Spleen: Reparative Regeneration and Influence on Liver

Chronic liver fibrosis induction in aging causes significant ultra-structural deterioration in liver and alteration on immune response gene expressions in liver-spleen axis

The relationship between damage to the liver and spleen by aging and the immune response status in these two organs, which are anatomically and immunologically interconnected, is unknown. The authors investigated the histopathological, ultrastructural, and immunological effects of aging in young and aged fibrotic mice by using an experimental model. Four groups were planned, with 10 mice in each experimental group. The levels of fibrosis and ultrastructural destruction in the liver were determined by α-SMA staining and TEM analysis. Expression levels of immunity genes (Il2, Il4, Il6, Il10, Il12, Il17, Tnf, Ifng, Tgfb1, Gata3, Rorc, Tbx21, Foxp3, Ccl2, Ccr2, Cxcr3, Pf4, Cxcl10) were carried out by qRT-PCR. While structural disorders were detected in the mitochondria of aged healthy group, cellular destruction in the fibrosis-induced elderly group was at a dramatic level. Fibrosis induction in aged mice caused an elevation in the expression of chemokines (CCl2, CXCL10, CCR2) and cytokine (IL-17a) genes that induce autoinflammatory response in the liver. Unlike the cellular pathology and genes activated in fibrosis in youth and the natural occurrence of fibrosis with aging, induction of fibrosis during aging causes deterioration in the liver and expression of genes responsible for autoimmunity in both the liver and spleen.

A large gastric splenosis mimicking gastrointestinal stromal tumor: A case report and literature review

Splenosis pertains to the phenomenon wherein a segment of the spleen undergoes detachment and becomes embedded in other anatomical regions subsequent to traumatic rupture or therapeutic resection, and then progressively establishing blood circulation to foster the regeneration of splenic tissue. Existing literature posits that splenosis predominantly manifests within the confines of the abdominal and pelvic cavities. The objective of the current study was to present an uncommon case involving the occurrence of splenosis within the gastric myometrium, thereby contributing to the current knowledge regarding splenosis. A 16-year-old female sought medical assistance owing to recurrent abdominal pain persisting for a duration of six months, and had a history of splenectomy two years prior. Gastroscopy, endoscopic ultrasound and computed tomography (CT) examination collectively identified a lesion in the submucosal prominence of the fundus of the stomach. Initial considerations based on imaging examinations leaned towards a gastrointestinal stromal tumor. Consequently, an endoscopic resection was undertaken. Remarkably, the pathological findings and histochemistry concurred with the alterations associated with ectopic spleen implantation, leading to a stable postoperative course. In conclusion, splenosis denotes the implantation of a segment of the spleen into extraneous anatomical sites, attributable to traumatic rupture or therapeutic resection. The preoperative diagnosis of splenosis can pose a challenge, potentially culminating in unnecessary radical clinical interventions. Therefore, the acquisition of a comprehensive medical history, with a particular focus on surgical and trauma events, emerges as pivotal for an accurate diagnosis. In light of novel diagnostic modalities, the non-invasive technology of nuclear medicine can efficaciously visualize ectopic splenic tissue, thereby averting superfluous surgical procedures. It is both feasible and imperative to implement individualized treatment strategies for patients afflicted with splenosis.

Splenectomy ameliorates liver cirrhosis by restoring the gut microbiota balance

BACKGROUND

Dysbiosis of gut microbiota is frequent in liver cirrhosis (LC) patients, and splenectomy (SP) has been reported to improve LC. Herein, we report the effects of SP on gut microbiota, especially on Veillonella parvula, a Gram-negative coccus of the gastrointestinal tract, in LC mice, and the underlying mechanism.

METHODS

LC mice models were induced by tail vein injection of concanavalin A (ConA), followed by SP. 16 s rRNA sequencing was conducted to analyze the effects of ConA induction and SP on mouse gut microbiota and the gene expression affected by gut microbiota. LC mice receiving SP were gavaged with Veillonella parvula. Likewise, hepatic stellate cells (HSC) and hepatocytes (HC) were induced with conditioned medium (CM) of Veillonella parvula.

RESULTS

SP alleviated LC in mice by restoring gut barrier function and maintaining gut microbiota balance, with Veillonella as the key genus. The Veillonella parvula gavage on LC mice reversed the ameliorative effect of SP. The CM of Veillonella parvula promoted the activation of HSC and the release of IL-6, IL-1β, and TNF-α. Also, the CM of Veillonella parvula induced HC pyroptosis and the release of ALT and AST. Veillonella parvula represented an imbalance in the gut microbiota, thus enhancing gut-derived endotoxins in the liver with the main target being Tlr4/Nlrp3. Inhibition of Tlr4 blocked Veillonella parvula-induced HC damage, HSC activation, and subsequent LC progression.

CONCLUSION

SP-mediated gut microbiota regulation ameliorates ConA-related LC progression by inhibiting Tlr4/Nlrp3 in the liver.

The spleen as a possible source of serine protease inhibitors and migrating monocytes required for liver regeneration after 70% resection in mice

Introduction: The role of the immune system in liver repair is fundamentally complex and most likely involves the spleen. The close connection between the two organs via the portal vein enables delivery of splenic cytokines and living cells to the liver. This study evaluates expression of inflammation-related genes and assesses the dynamics of monocyte-macrophage and lymphocyte populations of the spleen during the recovery from 70% hepatectomy in mice. Methods: The study used the established mouse model of 70% liver volume resection. The animals were sacrificed 24 h, 72 h or 7 days post-intervention and splenic tissues were collected for analysis: Clariom™ S transcriptomic assay, immunohistochemistry for proliferation marker Ki-67 and macrophage markers, and flow cytometry for lymphocyte and macrophage markers. Results: The loss and regeneration of 70% liver volume affected the cytological architecture and gene expression profiles of the spleen. The tests revealed significant reduction in cell counts for Ki-67+ cells and CD115+ macrophages on day 1, Ly6C + cells on days 1, 3 and 7, and CD3+CD8+ cytotoxic lymphocytes on day 7. The transcriptomic analysis revealed significant activation of protease inhibitor genes Serpina3n, Stfa2 and Stfa2l1 and decreased expression of cell cycle regulatory genes on day 1, mirrored by inverse dynamics observed on day 7. Discussion and conclusion: Splenic homeostasis is significantly affected by massive loss in liver volume. High levels of protease inhibitors indicated by increased expression of corresponding genes on day 1 may play an anti-inflammatory role upon reaching the regenerating liver via the portal vein. Leukocyte populations of the spleen react by a slow-down in proliferation. A transient decrease in the local CD115+ and Ly6C+ cell counts may indicate migration of splenic monocytes-macrophages to the liver.

Spleen regeneration after subcutaneous heterotopic autotransplantation in a mouse model

BACKGROUND

Splenectomy may lead to severe postoperative complications, including sepsis and cancers. A possible solution to this problem is heterotopic autotransplantation of the spleen. Splenic autografts rapidly restore the regular splenic microanatomy in model animals. However, the functional competence of such regenerated autografts in terms of lympho- and hematopoietic capacity remains uncertain. Therefore, this study aimed to monitor the dynamics of B and T lymphocyte populations, the monocyte-macrophage system, and megakaryocytopoiesis in murine splenic autografts.

METHODS

The model of subcutaneous splenic engraftment was implemented in C57Bl male mice. Cell sources of functional recovery were studied using heterotopic transplantations from B10-GFP donors to C57Bl recipients. The cellular composition dynamics were studied by immunohistochemistry and flow cytometry. Expression of regulatory genes at mRNA and protein levels was assessed by real-time PCR and Western blot, respectively.

RESULTS

Characteristic splenic architecture is restored within 30 days post-transplantation, consistent with other studies. The monocyte-macrophage system, megakaryocytes, and B lymphocytes show the highest rates, whereas the functional recovery of T cells takes longer. Cross-strain splenic engraftments using B10-GFP donors indicate the recipient-derived cell sources of the recovery. Transplantations of scaffolds populated with splenic stromal cells or without them afforded no restoration of the characteristic splenic architecture.

CONCLUSIONS

Allogeneic subcutaneous transplantation of splenic fragments in a mouse model leads to their structural recovery within 30 days, with full reconstitution of the monocyte-macrophage, megakaryocyte and B lymphocyte populations. The circulating hematopoietic cells provide the likely source for the cell composition recovery.

The Role of the Spleen in Portal Hypertension

As liver disease progresses, intrahepatic vascular resistance increases (backward flow theory of portal hypertension) and collateral veins develop. Adequate portal hypertension is required to maintain portal flow into the liver through an increase in blood flow into the portal venous system (forward flow theory of portal hypertension). The splenic artery resistance index is significantly and selectively elevated in cirrhotic patients. In portal hypertension, a local hyperdynamic state occurs around the spleen. Splenomegaly is associated with a poor prognosis in cirrhosis and is caused by spleen congestion and by enlargement and hyperactivation of splenic lymphoid tissue. Hypersplenism can lead to thrombocytopenia caused by increased sequestering and breakdown of platelets in the spleen. The close relationship between the spleen and liver is reflected in the concept of the hepatosplenic axis. The spleen is a regulatory organ that maintains portal flow into the liver and is the key organ in the forward flow theory of portal hypertension. This review summarizes the literature on the role of the spleen in portal hypertension.

An Eye on Kupffer Cells: Development, Phenotype and the Macrophage Niche

Macrophages are key participants in the maintenance of tissue homeostasis under normal and pathological conditions, and implement a rich diversity of functions. The largest population of resident tissue macrophages is found in the liver. Hepatic macrophages, termed Kupffer cells, are involved in the regulation of multiple liver functionalities. Specific differentiation profiles and functional activities of tissue macrophages have been attributed to the shaping role of the so-called tissue niche microenvironments. The fundamental macrophage niche concept was lately shaken by a flood of new data, leading to a revision and substantial update of the concept, which constitutes the main focus of this review. The macrophage community discusses contemporary evidence on the developmental origins of resident macrophages, notably Kupffer cells and the issues of heterogeneity of the hepatic macrophage populations, as well as the roles of proliferation, cell death and migration processes in the maintenance of macrophage populations of the liver. Special consideration is given to interactions of Kupffer cells with other local cell lineages, including Ito cells, sinusoidal endothelium and hepatocytes, which participate in the maintenance of their phenotypical and functional identity.