The effects of Ca2SiO4-Ca3(PO4)2 ceramics on adult human mesenchymal stem cell viability, adhesion, proliferation, differentiation and function.

Bioceramic samples with osteogenic properties, suitable for use in the regeneration of hard tissue, were synthesized. The materials consisting of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 wt.% or 3.0 wt.% of dicalcium silicate (C2S) in the system Dicalcium Silicate-Tricalcium Phosphate (C2S-TCP) were obtained by solid state reaction. All materials were composed of a single phase, αTCP in the case of a pure material, or solid solution of C2S in αTCP (αTCPss) for the doped αTCP. Viability, proliferation and in vitro osteoinductive capacity were investigated by seeding, adult mesenchymal stem cells of human origin (ahMSCs) which were CD73(+), CD90(+), CD105(+), CD34(-) and CD45(-) onto the 3 substrates for 30 days. Results show a non-cytotoxic effect after applying an indirect apoptosis test (Annexin V/7-AAD staining), so ahMSCs adhered, spread, proliferated and produced extracellular matrix (Heparan-sulfate proteoglycan (HS) and osteopontin (OP)) on all the ceramics studied. Finally, the cells lost the cluster differentiation marker expression CD73, CD90 y CD105 characteristic of ahMSCs and they showed an osteoblastic phenotype (Alkaline phosphatase activity (ALP), Osteocalcin production (OC), Collagen type I expression (Col-I), and production of mineralization nodules on the extracellular matrix). These observations were more evident in the αTCP ceramic doped with 1.5 wt.% C2S, indicating osteoblastic differentiation as a result of the increased concentration of solid solution of C2S in αTCP (αTCPss). Overall, these results suggest that the ceramics studied are cytocompatible and they are able to induce osteoblastic differentiation of undifferentiated ahMSCs.

IGF-I stimulates neurogenesis in the hypothalamus of adult rats.

In the brain of adult rats neurogenesis persists in the subventricular zone of the lateral ventricles and in the dentate gyrus of the hippocampus. By contrast, low proliferative activity was observed in the hypothalamus. We report here that, after intracerebroventricular treatment with insulin-like growth factor I (IGF-I), cell proliferation significantly increased in both the periventricular and the parenchymal zones of the whole hypothalamus. Neurons, astrocytes, tanycytes, microglia and endothelial cells of the local vessels were stained with the proliferative marker 5-bromo-2'-deoxyuridine (BrdU) in response to IGF-I. Conversely, we never observed BrdU-positive ciliated cubic ependymal cells. Proliferation was intense in the subventricular area of a distinct zone of the mid third ventricle wall limited dorsally by ciliated cubic ependyma and ventrally by tanycytic ependyma. In this area, we saw a characteristic cluster of proliferating cells. This zone of the ventricular wall displayed three cell layers: ciliated ependyma, subependyma and underlying tanycytes. After IGF-I treatment, proliferating cells were seen in the subependyma and in the layer of tanycytes. In the subependyma, proliferating glial fibrillary acidic protein-positive astrocytes contacted the ventricle by an apical process bearing a single cilium and there were many labyrinthine extensions of the periventricular basement membranes. Both features are typical of neurogenic niches in other brain zones, suggesting that the central overlapping zone of the rat hypothalamic wall could be considered a neurogenic niche in response to IGF-I.

Visualization of Bonghan microcells by electron and atomic force microscopy.

OBJECTIVES: The origin of adult stem cells remains an open question. If they derive from embryos, it is difficult to determine the mechanism which interrupts their differentiation during tissue formation. In the 1960s, the Bonghan microcell was suggested as one possible, yet to be described, route of stem cell production, such that they have the potential to proliferate to produce normal cells. MATERIALS AND METHODS: In this study, Bonghan microcells were isolated from Bonghan tissues on rat organ surfaces, and their detailed morphology examined by electron and atomic force microscopy. RESULTS: The ultrastructure observed distinguished them from apoptotic bodies and other microorganisms, and their unique, possible proliferation feature, as protruding threads, was imaged by atomic force microscopy. CONCLUSIONS: The unique threadlike structure of the Bonghan microcell is consistent with Prof. Kim's observation in the first step of making a cell. Understanding of the functions of this threadlike structure may give a clue to understand the origin or the differentiation cue of adult stem cells.