Regenerative response in ischemic brain restricted by p21cip1/waf1.
Neural precursor cells from adults have exceptional proliferative and differentiative capability in vitro yet respond minimally to in vivo brain injury due to constraining mechanisms that are poorly defined. We assessed whether cell cycle inhibitors that restrict stem cell populations in other tissues may participate in limiting neural stem cell reactivity in vivo. The cyclin-dependent kinase inhibitor, p21cip1/waf1 (p21), maintains hematopoietic stem cell quiescence, and we evaluated its role in the regenerative response of neural tissue after ischemic injury using the mice deficient in p21. Although steady-state conditions revealed no increase in primitive cell proliferation in p21-null mice, a significantly larger fraction of quiescent neural precursors was activated in the hippocampus and subventricular zone after brain ischemia. The hippocampal precursors migrated and differentiated into a higher number of neurons after injury. Therefore, p21 is an intrinsic suppressor to neural regeneration after brain injury and may serve as a common molecular regulator restricting proliferation among stem cell pools from distinct tissue types.
Qiu
Jianhua
J
Neuroscience Center, Harvard Medical School, Boston, MA 02129, USA.
Takagi
Yasushi
Y
Harada
Jun
J
Rodrigues
Neil
N
Moskowitz
Michael A
MA
Scadden
David T
DT
Cheng
Tao
T
D000818:Animals; D001483:Base Sequence; D001930:Brain Injuries / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D002545:Brain Ischemia / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D002454:Cell Differentiation; D002455:Cell Division; D002465:Cell Movement; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D016158:Genes, p53; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D009416:Nerve Regeneration / Q000235:genetics / Q000502:physiology*
C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers