Compartmentalized organization: a common and required feature of stem cell niches?

A key question in the stem cell field is how to balance the slow cycling of stem cells with active organ growth. Recent studies of the hair follicle stem cell niche have shown that this can be achieved by organizing the stem cell niche into two compartments: one that engages in immediate, rapid new growth and one that contributes later to long-term growth that fuels hair regeneration. Based on these and other recent findings, we propose that several other adult stem cell niches, including those in the blood, intestine and brain, have a similar bi-compartmental organization and that stem cells might work cooperatively with their progeny to sustain tissue regeneration.