Temporal and spatial expression profiles of BMP receptors and noggin during BMP-2-induced ectopic bone formation.
The mechanism of ectopic bone formation has not been clear. After BMP-2 implantation into the back muscles of 198 mice, expression of BMPR-1A, -2, and Noggin was increased during the early phase of the reaction. The results suggest that positive and negative feedback mechanisms modulate ectopic osteogenesis induced by this growth factor.


BACKGROUND
The expression of bone morphogenetic protein receptors (BMPRs) and Noggin during ectopic bone formation after implantation of BMP-2 into the back muscles of adult mice was investigated in this study.


METHODS
One hundred ninety-eight male ddy mice were divided into groups and received either collagen disks containing BMP-2, collagen disks alone, or sham surgery with no disk implantation. Changes in the temporal and spatial expression profiles of BMPRs and Noggin were examined by Northern blotting, in situ hybridization, Western blotting, and immunohistochemistry.


CONCLUSIONS
In the BMP group, expression of BMPR-1A, -2, and Noggin mRNA and protein was enhanced 2-4 days after implantation in undifferentiated mesenchymal cells and regenerating muscle fibers located close to the BMP-retaining implants. On day 7, the expression was also observed in cartilage cells, and after day 14, in the osteoblastic cells around bone tissue. The level of expression peaked at day 4 after implantation and persisted at a much lower level during the bone forming process. No significant expression of BMPR-1B was detected at the mRNA and protein levels during the bone-forming reaction. In the BMP free control groups, a mild enhancement of BMPR-2 expression was also noted around the implant, but this was not observed for BMPR-1A, -1B, or Noggin. Upregulated expression of BMPR-1A, -2, and Noggin in undifferentiated mesenchymal cells and regenerating muscle fibers occurs during the early phase of BMP-2-induced bone formation. The coordinate expression of these positive and negative regulators of BMP signaling points to a potential regulatory mechanism for bone induction.
Department of Orthopaedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan.
Yukio
Y
Nakamura
Shigeyuki
S
Wakitani
Jun
J
Nakayama
Shinji
S
Wakabayashi
Hiroshi
H
Horiuchi
Kunio
K
Takaoka
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D055396:Bone Morphogenetic Protein 2; D052005:Bone Morphogenetic Protein Receptors, Type I; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis* / Q000378:metabolism*; D001842:Bone and Bones / Q000378:metabolism*; D002352:Carrier Proteins; D002454:Cell Differentiation; D003094:Collagen / Q000378:metabolism; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D009132:Muscles / Q000378:metabolism / Q000473:pathology; D010012:Osteogenesis; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis*; D011506:Proteins; D012313:RNA / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000096:biosynthesis*; D013997:Time Factors; D016212:Transforming Growth Factor beta; D000099176:Noggin Protein
D055396:Bone Morphogenetic Protein 2; D052005:Bone Morphogenetic Protein Receptors, Type I; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012313:RNA; D017978:Receptors, Growth Factor; D016212:Transforming Growth Factor beta; D000099176:Noggin Protein; C525719:Bmp2 protein, mouse; C498212:Bmpr1a protein, mouse