The population of Brazil, formed by extensive admixture between Amerindians, Europeans and Africans, is one of the most variable in the world. We have recently published a study that used ancestry-informative markers to conclude that in Brazil, at an individual level, color, as determined by physical evaluation, was a poor predictor of genomic ancestry, estimated by molecular markers. To corroborate these findings we undertook the present investigation based on data from 12 commercially available forensic microsatellites that were utilized to estimate the personal genomic origin for each of 752 individuals from the city of São Paulo, belonging to different Brazilian color categories (275 Whites, 192 Intermediates and 285 Blacks). The genotypes permitted the calculation of a personal likelihood-ratio estimator of African or European ancestry. Although the 12 marker set proved capable of discriminating between European and African individuals, we observed very significant overlaps among the three color categories of Brazilians. This was confirmed quantitatively using a Bayesian analysis of population structure that did not demonstrate significant genetic differentiation between the three color groups. These results corroborate and validate our previous conclusions using ancestry-informative markers that in Brazil at the individual level there is significant dissociation of color and genomic ancestry.

Células-tronco são células indiferenciadas. Como tal, apresentam uma série de características que as tornam candidatas à utilização terapêutica. As principais características das células-tronco são a capacidade de autorrenovação e de se diferenciarem em diversos tipos celulares. Desta forma, acredita-se que células-tronco presentes nos diferentes tecidos tenham papel regenerativo quando estes sofrem uma lesão ou injúria. Entre os tecidos conhecidos por apresentarem células-tronco após a vida pós-natal, a medula óssea foi a mais estudada, por muitos anos, como fonte tanto de células-tronco hematopoéticas quanto de células-tronco mesenquimais, também denominadas de células mesenquimais estromais da medula óssea ou células estromais mesenquimais multipotentes. Estas células são um grupo de células clonogênicas, presentes no estroma da medula óssea, que, quando submetidas a diferentes estímulos apropriados, são capazes de se diferenciarem em várias linhagens de células, como a osteogênica, a condrogênica e a adipogênica e, possivelmente, em outros tipos celulares não mesodérmicos, como células neurais ou hepatócitos. Nesta revisão, as principais características das células-tronco mesenquimais serão abordadas, incluindo os marcadores moleculares e de membrana, as características de divisão e de diferenciação, a heterogeneidade e as aplicações clínicas potenciais. Rev.

Células-tronco do líquido amniótico Amniotic fluid stem cells IntroduçãoO fluido amniótico humano tem sido utilizado no diagnóstico pré-natal já há mais de 70 anos. O primeiro relato sobre amniocentese foi em 1930, no qual os autores tentaram correlacionar o número de células presentes no líquido amniótico e o fenótipo celular com o sexo e a saúde do feto. Atualmente, uma das principais utilizações diagnósticas do líquido amniótico é no isolamento de células fetais para cariotipagem, no exame de anormalidades cromossômicas. Recentemente, foram apresentadas evidências de que o lí-quido amniótico pode ter outras aplicações, além da utilização como ferramenta diagnóstica. Ele pode ser importante fonte de células terapêuticas para vários distúrbios, tanto congênitos quanto no adulto.O líquido amniótico contém uma quantidade muito grande de células em suspensão, população celular que é variá-vel com a fase da gestação e que traduz as mudanças na formação do líquido amniótico e da maturação fetal e de seus anexos.

It is well known that antisense oligonucleotides (OAS) are able to inhibit gene expression in a sequence-specific way. The potencial use of an artificial lipid nanoemulsion (LDE) as a vector to carry OAS has been described. LDE was shown to bind 3’-cholesteryl- OAS (C-OAS) and to be internalized into cells through LDL receptors. Here we further explore these findings by examining the capacity of this complex to inhibit MDR-1 gene expression in a sarcoma cell line (MES-DX), which express P-glycoprotein. LDE was prepared as described (Bydlowski et al. ,1995). The capacity of LDE to bind C-OAS was examined by fluorescence spectra analysis using a Hitachi F4500 fluorimeter. Human plasma was obtained from healthy blood donors and LDL, HDL and lipoprotein free serum (LPDS) were separated by sequencial ultracentrifugation. C-OAS/LDE complex was incubated with HDL (apoE donor) before cell experiments were performed. Binding of [3H] LDE/C-OAS complex to LDL receptors from MES-DX cells was studied by competition assay. Two different C-OASs, both complementary to regions flanking the AUG initiation codon were used. Inhibition of MDR-1 gene expression was evaluated by RT-PCR. The binding constant for C-OAS/LDE was 4,2 × 10−3M−1 indicating a high specific capacitiy of conjugation.The C-OAS/LDE complex was shown, by the competition assays and confocal microscopy, to bind to LDL receptors and then to be internalized into cells. Both C-OAS/ LDE complexes strongly inhibited (70% inhibition) the MDR-1 gene expression after 48 hours of cell incubation. This inhibition was not observed when LDE was used alone or complexed with scrambled OAS sequences. The results show that this nanoemulsion binds to cholesteryl-OASs. Moreover, this nanoparticle is an efficient carrier for OAS to target cells expressing LDL receptors. This complex is able to internalize oligonucleotides into cells specifically through the LDL receptor-mediated pathway. The internalized ODN was able to act on nucleic acid sequences as determined by the inhibition of MDR-1 gene expression. Therefore, LDE/C-OAS is promissing nanoparticle complex to be used in gene therapy studies.