them = the cells?

Context:
For this new platform, researchers engineered the surface of cells to include receptors that act as a homing device. “The central hypothesis of our work is that the ability of cells to home to specific tissues can be enhanced, without otherwise altering cell function,” said Jeffrey M. Karp, HMS assistant professor of medicine and co-director of the Regenerative Therapeutics Center at BWH and “By knowing the ‘zip code’ of the blood vessels in specific tissues, we can program the ‘address’ onto the surface of the cells to potentially target them with high efficiencies.”