Blood clearance of Howell-Jolly bodies in an experimental autogenic splenic implant model.

BACKGROUND: Autogenic splenic implant (ASI) is one of the few alternatives for preservation of splenic tissue when total splenectomy is inevitable. The aim of this study was to determine the morphological and functional regeneration of ASIs, as indicated by the clearance of Howell-Jolly (HJ) bodies, in an experimental model. METHODS: Ninety-nine male Wistar rats were divided into three groups: sham-operated (group 1), total splenectomy alone (group 2), and total splenectomy combined with ASI (group 3). Animals in group 3 were further allocated to nine subgroups of nine rats each, and analysed at different time points (1, 4, 8, 12, 16, 20, 24, 28 and 32 weeks after surgery). Blood smears were prepared at predetermined times for detection of HJ bodies. Morphological regeneration of tissue in the ASI was analysed by histology. RESULTS: At 1 week, the regenerated mass corresponded to about 7 per cent of the tissue implanted, reaching approximately 54 per cent at 24 weeks. The HJ body levels were increased in groups 2 and 3 until 8 weeks after surgery, following which levels in the ASI group became similar to those in the sham-operated group. HJ bodies were difficult to detect when a level of 22.5 per cent of regenerated ASI mass was reached. CONCLUSION: Functional regeneration of ASIs occurred from 8 weeks after surgery. When 22.5 per cent of regenerated ASI mass was reached almost no HJ bodies could be observed in the bloodstream, resembling a spleen in situ. SURGICAL RELEVANCE: Splenectomy has been practised routinely, both in the emergency setting and as a therapeutic elective procedure. There is a correlation between asplenia/hyposplenia and the occurrence of fulminant sepsis, underlining the importance of developing surgical methods for preserving splenic function. Both clinical and experimental studies have shown at least partial morphological and functional regeneration of autogenic splenic implants (ASIs). Experimental studies investigating the immunoprotective effect of ASIs, based mostly on exposure of animals to various bacteria, have demonstrated that ASIs can increase the rate of bacterial clearance and decrease mortality from sepsis. Clinical studies have shown their ability to remove colloidal substances and altered erythrocyte corpuscular inclusions, such as Howell-Jolly, Heinz and Pappenheimer bodies, from the bloodstream. In this experimental study the functional and morphological regeneration of ASIs was studied over time in rats.

Critical mass of splenic autotransplant needed for the development of phagocytic activity in rats.

When total splenectomy is inevitable, heterotopic splenic autotransplantation seems to be the only alternative to maintain the functions of the spleen. The present study was carried out to analyse the critical mass of splenic autotransplant (SAT) for the development of phagocytic activity in rats. Wistar rats were submitted to total splenectomy (TS) alone or in combination with slices of SAT ranging from an average rate of 21·9% (one slice) to 100% (five slices) of the total splenic mass implanted into the greater omentum. Sixteen weeks after the beginning of the experiment, the animals were inoculated intravenously with a suspension of Escherichia coli labelled with Tc-99m. After 20 min, the rats were killed and the liver, lung and spleen or SAT, as well as blood samples were removed to determine the percentage of labelled bacteria uptake in these tissues. As the percentage of the total splenic mass contained in the SAT increased, the bacteria remaining in the blood decreased. From the implant of 26% up to the implant of the total splenic mass (100%) there was no difference in the bacteria remaining in the blood between the healthy animals of the control group and those submitted to TS combined with SAT. This finding shows that the critical mass needed for the development of phagocytic activity of macrophages in splenic autotransplants in adult rats is 26% of the total splenic mass.