PURPOSE: To evaluate which is the best route of administration for cell therapy in experimental rat model of small-for size syndrome. METHODS: A total of 40 rats underwent partial hepatectomy (70%) that induces the small-for-size syndrome and were divided into four groups of route administration: intravenous, intraperitoneal, enteral and tracheal. The small-for-size syndrome model was designed with extended partial hepatectomy (70%). The animals were divided into four groups of routes administration: intravenous (n=10) - intravenously through the dorsal vein of the penis; intraperitoneal (n=10) - intraperitoneally in the abdominal cavity; enteral (n=10) - oroenteral with the placement of a number 4 urethral probe and maintained at third duodenal portion; tracheal (n=10) - after tracheal intubation. We track the animals and monitor them for 21 days; during this follow-up we evaluated the result of cell therapy application tracking animals using ultrasound, radiography and PET-scan. Statistical analysis was performed using GraphPad Prism Software(r). Differences were considered significant with the p<0.05. Data are presented as the median and variation for continuous variables. Comparisons between groups were made using analysis of the imaging test by the researchers. RESULTS: All four groups underwent partial hepatectomy of 70% liver tissue targeting the same weight of resected liver. Initially the PET-scan tests showed similarity in administered cells by different routes. However, in few days the route of intravenous administration showed to be the most appropriated to lead cells to the liver followed by enteral. The tracheal and peritoneal routes were not as much successful for this goal. CONCLUSION: The intravenous route is the best one to cell therapy in experimental rat model of small-for size-syndrome.

Os ratos apresentam desenvolvimento embrionário similar aos de animais domésticos e humanos, sendo assim um modelo válido para estudos científicos. Dentre eles, o F344 se destaca por ser uma linhagem isogênica, facilitando a leitura dos resultados obtidos, devido a sua homogeneidade gênica. Devido à falta de estudos histológicos acerca do desenvolvimento hepático em ratos, o presente estudo tem como objetivo caracterizar histologicamente pela primeira vez o processo de desenvolvimento hepático nos estágios embrionários de E12,5 (12,5 dias de gestação), E13,5, E14,5, E15,5 e E16,5 em ratos F344. Cinco embriões de cada estágio embrionário foram coletados, fixados em Metacarn, incluídos em paraplast e realizadas colorações histológicas e histoquímica. Os brotos hepáticos de embriões entre 12,5-14,5 dias apresentaram-se como aglomerados de hepatoblastos, ainda desorganizados e circundados por inúmeras células precursoras sanguíneas nucleadas. Observou-se que os hepatoblastos possuem um núcleo grande basofílico com pouco citoplasma. Sinusoides com eritroblastos e células de Kupffer também foram encontrados. Com 14,5 dias, foi observada a coexistência de hepatoblastos e hepatócitos, além de megacariócitos. Nos embriões com 15,5 dias, começou a verificar-se distinção entre os cordões de hepatócitos em formação, limitados pelos capilares sinusoides. Tais cordões começavam a confluir para as presentes veias centrolobulares. Com 16,5 dias, a arquitetura parenquimal estava mais próxima da encontrada em fígados adultos, sendo a quantidade de hepatócitos superior à de hepatoblastos. Nesse prazo gestacional, o fígado ainda tinha função hematopoiética. O estudo traz histologicamente o desenvolvimento hepático entre 12,5-16,5 dias de ratos da linhagem F344, evidenciando as células que compõem cada período gestacional, gerando subsídios para futuros estudos.

The rats have embryonic development similar to other domestic animals and human beings, thus a valid model for scientific studies. Among them, the F344 stands out for be isogenic, facilitating the reading of the results obtained because of their genetic homogeneity. Due to the lack of histological studies concerning hepatic development in rats, the present study aimed to characterize histologically for the first time the process of developing liver in the stages of gestation of E12.5 (12.5 days of gestation), E13.5, E14.5, E15.5 and E16.5 in rats F344. Five embryos of each embryonic stage were collected, fixed in Metacarn, embedded in Paraplast and then histological stains and histochemistry were performed. The hepatic bud of embryo among 12.5-14.5 days presented themselves a cluster of hepatoblasts still disorganized and surrounded by numerous nucleated blood precursor cells. It was observed that the hepatoblasts have a large nucleus basophilic with little cytoplasm. Sinusoids with erythroblasts and Kupffer cells also have been found. At 14.5 days it was observed the coexistence of hepatoblasts and hepatocytes. In the embryos with 15.5 days began the verify distinction between the cords of hepatocytes in formation limited by capillary sinusoids. Such cords began to converge for the present centrilobular veins. At 16.5 days the parenchymal architecture was nearer found in the adult liver, being the quantity of hepatocytes greater than hepatoblasts. During this gestation period the liver also had hematopoietic function. The study brings histologically the rats F344 hepatic development between 12.5-16.5 days, evidencing the cells that comprise each gestational period generating subsidies for future studies.

O uso de animais isogênicos apresenta grandes vantagens experimentais, como uniformidade fenotípica e genotípica (reduzindo o número de animais em experimentos) e histocompatibilidade, permitindo, assim, o acúmulo de informações e a repetibilidade dos experimentos. A linhagem isogênica de Rattus norvegicus Fischer 344 existe há 90 anos, entretanto pouco se sabe sobre as razões de seu baixo índice reprodutivo. O presente estudo demonstrou que ratos Fischer F344 são fotorresponsivos quanto à reprodução, tendo seus índices de prenhezes acrescidos com o aumento do fotoperíodo. Os melhores índices são obtidos quando os machos são submetidos a 14 horas de luz e fêmeas a 16 horas de luz, indicando dimorfismo sexual na fotorresponsividade.

The use of isogenic animals presents great experimental advantages, as phenotypic and genotypic uniformity (reducing the number of experimental animals) and histocompatibility, thus allowing, the accumulation of information, and the repeatability of the experiments. The isogenic strain of Rattus norvegicus Fischer 344 has existed for 90 years, however the reasons of its low reproductive index are not knew. The present study has demonstrated that Fischer F344 rats are photoresponsive regarding reproduction, having improved its pregnancy index with the increase of the photoperiod. The best indexes were achieved when the males had been submitted to 14 hours of light and females to 16 hours of light, indicating sexual dimorphism in photoresponsivity.