipient body surface area and weight, as well as the intraoperative portal- and arterial graft perfusion.

The Role of Endoplasmic Reticulum Stress Response in Liver Regeneration

Exposure to hepatotoxic chemicals is involved in liver disease-related morbidity and mortality worldwide. The liver responds to damage by triggering compensatory hepatic regeneration. Physical agent or chemical-induced liver damage disrupts hepatocyte proteostasis, including endoplasmic reticulum (ER) homeostasis. Post-liver injury ER experiences a homeostatic imbalance, followed by active ER stress response signaling. Activated ER stress response causes selective upregulation of stress response genes and downregulation of many hepatocyte genes. Acetaminophen overdose, carbon tetrachloride, acute and chronic alcohol exposure, and physical injury activate the ER stress response, but details about the cellular consequences of the ER stress response on liver regeneration remain unclear. The current data indicate that inhibiting the ER stress response after partial hepatectomy-induced liver damage promotes liver regeneration, whereas inhibiting the ER stress response after chemical-induced hepatotoxicity impairs liver regeneration. This review summarizes key findings and emphasizes the knowledge gaps in the role of ER stress in injury and regeneration.

Role of the Hippo pathway in liver regeneration and repair: recent advances

Although the signaling pathways involved in normal liver regeneration have been well characterized, less has been done for livers affected by chronic tissue damage. These "abnormal livers" have an impaired regenerative response that leads to liver repair and fibrosis. The tumor suppressor Hippo pathway plays a key role in liver regeneration and repair. On this basis, this review discusses recent studies focusing on the involvement of the Hippo signaling pathway during "normal healthy liver regeneration" (i.e., in a normal liver after 2/3 partial hepatectomy) and "abnormal liver regeneration" (i.e., in a liver damaged by chronic disease). This could be an important question to address with respect to new therapies aimed at improving impaired liver regenerative responses. The studies reported here have shown that activation of the Hippo coactivators YAP/TAZ during normal liver regeneration promotes the formation of a new bile duct network through direct BEC proliferation or/and hepatocyte dedifferentiation to HPCs which can trans-differentiate to BECs. Moreover, YAP/TAZ signaling interaction with other signaling pathways mediates the recruitment and activation of Kupffer cells, which release mitogenic cytokines for parenchymal and/or non-parenchymal cells and engage in phagocytosis of cellular debris. In addition, YAP-mediated activation of stellate cells (HSCs) promotes liver regeneration through the synthesis of extracellular matrix. However, in chronically diseased livers, where the predetermined threshold for proper liver regeneration is exceeded, YAP/TAZ activation results in a reparative process characterized by liver fibrosis. In this condition, YAP/TAZ activation in parenchymal and non-parenchymal cells results in (i) differentiation of quiescent HSCs into myofibroblastic HSCs; (ii) recruitment of macrophages releasing inflammatory cytokines; (iii) polarization of macrophages toward the M2 phenotype. Since accumulation of damaged hepatocytes in chronic liver injury represent a significant risk factor for the development of hepatocarcinoma, this review also discussed the involvement of the Hippo pathway in the clearance of damaged cells.

Liver Regeneration: Changes in Oxidative Stress, Immune System, Cytokines, and Epigenetic Modifications Associated with Aging

The regenerative capacity of the liver decreases with increase in age. In recent years, studies in mice have found that the regenerative capacity of the liver is associated with changes in the immune system of the liver, cytokines in the body, aging-related epigenetic modifications in the cell, and intracellular signaling pathways. In the immune system of the aging liver, monocytes and macrophages play an important role in tissue repair. During tissue repair, monocytes and macrophages undergo a series of functional and phenotypic changes to initiate and maintain tissue repair. Studies have discovered that knocking out macrophages in the liver during the repair phase results in significant impairment of liver regeneration. Furthermore, as the body ages, the secretion and function of cytokines undergo a series of changes. For example, the levels of interleukin-6, transforming growth factor-alpha, hepatocyte growth factor, and vascular endothelial growth factor undergo changes that alter hepatocyte regulation, thereby affecting its proliferation. In addition, body aging is accompanied by cellular aging, which leads to changes in gene expression and epigenetic modifications. Additionally, this in turn causes alterations in cell function, morphology, and division and affects the regenerative capacity of the liver. As the body ages, the activity of associated functional proteins, such as CCAAT-enhancer-binding proteins, p53, and switch/sucrose nonfermentable complex, changes in the liver, leading to alterations in several signaling pathways, such as the Hippo, PI3K-Akt, mTOR, and STAT3 pathways. Therefore, in recent years, research on aging and liver regeneration has primarily focused on the immune system, signaling pathways, epigenetic changes of senescent cells, and cytokine secretion in the liver. Hence, this review details the roles of these influencing factors in liver regeneration and impact of aging-related factors.

Liver regeneration in aged mice: new insights

The regenerative capacity of the liver after resection is reduced with aging. Recent studies on rodents revealed that both intracellular and extracellular factors are involved in the impairment of liver mass recovery during aging. Among the intracellular factors, age-dependent decrease of BubR1 (budding uninhibited by benzimidazole-related 1), YAP (Yes-associated protein) and SIRT1 (Sirtuin-1) have been associated to dampening of tissue reconstitution and inhibition of cell cycle genes following partial hepatectomy. Extra-cellular factors, such as age-dependent changes in hepatic stellate cells affect liver regeneration through inhibition of progenitor cells and reduction of liver perfusion. Furthermore, chronic release of pro-inflammatory proteins by senescent cells (SASP) affects cell proliferation suggesting that senescent cell clearance might improve tissue regeneration. Accordingly, young plasma restores liver regeneration in aged animals through autophagy re-establishment. This review will discuss how intracellular and extracellular factors cooperate to guarantee a proper liver regeneration and the possible causes of its impairment during aging. The possibility that an improvement of the liver regenerative capacity in elderly might be achieved through elimination of senescent cells via autophagy or by administration of direct mitogenic agents devoid of cytotoxicity will also be entertained.

Modeling the dynamics of hepatitis B infection, immunity, and drug therapy

Hepatitis B virus infection is the cause of liver diseases such as cirrhosis and liver cancer. Understanding the host-virus mechanisms that mediate virus pathogenesis can help design better preventive measures for disease control. Mathematical models have been used alongside experimental data to provide insight into the role of immune responses during the acute and chronic hepatitis B infections as well as virus dynamics following administration of combined drug therapy. In this paper, we review several modeling studies on virus-host interactions during acute infection, the virus-host characteristics responsible for transition to chronic disease, and the efficacy and optimal control measures of drug therapy. We conclude by presenting our opinion on the future directions of the field.

Understanding the Complex Patterns Observed during Hepatitis B Virus Therapy

Data from human clinical trials have shown that the hepatitis B virus (HBV) follows complex profiles, such as bi-phasic, tri-phasic, stepwise decay and rebound. We utilized a deterministic model of HBV kinetics following antiviral therapy to uncover the mechanistic interactions behind HBV dynamics. Analytical investigation of the model was used to separate the parameter space describing virus decay and rebound. Monte Carlo sampling of the parameter space was used to determine the virological, pharmacological and immunological factors that separate the bi-phasic and tri-phasic virus profiles. We found that the level of liver infection at the start of therapy best separates the decay patterns. Moreover, drug efficacy, ratio between division of uninfected and infected cells, and the strength of cytotoxic immune response are important in assessing the amount of liver damage experienced over time and in quantifying the duration of therapy leading to virus resolution in each of the observed profiles.

Delayed Liver Regeneration after Partial Hepatectomy in Aged Nos2 Knockout Mice

Objective

Patients over 60 years of age have higher mortality and morbidity after major liver resections. Nitric oxide (NO) derived from the catalytic activity of Nos2 plays a beneficial role in liver regeneration (LR) after partial hepatectomy (PH). In this experiment, we evaluated the effect of Nos2 knockout (KO) on LR in aged mice after PH.

Materials and Methods

In this experimental study, 52 two-year-old Nos2 KO and 46 the same age wild-type (WT) C57BL/6J mice were subjected to 2/3 PH. Liver tissues were collected at 11 time points after PH. Mice survival ratio and liver coefficient (liver-weight/ body-weight) was calculated. Transcript and protein levels were estimated by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blot, respectively.

Results

The aged Nos2 KO mice had lower survival ratio (P=0.039) and liver coefficient (P=0.002) at the termination phase. Nos2 transcript level was obviously increased after PH in WT mice and undetected in the Nos2 KO mice. During LR, the expression at the transcript level of Cyclin D1, Cyclin A2 and Cyclin B1 and protein expression level of proliferation marker Ki67 and proliferation-associated transcription factors JNK1, NF-kB and STAT3 were decreased or delayed. The expression of pro-apoptotic proteins, CASPASE3, CASPASE9 and BAX, was increased in the Nos2 KO mice.

Conclusion

Decreased survival ratio and impaired LR in aged Nos2 KO mice is probably due to decreased liver cell proliferation and increased liver cell apoptosis.

Liver graft hyperperfusion in the early postoperative period promotes hepatic regeneration 2 weeks after living donor liver transplantation: A prospective observational cohort study

Hepatic regeneration is essential to meet the metabolic demands of partial liver grafts following living donor liver transplantation (LDLT). Hepatic regeneration is promoted by portal hyperperfusion of partial grafts, which produces shear stress on the sinusoidal endothelium. Hepatic regeneration is difficult to assess within the first 2 weeks after LDLT as the size of liver graft could be overestimated in the presence of postsurgical graft edema. In this study, we evaluated the effects of graft hyperperfusion on the rate of hepatic regeneration 2 weeks after LDLT by measuring hepatic hemodynamic parameters. Thirty-six patients undergoing LDLT were enrolled in this study. Hepatic hemodynamic parameters including peak portal venous flow velocity (PVV) were measured using spectral Doppler ultrasonography on postoperative day 1. Subsequently, we calculated the ratio of each velocity to 100 g of the initial graft weight (GW) obtained immediately after graft retrieval on the day of LDLT. Ratios of GW to recipient weight (GRWR) and to standard liver volume (GW/SLV) were also obtained. The hepatic regeneration rate was defined as the ratio of the regenerated volume measured using computed tomographic volumetry at postoperative week 2 to the initial GW. Correlations of the hemodynamic parameters, GRWR, and GW/SLV with the hepatic regeneration rate were assessed using a linear regression analysis. The liver grafts regenerated to approximately 1.7 times their initial GW (1.7 ± 0.3 [mean ± standard deviation]). PVV/100 g of GW (r = 0.224, β1 [slope coefficient] = 2.105, P = 0.004) and velocities of the hepatic artery and vein per 100 g of GW positively correlated with the hepatic regeneration rate, whereas GRWR (r = 0.407, β1 = -81.149, P < 0.001) and GW/SLV (r = 0.541, β1 = -2.184, P < 0.001) negatively correlated with the hepatic regeneration rate. Graft hyperperfusion demonstrated by increased hepatic vascular velocities and a small-sized graft in the early postoperative period contributes to hepatic regeneration 2 weeks after LDLT.

Serial volumetric assessment of large for size liver grafts after whole cadaveric liver transplant in adults: do large liver grafts shrink in size?

BACKGROUND

After whole graft orthotopic liver transplantation (OLT), adaptation of the large grafts' volume to recipient weight is widely accepted despite the paucity of evidence on this subject.

METHODS

Thirty nine patients with GRWR > 2.5% were included in this study and subsequently divided into two groups with 3 ≥ GRWR > 3%. Patients had CT scans at three predetermined time points after OLT used for measuring the liver volume. The objective of this study is to evaluate the volumetric changes of whole large liver grafts after adult OLT.

RESULTS

At LT, the mean graft recipient body weight ratio (GRWR) was 3.1 ± 0.4%. The mean liver weight was 1881 ± 68 g at LT, 2014 ± 99 ml at one week, 1725 ± 126 ml at 3 months, and 1632 ± 117 (ml) at >6 months. There is an initial increase at 1 week after LT and a subsequent decrease of liver volume on later measurements. None of the late volume measurements were significantly different from the initial graft volume at liver transplant in pair wise comparisons ANOVA repeated measures (p > 0.05). Similarly, the mean GRWR did not change significantly between the initial calculation at transplantation date and the subsequent measurements during the different study time points (F = 0.04, p = 0.96) with a mean of 3.1% (95% CI = 2.2-4.2). AUC ROC discriminated a cutoff of 3% for the initial GRWR above which grafts tend to decrease in size over time (c statistics = 0.74, p = 0.036). In a Clustered ANOVA repeated measures, there was no significant difference in the changes of liver volume between both groups. However, patients with GRWR > 3 showed a trend towards a latent reduction in volume over the tracing period. There was a tendency, but none significant; towards a higher bilirubin, AST, ALT levels over the first postoperative days in recipients with GRWR > 3.

CONCLUSION

Large grafts do not significantly decrease in size. Nonetheless, grafts weighing >3% of the GRWR show a different trend towards decrease in size over time.

Hepatocytes in liver injury: Victim, bystander, or accomplice in progressive fibrosis?

Chronic liver disease causes significant morbidity and mortality through progressive fibrosis, cirrhosis, and liver cancer. The classical theory of fibrogenesis has hepatic stellate cells (HSCs) as the principal and only significant source of abnormal extracellular matrix (ECM). Further, HSCs have the major role in abnormal ECM turnover. It is the death of hepatocytes, as the initial target of injury, that initiates a sequence of events including the recruitment of inflammatory cells and activation of HSCs. Following this initial response, the ongoing insult to hepatocytes is regarded as perpetuating injury, but otherwise, hepatocytes are regarded as "victims" and "bystanders" in progressive fibrosis. Recent developments, however, challenge this view and suggest the concept of the hepatocyte being an active participant in liver injury. It is clear now that hepatocytes undergo phenotypic changes, adapt to injury, and react to the altered microenvironment. In this review, we describe studies showing that hepatocytes contribute to progressive fibrosis by direct manipulation of the surrounding ECM and through signaling to effector cells, particularly HSCs and intrahepatic immune cells. Together, these findings suggest an active "accomplice" role for the hepatocyte in progressive liver fibrosis and highlight novel pathways that could be targeted for development of future anti-fibrotic therapies.

The influence of skeletal muscle on the regulation of liver:body mass and liver regeneration

The relationship between liver and body mass is exemplified by the precision with which the liver:body mass ratio is restored after partial hepatic resection. Nevertheless, the compartments, against which liver mass is so exquisitely regulated, currently remain undefined. In the studies reported here, we investigated the role of skeletal muscle mass in the regulation of liver:body mass ratio and liver regeneration via the analysis of myostatin-null mice, in which skeletal muscle is hypertrophied. The results showed that liver mass is comparable and liver:body mass significantly diminished in the null animals compared to age-, sex-, and strain-matched controls. In association with these findings, basal hepatic Akt signaling is decreased, and the expression of the target genes of the constitutive androstane receptor and the integrin-linked kinase are dysregulated in the myostatin-null mice. In addition, the baseline expression levels of the regulators of the G1-S phase cell cycle progression in liver are suppressed in the null mice. The initiation of liver regeneration is not impaired in the null animals, although it progresses toward the lower liver:body mass set point. The data show that skeletal muscle is not the body component against which liver mass is positively regulated, and thus they demonstrate a previously unrecognized systemic compartmental specificity for the regulation of liver:body mass ratio.

Hepatic hyperplasia associated with discordant xenogeneic parenchymal-nonparenchymal interactions in human hepatocyte-repopulated mice

Liver mass is optimized in relation to body mass. Rat (r) and human (h) hepatocytes were transplanted into liver-injured immunodeficient mice and allowed to proliferate for 3 or 11 weeks, respectively, when the transplants stopped proliferating. Liver/body weight ratio was normal throughout in r-hepatocyte-bearing mice (r-hep-mice), but increased continuously in h-hepatocyte-bearing mice (h-hep-mice), until reaching approximately three times the normal m-liver size, which was considered to be hyperplasia of h-hepatocytes because there were no significant differences in cell size among host (mouse [m-]) and donor (r- and h-) hepatocytes. Transforming growth factor-beta (TGF-beta) type I receptor, TGF-beta type II receptor, and activin A type IIA receptor mRNAs in proliferating r-hepatocytes of r-hep-mice were lower than in resting r-hepatocytes (normal levels) and increased to normal levels during the termination phase. Concomitantly, m-hepatic stellate cells began to express TGF-beta proteins. In stark contrast, TGF-beta type II receptor and activin A type IIA receptor mRNAs in h-hepatocytes remained low throughout and m-hepatic stellate cells did not express TGF-beta in h-hep-mice. As expected, Smad2 and 3 translocated into nuclei in r-hep-mice but not in h-hep-mice. Histological analysis showed a paucity of m-stellate cells in h-hepatocyte colonies of h-hep-mouse liver. We conclude that m-stellate cells are able to normally interact with concordant r-hepatocytes but not with discordant h-hepatocytes, which seems to be at least partly responsible for the failure of the liver size optimization in h-hep-mice.

Hepatotrophic factors reduce hepatic fibrosis in rats

CONTEXT: Hepatic fibrosis occurs in response to several aggressive agents and is a predisposing factor in cirrhosis. Hepatotrophic factors were shown to stimulate liver growth and to restore the histological architecture of the liver. They also cause an improvement in liver function and accelerate the reversion of fibrosis before it progresses to cirrhosis. OBJECTIVE: To test the effects of hepatic fibrosis solution composed by amino acids, vitamins, glucose, insulin, glucagon and triiodothyronine on hepatic fibrosis in rats. METHODS: Fibrosis was induced in rats by gastric administration of dimethylnitrosamine (10 mg/kg) for 5 weeks. After liver biopsy, the rats received either hepatotrophic factors solution (40 mg/kg/day) or saline solution for 10 days by intraperitoneal injection. Blood samples and liver fragments were collected for hepatic function analysis, standard histopathology evaluation, and morphometric collagen quantification. RESULTS: Rats in the hepatotrophic factors group showed a decrease of the histopathological components of fibrosis and an increase of their hepatic mass (12.2%). There was no development of neoplasic lesions in both groups. Compared with the saline group, the hepatotrophic factors group also had a decrease of blood levels of hepatic-lesion markers (AST, ALT) and a decrease of collagen content in the portal spaces (31.6%) and perisinusoidal spaces (42.3%), as well as around the hepatic terminal vein (57.7%). Thus, hepatotrophic factors administration in the portal blood promoted a regenerative hepatic response, with an overall reduction of the volumetric density of collagen, improved hepatic function, and a general improvement in the histopathological aspects of fibrosis. CONCLUSION: Taken together, these results suggest the potential therapeutic use of this hepatotrophic factors solution to treat chronic liver diseases.

In vivo modeling of human liver for pharmacological study using humanized mouse

The liver occupies a central place in the treatment of the substances taken into the body. If we could devise an in vivo or in vitro model that perfectly mimics the naturally-created human (h) liver, the work required for making effective and safe medicines would become easier and could be undertaken more cost effectively than it is currently. Considering the advantages of in vivo modeling over in vitro modeling under the current technological state of life sciences research, we have created an experimentally workable in vivo h-liver model, a liver-humanized mouse, in which host hepatocytes are largely replaced with healthy normal h-hepatocytes. Xenogenic h-hepatocytes are capable of constructing a histologically normal liver by collaborating with mouse-nonparenchymal cells in an elaborately organized manner. Considering its potential use for drug development, we have extensively characterized the mouse regarding the infectivity toward h-hepatitis viruses, activities of h-enzymes in Phase I and II of drug metabolisms, and h-hepatocyte-related drug transporters. These studies indicate that the humanized mouse liver mimics h-phenotypes at a level appropriate for pharmacological studies, and, thus, can be used not only for developing new medicines, but also for examining biological and pathological mechanisms in the h-liver.

Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome

The aim of the study is to define the role of the HABR in the pathophysiology of the SFS liver graft and to demonstrate that restoration of hepatic artery flow (HAF) has a significant impact on outcome and improves survival. Nine pigs received partial liver allografts of 60% liver volume, Group 1; 8 animals received 20% LV grafts, Group 2; 9 animals received 20% LV grafts with adenosine infusion, Group 3. HAF and portal vein flow (PVF) were recorded at 10 min, 60 min and 90 min post reperfusion, on POD 3 and POD 7 in Group 1, and daily in Group 2 and 3 up to POD 14. Baseline HAF and PVF (ml/100 g/min) were 29 +/- 12 (mean +/- SD) and 74 +/- 8 respectively, with 28% of total liver blood flow (TLBF) from the HA and 72% from the PV. PVF peaked at 10 mins in all groups, increasing by a factor of 3.8 in the 20% group compared to an increase of 1.9 in the 60% group. By POD 7-14 PVF rates approached baseline values in all groups. The HABR was intact immediately following reperfusion in all groups with a reciprocal decrease in HAF corresponding to the peak PVF at 10 min. However in the 20% group HAF decreased to 12 +/- 8 ml/100 g/min at 90 min and remained low out to POD 7-14 despite restoration of normal PVF rates. Histopathology confirmed evidence of HA vasospasm and its consequences, cholestasis, centrilobular necrosis and biliary ischemia in Group 2. HA infusion of adenosine significantly improved HAF (p < .0001), reversed pathological changes and significantly improved survival (p = .05). An impaired HABR is important in the pathophysiology of the SFSS. Reversal of the vasospasm significantly improves outcome.

T Cells Survey the Stability of the Self: A Testable Hypothesis on the Homeostatic Role of TCR-MHC Interactions

In the lifetime of an individual, every single gene will have undergone mutation on about 10(10) separate occasions. Nevertheless, cancer occurs mainly with advancing age. Here, we hypothesize that the evolutionary pressure driving the creation of the T cell receptor (TCR) repertoire was primarily the homeostatic surveillance of the genome. The subtly variable T cells may in fact constitute an evolutionary link between the invariable innate and hypervariable B cell systems. The new model is based on the homeostatic role of T cells, suggesting that molecular complementarity between the positively selected TCR and the self peptide-presenting major histocompatibility complex molecules establishes and regulates homeostasis, strictly limiting variations of its components. Notwithstanding, the 'homeostatic role of T cells' model offers a more realistic explanation as to how a naïve clonal immune system can cope with the much faster replicating pathogens, despite a limited repertoire that is capable of facing only a small fraction of the vast antigenic universe at a time.

The role of cells refractory to productive infection in acute hepatitis B viral dynamics

During acute hepatitis B virus (HBV) infection viral loads reach high levels ( approximately 10(10) HBV DNA per ml), and nearly every hepatocyte becomes infected. Nonetheless, approximately 85-95% of infected adults clear the infection. Although the immune response has been implicated in mediating clearance, the precise mechanisms remain to be elucidated. As infection clears, infected cells are replaced by uninfected ones. During much of this process the virus remains plentiful but nonetheless does not rekindle infection. Here, we analyze data from a set of individuals identified during acute HBV infection and develop mathematical models to test the role of immune responses in various stages of early HBV infection. Fitting the models to data we are able to separate the kinetics of the noncytolytic and the cytolytic immune responses, thus explaining the relative contribution of these two processes. We further show that we need to hypothesize that newly generated uninfected cells are refractory to productive infection. Without this assumption, viral resurgence is observed as uninfected cells are regenerated. Such protection, possibly mediated by cytokines, may also be important in resolving other acute viral infections.

Progenitor cells in liver regeneration: molecular responses controlling their activation and expansion

Although normally quiescent, the adult mammalian liver possesses a great capacity to regenerate after different types of injuries in order to restore the lost liver mass and ensure maintenance of the multiple liver functions. Major players in the regeneration process are mature residual cells, including hepatocytes, cholangiocytes and stromal cells. However, if the regenerative capacity of mature cells is impaired by liver-damaging agents, hepatic progenitor cells are activated and expand into the liver parenchyma. Upon transit amplification, the progenitor cells may generate new hepatocytes and biliary cells to restore liver homeostasis. In recent years, hepatic progenitor cells have been the subject of increasing interest due to their therapeutic potential in numerous liver diseases as alternative or supportive/complementary tools to liver transplantation. While the first investigations on hepatic progenitor cells have focused on their origin and phenotypic characterization, recent attention has focused on the influence of the hepatic microenvironment on their activation and proliferation. This microenvironment comprises the extracellular matrix, epithelial and non-epithelial resident liver cells, and recruited inflammatory cells as well as the variety of growth-modulating molecules produced and/or harboured by these elements. The cellular and molecular responses to different regenerative stimuli seem to depend on the injury inflicted and consequently on the molecular microenvironment created in the liver by a certain insult. This review will focus on molecular responses controlling activation and expansion of the hepatic progenitor cell niche, emphasizing similarities and differences in the microenvironments orchestrating regeneration by recruitment of progenitor cell populations or by replication of mature cells.

A Multiphase Model of the Dynamics of HBV Infection in Hbeag-Negative Patients during Pegylated Interferon-α2A, Lamivudine and Combination Therapy

Using a multiphase bio-mathematical model, we studied the dynamics of hepatitis B virus (HBV) infection in 72 HBeAg-negative patients who received 48 weeks of either lamivudine (3TC; 25 patients); pegylated interferon-α2a (peg-IFN-α2a) 180 mg weekly plus 3TC (23 patients), or peg-IFN-α2a 180 mg weekly plus placebo (24 patients).

During the first month of therapy most of the 3TC -/+ peg-IFN-α2a treated patients showed a multiphase decay of viral load: during the first two phases, where we hypothesized a direct inhibition of virus production, the mean viral production per infected cell was reduced by 2.22 log10 and 2.36 log10, respectively. At variance, peg-IFN-α2a treated patients had a biphasic profile: the first phase HBV DNA decline was slower than that observed in 3TC patients (mean HBV DNA t1/2=1.6 ±1.1 days and 9.5 ±3.0 h, respectively) and the direct antiviral effect reduced virus production by 1.14 log10 From day 14 onwards (third or second phase according to multi- or biphasic patterns), HBV DNA declined mainly because of the infected hepatocyte clearance that slowed down in approximately 50% of the patients from day 35, possibly because of a negative feedback on the immune system activity. Computing the number of infected cells at the end of therapy we found that peg-IFN-α2a and 3TC monotherapy determined a similar reduction of infected hepatocytes (mean: -3.3 log10), whereas there was a greater reduction in combination therapy patients (-5.0 versus -3.3 log10, P=0.039). In conclusion, peg-IFN-α2a, in spite of having direct antiviral activity lower than that of 3TC, achieved a comparable reduction of infected hepatocytes, possibly because of a higher infected cell clearance rate.

Classification of proliferative hepatocellular lesions in harlan sprague-dawley rats chronically exposed to dioxin-like compounds

Over the years, the most appropriate classification scheme for nodular proliferative lesions of the hepatocyte has been heavily debated. In the most recent guidelines there appears to be a consensus for classifying these lesions as hepatocellular adenoma, hepatocellular carcinoma, or regenerative hyperplasia. Also, large foci of cellular alteration may appear somewhat nodular. Some nodular hepatocellular lesions from a group of 7 studies of dioxin and dioxin-like compounds conducted by the National Toxicology Program did not readily fit into these categories. Some of these lesions had morphologic features consistent with hyperplasia. However, there was not sufficient morphological or biological evidence to conclude that the entire response was regenerative. In other instances, these lesions had some features resembling adenoma, but contained a prominent component of biliary epithelium and/or oval cells. This component does not appear to be well described in the literature, and while its presence suggested a nodule to be nonneoplastic, this is inconclusive. This paper describes the morphology of these lesions, as well as the diagnostic approach taken in this series of studies.

Porcine partial liver transplantation: a novel model of the "small-for-size" liver graft

Increasing shortage of cadaveric grafts demands the utilization of living donor and split liver grafts. The purpose of this study was to 1) define the "small-for-size" graft in a pig liver transplant model 2) evaluate pathological changes associated with small-for-size liver transplantation. Pigs were divided into four groups based on the volume of transplanted liver: (a) control group (n=4), 100% liver volume (LV) (b) group I (n=8), 60% LV (c) group II (n=8), 30% LV (d) group III (n=15), 20% LV. Tacrolimus and methyl prednisone were administered as immunosuppression. Animals were followed for 5 days with daily serum biochemistry, liver biopsies on day 3 and 5 for light microscopy, and tissue levels of thymidine kinase (TK) and ornithine decarboxylase (ODC). Liver grafts were weighed pretransplant and at sacrifice. All the recipients of 100%, 60%, and 30% grafts survived. Transplantation of 20% grafts (group III) resulted in a 47% mortality rate. Group III animals showed significantly prolonged prothrombin times (p<0.05), elevated bilirubin levels (p<0.05), and ascites. The rate of regeneration, as indicated by TK activity and graft weight was inversely proportional to the size of the transplanted graft. The severity of the microvascular injury was inversely proportional to graft size and appeared to be the survival-limiting injury. Frank rupture of the sinusoidal lining, parenchymal hemorrhage, and portal vein injury were prominent in group III animals 1 hour following reperfusion. This study established a reproducible large animal model of partial liver grafting; it defined the small-for-size syndrome in this model and described the associated microvascular injury.

Adenovirus-mediated overexpression of follistatin enlarges intact liver of adult rats

Under normal physiologic conditions, liver size is under strict regulatory control. Activin, a member of the transforming growth factor beta (TGF-beta) superfamily, is expressed in the intact adult liver and is an inhibitor of hepatocyte growth. However, the exact role played by endogenous activin in maintaining the size of a normal adult liver has yet to be completely examined in vivo. Here, we report the development of an adenoviral vector (AdexCAFS288) that expressed human follistatin-288, which binds to activin and neutralizes its biologic activities. AdexCAGFP, a control virus, expressed green fluorescent protein. AdexCAFS288 effectively expressed follistatin-288, as measured both in HepG2 cell lysate and conditioned medium and blocked activin signaling and its biologic functions in vitro. Intraperitoneal injection of AdexCAFS288 in vivo resulted in significant liver growth (146% of control) in intact liver of adult male rats 12 days following treatment without significant dysfunctions. The increase in liver size was attributed to increased hepatocyte proliferation, as monitored by the mitotic index. Furthermore, there was a significant correlation between serum follistatin levels and liver weight. In conclusion, our results suggest that activin plays a critical role in maintaining optimal liver size and implicates the endogenous activin system as a therapeutic target in the treatment of liver disease.

Small-for-size graft in living donor liver transplantation: how far should we go?

With the extensive use of living donor liver grafts in adult patients, controversy over small-for-size syndrome has escalated in recent years. Although several symptoms have been suggested as manifestations of the syndrome, small-for-size syndrome remains difficult to diagnose because these symptoms are neither specific nor inevitable. The occurrence of small-for-size syndrome also seems to depend on a number of recipient and graft factors. Potential pathogenic mechanisms include persistent portal hypertension and portal overperfusion. At present, several techniques are being explored in an attempt to ameliorate the impact of small-for-size syndrome. Recent experience suggests that the occurrence of small-for-size syndrome is multifactorial and that complications relating to small-for-size grafts should be examined in relation to a variety of graft, recipient, and technical factors.

Relationship between portal venous flow and liver regeneration in patients after living donor right-lobe liver transplantation

The purpose of this study is to evaluate the relationship between portal venous (PV) velocity and degree of liver regeneration in humans after living donor liver transplantation (LDLT). Between July 1997 and September 2002, a total of 15 adult-to-adult LDLTs with right-lobe grafts were performed, and 13 of these patients were enrolled in this study. Postoperative PV dynamics differed according to the primary liver disease; therefore, patients were divided into two groups: a fulminant hepatic failure (FHF) group (n = 4) and a liver cirrhosis (LC) group (n = 9). Right-lobe donors (n = 13; D group) were used as controls. Doppler ultrasound was used to measured changes in PV velocity preoperatively; postoperative days (PODs) 1, 3, 7, 14, and 28; and 3 months after LDLT. To assess hepatic regeneration, the increase in liver volume ratio (postoperative liver volume to standard liver volume [SLV]) was measured. PV velocity after LDLT in the LC group increased sharply until POD 7, whereas those in the FHF and D groups were constant. In the first 3 months after LDLT, mean PV velocity was greater in the LC group than the other groups, reflecting the persistent hyperdynamic state in chronic end-stage liver disease. Liver regeneration also was more rapid in the LC group than the FHF and D groups and reached 100% as early as 2 weeks posttransplantation, whereas both the FHF and D livers reached approximately 80% of SLV at 3 months. PV velocity POD 7 correlated significantly with regeneration of the partial-liver allograft at 1 month (r = 0.84; P =.0091). In conclusion, the PV persistent hyperdynamic state in the LC group could directly trigger early liver regeneration in partial-liver allografts after LDLT.

Liver regeneration investigated in a non-human primate model (Macaca mulatta)

BACKGROUND/AIMS

An adequate model to study liver regeneration in humans is presently unavailable. We explored the feasibility of studying liver regeneration in a genetically similar species to man, the non-human primate Rhesus macaque.

METHODS

Five animals were studied; two underwent 60% hepatectomy, one underwent 30% hepatectomy, and cholecystectomy alone was performed on two animals. Laparoscopic-guided or open liver biopsies were performed on days 1, 2, 7, 14, 21, 30 and 60 following all surgeries. Liver regeneration was evaluated by measuring Ki-67, proliferating cell nuclear antigen expression and mitotic index, calculating changes in the surface area of the liver remnant and assessing intrahepatic production of cytokines.

RESULTS

Significant liver regeneration was induced in the animals that underwent 60% hepatectomy, peaking between days 21-30 postoperatively. Regeneration was minimal in all other animals studied. Cytokine production followed a similar pattern. Maximal liver regeneration correlated with restoration of surface area in the liver remnant.

CONCLUSIONS

Sixty percent hepatectomy in a non-human primate model induced significant liver regeneration, maximizing 21-30 days following partial hepatectomy, suggesting a significant interspecies difference when compared to a rodent hepatectomy model. A partial hepatectomy model in Rhesus macaques may allow further characterization of liver regeneration in a species closer to humans.

Sustained Response to Interferon–Ribavirin Combination Therapy Predicted by a Model of Hepatitis C Virus Dynamics Using Both Hcv Rna and Alanine Aminotransferase

Background and aims

Standard models simulate the dynamics of hepatitis C virus (HCV) infection using HCV RNA kinetics and show a correlation between the clearance of infected hepatocytes and response to interferon. However, they are unable to predict whether the response will be maintained. The aim of our work was to identify criteria by which sustained responses may be predicted and defined.

Methods

In our model the clearance rate of infected cells is a function of their number and the baseline rate is computed by the alanine aminotransferase (ALT) kinetics during the first month of therapy. We simulated the variations of viral and infected cell loads in 31 consecutive patients treated with IFN-α2b 3–5 MU every other day, with or without ribavirin, for 6 or 12 months depending on HCV genotype.

Results

At baseline the computed (in 28 of 31 cases) percentage of infected cells was lower in seven sustained responders (mean: 11.7%, range: 1–24.6%) than in 14 transient responders (mean: 28.2%, range: 7.4–75.5%) and in seven non-responders (mean: 41%, range: 8.8–86%) ( P=0.036). At the end of therapy the computed infected cell number was <100 cells/ml of extracellular fluid in all sustained responders (mean: 18.4, range: 1.7–48), in three transient responders (mean: 3500, range: 1.52–17500) and in none non-responders (mean: 28500, range: 1200–96000) ( P=0.003). Overall of 10 patients with less than 100 infected cells/ml at the end of therapy seven (six had combination therapy) showed sustained response. All three relapsers received interferon monotherapy.

Conclusion

The analysis of infected cells dynamics using the new model might be useful to tailor treatment duration in patients with combination therapy.

Living donor liver transplant recipients achieve relatively higher immunosuppressant blood levels than cadaveric recipients

Two recent brief reports suggest that recipients of living donor liver transplants achieve higher levels of immunosuppressive agents than cadaveric (CAD) liver transplant recipients administered the same dose. These results could have important implications regarding the dosing of immunosuppressives in living donor liver transplant recipients. We report our findings relative to immunosuppressive doses and levels in a cohort of 46 living donor liver transplant recipients. Immunosuppressive blood levels and doses were recorded weeks 1, 2, 3, and 4 and months 2, 3, 4, 5, and 6 for 46 living donor liver transplant recipients and 66 matched CAD liver transplant recipients who underwent transplantation between August 1997 and May 2001. The ratio of level to dose also was recorded at each interval. The mean overall cyclosporine A dose was similar in living donor liver transplant recipients (323 mg/d) compared with CAD recipients (344 mg/d; P = not significant [NS]). The mean overall tacrolimus dose was 15% lower in patients who underwent living donor liver transplantation (LDLT; 5.7 mg/d) than CAD transplantation (6.7 mg/d), although statistical significance was not achieved (P =.08). The mean overall cyclosporine A level was 18% higher in those undergoing LDLT (275 ng/mL) than CAD transplantation (234 ng/mL; P =.015). The mean overall tacrolimus level was the same in living donor liver transplant recipients (10.8 ng/mL) and CAD recipients (10.2 ng/mL; P = NS). The overall cyclosporine A level-dose ratio was 26% higher for those undergoing LDLT (0.83) than CAD transplantation (0.66; P =.01). The overall tacrolimus level-dose ratio was 26% higher for those undergoing LDLT (1.82) than CAD transplantation (1.44; P =.01). In conclusion, (1) living donor liver transplant recipients achieve higher blood levels of tacrolimus and cyclosporine A for a given dose compared with CAD recipients, and (2) this difference is observed up to 6 months after transplantation, when hepatic regeneration is completed.

Living-related liver transplantation for fulminant hepatic failure in children

Liver transplantation is increasingly accepted as a choice of treatment for fulminant hepatic failure (FHF) since it has been proved to significantly improve the survival rate in these patients compared with other therapeutic modalities. We have successfully performed a total of 76 living related liver transplantations (LRLT) three of which were for FHF. The first case was an 11-year-old boy with FHF due to an unidentified cause. He had required plasmapheresis a total of 24 times and haemofiltration to save his life before LRLT. He was transplanted with a left lobe (420 g) graft, calculated as 1.05% of his weight (40 kg). He recovered hepatic function uneventfully and was discharged from hospital after 7 weeks. The second case was a 13-year-old girl who developed FHF with grade III encephalopathy due to acute Wilson's disease, and was referred to us. She underwent LRLT with a left lobe graft (440 g), estimated as 0.95% of her weight (47 kg), which functioned well after surgery. The third case was a 13-year-old girl with grade II encephalopathy due to acute Wilson's disease. She was 27% obese with a body weight of 58 kg. She underwent LRLT with ABO blood group incompatibility with a left lobe (352 g), estimated as 0.80% of her weight (modified 44 kg). She was discharged with sensorimotor neuropathy due to vitamin B deficiency. The present results suggest that LRLT is feasible for FHF both clinically and ethically, and that a partial liver graft weighing around 1% of the recipient's weight can maintain the recipient's life. We limit the diagnostic indication for LRLT to chronic liver disease, since an urgent situation may affect a voluntary decision for the patient's parents to donate the partial liver. However, LRLT is thought to be an acceptable choice of treatment provided it is requested by the patient and family. Furthermore, it is a potential option for resolving the graft shortage in paediatric liver transplantation, being independent of cadaver donor availability.

Right hepatic lobectomy as a liver graft-saving procedure

Retransplantation is common after liver transplantation (LT). However, in the present era of organ shortages, every attempt to save the liver graft should be performed before considering retransplantation. We report our experience with right hepatic lobectomy (RHL) for liver graft salvage. In a retrospective series of 180 adult LTs, 4 patients underwent RHL (Couinaud's segments V, VI, VII, VIII) in the post-LT period. In all cases, the procedure was performed without Pringle's maneuver or mobilization of the left liver lobe to preserve its vascularization. Three liver graft recipients developed intrahepatic biliary strictures, mainly localized to the right lobe of the graft, and RHL was performed 14, 75, and 78 months after LT. These patients were alive at last follow-up without further episodes of cholangitis or retransplantation (mean follow-up, 38 months). The fourth patient developed early post-LT right liver necrosis with a functioning hepatic artery and underwent right lobectomy 48 hours after LT. He later developed cholangitis secondary to late hepatic artery thrombosis, requiring retransplantation after 18 months. We conclude that RHL can be considered a graft-saving option in selected liver transplant recipients with localized biliary strictures, with excellent patient and graft survival.

Liver regeneration and function in donor and recipient after right lobe adult to adult living donor liver transplantation

BACKGROUND

Regeneration of the liver to a predetermined size after resection or transplantation is a well described phenomenon, but the time course over which these events occur has not been well defined. It is not clear how initial liver mass, reperfusion, immunosuppression, or steatosis influence this process.

METHODS

Liver regeneration was assessed prospectively by volumetric magnetic resonance imaging (MRI) in living right lobe liver donors and the recipients of these grafts. Imaging was performed at regular intervals through 60 days after resection/transplantation, and liver mass was determined. Liver function tests and synthetic function were monitored throughout the study period in donors and recipients of these grafts as well as recipients of cadaveric grafts.

RESULTS

MRI consistently overestimated liver mass by a mean of 45 g (+/-65) (range 10-123). Donor liver mass increased by 101%, 110%, 115%, and 144% at 7, 14, 30, and 60 days after resection, respectively. Recipient liver mass increased by 87,101, 119, and 99% at 7, 14, 30, and 60 days after transplantation, respectively. Steatosis did not influence the degree of regeneration or graft function, nor was there a functional difference between grafts of >1% graft to recipient body weight ratio or <1%.

CONCLUSIONS

MRI accurately determines right lobe mass. Most liver regeneration occurs in the 1st week after resection or transplantation, and the time course does not differ significantly in donors or recipients. The mass of the graft or remnant segment affects the duration of the regeneration process, with a smaller initial liver mass prolonging the course. Steatosis of <30% had no bearing on liver function or regeneration and, therefore, should not be an absolute criterion for exclusion of donors. A calculated graft to recipient body weight ratio of 0.8% is adequate for right lobe living donor liver transplantation.

Changes in liver regenerative factors in a case of living-related liver transplantation

Liver regeneration in a patient with fulminant hepatic failure (FHF) who underwent living-related partial liver transplantation (LRLT) was investigated regarding hepatic growth factors. The patient was a 16-yr-old Japanese male who developed severe subacute FHF. LRLT was performed using an extended left lobe of the ABO matched patient's mother. In the recipient, the pre-transplant levels of both plasma hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta were extremely high and rapidly decreased following the liver replacement. The liver volume evaluated using a CAT scan increased 195% after 2 wk in graft liver and 110% after 2 wk in the hepatectomized donor. The explanted liver (FHF liver), the liver from donor (normal liver), and the graft liver [the 3rd post-transplant day (POD 3)] were all investigated immunohistochemically. FHF liver: No liver regeneration was observed [proliferative cell nuclear antigen (PCNA) labeling index (L.I.): 0%]. In the liver, both HGF in the hepatocytes and c-met on the membrane of the hepatocytes were positive. TGF-beta was positive in the hepatocytes and no apoptosis was detected by the TUNEL method. Donor liver (POD 0): Few PCNA stained hepatocytes were detected. No HGF was detected but c-met was clearly detected on the cell membrane of the hepatocytes. Neither TGF-beta nor apoptosis was detected. Graft liver (POD 3): The PCNA L.I. was conspicuous at 40%. HGF was positive in non-parenchymal cells and c-met was positive in the cytoplasm of the hepatocytes. TGF-beta was negative while apoptosis was positive in the zone 3 hepatocytes. In conclusion, these findings suggested that the liver of the patient with FHF did not respond to liver regenerative stimulus, in part, through involvement of inhibitor TGF-beta. On POD 3, the transplanted graft was in a vigorous regenerative status in comparison to that in the hepatectomized donor. The HGF/c-met system is thought to be involved in the mechanism of regeneration. Intrahepatic apoptosis was detected in the graft on the 3rd post-transplant day probably due to transient ischemia in the liver, which was not related to the Fas/Fas-ligand system.

Minimum graft size for successful living donor liver transplantation

BACKGROUND

The extension of living donor liver transplantation to adult recipients is limited by the adequacy of the size of the graft. We evaluate the effect of the graft size on the survival of the recipient in order to establish a clinical guide for the minimum requirement.

METHODS

The clinical records of 14 adults and 11 children (body weight 6.1-100 kg) who underwent living donor liver transplantation for chronic or acute liver failure were reviewed. The effect of the graft weight ratio (graft weight divided by standard liver weight of recipient) on graft function and survival was studied.

RESULTS

The graft weight ratio ranged from 31 to 203%. The overall graft and patient survival rates were 84% at a median follow-up of 29 months. The survival rate was 95% for recipients with a graft weight ratio >40%, and 40% only for those with a ratio < or =40% (P = 0.016). It was 88% (7/8) when the ratio was >100%, 100% (5/5) when the ratio was 71 to 100%, 100% (7/7) when the ratio was 41 to 70%, and 40% (2/5) only when the ratio was < or =40%. When the graft weight ratio was < or =40%, early graft dysfunction was evident and contributed to the causes of death in three patients.

CONCLUSIONS

Preoperative computed tomographic measurement of liver size of a living donor is essential. A graft that represented 40% or less of the recipient's standard liver weight should be regarded as a marginal graft with a lower success rate.

Progression through G1 and S phases of adult rat hepatocytes

Regenerating liver, hepatocyte primary cultures and differentiated hepatoma cell lines are widely used to study the proliferation/differentiation/apoptosis equilibrium in liver. In hepatocytes, priming factors (TNF alpha, IL6) target G0/G1 transition while growth factors (HGF, EGF, TGF alpha) control a mid-late G1 restriction point. A characteristic pattern of cdk/cyclin expression is observed in hepatocytes, presumably related to their ability to proliferate a limited number of times and to undergo a reversible differentiation. Interestingly, cell-cell interactions between hepatocytes and liver biliary cells in co-cultures, result in a cell cycle arrest in mid G1 of hepatocytes which are insensitive to mitogens. Apoptosis exists in hepatocytes but is still poorly documented. However, hepatoma cell lines stimulated by TGF beta undergo cell death in a p53-independent pathway. In conclusion, the interplay of growth and apoptosis regulators and cell-cell interactions control the proliferation/differentiation/apoptosis balance which is a specific feature of hepatocytes.

Functional analysis of grafts from living donors. Implications for the treatment of older recipients

OBJECTIVE

Living-related liver transplantation (LRLT) has established efficacy in children. In a larger recipient, LRLT requires the use of a small graft because of limits on the donor hepatectomy.

SUMMARY BACKGROUND DATA

The minimum graft weight required for successful transplantation has not been well established, although a characteristic pattern of graft dysfunction has been observed in our patients who receive small grafts. The authors present a clinicopathologic study of small liver grafts obtained from living donors.

METHODS

Clinical and histologic data were reviewed for 25 patients receiving LRLT. In five older recipients (small group), the graft represented 50% or less of expected liver weight, whereas in 20 others (large group), the graft represented at least 60% of expected liver weight. A retrospective analysis of graft function was conducted by analyzing clinical parameters and histology.

RESULTS

In the small group, 2 of 5 grafts (40%) were lost due to poor function, leading to one patient death (20% mortality), whereas in the large group, 2 of 20 grafts (10%) were lost due to arterial thrombosis without patient mortality. Early ischemic damage related to transplant was comparable with aspartate aminotransferase 203 +/- 23 (small group) and 290 +/- 120 (large group) at 24 hours (p = not significant). Early function was significantly decreased in the small group, with prothrombin time 18.2 +/- 2.2 seconds versus 14.8 +/- 1.6 seconds (large group) on day 3 (p = 0.034). All small group patients developed cholestasis with significantly increased total bilirubin levels at day 7 (16 +/- 5.2 mg% vs. 3.7 +/- 2.7 mg%; p = 0.021) and day 14 (12.0 +/- 7.4 vs. 1.8 +/- 0.7; p = 0.021) compared with the large group. Protocol biopsies in the small group revealed a diffuse ischemic pattern with cellular ballooning on day 7, which progressed to cholestasis in subsequent biopsies. Large group biopsies showed minimal ischemic changes. Three small group patients recovered with normal liver function by 12 weeks.

CONCLUSIONS

Clinical recovery after a small-for-size transplant is characterized by significant functional impairment associated with paradoxical histologic changes typical of ischemia. These changes apparently are due to graft injury, which can only be the result of small graft size. These findings have significant implications for the extension of LRLT to adults.

Functional analysis of grafts from living donors. Implications for the treatment of older recipients

OBJECTIVE

Living-related liver transplantation (LRLT) has established efficacy in children. In a larger recipient, LRLT requires the use of a small graft because of limits on the donor hepatectomy.

SUMMARY BACKGROUND DATA

The minimum graft weight required for successful transplantation has not been well established, although a characteristic pattern of graft dysfunction has been observed in our patients who receive small grafts. The authors present a clinicopathologic study of small liver grafts obtained from living donors.

METHODS

Clinical and histologic data were reviewed for 25 patients receiving LRLT. In five older recipients (small group), the graft represented 50% or less of expected liver weight, whereas in 20 others (large group), the graft represented at least 60% of expected liver weight. A retrospective analysis of graft function was conducted by analyzing clinical parameters and histology.

RESULTS

In the small group, 2 of 5 grafts (40%) were lost due to poor function, leading to one patient death (20% mortality), whereas in the large group, 2 of 20 grafts (10%) were lost due to arterial thrombosis without patient mortality. Early ischemic damage related to transplant was comparable with aspartate aminotransferase 203 +/- 23 (small group) and 290 +/- 120 (large group) at 24 hours (p = not significant). Early function was significantly decreased in the small group, with prothrombin time 18.2 +/- 2.2 seconds versus 14.8 +/- 1.6 seconds (large group) on day 3 (p = 0.034). All small group patients developed cholestasis with significantly increased total bilirubin levels at day 7 (16 +/- 5.2 mg% vs. 3.7 +/- 2.7 mg%; p = 0.021) and day 14 (12.0 +/- 7.4 vs. 1.8 +/- 0.7; p = 0.021) compared with the large group. Protocol biopsies in the small group revealed a diffuse ischemic pattern with cellular ballooning on day 7, which progressed to cholestasis in subsequent biopsies. Large group biopsies showed minimal ischemic changes. Three small group patients recovered with normal liver function by 12 weeks.

CONCLUSIONS

Clinical recovery after a small-for-size transplant is characterized by significant functional impairment associated with paradoxical histologic changes typical of ischemia. These changes apparently are due to graft injury, which can only be the result of small graft size. These findings have significant implications for the extension of LRLT to adults.

Growth of oversized grafts in neonatal heart transplantation

BACKGROUND

Because of the severe shortage of neonatal organ donors, oversized cardiac allografts are frequently transplanted. This study examined body and graft growth of neonates who receive an oversized heart.

METHODS

We studied 51 neonates, who received transplants between November 1986 and August 1992, for changes in body weight, left ventricular mass, and end-diastolic volume measured at 1 week, 1, 3, and 6 months, and yearly after cardiac transplantation. Patients were divided into two groups according to donor/recipient weight ratios: the normal group, where the donor/recipient weight ratio was 1.5 or less (1.06 +/- 0.05; n = 24), and the oversized group, where the donor/recipient weight ratio was more than 1.5 (2.22 +/- 0.10; n = 27).

RESULTS

After cardiac transplantation, body weight increased continuously in both groups with no difference between groups. In the oversized group, left ventricular end-diastolic volume at 1 week and left ventricular mass at 1 week and 1 month were significantly higher than those in the normal group (p < 0.01). In the normal group, end-diastolic volume and left ventricular mass increased continuously. In the oversized group, however, left ventricular mass significantly decreased until 3 months after cardiac transplantation and then increased continuously, whereas end-diastolic volume increased continuously throughout the posttransplantation period.

CONCLUSIONS

These data suggest that oversized cardiac allografts shrink at first and then grow as the recipient grows. There appears to be a size adaptation of the large cardiac allograft to accommodate to the reduced requirements of the neonate.

Enhancement of liver size by stimulation of intact rat liver with exogenous hepatotrophic factors

In mammals, liver size is related to animal body weight at the 2.5 to 3% proportion, a ratio mediated by the afflux of hepatotrophic factors. Formulas capable of modifying this ratio have been developed in previous studies on the rat, with enhancement of liver size brought about by intraperitoneal (portal) infusion of exogenous factors such as glucose, amino acids, insulin, glucagon, vitamins, electrolytes, and triiodothyronine. However, the efficacy of these formulations was accompanied by increased animal mortality (PARRA et al.). The present study, which was carried out with small methodological modifications on a larger number of rats using daily intraperitoneal injections of a solution of exogenous hepatotrophic factors (40 ml/kg) for seven days, confirms the previous findings, with a 114.16 +/- 7.90% enhancement of liver size beyond the expected value for the body weight of the animal. However, the problem of animal mortality was not fully resolved.

Reduction of liver mass due to malnutrition in rats. Correlation with emaciation of animals and size of organs not inserted in the portal system

We studied the effects of protein-energy malnutrition on the liver morphology of rats as compared to animal emaciation and to reduction in size of the organs not irrigated by splanchnic blood such as kidneys and spleen. The animals were divided into two groups, one of them fed ad libitum rate (N = 10) and the other (N = 14) receiving water but no food for 7 days, and the changes in animal weight, liver, kidney and spleen mass were determined. DNA and the protein/DNA ratio, as well as hepatocyte size, were determined in liver tissue. The liver decreased in mass (27.14%) at a significantly higher proportion (p < 0.05) when compared to body emaciation (19.22%). Similar to the reduction in body weight, the masses of kidneys and spleen were reduced by 18.68% and 24.28%, respectively. The reduction in liver mass occurred due to hypoplasia and atrophy, i.e., a decrease in hepatocyte number and size, respectively. We conclude that there is a preferential consumption of liver protein in protein-energy malnutrition which is suggested to result from the additive action of the effects of overall consumption of organic reserves due to malnutrition proper and to the reduction of the hepatotrophic stimulus.