Liver regeneration: immunohistochemical study of intrinsic hepatic innervation after partial hepatectomy in rats

Role of cholinergic innervation in biliary remnants of patients with biliary atresia

Objective

Biliary innervation is considered important in regulating the function of bile ducts, whereas the role of innervation in the hepatobiliary system of patients with biliary atresia (BA) remains unknown. This current study aims to investigate the role of innervation in biliary remnants and analyze the relationship between the innervation and prognosis of BA after surgery.

Methods

Eighty-seven patients with type III BA who underwent the Kasai procedure were consecutively enrolled from January 2017 to September 2020. Innervation and ductules in remnants were examined by pathologists. Liver function, onset of cholangitis, jaundice clearance, and survival with the native liver were recorded. Patients were followed up for 24 months. The relationship between innervation and prognosis was analyzed.

Results

In total, 67 patients had bile drainage postoperatively, and 21 biliary remnants contained neuronal plexuses where there was no neuron but nerve fiber bundles. Acetylcholinesterase staining was positive in all plexuses. In patients with bile drainage, those with plexuses had improved postoperative liver function, significantly better jaundice clearance 3 or 6 months postoperatively (50.0% vs. 19.1%, or 90.0% vs. 63.8%, respectively), fewer episodes of early cholangitis (10.0% vs. 34.0%), and better survival (80.0% vs. 61.7%) compared to those without. In addition, a larger area of plexuses was associated with a larger area of ductules (R2 = 0.786, p = 0.000), less frequent (p = 0.000) and later cholangitis onset (p = 0.012), and better jaundice clearance (p = 0.063).

Conclusions

Increased cholinergic innervation in biliary remnants may help reduce the onset of cholangitis and lead to better and earlier jaundice clearance. Thus, it improves the postoperative prognosis of patients with BA.

Nerve regeneration in transplanted organs and tracer imaging studies: A review

The technique of organ transplantation is well established and after transplantation the patient might be faced with the problem of nerve regeneration of the transplanted organ. Transplanted organs are innervated by the sympathetic, parasympathetic, and visceral sensory plexuses, but there is a lack of clarity regarding the neural influences on the heart, liver and kidneys and the mechanisms of their innervation. Although there has been considerable recent work exploring the potential mechanisms of nerve regeneration in organ transplantation, there remains much that is unknown about the heterogeneity and individual variability in the reinnervation of organ transplantation. The widespread availability of radioactive nerve tracers has also made a significant contribution to organ transplantation and has helped to investigate nerve recovery after transplantation, as well as providing a direction for future organ transplantation research. In this review we focused on neural tracer imaging techniques in humans and provide some conceptual insights into theories that can effectively support our choice of radionuclide tracers. This also facilitates the development of nuclear medicine techniques and promotes the development of modern medical technologies and computer tools. We described the knowledge of neural regeneration after heart transplantation, liver transplantation and kidney transplantation and apply them to various imaging techniques to quantify the uptake of radionuclide tracers to assess the prognosis of organ transplantation. We noted that the aim of this review is both to provide clinicians and nuclear medicine researchers with theories and insights into nerve regeneration in organ transplantation and to advance imaging techniques and radiotracers as a major step forward in clinical research. Moreover, we aimed to further promote the clinical and research applications of imaging techniques and provide clinicians and research technology developers with the theory and knowledge of the nerve.

Hepatic Nervous System in Development, Regeneration, and Disease

The liver is innervated by autonomic and sensory fibers of the sympathetic and parasympathetic nervous systems that regulate liver function, regeneration, and disease. Although the importance of the hepatic nervous system in maintaining and restoring liver homeostasis is increasingly appreciated, much remains unknown about the specific mechanisms by which hepatic nerves both influence and are influenced by liver diseases. While recent work has begun to illuminate the developmental mechanisms underlying recruitment of nerves to the liver, evolutionary differences contributing to species-specific patterns of hepatic innervation remain elusive. In this review, we summarize current knowledge on the development of the hepatic nervous system and its role in liver regeneration and disease. We also highlight areas in which further investigation would greatly enhance our understanding of the evolution and function of liver innervation.

Resina Draconis Reduces Acute Liver Injury and Promotes Liver Regeneration after 2/3 Partial Hepatectomy in Mice

Aim

To investigate the protective effects and possible mechanisms of action of resina draconis (RD) on acute liver injury and liver regeneration after 2/3 partial hepatectomy (PH) in mice.

Methods

2/3 PH was used to induce acute liver injury. Mice were divided into three groups: sham, vehicle + 2/3 PH, and RD + 2/3 PH. Resina draconis was administered intragastrically after 2/3 PH into the RD + 2/3 PH group, and the same volume of vehicle (1% sodium carboxymethyl cellulose) was injected into the vehicle + 2/3 PH group and sham group mice. The index of liver to body weight (ILBW) and proliferating cell nuclear antigen (PCNA) were assayed to evaluate liver regeneration. Blood and liver tissues were collected for serological and western blotting analysis.

Results

Resina draconis protected against 2/3 PH-induced acute severe liver injury and promoted liver regeneration as shown by significantly increased ILBW compared with that of controls. 2/3 PH increased serum AST and ALT levels, which were significantly decreased by RD treatment, while 2/3 PH decreased serum TP and ALB, which were increased by RD treatment. In the RD + 2/3 PH group, PCNA expression was significantly increased compared with the 2/3 PH group. Further, hepatocyte growth factor (HGF), TNFα, and EGFR levels were increased in the RD group at postoperative days 2 and 4 compared with the those in the 2/3 PH group.

Conclusion

Our results suggest that RD ameliorates acute hepatic injury and promotes liver cell proliferation, liver weight restoration, and liver function after 2/3 PH, probably via HGF, TNFα, and EGFR signaling.

Liver structural transformation after partial hepatectomy and repeated partial hepatectomy in rats: A renewed view on liver regeneration

BACKGROUND

The phenomenon of liver regeneration after partial hepatectomy (PH) is still a subject of considerable interest due to the increasing frequency of half liver transplantation on the one hand, and on the other hand, new surgical approaches which allow removal of massive space-occupying hepatic tumors, which earlier was considered as inoperable. Interestingly, the mechanisms of liver regeneration are extensively studied after PH but less attention is paid to the architectonics of the regenerated organ. Because of this, the question “How does the structure of regenerated liver differ from normal, regular liver?” has not been fully answered yet. Furthermore, almost without any attention is left the liver's structural transformation after repeated hepatectomy (of the re-regenereted liver).

AIM

To compare the architectonics of the lobules and circulatory bed of normal, re-generated and re-regenerated livers.

METHODS

The livers of 40 adult, male, albino Wistar rats were studied. 14 rats were subjected to PH - the 1^st study group (SG1); 10 rats underwent repeated PH – the 2^nd study group (SG2); 16 rats were subjected to sham operation - control group (CG); The livers were studied after 9 months from PH, and after 6 months from repeated PH. Cytological (Schiff reaction for the determination of DNA concen-tration), histological (H&E, Masson trichrome, CK8 Immunohistochemical marker, transparent slides after Indian Ink injection, ), morphometrical (hepatocytes areas, perimeters and ploidy) and Electron Microscopical (Scanning Electron Microscopy of corrosion casts) methods were used.

RESULTS

In the SG1 and SG2, the area of hepatocytes and their perimeter are increased compared to the CG (P < 0.05). However, the areas and perimeters of the hepatocytes of the SG₁ and SG₂ groups reveal a lesser difference. In regenerated (SG₁) and re-regenerated (SG₂) livers, the hepatocytes form the remodeled lobules, which size (300-1200 µm) exceeds the sizes of the lobules from CG (300-600 µm). The remodeled lobules (especially the “mega-lobules” with the sizes 1000-1200 µm) contain the transformed meshworks of the sinusoids, the part of which is dilated asymmetrically. This meshwork might have originated from the several portal venules (interlobular and/or inlet). The boundaries between the adjacent lobules (including mega-lobules) are widened and filled by connective tissue fibers, which gives the liver parenchyma a nodular look. In SG₂ the unevenness of sinusoid diameters, as well as the boundaries between the lobules (including the mega-lobules) are more vividly expressed in comparison with SG₁. The liver tissue of both SG₁ and SG₂ is featured by the slightly expressed ductular reaction.

CONCLUSION

Regenerated and re-regenerated livers in comparison with normal liver contain hypertrophied hepatocytes with increased ploidy which together with transformed sinusoidal and biliary meshworks form the remodeled lobulli.

Prostaglandin E2 mediates sensory nerve regulation of bone homeostasis

Whether sensory nerve can sense bone density or metabolic activity to control bone homeostasis is unknown. Here we found prostaglandin E2 (PGE2) secreted by osteoblastic cells activates PGE2 receptor 4 (EP4) in sensory nerves to regulate bone formation by inhibiting sympathetic activity through the central nervous system. PGE2 secreted by osteoblasts increases when bone density decreases as demonstrated in osteoporotic animal models. Ablation of sensory nerves erodes the skeletal integrity. Specifically, knockout of the EP4 gene in the sensory nerves or cyclooxygenase-2 (COX2) in the osteoblastic cells significantly reduces bone volume in adult mice. Sympathetic tone is increased in sensory denervation models, and propranolol, a β2-adrenergic antagonist, rescues bone loss. Furthermore, injection of SW033291, a small molecule to increase PGE2 level locally, significantly boostes bone formation, whereas the effect is obstructed in EP4 knockout mice. Thus, we show that PGE2 mediates sensory nerve to control bone homeostasis and promote regeneration.

Silymarin Accelerates Liver Regeneration after Partial Hepatectomy

Partial hepatectomy (PHx) is a liver regeneration physiological response induced to maintain homeostasis. Liver regeneration evolved presumably to protect wild animals from catastrophic liver loss caused by toxins or tissue injury. Silymarin (Sm) ability to stimulate liver regeneration has been an object of curiosity for many years. Silymarin has been investigated for use as an antioxidant and anticarcinogen. However, its use as a supportive treatment for liver damage is elusive. In this study, we fed silymarin (Sm, 25 mg/kg) to male Sprague-Dawley rats for 7 weeks. Surgical 2/3 PHx was then conducted on the rats at 6 hrs, 24 hrs, and 72 hrs. Western blot and RT-PCR were conducted to detect the cell cycle activities and silymarin effects on hepatic regeneration. The results showed that silymarin enhanced liver regeneration by accelerating the cell cycle in PHx liver. Silymarin led to increased G1 phase (cyclin D1/pRb), S phase (cyclin E/E2F), G2 phase (cyclin B), and M phase (cyclin A) protein and mRNA at 6 hrs, 24 hrs, and 72 hrs PHx. HGF, TGFα, and TGFβ1 growth factor expressions were also enhanced. We suggest that silymarin plays a crucial role in accelerated liver regeneration after PHx.