Non-invasive Imaging and Modeling of Liver Regeneration After Partial Hepatectomy

Longitudinal ultrasound imaging and network modeling in rats reveal sex-dependent suppression of liver regeneration after resection in alcoholic liver disease

Liver resection is an important surgical technique in the treatment of cancers and transplantation. We used ultrasound imaging to study the dynamics of liver regeneration following two-thirds partial hepatectomy (PHx) in male and female rats fed via Lieber-deCarli liquid diet protocol of ethanol or isocaloric control or chow for 5–7 weeks. Ethanol-fed male rats did not recover liver volume to the pre-surgery levels over the course of 2 weeks after surgery. By contrast, ethanol-fed female rats as well as controls of both sexes showed normal volume recovery. Contrary to expectations, transient increases in both portal and hepatic artery blood flow rates were seen in most animals, with ethanol-fed males showing higher peak portal flow than any other experimental group. A computational model of liver regeneration was used to evaluate the contribution of physiological stimuli and estimate the animal-specific parameter intervals. The results implicate lower metabolic load, over a wide range of cell death sensitivity, in matching the model simulations to experimental data of ethanol-fed male rats. However, in the ethanol-fed female rats and controls of both sexes, metabolic load was higher and in combination with cell death sensitivity matched the observed volume recovery dynamics. We conclude that adaptation to chronic ethanol intake has a sex-dependent impact on liver volume recovery following liver resection, likely mediated by differences in the physiological stimuli or cell death responses that govern the regeneration process. Immunohistochemical analysis of pre- and post-resection liver tissue validated the results of computational modeling by associating lack of sensitivity to cell death with lower rates of cell death in ethanol-fed male rats. Our results illustrate the potential for non-invasive ultrasound imaging to assess liver volume recovery towards supporting development of clinically relevant computational models of liver regeneration.

Macrophages play a key role in tissue repair and regeneration

Tissue regeneration after body injury has always been a complex problem to resolve for mammals. In adult mammals, the repair process after tissue injury is often accompanied by continuous and extensive fibrosis, which leads to scars. This process has been shown to severely hinder regeneration. Macrophages, as widely distributed innate immune cells, not only play an important role in various pathological processes, but also participate in the repair process before tissue regeneration and coordinate the regeneration process after repair. This review will discuss the various forms and indispensability of macrophages involved in repair and regeneration, and how macrophages play a role in the repair and regeneration of different tissues.

Shear stress-induced cellular senescence blunts liver regeneration through Notch-sirtuin 1-P21/P16 axis

BACKGROUND AND AIMS

The mechanisms involved in liver regeneration after partial hepatectomy (pHx) are complicated. Cellular senescence, once linked to aging, plays a pivotal role in wound repair. However, the regulatory effects of cellular senescence on liver regeneration have not been fully elucidated.

APPROACH AND RESULTS

Mice subjected to pHx were analyzed 14 days after surgery. The incomplete remodeling of liver sinusoids affected shear stress-induced endothelial nitric oxide synthase (eNOS) signaling on day 14, resulting in the accumulation of senescent LSECs. Removing macrophages to augment LSEC senescence led to a malfunction of the regenerating liver. A dynamic fluctuation in Notch activity accompanied senescent LSEC accumulation during liver regeneration. Endothelial Notch activation by using Cdh5-CreERT NIC^eCA mice triggered LSEC senescence and senescence-associated secretory phenotype, which disrupted liver regeneration. Blocking the Notch by γ-secretase inhibitor (GSI) diminished senescence and promoted LSEC expansion. Mechanically, Notch-hairy and enhancer of split 1 signaling inhibited sirtuin 1 (Sirt1) transcription by binding to its promoter region. Activation of Sirt1 by SRT1720 neutralized the up-regulation of P53, P21, and P16 caused by Notch activation and eliminated Notch-driven LSEC senescence. Finally, Sirt1 activator promoted liver regeneration by abrogating LSEC senescence and improving sinusoid remodeling.

CONCLUSIONS

Shear stress-induced LSEC senescence driven by Notch interferes with liver regeneration after pHx. Sirt1 inhibition accelerates liver regeneration by abrogating Notch-driven senescence, providing a potential opportunity to target senescent cells and facilitate liver repair after injury.

Acetylsalicylic acid (Aspirin®) and liver regeneration: experimental study in rats

OBJECTIVE

to evaluate the influence of acetylsalicylic acid (ASA) on cell proliferation after partial hepatectomy in rats.

METHODS

40 male Wistar rats were separated into four groups of ten rats each. Groups 1 and 2 (controls): undergoing 30% partial hepatectomy and, after one day (group 1) and seven days (group 2), to euthanasia; daily administration of 0.9% saline solution (1mL per 200g of body weight). Groups 3 and 4 (experimental): undergoing 30% partial hepatectomy and, after one day (group 3) and seven days (group 4), to euthanasia; daily administration of ASA (40mg/mL, 1mL per 200g of body weight). The absolute number of cells stained with PCNA was counted in photomicrographs, in five fields, and it was calculated the mean of positive cells per animal and per group.

RESULTS

the final mean of PCNA+ cells per group was: in group 1, 17.57 ± 6.77; in group 2, 19.31 ± 5.30; in group 3, 27.46 ± 11.55; and, in group 4, 12.40 ± 5.23. There was no significant difference at the two evaluation times in the control group (p=0.491), but there was in the experimental group (p=0.020), with a lower number of PCNA+ cells on the seventh day. The comparison between the two groups, on the first day, showed more PCNA+ cells in the livers of the animals that received ASA (p=0.047), and on the seventh day the number was lower in the experimental group (p=0.007).

CONCLUSION

ASA induced greater hepatocyte proliferation.

HO-1 Protects Remnant Liver against Dysfunction after Major Hepatectomy in Humans

OBJECTIVE

During major resection of liver carcinoma, liver regeneration (LR) is induced by various clinical and biological factors. Heme oxygenase (HO)-1 has been found as a key inducer of LR in preclinical trial. The clinical evidence for the role of HO-1 in liver dysfunction (LD) including LR is still unknown and has been included in this study.

METHODS

Therefore, plasma HO-1 were monitored during perioperative period in 65 patients with hepatectomy, with 35 training and 30 validation cohorts. LD were evaluated by liver function serum markers and calculation of regeneration indices, respectively.

RESULTS

In the training setting, HO-1 levels were remarkably reduced after liver resection (P < 0.001) and gradually recovered within 7 days after surgery. Preoperative HO-1 specifically predicted LD during the first week after surgery (AUC: 0.757; P = 0.01). In patients with LD and complications after surgery, HO-1 levels decreased throughout the perioperative period. In addition, we had also confirmed that low levels of HO-1 (<169 ng/ml) before surgery were associated with an increase in the incidence of postoperative LD and morbidity (P = 0.007, P = 0.045), and decrease of liver regeneration (P = 0.005). And HO-1 was an independent predictor for poor clinical outcome.

CONCLUSIONS

We had provided the first clinical data verifying that human HO-1 was related to LD. Consequently, HO-1 levels can be used as effective clinical indicators to predict LD and clinical outcome, and can be used as intervention target before liver resection.

Liver regeneration in traditional Chinese medicine: advances and challenges

Liver diseases pose a serious problem for national health care system all over the world. Liver regeneration has profound impacts on the occurrence and development of various liver diseases, and it remains an extensively studied topic. Although current knowledge has suggested two major mechanisms for liver regeneration, including compensatory hyperplasia of hepatocytes and stem or progenitor cell-mediated regeneration, the complexity of this physiopathological process determines that its effective regulation cannot be achieved by single-target or single-component approaches. Alternatively, using traditional Chinese medicine (TCM) to regulate liver regeneration is an important strategy for prevention and treatment of liver disorder and the related diseases. From the perspectives of TCM, liver regeneration can be caused by the disrupted balance between hepatic damage and regenerative capacity, and the "marrow"-based approaches have important therapeutic implications for liver regeneration. These two points have been massively supported by a number of basic studies and clinical observations during recent decades. TCM has the advantages of overall dynamic fine-tuning and early adjustment, and has exhibited enormous therapeutic benefits for various liver diseases. Here, we review the recent advances in the understanding of liver regeneration in TCM system in the hope of facilitating the application of TCM for liver diseases via regulation of liver regeneration.