ACS MEETING NEWS: Growing stem
cells in stiff or soft environments influences their future differentiation
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grow best in environments mimicking the stiffness or softness of their natural niche, Huck said. But he added, “Nobody had studied whether cells could shake the memory of their past environments.” Anseth’s team studied human mesenchymal stem cells, one of three major groups of human stem cells. They found two proteins, called YAP and TAZ, that can modulate the cells’ mechanical memory. Both can activate gene transcription. CHUN YANG & KRISTI ANSETH
STEM CELL MEMORIES
UMAN STEM CELLS can remember whether
researchers grew them on a soft bed of polyethylene glycol or on a stiff floor of polystyrene. This mechanical memory in turn influences the fate of these stem cells, such as whether they start differentiating into fat or bone cells. That’s one take-home message of a presentation given last week by University of Colorado, Boulder, materials scientist Kristi S. Anseth at the American Chemical Society meeting in Dallas. The work, which Anseth described to the Division of Biochemical Technology, is also the subject of a recent report in Nature Materials (2014, DOI: 10.1038/nmat3889). Stem cell researchers already attempt to control differentiation by carefully selecting the chemical constituents in their stem cell growth media. The new results suggest that they should also consider the physical constraints of this growing environment, Anseth and her colleagues argue. “Just as you would dose stem cells with chemical factors over time to direct differentiation, researchers should add the properties of the mechanical environment to their laboratory repertoire,” commented Wilhelm T. S. Huck, who studies cellular growth conditions at Radboud University, Nijmegen, the Netherlands. Researchers previously had evidence that stem cells
When the stem cells are cultured on stiff beds, these proteins relocate from the cytoplasm to the nucleus. If the stem cells spend just a few days on stiff or soft beds, the future impact of this mechanical history is not set in stone. But spending 10 days on a particular bed leads to irreversible future differentiation of the stem cells into stiff-environment-loving bone or softloving fat cells. “I think this study will prompt many groups to consider with greater care the importance of their culture conditions,” commented Dennis E. Discher, who studies stem cell culture conditions at the University of Pennsylvania.—SARAH EVERTS
Human mesenchymal stem cells (left) grown for 10 days on a hard bed remember that environment and differentiate toward bone cells (right).
FINANCE Polymers maker Trinseo tries again to go public with stock offering Trinseo is making a second attempt at becoming a public company. The polymers producer has filed a prospectus with the Securities & Exchange Commission (SEC) for an initial public offering (IPO) of stock worth $200 million. Once known as Styron, Trinseo is a collection of polymer operations that Dow Chemical sold to the private equity firm Bain Capital in 2010. Trinseo had filed for a $400 million IPO in 2011 but withdrew its prospectus two years later. Trinseo makes acrylonitrile-butadienestyrene resins, synthetic rubber, latex,
and polycarbonate. It is also partners with Chevron Phillips Chemical in the polystyrene joint venture Americas Styrenics. Trinseo lost $22 million on $5.3 billion in sales last year, largely because of financing costs and weakness in the polycarbonate business. The company raised $1.3 billion in a junk-bond offering last year, leaving it with an ample level of high-interest-rate debt. When Trinseo issued the new bonds, Moody’s analyst John Rogers rated them below investment grade. He lowered the rating later in the year because of poly-
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mer price volatility and weak demand. In its SEC filing, Trinseo says it will use the proceeds from the stock offering to pay down debt. The company is trying to focus on its latex and synthetic rubber businesses, which have been more profitable than styrenics or polycarbonate. It recently acquired rubber capacity from Japan’s JSR at a plant the companies shared in Germany. It is also expanding latex capacity in China. “I am cautiously optimistic for a better 2014,” CEO Christopher D. Pappas said earlier this month.—ALEX TULLO
