RESUMO
BACKGROUND AND OBJECTIVE: The characteristics of human hematopoietic stem cells are conditioned by the microenvironment of the bone marrow, where they interact with other cell populations, such as mesenchymal stem cells and endothelial cells; however, the study of this microenvironment is complex. The objective of this work was to develop a 3D culture system by magnetic levitation that imitates the microenvironment of human HSC. METHODS AND RESULTS: Human bone marrow-mesenchymal stem cells, umbilical cord blood-hematopoietic stem cells and a non-tumoral endothelial cell line (CC2811, Lonzaâ) were used to develop organotypic multicellular spheres by the magnetic levitation method. We obtained viable structures with an average sphericity index greater than 0.6, an average volume of 0.5 mm3 and a percentage of aggregation greater than 70%. Histological studies of the organotypic multicellular spheres used hematoxylin and eosin stains, and an evaluation of vimentin expression by means of immunohistochemistry demonstrated an organized internal structure without picnotic cells and a high expression of vimentin. The functional capacity of human hematopoietic stem cells after organotypic multicellular spheres culture was evaluated by multipotency tests, and it was demonstrated that 3D structures without exogenous Flt3L are autonomous in the maintenance of multipotency of human hematopoietic stem cells. CONCLUSIONS: We developed organotypic multicellular spheres from normal human cells that mimic the microenvironment of the human hematopoietic stem cells. These structures are the prototype for the development of complex organoids that allow the further study of the biology of normal human stem cells and their potential in regenerative medicine.
RESUMO
BACKGROUND AND OBJECTIVE: Dementia is a growing public health problem. It involves the impairment of several cognitive functions, generating mental and physical disability, and therefore greater functional dependence. There is limited epidemiological information which reveals an approximate prevalence in older adults from Latin America. The objective of this study was to determine the prevalence of dementia in the older adult population of Latin America, and its distribution according to geographic area and gender. MATERIALS AND METHODS: A systematic review was carried out in databases: PubMed, Ovid, Lilacs, Cochrane, Scielo and Google Scholar, in order to identify studies that estimate the prevalence of dementia in urban and / or rural population over 65 years of age. RESULTS: On February 2018, the literature search yielded 357 publications. The overall prevalence of dementia in the older adult population of Latin America was found to be 11%, prevailing more in female gender and urban people. CONCLUSION: The prevalence of dementia in Latin America is higher than registered previously, and even than in other continents.