Massachusetts Institute of Technology (MIT) researchers have developed a new, more efficient way to pair cells so that they can be fused together into a hybrid cell, the university said Sunday.

The new technique would make it much easier for scientists to study what happens when two cells are combined. For example, fusing an adult cell with an embryonic stem cell would allow researchers to study the genetic reprogramming that occurs in such hybrids.

The researchers, led by Joel Voldman, associate professor of electrical engineering and computer science, and Rudolf Jaenisch, professor of biology and a member of the Whitehead Institute for Biomedical Research, reported the new technique in the Jan. 4 online edition of Nature Methods.

The team's simple but ingenious sorting method increases the rate of successful cell fusion from around 10 percent to about 50 percent, and allows thousands of cell pairings at once.

Though cell fusion techniques have been around for a long time, there are many technical limitations, Voldman said.

Getting the right cells to pair up before fusing them is one major obstacle. If scientists are working with a mixture of two cell types, for example A and B, they end up with many AA and BB pairings, as well as the desired AB match.

Researchers had previously trapped cells in tiny cups as they flowed across a chip. Each cup can hold only two cells, but there was no way to control whether the cups capture an A and a B, two As or two Bs.

In contrast, the cell-trapping cups on Voldman and Jaenisch's new sorting device are strategically arranged to capture and pair cells of different types.

First, type A cells are sent across the chip in one direction and are caught in traps large enough to hold only one cell. Once the cells are trapped, liquid is sent across the chip in the opposite direction, pushing the cells out of the small cups and into larger ones.

Once one A cell is in each large cup, type B cells are then sent into the large cups. Each cup can only hold two cells, so each ends up with one A and one B. After the cells are paired in the traps, they can be joined by an electric pulse that fuses the cell membranes.

In addition to helping with studies of stem cell reprogramming, the technique also can be used to study interactions between any types of cells.

"It's a very general type of device," Voldman said.