Postmitotic osteoclast precursors are mononuclear cells which express macrophage-associated phenotypes.
We previously demonstrated that osteoclast-like multinucleated cells were formed within 6 days in cocultures of mouse osteoblastic cells and spleen cells in response to 1 alpha,25-dihydroxyvitamin D3[1 alpha,25(OH)2D3] which was added together with hydroxyurea on Days 4-6 (final 2 days of the 6-day coculture period). Using this coculture system, chronological changes of macrophage-associated phenotypes such as nonspecific esterase (NSE) and antigens to Mac-1, Mac-2, and F4/80 were examined in postmitotic osteoclast precursors during differentiation into osteoclasts induced by 1 alpha,25(OH)2D3 (10 nM) added on Day 4. Osteoclast differentiation was assessed by examining expression of calcitonin receptors (CTRs) by autoradiography using 125I-labeled salmon CT. CTRs were first detected on small mononuclear cells within 12 hr after adding 1 alpha,25(OH)2D3. The number of CTR-positive mononuclear cells attained a maximum at 24 hr and decreased thereafter. CTR-positive multinucleated cells were first observed at 24 hr and reached a maximum population at 48 hr. All CTR-positive cells showed tartrate-resistant acid phosphatase activity (a marker enzyme of osteoclasts). Most of the CTR-positive mononuclear cells which appeared at 12 hr were positive for NSE and antigens to Mac-1 and Mac-2, but negative for F4/80 antigen. The proportion of CTR-positive cells expressing NSE and Mac-1 to total CTR-positive mononuclear cells decreased time dependently. Like authentic osteoclasts, CTR-positive multinucleated cells were negative for NSE and antigens to Mac-1 and F4/80, but positive for Mac-2. These results indicate that postmitotic osteoclast precursors are mononuclear phagocytes with macrophage-associated phenotypes, some of which disappear rapidly during their differentiation into osteoclasts.
Takahashi
N
N
Department of Biochemistry, School of Dentistry, Showa University, Tokyo, Japan.
Udagawa
N
N
Tanaka
S
S
Murakami
H
H
Owan
I
I
Tamura
T
T
Suda
T
T
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D008264:Macrophages / Q000737:chemistry*; D008297:Male; D051379:Mice; D008938:Mitosis; D010010:Osteoclasts / Q000737:chemistry*; D018003:Receptors, Calcitonin / Q000032:analysis; D013234:Stem Cells / Q000737:chemistry*
D018003:Receptors, Calcitonin; D000135:Acid Phosphatase