TY - JOUR
T1 - Matrix IGF-1 maintains bone mass by activation of mTOR in mesenchymal stem cells
AU - Xian, Lingling
AU - Wu, Xiangwei
AU - Pang, Lijuan
AU - Lou, Michael
AU - Rosen, Clifford J.
AU - Qiu, Tao
AU - Crane, Janet
AU - Frassica, Frank
AU - Zhang, Liming
AU - Rodriguez, Juan Pablo
AU - Jia, Xiaofeng
AU - Yakar, Shoshana
AU - Xuan, Shouhong
AU - Efstratiadis, Argiris
AU - Wan, Mei
AU - Cao, Xu
N1 - Funding Information:
The project described was supported by grant AR 053973 (X.C.) from NIAMS/ NIH. J.C. is supported by grant T32DK007751v from the US National Institutes of Health. The authors thank B.J. Canning (Asthma and Allergy Center, Johns Hopkins University) for providing guinea pig marrow cells.
PY - 2012/7
Y1 - 2012/7
N2 - Insulin-like growth factor 1 (IGF-1), the most abundant growth factor in the bone matrix, maintains bone mass in adulthood. We now report that IGF-1 released from the bone matrix during bone remodeling stimulates osteoblastic differentiation of recruited mesenchymal stem cells (MSCs) by activation of mammalian target of rapamycin (mTOR), thus maintaining proper bone microarchitecture and mass. Mice with knockout of the IGF-1 receptor (Igf1r) in their pre-osteoblastic cells showed lower bone mass and mineral deposition rates than wild-type mice. Further, MSCs from Igf1r flox/flox mice with Igf1r deleted by a Cre adenovirus in vitro, although recruited to the bone surface after implantation, were unable to differentiate into osteoblasts. We also found that the concentrations of IGF-1 in the bone matrix and marrow of aged rats were lower than in those of young rats and directly correlated with the age-related decrease in bone mass. Likewise, in age-related osteoporosis in humans, we found that bone marrow IGF-1 concentrations were 40% lower in individuals with osteoporosis than in individuals without osteoporosis. Notably, injection of IGF-1 plus IGF binding protein 3 (IGFBP3), but not injection of IGF-1 alone, increased the concentration of IGF-1 in the bone matrix and stimulated new bone formation in aged rats. Together, these results provide mechanistic insight into how IGF-1 maintains adult bone mass, while also providing a further rationale for its therapeutic targeting to treat age-related osteoporosis.
AB - Insulin-like growth factor 1 (IGF-1), the most abundant growth factor in the bone matrix, maintains bone mass in adulthood. We now report that IGF-1 released from the bone matrix during bone remodeling stimulates osteoblastic differentiation of recruited mesenchymal stem cells (MSCs) by activation of mammalian target of rapamycin (mTOR), thus maintaining proper bone microarchitecture and mass. Mice with knockout of the IGF-1 receptor (Igf1r) in their pre-osteoblastic cells showed lower bone mass and mineral deposition rates than wild-type mice. Further, MSCs from Igf1r flox/flox mice with Igf1r deleted by a Cre adenovirus in vitro, although recruited to the bone surface after implantation, were unable to differentiate into osteoblasts. We also found that the concentrations of IGF-1 in the bone matrix and marrow of aged rats were lower than in those of young rats and directly correlated with the age-related decrease in bone mass. Likewise, in age-related osteoporosis in humans, we found that bone marrow IGF-1 concentrations were 40% lower in individuals with osteoporosis than in individuals without osteoporosis. Notably, injection of IGF-1 plus IGF binding protein 3 (IGFBP3), but not injection of IGF-1 alone, increased the concentration of IGF-1 in the bone matrix and stimulated new bone formation in aged rats. Together, these results provide mechanistic insight into how IGF-1 maintains adult bone mass, while also providing a further rationale for its therapeutic targeting to treat age-related osteoporosis.
UR - http://www.scopus.com/inward/record.url?scp=84863726841&partnerID=8YFLogxK
U2 - 10.1038/nm.2793
DO - 10.1038/nm.2793
M3 - Article
C2 - 22729283
AN - SCOPUS:84863726841
SN - 1078-8956
VL - 18
SP - 1095
EP - 1101
JO - Nature Medicine
JF - Nature Medicine
IS - 7
ER -