Regeneration Of Splenic Tissue Research Articles

Effects of splenic allograft in lipid profile of non-splenectomized rats: the immune and metabolic role of the "double spleen"

To elucidate the role of the spleen and splenic allograft in lipid control and evaluate its effect on the lipid profile of rats. 32 male Wistar rats were randomly assigned into four groups: control group (1), total splenectomy group (2), splenectomy and implantation of allograft group (3) and double spleen group (4). Each group was subdivided into two subgroups: A and B, based on the death of the animals after 30 or 120 days of monitoring. The procedures in groups 2, 3 and 4 were made simultaneously, and splenectomized animals, groups 2 and 3 were donors, respectively, for the animals of groups 3 and 4. In group 4 the spleen was preserved and the animals received implants from the spleens of rats from group 3. The regeneration of splenic tissue was evaluated by macroscopic and microscopic analyzes of the grafts and own spleens, as well as with measurements of VLDL, HDL, LDL, total cholesterol and triglycerides. after 120 days, Group 4 showed levels of total cholesterol and LDL lower than the other groups. Group 1 had higher levels of lipids. The technique of double spleen was effective in the control of lipid metabolism, corroborating the function of the spleen as a reserve of lipids.

IgG-mediated phagocytosis in regenerated splenic tissue.

The risk of severe infections after splenectomy is well established. Operations such as auto-transplantation, splenic artery ligation or partial resection have been advocated for the retention or regeneration of splenic tissue following splenic trauma. The potential of such tissue to protect from infection is unclear. The ability of splenic tissue to phagocytose IgG opsonized syngeneic erythrocytes was measured in rats 6 months following splenectomy and splenic autotransplantation, splenic artery ligation, total or partial splenectomy, and compared with eusplenic controls. In eusplenic and partially splenectomized rats 71% of the label was cleared at 3 h, compared with approximately 50% in rats following total splenectomy, splenectomy and splenic autotransplantation or splenic artery ligation. The autotransplanted and the ligated splenic tissue cleared less than 10% compared with control spleen, but there was no difference between them when clearance was expressed as uptake per gram of tissue. Splenic autotransplants and ligated spleens were small and histologically abnormal, with an increase in the red pulp, significantly less white pulp and marginal zone, and the frequent absence of a central arteriole in the white pulp. The clearance of label was proportional to the amount of red pulp in the tissue, although the red pulp from the regenerated tissues was not as efficient at phagocytosis as control red pulp. The tissue which regenerated following autotransplantation or splenic artery ligation did not result in greater clearance of erythrocytes from the circulation than that which occurred in splenectomized rats.

Structural characteristic of splenic sinuses in idiopathic portal hypertension.

Splenic sinuses in idiopathic portal hypertension (IPH; 8 patients), liver cirrhosis (LC; 14 patients) and in regenerating autotransplanted spleens from 25 rats were compared with each other by scanning electron microscopy (SEM) and immunohistochemistry using antibodies against proliferating cell nuclear antigen (PCNA). Spleens obtained from six patients with gastric carcinoma and from five untreated adult rats were examined as controls. SEM of the sinuses showed that in IPH endothelial cells became irregular in shape, and the interendothelial slits of sinuses were irregularly enlarged. Sinus endothelial processes traversing the sinusal lumen were also found. The same changes were observed in the proliferating sinuses during regeneration of splenic tissue after autotransplantation in rats, but disappeared when the regeneration was completed. Irregular endothelial cells were few in LC. PCNA-positive sinus endothelial cells were increased in number in IPH as compared with those in LC; the mean number of PCNA-positive ones per cm2 was 45.4 in IPH and 8.2 in LC. It was suggested that, from SEM observation of sinus endothelial cells and counting PCNA-positive sinus endothelial cells, the sinuses of the spleen in IPH consist of proliferating endothelial cells or are in the state of increased proliferation. In conclusion, splenomegaly in IPH was presumed to be caused by proliferation of sinus endothelial cells, and by the increased splenic blood flow in the irregularly widened interendothelial slits of the sinuses.

Splenic autotransplantation provides protection against fatal sepsis in young but not in old rats

Splenectomy increases the risk of contracting infections with high mortality. Thus, splenic tissue should be repaired orthotopically whenever possible. If all attempts fail, splenic autotransplantation might be a suitable method for splenic salvage. The protective function of such transplants in adults has been questioned, leading to a decreased frequency of splenic autotransplantations. However, the regeneration of splenic tissue is better in the young organism than in the old, suggesting that the protection provided by regenerated splenic tissue might be more reliable in children than in adults. In addition, children are at a higher risk in the case of overwhelming postsplenectomy sepsis. The protection warranted by regenerated splenic tissue after autotransplantation at different ages was examined using a highly standardized animal model. Sham operation, splenectomy, and splenic autotransplantation were performed on adult, weanling, and newborn rats, and Streptococcus pneumoniae was applied intranasally 9 months after the operation. After pneumococcal challenge about 80% of the splenectomized animals in the different age groups died of infection, whereas only 20% of the sham operated rats died. Regenerated splenic tissue resulting from splenic autotransplantation performed on adult or weanling rats demonstrated no protective function. However, in newborn rats with transplanted splenic tissue, both survival rate and survival time were increased significantly. Determination of lymphocyte subsets in the blood did not allow the protective role of splenic transplants to be predicted. This study indicates that disappointing results of splenic autotransplantation in adult patients should not lead to false pessimism about the role of this operation in children.

Regeneration of splenic tissue

The ability of splenic tissue to regenerate after avascular transplantation at different target tissues is well documented but the capacity of splenic transplants to compensate the loss of spleen and the influence of the implantation site on the functional development of replants are still discussed contradictory, because little is known about specific functions of the transplants. Therefore, we investigated splenic implants in rats at different states of development and in different target tissues (intraomental and subcutaneous implantation site).Monoclonal antibodies directed against ϰ-light-chain (B-cells), B-type leucocyte common antigen (B-cells), CD5 (thymocytes and T-cells), CD4 (Thelper-cells), CD8 (Tsupp/cyt-cells), α/β heterodimer of the T-cell receptor (T-cell receptor bearing cells), ED-1 and ED-3 antigen (different functional macrophage subsets) and MHC class II molecules (la on B-cells and dendritic cells) were used to characterize splenic replants.The descriptive immunohistological characterization of both transplant groups revealed that within 40 days of regeneration all splenic compartments developed and cell classes and subsets were distributed similar to the spleen. Only slight differences concerning a reduced size of the T-cell area (including a decreased amount of CD8+ cells) and a delayed development of the immunoarchitecture in subcutaneous implants could be demonstrated. A quantitative immunohistological analysis of the red pulp (RP), periarteriolar lymphoid sheath (PALS), marginal zone (MZ) and follicles (F) elicited a number of subtle changes with respect to the cell density of transplant compartments. The alterations were restricted to an increase of B-cells and a decrease of Tsupp/cyt-cells in PALS, a reduction of B-cells as well as Thelper-cells in the marginal zone and a striking increase of la bearing cells in the follicles of both transplant groups. The results of a functional analysis using antigenic and allogenic stimulation of transplant cells confirmed the assumption that despite a spleen-like morphology and histology several alterations of the immunoarchitecture led to transplant-specific deficiencies on a subtle functional level.

Regeneration of splenic tissue after autologous subcutaneous implantation: homing of T- and B- and Ia-positive cells in the white pulp of the rat spleen.

The localization of T- and B lymphocytes and interdigitating cells (IDC) was investigated during the regeneration process of splenic implants. For this purpose a two-step immunoperoxidase technique was used to visualize T-cell antigen, immunoglobulins and Ia-antigen on cryostat sections. The specific localization of the repopulating lymphocytes occurred simultaneously with the development of non-lymphoid elements characteristic for the different compartments of the white pulp, i.e., the periarteriolar lymphocyte sheaths (PALS) and follicles. The marginal zone (MZ) developed after the PALS and primary follicles, but before germinal center reactions were found. During ontogeny, however, the development of a broad MZ precedes the formation of follicles. This difference in sequence of events is discussed.

Regeneration of splenic tissue after autologous subcutaneous implantation: development of non-lymphoid cells in the white pulp of the rat spleen.

Regeneration of splenic tissue after autologous subcutaneous implantation provides a useful model for studying the development of splenic tissue. The development of the various non-lymphoid cells of the white pulp in the rat is described. It appears that regeneration of the implants is initiated by ingrowing vessels and a newly formed reticulum, which forms the microenvironment for the homing lymphocytes. Marginal metallophils are found at their characteristic location at the inner border of the marginal sinus five weeks after implantation. Trapping of antigen-antibody complexes reappears when the first primary follicles can be recognized.