p21cip/WAF is a key regulator of long-term radiation damage in mesenchyme-derived tissues.
This study aimed to determine the mechanisms responsible for long-term tissue damage following radiation injury. We irradiated p21-knockout (p21(-/-)) and wild-type (WT) mice and determined the long-term deleterious effects of this intervention on mesenchyme-derived tissues. In addition, we explored the mechanisms of radiation-induced mesenchymal stem cell (MSC) dysfunction in isolated bone marrow-derived cells. p21 expression was chronically elevated >200-fold in irradiated tissues. Loss of p21 function resulted in a >4-fold increase in the number of skin MSCs remaining after radiation. p21(-/-) mice had significantly less radiation damage, including 6-fold less scarring, 40% increased growth potential, and 4-fold more hypertrophic chondrocytes in the epiphyseal plate (P<0.01). Irradiated p21(-/-) MSCs had 4-fold increased potential for bone or fat differentiation, 4-fold greater proliferation rate, and nearly 7-fold lower senescence as compared to WT MSCs (P<0.01). Ectopic expression of p21 in knockout cells decreased proliferation and differentiation potential and recapitulated the WT phenotype. Loss of p21 function markedly decreases the deleterious effects of radiation injury in mesenchyme-derived tissues and preserves tissue-derived MSCs. In addition, p21 is a critical regulator of MSC proliferation, differentiation, and senescence both at baseline and in response to radiation.
Mehrara
Babak J
BJ
Division of Plastic and Reconstructive Surgery, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York, USA. mehrarab@mskcc.org
Avraham
Tomer
T
Soares
Marc
M
Fernandez
John G
JG
Yan
Alan
A
Zampell
Jamie C
JC
Andrade
Victor P
VP
Cordeiro
Andrew P
AP
Sorrento
Cristina M
CM
D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000528:radiation effects; D002454:Cell Differentiation / Q000528:radiation effects*; D049109:Cell Proliferation / Q000528:radiation effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000528:radiation effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D051379:Mice; D018345:Mice, Knockout; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction
C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21