Quantification of CD[34.sup.+] hematopoietic stem cells from the umbilical cord of dogs/Quantificacao de celulas CD[34.sup.+] do sangue do cordao umbilical de caes

Stem cells promote the reconstitution of the hematopoietic and other tissues, and are present in the embryo, peripheral blood, bone marrow and umbilical cord blood (UCB). The experimental models of bone marrow and peripheral blood stem cells in dogs provide important information for stem cells transplants in humans. However, there are no studies on the UCB cells of dogs in Brazil. This experiment aimed at quantifying nucleated and stem cells in the umbilical cord of dogs having as its purpose the hematological recuperation. In this assay, UCB of 40 neonates dogs was collected for nucleated cell count in automatic cell counter and stem cell CD[34.sup.+] count in flow cytometer. The method of UCB collection at the juxta-placental portion of the umbilical vessels allowed UCB blood and stem cell CD[34.sup.+] quantification. The nucleated cell values of UCB were reduced as compared to the reference values of the peripheral blood of healthy neonate and adult dogs. Despite the small volume of UCB (1325 µL), the quantity of stem cells in the canine umbilical cord (3.38±2.72 CD[34.sup.+] x [10.sup.6] [kg.sup.-1]) is similar to that reported in the bone marrow and mobilized peripheral blood of adult dogs, coinciding with the amount recommend for hematopoetic reconstitution. Key words: stem cell, CD34, hematopoietic, umbilical cord, cytometry, dogs. As celulas-tronco promovem a reconstituicao hematopoetica e de outros tecidos, estando presentes no embriao, no sangue periferico, na medula ossea e no sangue do cordao umbilical (SCU). Os modelos experimentais de celulas-tronco do sangue periferico e da medula ossea em caes tem propiciado informacoes relevantes para transplantes de celulas-tronco em humanos. Entretanto, nao existe estudo sobre as celulas-tronco no SCU canino no Brasil. O objetivo deste ensaio foi quantificar as celulas nucleadas e as celulastronco CD[34.sup.+] no SCU de caes para propostas de reconstituicao hematologica. No presente protocolo experimental, a coleta de SCU de 40 caes neonatos foi realizada para contagem das celulas nucleadas no contador automatico de celulas sanguineas e contagem das celulas-tronco CD[34.sup.+] no citometro de fluxo. O metodo de coleta do SCU na porcao justaplacentaria dos vasos umbilicais permitiu a quantificacao das celulas-tronco CD[34.sup.+]. Os valores das celulas nucleadas do SCU foram reduzidos em relacao aqueles do sangue periferico de caes sadios recem-nascidos e adultos. Apesar do volume escasso de SCU (1325 µL)