Police arrested a man today in the case of a pipe bomb explosion last Thursday at a Boston-area laboratory specializing in stem-cell research.

According to a Reuter’s report, the man had already been charged last year with trying to blow up the same building, the Amaranth Bio laboratory in Watertown, MA. No one was hurt in last Thursday’s blast, which did shatter windows and start a fire.

Watertown police said they arrested Brad Karger, 29, Wednesday morning. Karger is awaiting trial on charges he tried to cause a gas explosion in the same building in February 2003.

It seems that stem cell research, which has come out of the shadows in recent years, is again attracting the kind of violence that abortion clinics and providers have faced. Although opponents of stem cell research frequently try to link the field with abortion, there is no actual relationship between the two. And ironically, Amaranth’s research focuses on the less politically charged adult stem cells rather than embryonic stem cells, commonly harvested from embryos created during in vitro fertilization, cells that would otherwise be destroyed or frozen in perpetuity.