Mesenchymal stromal cells from amniotic fluid are less prone to senescence compared to those obtained from bone marrow: An in vitro study.

Mesenchymal stromal cells (MSCs) are considered to be an excellent source in regenerative medicine. They contain several cell subtypes, including multipotent stem cells. MSCs are of particular interest as they are currently being tested using cell and gene therapies for a number of human diseases. They represent a rare population in tissues; for this reason, they require, before being transplanted, an in vitro amplification. This process may induce replicative senescence, thus affecting differentiation and proliferative capacities. Increasing evidence suggests that MSCs from fetal tissues are significantly more plastic and grow faster than MSCs from bone marrow. Here, we compare amniotic fluid mesenchymal stromal cells (AF-MSCs) and bone marrow mesenchymal stromal cells (BM-MSCs) in terms of cell proliferation, surface markers, multidifferentiation potential, senescence, and DNA repair capacity. Our study shows that AF-MSCs are less prone to senescence with respect to BM-MSCs. Moreover, both cell models activate the same repair system after DNA damage, but AF-MSCs are able to return to the basal condition more efficiently with respect to BM-MSCs. Indeed, AF-MSCs are better able to cope with genotoxic stress that may occur either during in vitro cultivation or following transplantation in patients. Our findings suggest that AF-MSCs may represent a valid alternative to BM-MSCs in regenerative medicine, and, of great relevance, the investigation of the mechanisms involved in DNA repair capacity of both AF-MSCs and BM-MSCs may pave the way to their rational use in the medical field.

Misidentified Human Gene Functions with Mouse Models: The Case of the Retinoblastoma Gene Family in Senescence.

Although mice models rank among the most widely used tools for understanding human genetics, biology, and diseases, differences between orthologous genes among species as close as mammals are possible, particularly in orthologous gene pairs in which one or more paralogous (i.e., duplicated) genes appear in the genomes of the species. Duplicated genes can possess overlapping functions and compensate for each other. The retinoblastoma gene family demonstrates typical composite functionality in its three member genes (i.e., RB1, RB2/P130, and P107), all of which participate in controlling the cell cycle and associated phenomena, including proliferation, quiescence, apoptosis, senescence, and cell differentiation. We analyzed the role of the retinoblastoma gene family in regulating senescence in mice and humans. Silencing experiments with each member of the gene family in mesenchymal stromal cells (MSCs) and fibroblasts from mouse and human tissues demonstrated that RB1 may be indispensable for senescence in mouse cells, but not in human ones, as an example of species specificity. Furthermore, although RB2/P130 seems to be implicated in maintaining human cell senescence, the function of RB1 within any given species might differ by cell type, as an example of cell specificity. For instance, silencing RB1 in mouse fibroblasts induced a reduced senescence not observed in mouse MSCs. Our findings could be useful as a general paradigm of cautions to take when inferring the role of human genes analyzed in animal studies and when examining the role of the retinoblastoma gene family in detail.

Poly(ADP-ribosyl)ation of proteins and germ cell development in hyperthyroid rat testes.

The effect of increased serum levels of thyroid hormone (triiodothyronine, T3) on young rat testis spermatogenesis was studied by analysing molecular and morphological parameters. Hyperthyroidism was induced by either T3-treatment or 2- and 10-day cold exposure. The poly(ADP-ribosyl)ation of proteins catalysed by poly(ADP-ribose) polymerase, which is particularly active at specific stages of rat spermatogenesis, was analysed as molecular index of DNA damage and cell stress. Poly(ADP-ribose) polymerase activity rose after both T3-treatment and 2- and 10-day cold exposure, with a trend of 10-day cold-exposed rats towards control values. In all hyperthyroid rats poly(ADP-ribose) turnover, as a contribution of both poly(ADP-ribose) polymerase and poly(ADP-ribose) glycohydrolase), was enhanced with respect to euthyroid animals. Poly(ADP-ribosyl)ation of proteins occurred with long and branched polymers suggesting an increased involvement of the modification system in DNA repair. Morphological changes of germ tissue were observed in hyperthyroid rats, mainly a high reduction of mature cells in the seminiferous tubule, and evidence of germ cell apoptosis was obtained by TUNEL method. In control animals germ cell apoptosis was within physiological levels. Conversely, in hyperthyroid rats a dramatic increase in the number of TUNEL-positive cells (some spermatogonia and numerous primary spermatocytes) was found, even though the increase was lower in 10-day than in 2-day cold-exposed animals.