Adriana A. Debes

Color and genomic ancestry in Brazilians: a study with forensic microsatellites.

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.

Características biológicas das células-tronco mesenquimais

Celulas-tronco sao celulas indiferenciadas. Como tal, apresentam uma serie de caracteristicas que as tornam candidatas a utilizacao terapeutica. As principais caracteristicas das celulas-tronco sao a capacidade de autorrenovacao e de se diferenciarem em diversos tipos celulares. Desta forma, acredita-se que celulas-tronco presentes nos diferentes tecidos tenham papel regenerativo quando estes sofrem uma lesao ou injuria. Entre os tecidos conhecidos por apresentarem celulas-tronco apos a vida pos-natal, a medula ossea foi a mais estudada, por muitos anos, como fonte tanto de celulas-tronco hematopoeticas quanto de celulas-tronco mesenquimais, tambem denominadas de celulas mesenquimais estromais da medula ossea ou celulas estromais mesenquimais multipotentes. Estas celulas sao um grupo de celulas clonogenicas, presentes no estroma da medula ossea, que, quando submetidas a diferentes estimulos apropriados, sao capazes de se diferenciarem em varias linhagens de celulas, como a osteogenica, a condrogenica e a adipogenica e, possivelmente, em outros tipos celulares nao mesodermicos, como celulas neurais ou hepatocitos. Nesta revisao, as principais caracteristicas das celulas-tronco mesenquimais serao abordadas, incluindo os marcadores moleculares e de membrana, as caracteristicas de divisao e de diferenciacao, a heterogeneidade e as aplicacoes clinicas potenciais.

Evaluation of Distinct Freezing Methods and Cryoprotectants for Human Amniotic Fluid Stem Cells Cryopreservation

Amniotic fluid (AF) was described as a potential source of mesenchymal stem cells (MSCs) for biomedicine purposes. Therefore, evaluation of alternative cryoprotectants and freezing protocols capable to maintain the viability and stemness of these cells after cooling is still needed. AF stem cells (AFSCs) were tested for different freezing methods and cryoprotectants. Cell viability, gene expression, surface markers, and plasticity were evaluated after thawing. AFSCs expressed undifferentiated genes Oct4 and Nanog; presented typical markers (CD29, CD44, CD90, and CD105) and were able to differentiate into mesenchymal lineages. All tested cryoprotectants preserved the features of AFSCs however, variations in cell viability were observed. In this concern, dimethyl sulfoxide (Me2SO) showed the best results. The freezing protocols tested did not promote significant changes in the AFSCs viability. Time programmed and nonprogrammed freezing methods could be used for successful AFSCs cryopreservation for 6 months. Although tested cryoprotectants maintained undifferentiated gene expression, typical markers, and plasticity of AFSCs, only Me2SO and glycerol presented workable viability ratios.

Células-tronco do líquido amniótico

Desde o primeiro isolamento e cultivo de celulas-tronco embrionarias humanas, ha mais de 10 anos, seu uso na pesquisa e terapia foi inibida por consideracoes eticas complexas e pelo risco de transformacao maligna destas celulas indiferenciadas apos transplante no paciente. As celulas-tronco adultas sao eticamente aceitas e o risco de transformacao maligna e muito baixo. Entretanto, seu potencial de diferenciacao e sua capacidade proliferativa sao limitados. Cerca de 6 anos atras, a descoberta de celulastronco no liquido amniotico que expressavam Oct-4, um marcador especifico de pluripotencialidade, com alta capacidade de proliferacao e diferenciacao, iniciou um novo campo promissor na area das celulas-tronco. Estas celulas tem potencial de se diferenciar em celulas dos tres folhetos germinativos. Nao formam tumores in vivo e nao levantam os questionamentos eticos associados com as celulas-tronco embrionarias humanas. Futuras investigacoes revelarao se as celulas-tronco do liquido amniotico realmente irao representar um tipo intermediario com vantagens em relacao tanto as celulas-tronco embrionarias quanto as adultas. Este artigo faz uma revisao acerca destes topicos e das caracteristicas biologicas das celulas-tronco do liquido amniotico.