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Abstract. Embryo-derived tissues, such as umbilical cord (UC), can represent attractive sources of mesenchymal stem cells because their use is not related to any ethical issue. Abundant experimental evidence has already shown that Wharton's jelly contains cells able to differentiate in vitro into adipocytes, chondrocytes, osteocytes and neurons. Human UCs were obtained from term caesarean deliveries and processed within 24 h. Cells derived from the Wharton's jelly expressing mesenchymal markers, such as CD105, but not KDR and CD31 antigens, have been selected by positive and negative immunoseparation. These cells were characterized by an elongated shape and a good proliferation rate. Moreover, they were, at least in part, of fetal origin, as demonstrated by the expression of Sry mRNA. The expression of Myf5 and MyoD was detected after 7 and 11 days of in vitro myogenic induction, respectively. At two weeks from cell injection in the tibialis anterior muscle, previously damaged with bupivacaine, skeletal muscle appeared completely repaired and transplanted cells were present in the muscle for two weeks and differentiated into skeletal muscle cells, as demonstrated by the co-localization of HLA 1 and sarcomeric tropomyosine antigens. These observations provide the first demonstration that CD105(+)/CD31(-)/KDR(-) cells are able not only to differentiate in vivo towards the myogenic lineage, but also to contribute to the muscle regenerative process.

The miR-17 family of microRNAs has recently been recognized for its importance during lung development. The transgenic overexpression of the entire miR-17-92 cluster in the lung epithelium led to elevated cellular proliferation and inhibition of differentiation, while targeted deletion of miR-17-92 and miR-106b-25 clusters showed embryonic or early post-natal lethality. Herein we demonstrate that miR-17 and its paralogs, miR-20a, and miR-106b, are highly expressed during the pseudoglandular stage and identify their critical functional role during embryonic lung development. Simultaneous downregulation of these three miRNAs in explants of isolated lung epithelium altered FGF10 induced budding morphogenesis, an effect that was rescued by synthetic miR-17. E-Cadherin levels were reduced, and its distribution was altered by miR-17, miR-20a and miR-106b downregulation, while conversely, beta-catenin activity was augmented, and expression of its downstream targets, including Bmp4 as well as Fgfr2b, increased. Finally, we identified Stat3 and Mapk14 as key direct targets of miR-17, miR-20a, and miR-106b and showed that simultaneous overexpression of Stat3 and Mapk14 mimics the alteration of E-Cadherin distribution observed after miR-17, miR-20a, and miR-106b downregulation. We conclude that the mir-17 family of miRNA modulates FGF10-FGFR2b downstream signaling by specifically targeting Stat3 and Mapk14, hence regulating E-Cadherin expression, which in turn modulates epithelial bud morphogenesis in response to FGF10 signaling.

Several attemps have been performed to achieve a suitable tracheal replacement for the treatment of different conditions characterized by a lack of sufficient tissue for surgical reconstruction. Actually, tracheal homografts can induce long-term stenosis and their growth potential is not known. Thus, in this work porcine tracheal matrices have been obtained by a detergent-enzymatic method. The treatment decreased the antigenicity of matrices which were able to support the in vitro adhesion of both chondrocytes and tracheal epithelial cells. On the contrary, only few cells were observed in tracheal matrices prepared with formalin, Thimerosal, and acetone, suggesting that the long-term stenosis occuering in vivo is probably because of an insufficient cell ingrowth. In summary, our results indicate that the detergent-enzymatic method allows us to obtain tracheal matrices which can function as a promising support to achieve an in vitro tissue-engineered cell-matrix construc

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