Periosteum derived stem cells for regenerative medicine proposals: boosting current knowledge

Periosteum is a thin fibrous layer that covers most bones. It resides in a dynamic mechanically loaded environment and provides a niche for pluripotent cells and a source for molecular factors that modulate cell behaviour. Elucidating periosteum regenerative poten-tial has become a hot topic in orthopaedics. This review discusses the state of the art of osteochondral tissue engineering rested on periosteum derived progenitor cells(PDPCs) and suggests upcoming research direc-tions. Periosteal cells isolation, characterization and migration in the site of injury, as well as their differen-tiation, are analysed. Moreover, the role of cell mecha-nosensing and its contribution to matrix organization, bone microarchitecture and bone stenght is examined. In this regard the role of periostin and its upregulation under mechanical stress in order to preserve PDPC sur-vival and bone tissue integrity is contemplated. The re-view also summarized the role of the periosteum in the field of dentistry and maxillofacial reconstruction. The involvement of microRNAs in osteoblast differentiation and in endogenous tissue repair is explored as well. Fi-nally the novel concept of a guided bone regenerationbased on the use of periosteum itself as a smart mate-rial and the realization of constructs able to mimic the extracellular matrix features is talked out. Additionally, since periosteum can differentiate into insulin produc-ing cells it could be a suitable source in allogenic trans-plantations. That innovative applications would takeadvantage from investigations aimed to assess PDPCimmune privilege.

Cytotoxicity of a silorane-based dental composite on human gingival fibroblasts

AIM:To evaluate the direct and indirect biocompatibility of Filtek Silorane on human gingival fibroblastic cells.METHODS:Sixty-three standardized cylindrical specimens(8 mm diameter and 2 mm thickness)of restorative material were prepared using a light emitting diode-curing unit.The sample were built up in one increment and divided in 2 groups.In the first group,21samples(unpolished samples)were left without a specific polishing procedure;in the second one,42 samples(polished samples)were polished with 4 different grains of discs.Fibroblast cultures,obtained from gingiva of 2 subjects without systemic and oral disease,were used to assess the direct and indirect biocompatibility.Cells cultured for 48 h in normal culture medium were used as a control.RESULTS:The scanning electron microscope observations of fibroblasts cultured on the silorane samples,either polished or unpolished,confirmed the good biocompatibility of the material,favouring the cellular spreading.3-dimethylthiazol-2,5-diphenyltetrazolium bromide tests showed a significant reduction(P<0.01)of gingival fibroblasts viability cultured both in polished samples(90.05%±19.00%)and unpolished samples(78.15%±11.00%)compared with the control.Cells growth in medium conditioned with the samples for 1 wk showed a significant viability reduction(P<0.01)compared to the control.A reduction of cell viability was observed even in the groups containing the material for 3 wk(polished:89.45%±10.00%;unpolished:65.97%±10.00%),even if the cytotoxicity was reduced after this long time exposure.CONCLUSION:Although the poor chromatic availability of this material remains a big limit that restricts its use to posterior sectors,the silorane-based material can be considered an option to perform restorations when aesthetic demands are not the priority,such as the

miR-126, a new modulator of innate immunity

Plasmacytoid dendritic cells （pDCs） express intracellular Toll-like recep-tors （TLRs） 7 and 9 and, once activated, produce large amounts of （anti-viral） type I interferons. As such, pDCs play a key role in the physiopathology of the immune response and in infection, auto- immunity and tumors. In the current issue of Nature Immunology, Agudo and colleagues report that the survival and function of pDCs are modulated by the microRNA miR-126 via the VEGFR2 pathway. These findings unveil the unknown capacity of miR-126--a microRNA that had previously been associated only with angiogenesis--to control pDCs homeostasis,