Secretome of senescent hepatoma cells modulate immune cell fate by macrophage polarization and neutrophil extracellular traps formation.

Presence of dysfunctional senescent hepatocytes is a hallmark feature of liver cirrhosis which finally culminates in liver cancer. We now report the presence of senescent hepatocytes (p21 and p53 positive) in the vicinity of infiltrated immune cells in hepatocellular carcinoma tissue specimens by immunohistochemistry. Hence, we evaluated in vitro, the relevance of senescent hepatoma cells in altering the fate of monocytes and neutrophils by assaying for macrophage polarization and extracellular trap (NETs) formation, respectively. Premature senescence was induced in hepatoma cells (HepG2 and Huh7 cells) by treating cells with doxorubicin. Senescent hepatoma cells showed strong inflammatory phenotype with induced expression of cytokines (IL1ß, IL6, IL8 and IL13) as evaluated by flow cytometry. The senescent secretome from hepatoma cells when incubated with healthy monocytes caused it to differentiate predominantly towards M2 fate (CD80low CD86low CD163high CD206high) when analysed by flow cytometry. This was corroborated by the finding in clinical samples where human hepatocellular carcinoma harbouring senescent hepatocytes showed presence of M2 macrophages, while M1 macrophages were predominant in non-tumorous region. Additionally, the senescent secretome from Huh7 cells enhanced the NETs formation, while HepG2 secretome had an inhibitory effect. In conclusion, the "pro-inflammatory" senescent secretome drives non-inflammatory type M2 macrophage polarization and modulated neutrophil traps which in turn can influence the tumor microenvironment.

Senescent Hepatocytes in Decompensated Liver Show Reduced UPRMT and Its Key Player, CLPP, Attenuates Senescence In Vitro.

BACKGROUND AND AIMS: Non-dividing hepatocytes in end-stage liver disease indicates permanent growth arrest similar to senescence. Identifying senescence in vivo is often challenging and mechanisms inhibiting senescence are poorly understood. In lower organisms mitochondrial unfolded protein response (UPRMT) helps in increasing longevity; however, its role in senescence and liver disease is poorly understood. Aim of this study was to identify hepatocyte senescence and the role of UPRMT in cryptogenic cirrhosis. METHODS: Doxorubicin was used to induce senescence in non-neoplastic hepatocytes (PH5CH8) and hepatoma cells (HepG2 and Huh7). Senescence-associated markers and unfolded protein response was evaluated by fluorescence microscopy, immunoblotting and gene expression. Explants/biopsies from normal, fibrosis, compensated and decompensated cirrhosis without any known etiology were examined for presence of senescence and UPRMT by immunohistochemistry and gene expression. RESULTS: Accumulation of senescent hepatocytes in cryptogenic cirrhosis was associated with reduced proliferation, increased expression of γH2AX and p21, together with loss of LaminB1. Dysfunctional mitochondria and compromised UPRMT were key features of senescent hepatocytes both in vitro and also in decompensated cirrhosis. Intriguingly, compensated cirrhotic liver mounted strong UPRMT, with high levels of mitochondrial protease, CLPP. Overexpression of CLPP inhibited senescence in vitro, by reducing mitochondrial ROS and altering oxygen consumption. CONCLUSIONS: Our results implicate a role of hepatocyte senescence in cryptogenic cirrhosis together with a crucial role of UPRMT in preventing hepatocyte senescence. A compromised UPRMT may shift the fate of cirrhotic liver toward decompensation by exaggerating hepatocyte senescence. Restoring CLPP levels at least in cell culture appears as a promising strategy in mitohormesis, thereby, preventing senescence and possibly improving hepatocyte function.

Differentially regulated gene expression in quiescence versus senescence and identification of ARID5A as a quiescence associated marker.

In multicellular organisms majority of the cells remain in a non-dividing states of either quiescence (reversible) or senescence (irreversible). In the present study, gene expression signatures unique to quiescence and senescence were identified using microarray in osteosarcoma cell line, U2OS. It was noted that certain genes and pathways like NOD pathway was shared by both the growth arrest conditions. A major highlight of the present study was increased expression of number of chemokines and cytokines in both quiescence and senescence. While senescence-associated secretory phenotype (SASP) is well known, the quiescence-associated secretory phenotype (QASP) is relatively unknown and appeared novel in this study. ARID5A, a subunit of SWI/SNF complex was identified as a quiescence associated gene. The endogenous expression of ARID5A increased during serum starved condition of quiescence. Overexpression of ARID5A resulted in more number of cells in G0/G1 phase of cell cycle. Further ARID5A overexpressing cells when subjected to serum starvation showed a pronounced secretory phenotype. Overall, the present work has identified gene expression signatures which can distinguish quiescence from senescence.

Meiotic maturation of oocytes recovered from the ovaries of Indian big cats at postmortem.

In order to increase the available sources of genetic material for endangered members of the great cat family, this study was designed to assess the meiotic competence of oocytes recovered from postmortem ovaries of the Indian leopard, tiger and lion. The average number of oocytes that were recovered per ovary was 11.0 ± 5.0, 11.0 ± 3.5 and 21.3 ± 8.8 for tiger, lion and leopard, respectively. The proportion of culture grade oocytes for tiger, lion and leopard were 72.7, 78.8 and 71.9%, respectively. The culture grade oocytes were matured in tissue culture medium 199 modified with sodium bicarbonate supplemented with 0.3% BSA (fatty acid-free) (w/v), 10 µg/ml FSH, 6 IU/ml LH, 1 µg/ml 17ß-estradiol, 0.36 mM pyruvate, 2.2 mM calcium lactate, 2.0 mM L-glutamine, 100 IU/ml penicillin and 0.1 mg/ml streptomycin in an incubator with 5% CO2 under humidified air at 38.5°C for 36 h. After in vitro maturation, 56.3, 53.8 and 58.7% of the tiger, lion and leopard oocytes, respectively, were matured. The proportion of oocytes that extruded first polar body was significantly higher when the oocytes were collected from the animals of less than 15 yr of age compared to above 15 yr. These findings suggest that the oocytes recovered from ovaries of tiger, lion and leopard immediately postmortem can be successfully matured to MII stage.