Effect of omental angiogenic lipid factor on revascularization of autotransplanted spleen in dogs

Topical purified omental lipid formulations in the prevention of skin ulcers: a narrative review

The omentum is a large peritoneal fold. Its main function is to protect abdominal organs, exerting a defensive action against infective agents. The tissue promotes repair after several types of injury. An extensive vascularisation is the key characteristic of this tissue and the omentum has the highest level of production and content of vascular endothelial growth factor (VEGF). A component of omentum is the lipid compound, which carries out important activities for the organism. Omentum is rich in neutral glycerides, phospholipids, glycolipids and gangliosides. Dermatological products containing purified omental lipids are commercially available and topical omental extracts have been useful in the softening, moisturising and smoothing of skin. Animal-derived omental lipids could be use in topical products with different textures (creams, fluids, emulsions and cleansers) and at different concentrations (10-25%) for the treatment of fragile skin or skin conditions causing risk of ulcer formation. This review summarises the pharmacological rationale of purified omental lipids in topical formulations for use in fragile skin conditions, the clinical efficacy data available in the scientific literature and the potential future perspectives. Efficacy of topical purified omental lipids have been demonstrated in numerous clinical controlled trials involving a total of 320 subjects. These studies demonstrated that this product helps prevent the formation of pressure ulcers (PU) in hospitalised high-risk subjects, improves wound healing process, normalises skin hydration in diabetic subjects with moderate-severe skin xerosis and improve the clinical evolution of diabetic foot. Therefore, purified omental lipid could be an effective tool for the management of fragile skin and the skin at high risk of PU formation.

[The spleen in experimental surgery]

The injured but functionally intact spleen can be saved with various surgical techniques. Two of these techniques were developed in our department: partial spleen resection by embracing suture line, and spleen autotransplantation by implantation of spleen chips between the sheets of the greater omentum, the so called "spleen-apron" technique. Functional and structural postsurgical follow-up investigations were developed in the last three decades, including comprehensive laboratory tests (hematological, hemostaseological, hemorheological, enzymological, routine chemical, immunological), imaging procedures (abdominal US, scintigraphic methods, SPECT, as well as NanoSPECT/CT in the last years) with morphological analysis (conventional histological, immunohistochemical, electonmicroscopical), as well as the investigation of the role of hemopoetic stem cells. These investigations confirm the viability of spleen autotransplantation. The implanted spleen chips are able to restore the splenic functions partially following remodellation and recolonisation after neovascularisation. It is a critically important process in the prevention of overwhelming post-splenectomy infection and DIC. This paper summarizes the most important principles and the main conclusions of different experimental animal models.

Prevascularization of cardiac patch on the omentum improves its therapeutic outcome

The recent progress made in the bioengineering of cardiac patches offers a new therapeutic modality for regenerating the myocardium after myocardial infarction (MI). We present here a strategy for the engineering of a cardiac patch with mature vasculature by heterotopic transplantation onto the omentum. The patch was constructed by seeding neonatal cardiac cells with a mixture of prosurvival and angiogenic factors into an alginate scaffold capable of factor binding and sustained release. After 48 h in culture, the patch was vascularized for 7 days on the omentum, then explanted and transplanted onto infarcted rat hearts, 7 days after MI induction. When evaluated 28 days later, the vascularized cardiac patch showed structural and electrical integration into host myocardium. Moreover, the vascularized patch induced thicker scars, prevented further dilatation of the chamber and ventricular dysfunction. Thus, our study provides evidence that grafting prevascularized cardiac patch into infarct can improve cardiac function after MI.

Autogenous greater omentum, as a free nonvascularized graft, enhances bone healing: an experimental nonunion model

Reconstruction of vascularity is an early event in fracture healing and upregulation of angiogenesis may therefore promote the formation of bone. We have investigated the potentiality of autogenous free nonvascularized greater omentum to stimulate the formation of bone in an experimental hypertrophic nonunion model. Twelve dogs assigned into two identical groups underwent a standard nonunion operation. In the experimental group, this was followed by application of autogenous greater omentum as a free nonvascularized graft around the osteotomy gap. Radiographic assessments were conducted time-sequentially until euthanasia 16 weeks after surgery. Histological analysis was performed on the mid-radial diaphysis containing the 4-month-old osteotomy site. Radiological and histological properties of the group treated with free transplant of the greater omentum revealed complete union. In contrast, there was no evidence indicating union in the control group. Analyses of the radiological and histological scores confirmed that osteotomies treated with free transplant of the autogenous greater omentum had united, whereas the osteotomies of the control group failed to unite. Significant differences between the mean values for radiological and histological-grading score in the control and experimental groups were detected (p < 0.05). We showed that free graft of autogenous greater omentum could stimulate the formation of competent bone in an environment deprived of its normal vascularization. Hence, it could be recommended to enhance healing when the fractures are at risk of nonunion.

The effects of splenectomy and splenic autotransplantation on plasma lipid levels

PURPOSE

Atherosclerosis observations after splenectomy for trauma and hypersplenism suggests a possible role for the spleen in lipid metabolism. The authors examined the effects of splenectomy on serum lipids in rats and also cholesterol-fed rats with experimental atherosclerosis.

METHODS

This study was designed on rats. The rats were divided into five groups: splenectomy, normal diet (SP-N, n: 8), splenectomy, cholesterol-fed groups (SP-C, n: 8), splenic autotransplantation after splenectomy, normal diet (SA-N, n: 8), splenic autotransplantation after splenectomy, cholesterol-fed groups (SA-C, n: 8) and sham groups (n: 8). Total triglyceride, total cholesterol, HDL (high-density lipoprotein), LDL (low-density lipoprotein), and VLDL (very low-density lipoprotein) levels were determined in 40 rats. The rats were classified into five groups based on the surgical procedures. The spleens were removed and then the rats were fed a normal diet in Group SP-N (n = 8). The spleens were removed and then the rats were fed a diet containing 1% cholesterol in Group SP-C (n = 8). Splenectomy and splenic autotransplantations were performed and then the rats were fed a normal diet in Group SA-N (n = 8). Splenectomy and splenic autotransplantations were performed and then the rats were fed a diet containing 1% cholesterol in Group SA-C (n = 8). The rats were sham-operated in the control group (Group S, n = 8). An active splenic function was shown in rats that underwent splenic autotransplantation in both groups by using Technicium 99 m sulphurcolloide sintiscan on day 30. Blood lipid levels were repeated 6 months later.

RESULTS

There was no difference between pre- and postoperative lipid levels in the sham group and SA-N group (p >.05). All lipid levels including HDL were increased significantly in SP-C group (p <.05). Also VLDL and total tryglyceride levels were increased significantly in SP-N and SA-C groups (p <.05).

CONCLUSIONS

This study showed that the spleen might have an important effect on lipid metabolism and splenic autotransplantation may be protective in conditions with increased lipid levels.

Spleen autotransplantation. Morphological and functional follow-up after spleen autotransplantation in mice: A research summary

In 1986, we started the research on spleen surgery aimed at saving the splenic mass after its traumatic injury, with elaboration of special resection and autotransplantation techniques. The researches started on mongrel dogs and were continued on inbred mice and beagle dogs with complex histological, imaging, and laboratory investigations, following-up the function and the regeneration of autotransplanted spleen chips. Performing research on mice provided more immunological methods, such as lymphocyte subsets, immunoglobulin levels, and monitoring the phagocytic functions. Researches showed evidence also on the presence of apoptosis, furthermore, stem cell studies on regeneration and functional restoration of the spleen chips are in progress. Our results contributed to two multidisciplinary guidelines in Hungary: (1) One of them is under preparation and underlines the importance of spleen saving methods after traumatic splenic injury; (2) The second guideline shows that hemorheological changes can be early indicators of the increased sensitivity to postsplenectomy infections.

Hematological, hemorheological, immunological, and morphological studies of spleen autotransplantation in mice: Preliminary results

Using a spleen autotransplantation model, we conducted hematological, hemorheological, immunological, and morphological studies in mice 6 weeks after splenectomy. Sixty male and female A/J inbred mice were equally divided into 3 groups: 1) SE group, splenectomy was performed; 2) AU group, spleen chips were autotransplanted into the omentum without vascular anastomosis following splenectomy; and 3) C group (controls), no intervention in these mice. At postoperative week 6, the following studies were performed: 1) measurement of hematological parameters; 2) hemorheological studies, including relative cell transit time (RCTT) and fibrinogen levels; and 3) activity of peripheral phagocytes, measured by zymozan-induced chemiluminescence, which was calculated in stimulation index values (SI). In addition, histological investigations of autotransplants were conducted. Erythrocyte mean cell volume and platelet counts, RCTT, fibrinogen levels, and activity of phagocytes were significantly higher in the SE group, compared to those in the C group. In the AU group, these parameters were similar to those in the C group. Morphologically, the transplanted spleen showed normal histology. These data indicate that the transplanted spleens restored their function. We conclude that spleen autotransplantation reserves the normal morphology of spleen and restores most of the spleen's hematological, hemorheological, and immunological functions. Both SI index and erythrocyte deformability can be an informative detection of decreasing splenic function. These data suggest that spleen autotransplantation may provide a useful tool to prevent complications following splenectomy in a clinical setting.

Multiorgan transplantation with a new organ-chip technique in mice: Preliminary histological data

A simple model was developed for multiorgan liver-kidney-spleen-intestine transplantation on 108 inbred mice. Donor operations included hepatectomy, nephrectomy, splenectomy, and jejunum segment resection. Following removal of the organ, small slices or abdominal organ "chips" were prepared. During multiorgan recipient operations, chips from each of these organs were transplanted into the omentum; in the control single-organ groups, only 1 organ was transplanted. All animals survived. Biopsies were taken for histology after 6 weeks. All organs were found to have developed a blood supply. In the liver chips, hypertrophied cells could be detected. In the margin of the kidney tissue, both the glomeruli and tubules were preserved. Lymphoid zone and red pulp were intact in spleen chips. All layers of the intestinal chips were identifiable and contained intraluminal mucinous substances. This model is a simple surgical intervention with the possibility of the investigation of 4 organs.

Omental transposition decreases ischemic brain damage examined in a new ischemia model

PURPOSE

The aim of this study was to determine whether omental transposition at the time of focal cerebral ischemia can decrease ischemic brain damage produced in dogs, in a new ischemia model, which had been described by us.

METHODS

In group 1 (n = 5), the left internal carotid artery and arterial circle of the brain (posterior communicating artery in humans) were occluded permanently. In group 2 (n = 5), additionally to this ischemia model, omental transposition was performed simultaneously. In the postoperative early period (first 24 h), single photon emission computed tomography (SPECT) and in the late period (72-96 h) SPECT and magnetic resonance imaging (MRI) of the brain were performed. Mann-Whitney U, paired t and Wilcoxon signed rank tests were used for statistical analyses, and p < 0.05 was considered significant.

RESULTS

The dogs had a neurological score (NS) of 3.6 +/- 0.5 and 3.4 +/-0.5 in groups 1 and 2, respectively, in the early period (p > 0.05). In the late period, the dogs had an NS of 4.4 +/- 0.5 and 5.6 +/- 0.5 in groups 1 and 2, respectively (p < 0.05). The NS of each group differed significantly between the early and late period (p < 0.05). Early SPECT imaging showed 50 +/- 7.0% and 52 +/- 8.4% hypoperfusion corresponding to the left middle cerebral artery territory in groups 1 and 2, respectively (p > 0.05). In the late period, the degree of hypoperfusion decreased to 34 +/- 5.5% and 12 +/- 4.8% in groups 1 and 2, respectively (p < 0.05). The degree of hypoperfusion in both groups changed significantly between the early and late period (p < 0.05). In T(1)- and T(2)-weighted MRI images, the volume of the lesion in group 1 was significantly greater than in group 2 (p < 0.001).

CONCLUSION

In our new ischemia model, simultaneous omental transposition is helpful in reversing the neurologic deficit and cerebral ischemic damage.

Spleen autotransplantation in mice: a novel experimental model for immunology study

The aim of the experimental model to develop a spleen transplant model in mice to study the role of spleen in autoimmune and transplant rejection. After a midline incision, splenectomy was performed. Four tiny segments were cut from the removed spleen and were rinsed at room temperature in physiological salt solution. The greater omentum was lifted and four omental pockets were created; four thin segments were then placed into the "nests," subsequently marked, and fixed using 8-0 suture. The abdomen was then closed. The duration of the survival time was different among the nine groups (n = 3-3). Tissue samples were taken from the marked areas for histological examination stained with hematoxylin and eosin (H&E). H&E staining demonstrated large, well-circumscribed splenic nests with lymphoid zone and red pulp and well-formed trabecules in the spleen. Among the possible applications of this novel model is the ability to study the role of spleen in autoimmune and organ rejection.

Splenic "regeneration" after partial splenectomy for Gaucher disease: histological features

Partial splenectomy for Gaucher disease is often followed by reenlargement of the splenic remnant. It remains unclear if this process is due to tissue regeneration or to continued deposition of glucocerebroside in the reticuloendothelial system or both. We compared the splenic architecture before and after reenlargement in three cases of failed repeated partial splenectomy after two, six and five years. Using the number of lymphoid follicles per hundred low power fields (LF/LPF) as an arbitrary index, we found that prior to the first operation 18, 20 and 27 lymphoid follicles were present per one hundred low power fields, while at the second operation, the corresponding rates were 11, 15 and 17; in control spleens, an average of 712.5 lymphoid follicles were present in one hundred low power fields. The difference in the LF/LPF ratio before and after reenlargement, led us to speculate that splenic re-enlargement in Gaucher disease is mainly the result of the continued deposition of the glucocerebroside in the reticuloendothelial system of the splenic remnant, though some degree of true regeneration as well cannot be completely ruled out. These findings are compared with animal studies and results for partial splenectomy on humans, performed for trauma. Further studies in patients with Gaucher disease are warranted to better define the underlying mechanism of splenic reenlargement.