Bone and bone marrow pro-osteoclastogenic cytokines are up-regulated in osteoporosis fragility fractures.
This study evaluates cytokines production in bone and bone marrow of patients with an osteoporotic fracture or with osteoarthritis by real time PCR, Western blot and immunohistochemistry. We demonstrate that the cytokine pattern is shifted towards osteoclast activation and osteoblast inhibition in patients with osteoporotic fractures.


BACKGROUND
Fragility fractures are the resultant of low bone mass and poor bone architecture typical of osteoporosis. Cytokines involved in the control of bone cell maturation and function are produced by both bone itself and bone marrow cells, but the roles of these two sources in its control and the amounts they produce are not clear. This study compares their production in patients with an osteoporotic fracture and those with osteoarthritis.


METHODS
We evaluated 52 femoral heads from women subjected to hip-joint replacement surgery for femoral neck fractures due to low-energy trauma (37), or for osteoarthritis (15). Total RNA was extracted from both bone and bone marrow, and quantitative PCR was used to identify the receptor activator of nuclear factor kB Ligand (RANKL), osteoprotegerin (OPG), macrophage colony stimulating factor (M-CSF), transforming growth factor β (TGFβ), Dickoppf-1 (DKK-1) and sclerostin (SOST) expression. Immunohistochemistry and Western blot were performed in order to quantify and localize in bone and bone marrow the cytokines.


RESULTS
We found an increase of RANKL/OPG ratio, M-CSF, SOST and DKK-1 in fractured patients, whereas TGFβ was increased in osteoarthritic bone. Bone marrow produced greater amounts of RANKL, M-CSF and TGFβ compared to bone, whereas the production of DKK-1 and SOST was higher in bone.


CONCLUSIONS
We show that bone marrow cells produced the greater amount of pro-osteoclastogenic cytokines, whereas bone cells produced higher amount of osteoblast inhibitors in patients with fragility fracture, thus the cytokine pattern is shifted towards osteoclast activation and osteoblast inhibition in these patients.
Gerontology Section, Department of Surgical and Medical Disciplines, University of Torino, Corso Bramante 88/90, Torino, Italy. patrizia.damelio@unito.it
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D'Amelio
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Roato
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D'Amico
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Veneziano
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Suman
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Sassi
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Bisignano
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Ferracini
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Gargiulo
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Castoldi
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Pescarmona
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Isaia
D048868:Adaptor Proteins, Signal Transducing; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D001853:Bone Marrow / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D005270:Femur Head / Q000378:metabolism*; D005819:Genetic Markers; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism; D010010:Osteoclasts / Q000378:metabolism; D058866:Osteoporotic Fractures / Q000378:metabolism*; D053244:Osteoprotegerin / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D016207:Cytokines; C501126:DKK1 protein, human; D005819:Genetic Markers; D036341:Intercellular Signaling Peptides and Proteins; D053244:Osteoprotegerin; D053245:RANK Ligand; C422903:SOST protein, human; D016212:Transforming Growth Factor beta; D016173:Macrophage Colony-Stimulating Factor