Journal Club: Recent research presented by UCSF students

Graduate Division

Presentation: “Blurred lines in epidermal wounding but not homeostasis”

Presenter: David Pardo.

Paper: Page, M.E., et al., “The Epidermis Comprises Autonomous Compartments Maintained by Distinct Stem Cell Populations,” Cell Stem Cell, 2013 Oct 3;13(4):471-482.

In a nutshell:

Traditionally, we associate certain stem cell markers with certain tissues, but multiple stem cell (SC) populations can actually exist in a single tissue.  In the hair follicle, for instance, we’ve got Lrig1+ SCs and Bulge SCs. 

Hair follicle SCs can also contribute to wound healing, but we don’t know how the architecture is maintained or which population(s) might contribute to wound healing. To identify the population(s), the authors asked a few key questions: 

1. Is there a functional difference between the SC populations in the hair follicle?  If there is, then those differences might make one more likely to contribute to the wound-healing response than another.  They found that yes, there is a difference, and that Lrig1+ SCs proliferate more, suggesting that they are the likely culprits.

2. Are epidermal SCs maintained as a hierarchy, as in the gut, or in independent compartments?  It turns out that the different populations are never found outside their respective compartments at homeostasis. 

3. How does wounding change SC behavior? Surprisingly, the compartments become disrupted during the wound, and remain disrupted for up to a year after the wound has healed.  Understanding SC order is important, but what does that mean for the rest of us? 

This has implications in cancer.  If these proliferative cells lose their natural order during wounding, this suggests that a window is opened for cancers to form.  And indeed, the authors found that oncogenic (Kras) signaling induces additional tumors after wounding.  This information can be used to better understand cancer development and eventually prevention.