TY - JOUR
T1 - IGF-I regulates tight-junction protein claudin-1 during differentiation of osteoblast-like MC3T3-E1 cells via a MAP-kinase pathway
AU - Hatakeyama, Naoko
AU - Kojima, Takashi
AU - Iba, Kousuke
AU - Murata, Masaki
AU - Thi, Mia M.
AU - Spray, David C.
AU - Osanai, Makoto
AU - Chiba, Hideki
AU - Ishiai, Sumio
AU - Yamashita, Toshihiko
AU - Sawada, Norimasa
N1 - Funding Information:
This work was supported by Grants-in-Aid from the National Project “Knowledge Cluster Initiative” (2nd stage, “Sapporo Biocluster Bio-s”), the Ministry of Education, Culture, Sports, Science, and Technology, and the Ministry of Health, Labor, and Welfare of Japan, the Akiyama Foundation, and the Japan Science and Technology Agency. N.Hatakeyama.K.Iba.T.Yamashita Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, S1, W17, Sapporo 060-8556, Japan
PY - 2008/11
Y1 - 2008/11
N2 - Insulin-like growth factor I (IGF-I) is expressed in many tissues, including bone, and acts on the proliferation and differentiation of osteoblasts as an autocrine/paracrine regulator. Tight-junction proteins have been detected in osteoblasts, and direct cell-to-cell interactions may modulate osteoblast function with respect, for example, to gap junctions. In order to investigate the regulation of expression of tight-junction molecules and of function during bone differentiation, osteoblast-like MC3T3-E1 cells and osteocyte-like MLO-Y4 cells were treated with IGF-I. In both MC3T3-E1 cells and MLO-Y4 cells, the tight-junction molecules occludin, claudin-1, -2, and -6, and the gap-junction molecule connexin 43 (Cx43) were detected by reverse transcription with polymerase chain reaction. In MC3T3-E1 cells but not MLO-Y4 cells, mRNAs of claudin-1, -2, and -6, Cx43, and type I collagen, and proteins of claudin-1 and Cx43 were increased after treatment with IGF-I. Such treatment significantly decreased paracellular permeability in MC3T3-E1 cells. The expression of claudin-1 in MC3T3-E1 cells after IGF-I treatment was mainly upregulated via a mitogen-activated protein (MAP)-kinase pathway and, in part, modulated by a PI3-kinase pathway, whereas Cx43 expression and the mediated gap-junctional intercellular communication protein did not contribute to the upregulation. Furthermore, in MC3T3-E1 cells during wound healing, upregulation of claudin-1 was observed together with an increase of IGF-I and type I collagen. These findings suggest that the induction of tight-junction protein claudin-1 and paracellular permeability during the differentiation of osteoblast-like MC3T3-E1 cells after treatment with IGF-I is regulated via a MAP-kinase pathway, but not with respect to gap junctions.
AB - Insulin-like growth factor I (IGF-I) is expressed in many tissues, including bone, and acts on the proliferation and differentiation of osteoblasts as an autocrine/paracrine regulator. Tight-junction proteins have been detected in osteoblasts, and direct cell-to-cell interactions may modulate osteoblast function with respect, for example, to gap junctions. In order to investigate the regulation of expression of tight-junction molecules and of function during bone differentiation, osteoblast-like MC3T3-E1 cells and osteocyte-like MLO-Y4 cells were treated with IGF-I. In both MC3T3-E1 cells and MLO-Y4 cells, the tight-junction molecules occludin, claudin-1, -2, and -6, and the gap-junction molecule connexin 43 (Cx43) were detected by reverse transcription with polymerase chain reaction. In MC3T3-E1 cells but not MLO-Y4 cells, mRNAs of claudin-1, -2, and -6, Cx43, and type I collagen, and proteins of claudin-1 and Cx43 were increased after treatment with IGF-I. Such treatment significantly decreased paracellular permeability in MC3T3-E1 cells. The expression of claudin-1 in MC3T3-E1 cells after IGF-I treatment was mainly upregulated via a mitogen-activated protein (MAP)-kinase pathway and, in part, modulated by a PI3-kinase pathway, whereas Cx43 expression and the mediated gap-junctional intercellular communication protein did not contribute to the upregulation. Furthermore, in MC3T3-E1 cells during wound healing, upregulation of claudin-1 was observed together with an increase of IGF-I and type I collagen. These findings suggest that the induction of tight-junction protein claudin-1 and paracellular permeability during the differentiation of osteoblast-like MC3T3-E1 cells after treatment with IGF-I is regulated via a MAP-kinase pathway, but not with respect to gap junctions.
KW - Cell culture (murine)
KW - Claudin-1
KW - IGF-I
KW - MAP-kinase
KW - Osteoblast
KW - Tight junction
UR - http://www.scopus.com/inward/record.url?scp=55649108173&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=55649108173&partnerID=8YFLogxK
U2 - 10.1007/s00441-008-0690-9
DO - 10.1007/s00441-008-0690-9
M3 - Article
C2 - 18855015
AN - SCOPUS:55649108173
SN - 0302-766X
VL - 334
SP - 243
EP - 254
JO - Cell and Tissue Research
JF - Cell and Tissue Research
IS - 2
ER -