Human hepatocytes and aging: a cytophotometrical analysis in 35 sudden-death cases

Improved assessment of donor liver steatosis using Banff consensus recommendations and deep learning algorithms

BACKGROUND & AIMS

The Banff Liver Working Group recently published consensus recommendations for steatosis assessment in donor liver biopsy, but few studies reported their use and no automated deep-learning algorithms based on the proposed criteria have been developed so far. We evaluated Banff recommendations on a large monocentric series of donor liver needle biopsies by comparing pathologists' scores with those generated by convolutional neural networks (CNNs) we specifically developed for automated steatosis assessment.

METHODS

We retrospectively retrieved 292 allograft liver needle biopsies collected between January 2016 and January 2020 and performed steatosis assessment using a former intra-institution method (pre-Banff method) and the newly introduced Banff recommendations. Scores provided by pathologists and CNN models were then compared, and the degree of agreement was measured with the intraclass correlation coefficient (ICC).

RESULTS

Regarding the pre-Banff method, poor agreement was observed between the pathologist and CNN models for small droplet macrovesicular steatosis (ICC: 0.38), large droplet macrovesicular steatosis (ICC: 0.08), and the final combined score (ICC: 0.16) evaluation, but none of these reached statistically significance. Interestingly, significantly improved agreement was observed using the Banff approach: ICC was 0.93 for the low-power score (p <0.001), 0.89 for the high-power score (p <0.001), and 0.93 for the final score (p <0.001). Comparing the pre-Banff method with the Banff approach on the same biopsy, pathologist and CNN model assessment showed a mean (±SD) percentage of discrepancy of 26.89 (±22.16) and 1.20 (±5.58), respectively.

CONCLUSIONS

Our findings support the use of Banff recommendations in daily practice and highlight the need for a granular analysis of their effect on liver transplantation outcomes.

IMPACT AND IMPLICATIONS

We developed and validated the first automated deep-learning algorithms for standardized steatosis assessment based on the Banff Liver Working Group consensus recommendations. Our algorithm provides an unbiased automated evaluation of steatosis, which will lay the groundwork for granular analysis of steatosis's short- and long-term effects on organ viability, enabling the identification of clinically relevant steatosis cut-offs for donor organ acceptance. Implementing our algorithm in daily clinical practice will allow for a more efficient and safe allocation of donor organs, improving the post-transplant outcomes of patients.

Morphological parameters of hepatocytes in the European mole (Talpa europaea) and herb field mouse (Sylvaemus uralensis) under industrial pollution: Qualitative and quantitative assessment

Morphological alterations of cells and tissues usually occur in biological organisms exposed to environmental contaminants, there by acting as a biomarker of environmental pollution, thus, making this study highly pertinent. The effect of industrial pollution on the qualitative and quantitative morphological parameters of hepatocytes (through histological analysis and cytomorphometry) was studied in two contrasting species of small mammals (Talpa europaea and Sylvaemus uralensis), taking into account the animal age (young and adult groups) and liver concentrations of heavy metals (Cu, Zn, Cd, Pb). Studies were performed in the regions exposed to emissions from two currently operating copper smelters: Middle Ural Copper Smelter (Middle Urals, T. europaea catching area) and Karabash Copper Smelter (Southern Urals, S. uralensis catching area). Seven morphometric parameters of hepatocytes were measured, of which two key parameters were selected by the method of principal components-the cell packing density and nuclear-cytoplasmic ratio (N/C). It was found that cell packing density in T. europaea from the impact zone decreased relative to the background area in young animals. At the same time, the differences in this parameter between the age groups from the background zone were leveled in the impact area of catching. The N/C ratio in T. europaea hepatocytes showed no correlation with either animal age or site of capture (background or impact area). In S. uralensis, both parameters, even taking into account the age, were found to be insensitive to indicate an effect of industrial pollution. Dystrophic changes (tested through histological analysis) in the liver tissue were revealed in all animal groups, but their frequency did not depend on any of the factors (age, zone) as well as the level of accumulation of toxic heavy metals (Cd, Pb). Morphometric parameters of hepatocytes have proved to be more reliable indicators of pollution, compared to the frequency of liver histopathology, due to lower subjectivity in their evaluation.

Digital twin demonstrates significance of biomechanical growth control in liver regeneration after partial hepatectomy

Partial liver removal is an important therapy option for liver cancer. In most patients within a few weeks, the liver is able to fully regenerate. In some patients, however, regeneration fails with often severe consequences. To better understand the control mechanisms of liver regeneration, experiments in mice were performed, guiding the creation of a spatiotemporal 3D model of the regenerating liver. The model represents cells and blood vessels within an entire liver lobe, a macroscopic liver subunit. The model could reproduce the experimental data only if a biomechanical growth control (BGC)-mechanism, inhibiting cell cycle entrance at high compression, was taken into account and predicted that BGC may act as a short-range growth inhibitor minimizing the number of proliferating neighbor cells of a proliferating cell, generating a checkerboard-like proliferation pattern. Model-predicted cell proliferation patterns in pigs and mice were found experimentally. The results underpin the importance of biomechanical aspects in liver growth control.

Hepatic macrophage accumulation with aging: cause for concern?

Aging is associated with chronic, low-grade inflammation that adversely affects physiological function. The liver regulates systemic inflammation; it is a source of cytokine production and also scavenges bacteria from the portal circulation to prevent infection of other organs. The cells with primary roles in these functions, hepatic macrophages, become more numerous in the liver with "normal" aging (i.e., in the absence of disease). Here, we demonstrate evidence and potential mechanisms for this phenomenon, which include augmented tumor necrosis factor-α (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) expression in the liver. Also, we discuss how an age-related impairment in autophagy within macrophages leads to a pro-oxidative state and ensuing production of proinflammatory cytokines, particularly interleukin 6 (IL-6). Given that the liver is a rich source of macrophages, we posit that it represents a major source of the elevated systemic IL-6 observed with aging, which is associated with physiological dysfunction. Testing a causal role for liver macrophage production of IL-6 during aging remains a challenge, yet interventions that have targeted macrophages and/or IL-6 have demonstrated promise in treating age-related diseases. These studies have demonstrated an age-related, deleterious reprogramming of macrophage function, which worsens pathology. Therefore, hepatic macrophage accrual is indeed a cause for concern, and therapies that attenuate the aged phenotype of macrophages will likely prove useful in promoting healthy aging.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

A mouse model of accelerated liver aging caused by a defect in DNA repair

The liver changes with age, leading to an impaired ability to respond to hepatic insults and increased incidence of liver disease in the elderly. Therefore, there is critical need for rapid model systems to study aging-related liver changes. One potential opportunity is murine models of human progerias or diseases of accelerated aging. Ercc1(-/Δ) mice model a rare human progeroid syndrome caused by inherited defects in DNA repair. To determine whether hepatic changes that occur with normal aging occur prematurely in Ercc1(-/Δ) mice, we systematically compared liver from 5-month-old progeroid Ercc1(-/Δ) mice to old (24-36-month-old) wild-type (WT) mice. Both displayed areas of necrosis, foci of hepatocellular degeneration, and acute inflammation. Loss of hepatic architecture, fibrosis, steatosis, pseudocapillarization, and anisokaryosis were more dramatic in Ercc1(-/Δ) mice than in old WT mice. Liver enzymes were significantly elevated in serum of Ercc1(-/Δ) mice and old WT mice, whereas albumin was reduced, demonstrating liver damage and dysfunction. The regenerative capacity of Ercc1(-/Δ) liver after partial hepatectomy was significantly reduced. There was evidence of increased oxidative damage in Ercc1(-/Δ) and old WT liver, including lipofuscin, lipid hydroperoxides and acrolein, as well as increased hepatocellular senescence. There was a highly significant correlation in genome-wide transcriptional changes between old WT and 16-week-old, but not 5-week-old, Ercc1(-/Δ) mice, emphasizing that the Ercc1(-/Δ) mice acquire an aging profile in early adulthood.

CONCLUSION

There are strong functional, regulatory, and histopathological parallels between accelerated aging driven by a DNA repair defect and normal aging. This supports a role for DNA damage in driving aging and validates a murine model for rapidly testing hypotheses about causes and treatment for aging-related hepatic changes.

Nuclear size measurement is a simple method for the assessment of hepatocellular aging in non-alcoholic fatty liver disease: Comparison with telomere-specific quantitative FISH and p21 immunohistochemistry

Telomere-specific quantitative fluorescent in situ hybridization (Q-FISH) accurately evaluates hepatocellular aging on histological sections, but it requires appropriate tissue processing. To establish a more simple method for the assessment of hepatocellular aging, the usefulness of nuclear size measurement was clarified using biopsy liver samples from 64 patients with non-alcoholic fatty liver disease (NAFLD), a model for oxidative stress-associated hepatocellular aging, and 11 control individuals. Relative telomere intensity (RTI) was measured on Q-FISH, and the relative nuclear size (RNS) was calculated as the average nuclear size of the hepatocytes divided by that of lymphocytes. In normal individuals and NAFLD patients, the RTI and RNS were negatively correlated. The degree of nuclear enlargement in NAFLD patients was larger than that in normal individuals with the same telomere length, possibly reflecting telomere-independent senescence. In NAFLD patients with RNS >2.0, the regenerative responses, indicated by the ratio of Ki-67-positive index to serum alanine aminotransferase level, were significantly reduced. The RNS positively correlated with the p21 expression, another marker of senescence. This all indicates that nuclear enlargement progresses in parallel with reduced regenerative responses, telomere shortening, and p21 upregulation. Nuclear size measurement is an effective method for estimation of hepatocellular aging.

Basal activity of Kupffer cells increases with old age

Age-related changes in Kupffer cell numbers and function may have important implications for systemic immune responses and hepatic function. We compared numbers of Kupffer cells in the hepatic sinusoids and phagocytic function of Kupffer cells in isolated perfused livers of young, middle-aged, and old rats. On light microscopy, the number of Kupffer cells per 29,500 mum(2) field increased with increasing age (young 2.0 +/- 0.2, n = 8; middle aged 3.3 +/- 0.3, n = 7; old 5.5 +/- 0.6, n = 7). After a single pass through the liver, the ratio of the fractional recovery of 500 nm polystyrene microspheres to that of sucrose decreased significantly with increasing age: young rats, 89 +/- 35% (n = 7); middle-aged rats, 58 +/- 18% (n = 9); and old rats, 49 +/- 24% (n = 10), suggesting increased Kupffer cell phagocytic activity. In old age, increased Kupffer cell numbers and activity were observed in the basal state.

Impact of donor age on the growth of young recipient rats after liver transplantation

PURPOSE

We studied the age-related changes in graft livers, and their impact on post-transplantation liver function and the growth of young recipient rats.

METHODS

Rats aged 11-68 weeks old were studied as controls to assess liver histology, liver function, and body weight. We performed orthotopic liver transplantation using Kamada's cuff technique without arterial reconstruction. Young rats aged 11 weeks were randomized to receive livers from either 11-week-old donors (YD group) or 52-week-old donors (OD group). Recipient rats were killed 0, 8, or 16 weeks after surgery and we assessed the same variables as in the controls.

RESULTS

We confirmed an age-related increase in the average size of hepatocytes and their nuclei. These age-related changes persisted and progressed in the graft liver after transplantation. There were no significant differences in the levels of serum transaminases or total bilirubin between the YD and OD groups, but the serum albumin level was significantly lower in the OD group. The YD group grew normally, whereas the OD group recipients lagged significantly in gaining body weight.

CONCLUSION

We found that 52-week-old grafts transplanted into 11-week-old recipients resulted in deficient growth and a decline in serum albumin, suggesting that grafted old livers fail to produce enough protein to meet the demands of growth adequately.

Gamma-glutamyltransferase induction by glucocorticoids in rat liver: age-dependence, time-dependence, dose-dependence, and intralobular distribution

Postnatal responsiveness of rat-liver gamma-glutamyltransferase (GGT) to glucocorticoids (GC) has been defined by investigating: age-dependence, time-dependence, hormonal dose-dependence, and lag-time of the enzyme re-expression; half-life of the induced enzyme activity; dynamics of the enzyme reappearance in the liver tissue. Hydrocortisone-acetate (HC) or dexamethasone (DEX) were administered to the animals starting 1, 2, 3, 4, or 5 d before killing, at the doses of 25 micrograms or 1 microgram/(g b. w. x d), respectively. In 14 d old rats, after a lag-time of about 20 h (DEX) or 30 h (HC), GGT activity progressively increased up to 38 and 31 times the control value, respectively, at 5th d; the enzyme re-expression was linearly hormone dose-dependent; half-life of the induced enzyme activity was about 36 h. In 21 d old rats, GGT re-induction behaved as in 14 d old animals, except that the induced activity was about half that of each correspondent treatment. In 28 d old rats, a very low but significant GGT activity was re-expressed only after hormonal treatments longer than 48 h. In 35 and 77 d old rats, significant GGT activity was never re-induced. GGT was re-expressed in liver parenchyma, with a defined space-course. In 14 d old rats, GGT reappeared first in periportal areas, then in acinar zone 1, finally in acinar zone 2. While the animals were ageing, GGT re-expression occurred to lesser and lesser extents in liver tissues, because of a progressive space-restriction from acinar zones 1 and 2 to zone 1 and finally, in 35 d old rats, to periportal areas. In adults, GGT was re-expressed only by rare hepatocytes in periportal spaces. Acinar zone-3 hepatocytes did never re-express GGT, irrespectively of the animal age. Thus, 2 rat hepatocyte populations could be distinguished (1 responsive, the other unresponsive to GC for GGT re-expression), the relative proportion of which changes in favour of the unresponsive one while the animal ages. Hepatic GGT re-induction by GC, occurring after a long lag-time, does not follow the typical model of hormonal induction. Previous permissive cell changes seem to be required. Hepatocyte-GGT re-expression by GC appears to be inversely correlated with the differentiation level and the cytochrome P-450 amount (activity) of the cell as limiting factors for the triggering of the enzyme induction.

An electron microscopic examination of age-related changes in the rat liver. The influence of diet

The influence of age and diet on the ultrastructure of hepatocytes is reported. The following dietary manipulations were investigated: Group 1, fed ad libitum a diet containing 21% protein; Group 2, fed a similar diet but restricted to 60% of the intake of Group 1 from 6 weeks of age onwards; Group 3, restricted from 6 weeks to 6 months of age and thereafter fed ad libitum; Group 4, restriction started at 6 months of age; Group 5, fed ad libitum a diet containing 12.6% protein. In all groups the size of hepatocytes was found not to increase during adult life. The size of hepatocytes in Groups 2 and 4 was the same as or larger than that of the other groups; thus food restriction resulted in a decreased number of hepatocytes. Changes in the structure of some organelles and the accumulation of lipofuscin granules occurred with advancing age and the extent of these age-related changes was less in Groups 2 and 4 than in the other groups. These morphologic findings in conjunction with our previously reported metabolic findings provide a new view of the action of food restriction on the aging process.

Cytological and quantitative cytochemical changes in the hepatocyte population of newborn rats following hydrocortisone administration

Changes have been assessed in cytological and quantitative cytochemical parameters of the hepatocyte population of newborn rats under glucocorticoid stimulation. Administration of hydrocortisone-acetate at the dose of 25 micrograms/g b.w./d during the 2nd week of postnatal life, caused: 1. an increase of the liver weight and of average dry mass, protein content, and volume of the hepatocytes; 2. a decrease of the number of hepatocytes per mg of liver tissue; 3. a reduction of the mitotic activity in liver parenchyma; 4. a gain in number of hepatocytes per liver lower than under normal conditions; 5. an increase of frequency of binuclear cells; 6. an increase of DNA-Feulgen per hepatocyte nucleus; 7. an increase per cell, greater than the mean protein increase per cell, in activity of arylhydrocarbonmonooxygenase and 7-ethoxycoumarin 0-deethylase, 2 enzymes dependent on cytochrome P-450. Induction of arylhydrocarbonmonooxygenase activity was prevalent in centrolobule. All the examined parameters, except that of DNA-Feulgen per nucleus and that of mitotic activity, changed strictly correlated with the duration of hormonal treatment. The values of a number of hepatocyte parameters (particularly: mean cell dry mass and volume, frequency of binuclear cells, enzymic activity) detected in the 12 d old rats after a 5 d long hormonal pretreatment, were in the range of those of animals 1 to 2 weeks older.

Changes in Polyploidy During Aging in Human Liver

The level of liver polyploidy was compared in three groups of humans: a young group aged 20–46, an older group aged 62–68 and the oldest group aged 70–79. The most important trend showed by the data was that there is a depletion of 2N and 4N cells, accompanied by an increase in 8N and 16N cells as a function of advancing age. There was a high degree of variability in the percentage of cells in each ploidy class from one individual to the next for all age groups. For this reason, polyploidy appears to be a less effective biomarker of aging in humans than it is in experimental animals.

A cytophotometrical study on the centenarian hepatocyte

Size alterations, both of cell and nucleus, of the centenarian hepatocyte followed a pattern proportionate to aging which was observed in the hepatocyte of non-centenarian groups and clearly followed nonagenarian in location on the graph. When size alterations of the hepatocyte were considered as an aging parameter, the present observation suggests that the centenarian could be a group next to the nonagenarian. The results obtained by present cytomorphometrical analysis do not favor a hypothesis that the centenarian is a select population in terms of longevity.

Age-related alterations in the size of human hepatocytes. A study of mononuclear and binucleate cells

Age-related alterations in the size of human hepatocytes (both mononuclear and binucleate forms), were studied in histological sections and in separated cells and nuclei using cytophotometrical and microspectrophotometrical methods. The following results were obtained: 1. The volume of nuclear DNA increased in proportion to nuclear size. The increase occurred in a group pattern reflecting nuclear polyploidization. 2. Cell size increased in proportion to nuclear size. Tetraploid cells (4C) were roughly two times greater than diploid cells (2C). 3. In most of the binucleate cells examined, the ploidy class of the two nuclei in a binucleate cell was observed to be equal. Heterogeneity of the ploidy class among the nuclei of a binucleate cell was present in less than 1% of total binucleate cells examined. The nuclear DNA volume of individual nuclei in binucleate cells appeared to be the same as that of mononuclear cells. 4. The cell size of binucleate cells corresponded with that of mononuclear cells whose ploidy class was the same as the sum of the ploidy classes of two nuclei of a binucleate cell. 5. The incidence of binucleate cells in the lobular periphery was about 4 to 6% in the third decade, and increased slightly with age up to 5 to 7% in the tenth decade. 6. The incidence of binucleate cells in the liver at different ages followed a similar pattern to that observed in mononuclear cells whose ploidy class was half of the sum of ploidy classes of the two nuclei of the binucleate cell.