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Is Biopsy-Free Embryo Screening on the Horizon?
a blog by Jennifer A. Redmond, May 9, 2013
Dr. Evan Rosenbluth, a reproductive endocrinologist with Reproductive Science Center of the Bay Area has performed award-winning research studying non-invasive methods for determining embryo implantation potential. Biopsies - including preimplantation genetic screening or PGS - are invasive and can add can $5,000 to $6,000 to an IVF cycle, he says. Currently that is the best option for determining which embryos are chromosomally normal. His goal is to develop biopsy-free methods for selecting healthy embryos.
A former colleague of Rosenbluth’s tried to look at proteins embryos secreted into the media in which they are grown, to determine whether there is a protein profile that would correlate with embryos that would implant. “She found one protein, but the media is already supplemented with protein. It’s like trying to find a needle in a haystack,” he says. But that sparked his interest.
He began studying microRNAs, small bits of RNA that have been discovered just a few years ago. “It turns out that these small RNAs are master regulators of gene expression. And I read early papers on microRNAs that on animal studies they are highly expressed during embryo development,” he says.
His fellowship project was to first determine whether microRNAs are in human embryos, and if so, are they being secreted by embryos into the media they are growing in. It turns out that they are – in very small amounts. Next up: determining if you could tell which embryos would implant by the microRNA makeup of these embryos; basically, trying to figure out a non-invasive way of detecting aneuploidy by using microRNAs.
“It turns out that indeed the embryos secrete microRNAs into the culture medium as they’re growing and that by day 4 or day 5 of the culture there’s enough in the media to be easily detected. And it also turns out that there are a couple of microRNAs that correlate with the chromosome status or aneuploidy.” Further research, currently being published in the journal Fertility & Sterility, demonstrates that microRNAs associated with aneuploidy relate to pregnancy outcomes.
“The next step is verifying this,” Rosenbluth says. “Really the benefit of this is to not have to biopsy the embryos. It’s simpler to take a little of the culture medium that would have been thrown away, and you can analyze it just within a matter of a few hour rather than freezing the embryos. “We can detect the levels as early as day four,” he says. “The ones that correlated, though, we took day 5 medium. We don’t have any prospective trials that say we’ve improved pregnancy rates – it’s preliminary.”
But that’s the goal.