title: Expression of parathyroid hormone-related peptide and insulin-like growth factor I during rat fracture healing.
abstract: Parathyroid hormone-related peptide (PTHrP) and insulin-like growth factor I (IGF-I) are both involved in the regulation of bone and cartilage metabolisms and their interaction has been reported in osteoblasts. To investigate the interaction of PTHrP and IGF-I during fracture healing, the expression of mRNA for PTHrP and IGF-I, and receptors for PTH/PTHrP and IGF were examined during rat femoral fracture healing using an in situ hybridization method and an immunohistochemistry method, respectively. During intramembranous ossification, PTHrP mRNA, IGF-I mRNA and IGF receptors were detected in preosteoblasts, differentiated osteoblasts and osteocytes in the newly formed trabecular bone. PTH/PTHrP receptors were markedly detected in osteoblasts and osteocytes, but only barely so in preosteoblasts. During cartilaginous callus formation, PTHrP mRNA was expressed by mesenchymal cells and proliferating chondrocytes. PTH/PTHrP receptors were detected in proliferating chondrocytes and early hypertrophic chondrocytes. IGF-I mRNA and IGF receptor were co-expressed by mesenchymal cells, proliferating chondrocytes, and early hypertrophic chondrocytes. At the endochondral ossification front, osteoblasts were positive for PTHrP and IGF-I mRNA as well as their receptors. These results suggest that IGF-I is involved in cell proliferation or differentiation in mesenchymal cells, periosteal cells, osteoblasts and chondrocytes in an autocrine and/or paracrine fashion. Furthermore, PTHrP may be involved in primary callus formation presumably co-operating with IGF-I in osteoblasts and osteocytes, and by regulating chondrocyte differentiation in endochondral ossification.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi Higashi-ku, Fukuoka 812, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Okazaki
authors.forename: Seiya
authors.initials: S
authors.lastname: Jingushi
authors.forename: Takashi
authors.initials: T
authors.lastname: Ikenoue
authors.forename: Ken
authors.initials: K
authors.lastname: Urabe
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sakai
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000818:Animals; D002356:Cartilage / Q000502:physiology; D005260:Female; D005264:Femoral Fractures / Q000503:physiopathology*; D005269:Femur / Q000737:chemistry / Q000502:physiology; D017102:Fracture Healing / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D010012:Osteogenesis / Q000502:physiology; D044162:Parathyroid Hormone-Related Protein; D036361:Peptide Hormones / Q000032:analysis / Q000235:genetics*; D010521:Periosteum / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000032:analysis
chemical_list: D044162:Parathyroid Hormone-Related Protein; D036361:Peptide Hormones; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1