PLoS One：多效蛋白可以增强小鼠的骨质保护能力

近日，研究者将一组小鼠置于太空中生活，然后对其进行研究，发现在小鼠经历了91天太空生活后，小鼠提高了其骨骼的保护程度。不同类型的骨骼细胞要么会堆积建立骨骼，要么中断骨骼的形成，对于负重骨骼来说，当其对骨骼没有任何影响的时候，分裂细胞便会变得非常有活性，比如处于微重力环境中就会出现这样的情况。

研究者Tavella表示，宇航员在太空中一般会经历20%-30%的骨质流失。宇航员会经常进行锻炼以及补充钙质以防治这种损伤，但是在在地球上确实很难恢复至最初的骨质状况。

研究者将6只小鼠送到国际空间站进行实验研究，其中三只小鼠进行过遗传修饰，可以产生额外的多效蛋白（PTN），这种多效蛋白可以促进骨的发育，研究结果表明，3只可以产生额外PTN的小鼠可以被保护而免于骨损伤，脊柱的骨质流失仅为3%，而正常小鼠的骨质流失却为41.5%。Tavella说，这种蛋白疗法将来可以用于准备进入太空的宇航员身上。相关的研究成果刊登在了于近日刊登在了国际杂志PLoS One上。（生物谷：T.Shen编译）

doi:10.1371/journal.pone.0033179
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Bone Turnover in Wild Type and Pleiotrophin-Transgenic Mice Housed for Three Months in the International Space Station (ISS)

Sara Tavella1,2#*, Alessandra Ruggiu1,2#, Alessandra Giuliani3#, Francesco Brun4,5, Barbara Canciani1,2, Adrian Manescu3,6, Katia Marozzi3,6, Michele Cilli2, Delfina Costa1,2, Yi Liu1,2, Federica Piccardi2, Roberta Tasso1,2, Giuliana Tromba5, Franco Rustichelli3, Ranieri Cancedda1,2

Bone is a complex dynamic tissue undergoing a continuous remodeling process. Gravity is a physical force playing a role in the remodeling and contributing to the maintenance of bone integrity. This article reports an investigation on the alterations of the bone microarchitecture that occurred in wild type (Wt) and pleiotrophin-transgenic (PTN-Tg) mice exposed to a near-zero gravity on the International Space Station (ISS) during the Mice Drawer System (MDS) mission, to date, the longest mice permanence (91 days) in space. The transgenic mouse strain over-expressing pleiotrophin (PTN) in bone was selected because of the PTN positive effects on bone turnover. Wt and PTN-Tg control animals were maintained on Earth either in a MDS payload or in a standard vivarium cage. This study revealed a bone loss during spaceflight in the weight-bearing bones of both strains. For both Tg and Wt a decrease of the trabecular number as well as an increase of the mean trabecular separation was observed after flight, whereas trabecular thickness did not show any significant change. Non weight-bearing bones were not affected. The PTN-Tg mice exposed to normal gravity presented a poorer trabecular organization than Wt mice, but interestingly, the expression of the PTN transgene during the flight resulted in some protection against microgravity’s negative effects. Moreover, osteocytes of the Wt mice, but not of Tg mice, acquired a round shape, thus showing for the first time osteocyte space-related morphological alterations in vivo. The analysis of specific bone formation and resorption marker expression suggested that the microgravity-induced bone loss was due to both an increased bone resorption and a decreased bone deposition. Apparently, the PTN transgene protection was the result of a higher osteoblast activity in the flight mice.