Efeitos da proliferação e morte celular sobre a eficiência da reprogramação química de astrócitos em neurônios

Abstract

Neural development is classically defined as a period during which stem cells progressively originate progenitors with restricted potential and, finally, neuronal cells (neurogenesis) and macroglia (gliogenesis). For many years, the neurogenesis process was considered unidirectional and not reversible, since differentiated neurons are not able to multiply or de-differentiate. In recent years, however, a number of works have been demonstrating the possibility of generating neurons through other somatic cells from adult tissues, both neural and nonneural. This technology, called cellular reprogramming, has contributed to our understanding of the cellular differentiation process, as well as offering new therapeutic approaches for the treatment of neurodegenerative diseases or central nervous system injuries. However, much of the research developed using cellular reprogramming involves the expression of exogenous genes, which limits its therapeutic potential. In order to circumvent this limitation, it has been proposed to use small molecule cocktails to reprogram somatic cells. These molecules are able to modulate intracellular signaling pathways and modify the pattern of internal gene expression of cells. In our laboratory, we used a cocktail of molecules previously shown to reprogram fibroblasts into neurons. We observed that astrocytes isolated from the neocortex of postnatal mice in the presence of this cocktail, unlike fibroblasts, present an incomplete reprogramming in neurons. In this work, we evaluated the effects of this cocktail on morphology, proliferation and cell survival using time-lapse video-microscopy. We observed an abrupt morphological change in the astrocytes treated with the cocktail, which does not appear to be associated with the reprogramming process in neurons. In addition, we observed a lower rate of proliferation and a higher rate of cell death among treated astrocytes when compared to controls. Taken together, our results help to understand the reduced reprogramming frequency observed in astrocytes when compared to fibroblasts treated with the same cocktail.