Microvesicle-mediated Wnt/ß-Catenin Signaling Promotes Interspecies Mammary Stem/Progenitor Cell Growth.

Signaling mechanisms that regulate mammary stem/progenitor cell (MaSC) self-renewal are essential for developmental changes that occur in the mammary gland during pregnancy, lactation, and involution. We observed that equine MaSCs (eMaSCs) maintain their growth potential in culture for an indefinite period, whereas canine MaSCs (cMaSCs) lose their growth potential in long term cultures. We then used this system to investigate the role of microvesicles (MVs) in promoting self-renewal properties. We found that Wnt3a and Wnt1 were expressed at higher levels in MVs isolated from eMaSCs compared with those from cMaSCs. Furthermore, eMaSC-MVs were able to induce Wnt/ß-catenin signaling in different target cells, including cMaSCs. Interestingly, the induction of Wnt/ß-catenin signaling in cMaSCs was prolonged when using eMaSC-MVs compared with recombinant Wnt proteins, indicating that MVs are not only important for transport of Wnt proteins, but they also enhance their signaling activity. Finally, we demonstrate that the eMaSC-MVs-mediated activation of the Wnt/ß-catenin signaling pathway in cMaSCs significantly improves the ability of cMaSCs to grow as mammospheres and, importantly, that this effect is abolished when eMaSC-MVs are treated with Wnt ligand inhibitors. This suggests that this novel form of intercellular communication plays an important role in self-renewal.

Relationship between summer vacation weight gain and lack of success in a pediatric weight control program.

The purpose was to measure the effect of holidays or season on changes in body weight to determine if this was the reason for the low success rate of weight control program participants. Changes in percent ideal body weight were gathered on 73 overweight youth (average age: 10.5+/-2.8 years; percent ideal body weight: 150+/-28%) over 2-month intervals in a 1-year time span. There was a statistically significant gain in percentage of body weight during July-August compared to January-February at p<0.004, March-April at p<0.04, May-June at p<0.001 and September-October at p<0.04. Sixty-six percent of subjects gained weight during the summer months. When the subjects who lost weight in the summer period were removed from the analysis, the average weight gain was 2.8% of ideal body weight. For a weight control program for children and adolescents to be effective, strategies need to be developed to deal with the summer vacation period as this can affect the overall success in the program.