Detection of osteoprotegerin (OPG) and its ligand (RANKL) mRNA and protein in femur and tibia of the rat.
Osteoprotegerin (OPG) and the receptor activator of nuclear factor (NF)-kB ligand (RANKL) are key regulators of osteoclastogenesis. The present study had the main aim of showing the localization of OPG and RANKL mRNA and protein in serial sections of the rat femurs and tibiae by immunohistochemistry (IHC) and in situ hybridization (ISH). The main results were: (1) OPG and RANKL mRNA and protein were co-localized in the same cell types, (2) maturative/hypertrophic chondrocytes, osteoblasts, lining cells, periosteal cells and early osteocytes were stained by both IHC and ISH, (3) OPG and RANKL proteins were mainly located in Golgi areas, and the ISH reaction was especially visible in active osteoblasts, (4) immunolabeling was often concentrated into cytoplasmic vacuoles of otherwise negative proliferative chondrocytes; IHC and ISH labeling increased from proliferative to maturative/hypertrophic chondrocytes, (5) the newly laid down bone matrix, cartilage-bone interfaces, cement lines, and trabecular borders showed light OPG and RANKL immunolabeling, (6) about 70% of secondary metaphyseal bone osteocytes showed OPG and RANKL protein expression; most of them were ISH-negative, (7) osteoclasts were mostly unstained by IHC and variably labeled by ISH. The co-expression of OPG and RANKL in the same bone cell types confirms their strictly coupled action in the regulation of bone metabolism.
Silvestrini
Giuliana
G
Department of Experimental Medicine and Pathology, Sezione di Anatomia Patologica, Policlinico Umberto I, Viale Regina Elena, 324, 00161, Roma, Italy. giuliana.silvestrini@uniroma1.it
Ballanti
Paola
P
Patacchioli
Francesca
F
Leopizzi
Martina
M
Gualtieri
Novella
N
Monnazzi
Paola
P
Tremante
Elisa
E
Sardella
Daniela
D
Bonucci
Ermanno
E
D000818:Animals; D001842:Bone and Bones / Q000737:chemistry* / Q000166:cytology; D002352:Carrier Proteins / Q000032:analysis* / Q000378:metabolism; D005269:Femur / Q000166:cytology; D006023:Glycoproteins / Q000032:analysis* / Q000378:metabolism; D007120:Immunochemistry; D017403:In Situ Hybridization; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000378:metabolism; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis* / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis* / Q000378:metabolism; D013977:Tibia / Q000166:cytology
D002352:Carrier Proteins; D006023:Glycoproteins; D008024:Ligands; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506032:Tnfrsf11b protein, rat