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1.
Stimulation by 1,25-dihydroxyvitamin D3 of in vitro mineralization induced by osteoblast-like MC3T3-E1 cells 总被引:8,自引:1,他引:7
Although vitamin D is essential for mineralization of bone, it is as yet unclear whether vitamin D has a direct stimulatory effect on the bone mineralization process. In the present study, the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on in vitro mineralization mediated by osteoblast-like MC3T3-E1 cells was examined. MC3T3-E1 cells continued to grow after they reached confluency, and DNA content and alkaline phosphatase activity increased linearly until about 16 days of culture, whereas 45Ca accumulation into cell and matrix layer remained low. After this period, DNA content plateaued, and 45Ca accumulation increased sharply. Histological examination by von Kossa staining revealed that calcium was accumulated into extracellular matrix. In addition, needle-shaped mineral crystals similar to hydroxyapatite crystals could be demonstrated in between collagen fibrils by electron microscopy. Thus, MC3T3-E1 cells differentiate in vitro into cells with osteoblastic phenotype and exhibit mineralization. When MC3T3-E1 cells were treated with 1,25(OH)2D3 at this stage of culture, there was a dose-dependent stimulation of 45Ca accumulation by 1,25(OH)2D3, and a significant stimulation of 45Ca accumulation was observed with 3 x 10(-10) M 1,25(OH)2D3. Although 1,25(OH)2D3 enhanced alkaline phosphatase activity and collagen synthesis at the early phase of culture, it did not affect any of these parameters at the late phase when 1,25(OH)2D3 stimulated mineralization. Neither 24,25-dihydroxyvitamin D3 nor human PTH(1-34) affected mineralization in the presence or absence of 1,25(OH)2D3. These results demonstrate that 1,25(OH)2D3 stimulates matrix mineralization induced by osteoblastic MC3T3-E1 cells, and are consistent with the possibility that 1,25(OH)2D3 has a direct stimulatory effect on bone mineralization process.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
2.
Kyoji Ikeda Toshio Matsumoto Keiko Morita Kiyoshi Kurokawa Etsuro Ogata 《Calcified tissue international》1986,39(5):319-323
Summary The direct effect of aluminum on mineralization was examined using an osteoblastlike cell line, MC3T3-E1. The mineralization
process was quantitated by measuring45Ca accumulation into the cell and matrix layer of MC3T3-E1 cells in culture. The accumulation of45Ca into the cell and matrix layer increased dramatically after 13 days of culture without a parallel change in the DNA content
of these cells. Because nodular clusters of cells appear around the same period in which a massive mineralization occurs,
the marked increase in45Ca accumulation after the 13th day of culture appears to represent deposition of45Ca into the extracellular matrix. Thus, this culture system offers a useful model for making a quantitative estimation of
osteoblast-mediated mineralizationin vitro. When aluminum was added to this system, the accumulation of45Ca into the cell matrix layer was inhibited in a dose-dependent manner: 10−6 M aluminum reduced45Ca accumulation to 40.8±2.7% of that in nontreated cells without affecting alkaline phosphatase activity or the DNA content
of these cells. Because the concentration of aluminum used in this study is well within the range of serum aluminum levels
seen in chronic dialysis patients, the direct effects of aluminum on osteoblast-mediated mineralization shown in the present
study may underlie the development of so-called aluminum-induced “osteomalacia” in certain dialysis patients. 相似文献
3.
Osamu Kozawa M.D. Kensuke Takatsuki Haruhiko Tokuda Masaichi Miwa Katsuhiro Kotake Masahiro Yoneda Yutaka Oiso Hidehiko Saito 《Journal of bone and mineral metabolism》1990,8(3):37-40
Summary The effect of insulin-like growth factor-I (IGF-I) on calcification in cloned osteoblast-like MC3T3-E1 cells was studied by
measuring accumulation of45Ca into sodium dodecyl sulfate-insoluble, EDTA-extractable structure that appeared after 2 weeks of culture. The accumulation
of45Ca was markedly enhanced by incubating cells with IGF-I after 6 weeks of culture. The enhancement was dose-dependent in a
range between 0.1 nM and 100 nM. IGF-I stimulated alkaline phosphatase activity in the cells cultured for 7 weeks dose-dependently
between 0.1 nM and 100 nM. DNA synthesis examined in the cells cultured for 7 weeks was not influenced by 100 nM IGF-I. These
results suggest that IGF-I stimulates Ca-accumulation in osteoblast-like cells without stimulating their proliferation. 相似文献
4.
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6.
Biological effects of low power laser irradiation on clonal osteoblastic cells (MC3T3-E1) 总被引:1,自引:0,他引:1
K Yamada 《Nippon Seikeigeka Gakkai zasshi》1991,65(9):787-799
Cultured osteoblastic cells were studied to determine the effects of laser irradiation on their rates of proliferation, differentiation, and calcification. A continuous wave Helium-Neon laser with a wavelength of 632.8 nm was used for this study. Clonal osteoblastic cells (MC3T3-E1) were exposed to laser beam at various energy densities. The cell growth rate and DNA synthesis were increased by laser irradiation only in the growing phase of culture. During long-term culture, 45Ca accumulation was enhanced by laser irradiation at 1.0 J/cm2, with four sessions of irradiation resulting in a 46% increase over controls. In contrast, no significant increase in alkaline phosphatase activity was produced by laser irradiation. Electron microscopy revealed a tendency of enlargement of the Golgi apparatus in the laser-treated cells. These results suggest that laser irradiation photoactivates osteoblastic cells, accelerates osteoblastic cell growth and calcification in vitro, and therefore, may promote bone regeneration. 相似文献
7.
Dr. Eiko Ikeda Masami Kusaka Yoshiyuki Hakeda Kazushige Yokota Masayoshi Kumegawa Shozo Yamamoto 《Calcified tissue international》1988,43(3):162-166
Summary The effect of recombinant interleukin 1 Beta (IL-1(β)) was investigated on osteoblastic cell line MC3T3-E1 cloned from mouse
calvaria. IL-1(β) stimulated cell proliferation which increased cell number and caused dose-related stimulation of DNA synthesis,
with a maximal effect at a concentration of 12.5 U/ml; suppressed alkaline phosphatase activity and collagen synthesis maximally
at 0.5 and 62.5 U/ml, respectively; and increased the amount of free [3H] hydroxyproline in the cultures, but the amount was quite low. Prostaglandin E2 synthesis was also stimulated dose dependently by the presence of IL-1(β), with a maximal increase at 2.5 U/ml, at which
concentration the prostaglandin E2 level in the medium was 1.61±0.10 ng/ml. The increased prostaglandin E2 synthesis did not affect either the IL-1(β)-mediated change in DNA or collagen synthesis or alkaline phosphatase activity.
These results extend the possibility that IL-1(β) is to act as a regulator of bone formation. 相似文献
8.
Krohn K Haffner D Hügel U Himmele R Klaus G Mehls O Schaefer F 《Calcified tissue international》2003,73(4):400-410
Growth plate chondrocytes are affected by 1,25(OH)2D3 and androgens, which may critically interact to regulate proliferation and differentiation during the male pubertal growth spurt. We investigated possible interactions of 1,25(OH)2D3 and the non-aromatizable androgen dihydrotestosterone (DHT) in primary chondrocyte cultures from young male rats. DHT and 1,25(OH)2D3 independently stimulated DNA synthesis and cell proliferation in a dose-dependent manner with maximally effective doses of [10-8 M] and [10-12 M], respectively. Both DHT and 1,25(OH)2D3 stimulated the expression and release of IGF-I, and the proliferative effects of each hormone were prevented by an IGF-I antibody. DHT and 1,25(OH)2D3 increased messenger RNAs (mRNAs) of their cognate receptors and of IGF-I receptor mRNA (IGF-I-R). 1,25(OH)2D3 also stimulated mRNA of the androgen receptor (AR), whereas DHT did not affect mRNA of the vitamin-D receptor (VDR). Coincubation with both steroid hormones did not stimulate receptor mRNAs more than either hormone alone. The proliferative effects of DHT and 1,25(OH)2D3 were completely inhibited by simultaneous incubation with both hormones, despite potentiation of IGF-I synthesis. In contrast, both hormones synergistically stimulated cell differentiation as judged by alkaline phosphatase activity, collagen X mRNA, and matrix calcification in long-term experiments. We conclude that DHT and 1,25(OH)2D3 interact with respect to chondrocyte proliferation and cell differentiation. The proliferative effects of both hormones are mediated by local IGF-I synthesis. Simultaneous coincubation with both hormones blunts the proliferative effect exerted by either hormone alone, in favor of a more marked stimulation of cell differentiation. 相似文献
9.
Protein tyrosyl phosphorylation is a key determinant of cell proliferation and differentiation. The aim of this study was
to test the hypothesis that the signal transduction pathway(s) responsible for human bone cell proliferation may involve different
groups of protein tyrosine kinase (PTKs) as compared with that for differentiation. To achieve this, we investigated the effects
of two structurally different PTK inhibitors, viz, tyrphostin A51 and genistein, on the proliferation ([3H]thymidine incorporation) and differentiation [alkaline phosphatase (ALP) specific activity and collagen synthesis] of two
normal human bone cell types: mandible-derived and vertebra-derived bone cells. Tyrphostin A51 and genistein each markedly
reduced cellular tyrosyl phosphorylation level (assessed by Western analysis using a commercial anti-phosphotyrosine antibody
and the enhanced chemiluminescence detection assay), confirming that these two effectors are potent PTK inhibitors in human
bone cells. Regarding bone cell proliferation, tyrphostin A51 (5–30 μM) caused, a dose-dependent inhibition of basal [3H]thymidine incorporation of both human bone cell types. In contrast, genistein (5–20 μM), not only did not inhibit, but significantly
stimulated [3H]thymidine incorporation of these same cell types in a dose-dependent, biphasic manner, with the optimal stimulatory dose
between 10 and 20 μM. These effects on cell proliferation were confirmed by cell number counting. In addition, whereas the
mitogenic activity of 10 ng/ml epidermal growth factor (EGF) on human mandible-derived bone cells was completely abolished
by 5–30 μM tyrphostin A51, genistein at 5–30 μM enhanced the EGF-induced bone cell proliferation in an additive manner. With
respect to bone cell differentiation, tyrphostin A51 and genistein each significantly increased basal ALP specific activity
and collagen synthesis in human bone cells. In summary, (1) PTKs are involved in human bone cell proliferation and differentiation;
(2) tyrphostin A51 inhibited both basal and EGF-induced cell proliferation, thus tyrphostin-sensitive PTKs are involved in
basal and EGF-induced human bone cell proliferation; (3) genistein stimulated basal proliferation and enhanced EGF-mediated
cell proliferation, suggesting that genistein-sensitive PTKs may play an inhibitory role in human bone cell proliferation;
and (4) these differential effects of PTK inhibitors on human bone cell proliferation and differentiation are independent
of basal differentiation status of the cells.
Received: 30 July 1997 / Accepted: 20 February 1998 相似文献
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11.
Kouji Yamanouchi Yuji Gotoh Masaru Nagayama 《Journal of bone and mineral metabolism》1997,15(1):23-29
We examined the effects of dexamethasone (Dex) on the differentiation of osteoblastic cells isolated from human bone in vitro.
The morphology of the cells exposed to Dex was transformed into a polygonal shape, while the cells exhibited a fibroblastic
spindle shape in the absence of Dex. Staining for alkaline phosphatase (ALP) was more intense in Dex-treated cultures. In
monolayer cultures, mineralization by the human osteoblastic cells was also stimulated by Dex treatment. The ALP activity
of the cells cultured for 6 days in 10−8–10−6 M Dex increased in a dose-dependent manner. Furthermore, the ALP activity of the cells treated with 10−7M Dex for 9 days was 1.4-fold higher than that of the cells treated with 10−7M Dex for the first 3 days, followed by withdrawal for 6 days. Biochemical indicators of osteoblastic differentiation, which
include ALP activity and secretion of procollagen type I carboxy-terminal peptide (PICP) and osteocalcin, were significantly
enhanced in the cells exposed to Dex at 10−7M for 5 days. On the other hand, the time-dependent increase of ALP activity and osteocalcin levels in the control cells suggested
that the cells gradually differentiate in continuous culture after they reached confluency. These findings suggest that Dex
at the indicated concentration in this study enhances differentiation of human osteoblastic cells in vitro. 相似文献
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13.
Human dermal fibroblasts are generally considered to be restricted to a fibroblastic lineage. Although dermal fibroblasts do not typically express markers of osteoblastic differentiation, they have previously been shown to undergo osteoinduction when stimulated with bone morphogenetic proteins (BMPs) or vitamin D3. However, involvement of BMP signaling in vitamin D3‐mediated osteoinduction has not been reported. In this study, human dermal fibroblasts were cultured in chemically defined medium containing vitamin D3, in the presence of the BMP antagonist noggin or neutralizing antibodies specific for BMP‐4 or BMP‐6, and characterized for markers of osteoblastic differentiation. Treatment of dermal fibroblasts with vitamin D3 induced expression of BMP‐4 (1.2 ± 0.2, 1.7 ± 0.2, and 1.8 ± 0.2 relative fold increase) and BMP‐6 (9.1 ± 0.3, 23.3 ± 2.1, and 30.4 ± 3.0 relative fold increase) at 3, 14, and 21 days, respectively. Vitamin D3 was also shown to induce the expression of the osteoblast‐specific markers, alkaline phosphatase and osteocalcin, in a dose‐dependent manner in human dermal fibroblasts. Addition of noggin, BMP‐4 antibodies, and BMP‐6 antibodies resulted in a downregulation of alkaline phosphatase activity (by 42%, 22%, and 20%, respectively) and secreted osteocalcin (by 20%, 31%, and 49%, respectively) after 21 days in culture. However, blocking BMP signaling did not result in complete recovery of a fibroblastic phenotype. Taken together, these results suggest that BMP signaling plays a role in the induction of an osteoblastic phenotype in human dermal fibroblasts in response to vitamin D3 stimulation. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:162–168, 2009 相似文献
14.
Transforming growth factor β (TGFβ) has been shown to influence the growth and differentiation of many cell types in vitro. We have examined the effects of TGFβ on cell morphology and cytoskeletal organization in relation to parameters of cell proliferation and differentiation in endosteal osteoblastic cells isolated from mouse caudal vertebrae. Treatment of mouse osteoblastic cells cultured in serum free medium for 24 hours with TGFβ (1.5–30 ng/mL) slightly (− 23%) inhibited alkaline phosphatase activity. In parallel, TGFβ (0.5–30 ng/mL, 24 hours) greatly increased cell replication as evaluated by [3H]-thymidine incorporation into DNA (157% to 325% of controls). At a median dose (1.5 ng/mL) that affected both alkaline phosphatase and DNA synthesis (235% of controls) TGFβ induced rapid (six hours) cell respreading of quiescent mouse osteoblastic cells. This effect was associated with increased polymerization of actin, actinin, and tubulins, as evaluated by both biochemical and immunofluorescence methods. In addition, TGFβ (1.5 ng/mL) increased the de novo biosynthesis of actin, actinin, vimentin, and tubulins, as determined by [35S] methionine labeling and fractionation of cytoskeletal proteins using two-dimensional gel electrophoresis. These effects were rapid and transient, as they occurred at six hours and were reversed after 24 hours of TGFβ exposure. The results indicate that the stimulatory effect of TGFβ on DNA synthesis in endosteal mouse osteoblastic cells is associated with a transient increase in cell spreading associated with enhanced polymerization and synthesis of cytoskeletal proteins. 相似文献
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16.
F. Varga M. Rumpler E. Luegmayr N. Fratzl-Zelman H. Glantschnig K. Klaushofer 《Calcified tissue international》1997,61(5):404-411
Thyroid hormones influence growth and differentiation of bone cells. In vivo and in vitro data indicate their importance for development and maintenance of the skeleton. Triiodothyronine (T3) inhibits proliferation
and accelerates differentiation of osteoblasts. We studied the regulatory effect of T3 on markers of proliferation as well
as on specific markers of the osteoblastic phenotype in cultured MC3T3-E1 cells at different time points. In parallel to the
inhibitory effect on proliferation, T3 down-regulated histone H4 mRNA expression. Early genes (c-fos/c-jun) are highly expressed
in proliferating cells and are down-regulated when the cells switch to differentiation. When MC3T3-E1 cells are cultured under
serum-free conditions, basal c-fos/c-jun expressions are nearly undetectable. Under these conditions, c-fos/c-jun mRNAs can
be stimulated by EGF, the effect of which is attenuated to about 46% by T3. In addition, T3 stimulated the expression at the
mRNA and protein level of osteocalcin, a marker of mature osteoblasts and alkaline phosphatase activity. All these effects
were more pronounced when cells were cultured for more than 6 days. These data indicate that T3 acts as a differentiation
factor in osteoblasts by influencing the expression of cell cycle–regulated, of cell growth–regulated, and of phenotypic genes.
Received: 10 May 1996 / Accepted: 5 June 1997 相似文献
17.
Chikahisa Higuchi Norimasa Nakamura Hideki Yoshikawa Kazuyuki Itoh 《Journal of bone and mineral metabolism》2009,27(2):158-167
Dynamic cytoskeletal changes appear to be one of intracellular signals that control cell differentiation. To test this hypothesis,
we examined the effects of short-term actin cytoskeletal changes on osteoblastic differentiation. We found an actin polymerization
interfering reagent, cytochalasin D, promoted osteoblastic differentiation in mouse preosteoblastic MC3T3-E1 cells. We also
found that these effects were mediated by the protein kinase D (PKD) pathway. Short-term cytochalasin D treatment increased
alkaline phosphatase (ALP) activity, osteocalcin (OCN) secretion, and mineralization of the extracellular matrix in MC3T3-E1
cells, with temporary changes in actin cytoskeleton. Furthermore, the disruption of actin cytoskeleton induced phosphorylation
of 744/748 serine within the activation loop of PKD in a dose-dependent manner. The protein kinase C (PKC)/PKD inhibitor Go6976
suppressed cytochalasin D-induced acceleration of osteoblastic differentiation, whereas Go6983, a specific inhibitor of conventional
PKCs, did not. Involvement of PKD signaling was confirmed by using small interfering RNA to knock down PKD. In addition, another
actin polymerization interfering reagent, latrunculin B, also stimulated ALP activity and OCN secretion with PKD activation.
On the other hand, the present data suggested that transient dynamic actin cytoskeletal reorganization could be a novel cellular
signal that directly stimulated osteoblastic differentiation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Distinct proliferative and differentiated stages of murine MC3T3-E1 cells in culture: an in vitro model of osteoblast development. 总被引:13,自引:0,他引:13
L D Quarles D A Yohay L W Lever R Caton R J Wenstrup 《Journal of bone and mineral research》1992,7(6):683-692
We examine clonal murine calvarial MC3T3-E1 cells to determine if they exhibit a developmental sequence similar to osteoblasts in bone tissue, namely, proliferation of undifferentiated osteoblast precursors followed by postmitotic expression of differentiated osteoblast phenotype. During the initial phase of developmental (days 1-9 of culture), MC3T3-E1 cells actively replicate, as evidenced by the high rates of DNA synthesis and progressive increase in cell number, but maintain a fusiform appearance, fail to express alkaline phosphatase, and do not accumulate mineralized extracellular collagenous matrix, consistent with immature osteoblasts. By day 9 the cultures display cuboidal morphology, attain confluence, and undergo growth arrest. Downregulation of replication is associated with expression of osteoblast functions, including production of alkaline phosphatase, processing of procollagens to collagens, and incremental deposition of a collagenous extracellular matrix. Mineralization of extracellular matrix, which begins approximately 16 days after culture, marks the final phase of osteoblast phenotypic development. Expression of alkaline phosphatase and mineralization is time but not density dependent. Type I collagen synthesis and collagen accumulation are uncoupled in the developing osteoblast. Although collagen synthesis and message expression peaks at day 3 in immature cells, extracellular matrix accumulation is minimal. Instead, matrix accumulates maximally after 7 days of culture as collagen biosynthesis is diminishing. Thus, extracellular matrix formation is a function of mature osteoblasts. Ascorbate and beta-glycerol phosphate are both essential for the expression of osteoblast phenotype as assessed by alkaline phosphatase and mineralization of extracellular matrix. Ascorbate does not stimulate type I collagen gene expression in MC3T3-E1 cells, but it is absolutely required for deposition of collagen in the extracellular matrix. Ascorbate also induces alkaline phosphatase activity in mature cells but not in immature cells. beta-glycerol phosphate displays synergistic actions with ascorbate to further stimulate collagen accumulation and alkaline phosphatase activity in postmitotic, differentiated osteoblast-like cells. Mineralization of mature cultures requires the presence of beta-glycerol phosphate. Thus, MC3T3-E1 cells display a time-dependent and sequential expression of osteoblast characteristics analogous to in vivo bone formation. The developmental sequence associated with MC3T3-E1 differentiation should provide a useful model to study the signals that mediate the switch between proliferation and differentiation in bone cells, as well as provide a renewable culture system to examine the molecular mechanism of osteoblast maturation and the formation of bone-like extracellular matrix. 相似文献
19.
Regis J. O'Keefe Ian D. Crabb J. Edward Puzas Randy N. Rosier 《Journal of orthopaedic research》1994,12(3):299-310
The local tissue metabolism is controlled through the complex interaction between systemic and local growth factors. In recent years, an increasing number of autocrine or paracrine growth regulators have been identified in physeal cartilage. While these factors act to alter chondrocytes phenotypically and presumably are important mediators in the process of endochondral ossification, the manner in which they interact with the systemically regulated growth factor insulin-like growth factor-I is unknown. In the present study, the interactive effects of insulin-like growth factor-I with transforming growth factor-β1 or basic fibroblast growth factor were examined in short-term monolayer cultures of chick growth plate chondrocytes. [3H]thymidine incorporation was maximally stimulated 11-fold by fibroblast growth factor (10 ng/ml) and 3.5-fold by transforming growth factor-β1 following a 24-hour exposure in serum-containing cultures. The effects of transforming growth factor-β1 and fibroblast growth factor at both high and low concentrations were enhanced in a dose-dependent manner by insulin-like growth factor-I, with a 40–50% increase in DNA synthesis in the presence of 100 ng/ml of insulin-like growth factor-I. Since insulin-like growth factor-I increased [3H]thymidine incorporation after 48 hours (50% increase) but not after 24 hours of exposure, these observations represent a synergistic interaction. Total DNA in cultures treated for 5 days confirmed the modulating effect of insulin-like growth factor-I with transforming growth factor-β1 and fibroblast growth factor. The growth factors were further examined for their effects on markers of chondrocyte differentiation. While all three caused a dose-dependent inhibition of alkaline phosphatase activity, the effects of insulin-like growth factor-I were additive only to those of transforming growth factor-β1 and fibroblast growth factor. Similarly, insulin-like growth factor-I did not affect the sulfate incorporation stimulated by fibroblast growth factor or transforming growth factor-β1. Insulin-like growth factor-I had no effect on total protein synthesis after 24 hours and, although type-II collagen mRNA levels were stimulated, it had no effect on type-X collagen mRNA, as determined by quantitative in situ hybridization. Finally, insulin-like growth factor-I did not alter the dose-dependent stimulation of noncollagen protein synthesis and the inhibition of collagen synthesis caused by fibroblast growth factor and transforming growth factor-β1 in 24-hour cultures. Thus, the data suggest that insulin-like growth factor-I may have a role in augmenting the effects of other growth factors found in cartilage. Since insulin-like growth factor-I is under systemic control by growth hormones, this permits an endocrine regulation of transforming growth factor-β1 and fibroblast growth factor activity and may bring local growth factor effects under systemic control. 相似文献
20.
Evidence for a role of p38 MAP kinase in expression of alkaline phosphatase during osteoblastic cell differentiation. 总被引:13,自引:0,他引:13
In the present study, we investigate the implication of the mitogen-activated protein kinases (MAPKs) Erk, p38, and JNK in mediating the effect of fetal calf serum (FCS) on the differentiation of MC3T3-E1 osteoblast-like cells. Erk is stimulated by FCS in proliferating, early-differentiating, as well as in mature cells. Activation of p38 by FCS is not detected in proliferating cells but is observed as the cells differentiate. JNK is activated in response to FCS throughout the entire differentiation process, but a maximal stimulation is observed in early differentiating cells. The roles of Erk and p38 pathways in mediating MC3T3-E1 cell differentiation was determined using specific inhibitors such as U0126 and SB203580, respectively. These experiments confirmed that the Erk pathway is essential for mediating cell proliferation in response to FCS, but indicated that this MAP kinase has little effect in regulating the differentiation of MC3T3-E1 cells. In contrast, p38 only marginally influenced proliferation, but appeared to be critical for the control of alkaline phosphatase (ALP) expression in differentiating cells. Finally, results obtained with high doses of SB203580, which also affected JNK activity, suggest that p38 and/or JNK are probably also involved in the control of type 1 collagen and osteocalcin expression in differentiating cells. The data indicate that MAPKs regulate different stages of MC3T3-E1 cell development in response to FCS. Distinct MAPK pathways seem to independently modulate osteoblastic cell proliferation and differentiation, with Erk playing an essential role in cell replication, whereas p38 is involved in the regulation of ALP expression during osteoblastic cell differentiation. JNK is also probably involved in the regulation of osteoblastic cell differentiation, but its precise role requires further investigation. 相似文献