TY - JOUR
T1 - Insulin-like growth factor-I and fibroblast growth factor, but not growth hormone, affect growth plate chondrocyte proliferation
AU - Hutchison, Michele R.
AU - Bassett, Mary H.
AU - White, Perrin C.
PY - 2007/7
Y1 - 2007/7
N2 - Of the many factors that regulate linear growth, IGF-I has a central role in epiphyseal chondrocyte development. Whether IGF-I is solely of systemic or also of local origin is uncertain, as is how other growth factors interact with IGF-I at the growth plate. We studied the proliferative effects of IGF-I on juvenile bovine epiphyseal chondrocytes fractionated by density gradient centrifugation. Cell density correlated with size, glycogen content, and gene expression patterns. There was a gradient of response to IGF-I, with the greatest proliferative response in high-density cells corresponding to the reserve zone, as measured by [3H]thymidine uptake. Low-density (hypertrophic zone) cells proliferated only when exposed to IGF-I and basic fibroblast growth factor (FGF). The gradient of IGF-I response correlated with [125I]IGF-I binding as determined by Scatchard analysis: IGF-I receptor number was 10-fold greater in reserve zone cells than in hypertrophic cells. When exposed to basic FGF for 24 hours, IGF-I binding in hypertrophic cells increased 3-fold. In contrast, no specific binding of GH was demonstrated in juvenile bovine chondrocytes. GH produced neither signal transducer and activator of transcription phosphorylation, increased proliferation, nor increased IGF-I mRNA levels in any chondrocyte fraction. IGF-I mRNA levels were extremely low at 800-1100 copies/μg 18S RNA in bovine chondrocytes. These results suggest that the major regulator of chondrocyte proliferation is systemic IGF-I; FGFs may influence the actions of IGF-I at the growth plate by altering its receptor number in chondrocytes.
AB - Of the many factors that regulate linear growth, IGF-I has a central role in epiphyseal chondrocyte development. Whether IGF-I is solely of systemic or also of local origin is uncertain, as is how other growth factors interact with IGF-I at the growth plate. We studied the proliferative effects of IGF-I on juvenile bovine epiphyseal chondrocytes fractionated by density gradient centrifugation. Cell density correlated with size, glycogen content, and gene expression patterns. There was a gradient of response to IGF-I, with the greatest proliferative response in high-density cells corresponding to the reserve zone, as measured by [3H]thymidine uptake. Low-density (hypertrophic zone) cells proliferated only when exposed to IGF-I and basic fibroblast growth factor (FGF). The gradient of IGF-I response correlated with [125I]IGF-I binding as determined by Scatchard analysis: IGF-I receptor number was 10-fold greater in reserve zone cells than in hypertrophic cells. When exposed to basic FGF for 24 hours, IGF-I binding in hypertrophic cells increased 3-fold. In contrast, no specific binding of GH was demonstrated in juvenile bovine chondrocytes. GH produced neither signal transducer and activator of transcription phosphorylation, increased proliferation, nor increased IGF-I mRNA levels in any chondrocyte fraction. IGF-I mRNA levels were extremely low at 800-1100 copies/μg 18S RNA in bovine chondrocytes. These results suggest that the major regulator of chondrocyte proliferation is systemic IGF-I; FGFs may influence the actions of IGF-I at the growth plate by altering its receptor number in chondrocytes.
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U2 - 10.1210/en.2006-1264
DO - 10.1210/en.2006-1264
M3 - Article
C2 - 17395707
AN - SCOPUS:34347220127
SN - 0013-7227
VL - 148
SP - 3122
EP - 3130
JO - Endocrinology
JF - Endocrinology
IS - 7
ER -