PI3K/Akt signaling as a key regulatory pathway for chondrocyte terminal differentiation

Kita, Keisuke; Kimura, Tohru; Nakamura, Norimasa; Yoshikawa, Hideki; Nakano, Toru

doi:10.1111/j.1365-2443.2008.01209.x

Cited by 103 publications

(92 citation statements)

References 50 publications

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“…A possible explanation for this discrepancy is that delayed ossification in Akt knockout mice is caused by Akt deletion in osteoblasts or bone collar cells. Akt signaling enhances chondrocyte proliferation (Kita et al, 2008) and PI3K decreases apoptosis (Ulici et al, 2008), consistent with the phenotypes of 11Prom-Cre; Sox9 flox/flox mice. The effects on hypertrophy are controversial, as PI3K enhances hypertrophy (Fujita et al, 2004), whereas Akt signaling inhibits hypertrophy (Kita et al, 2008).…”

Section: Discussionsupporting

confidence: 51%

Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

et al. 2011

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SUMMARYDuring endochondral bone formation, Sox9 expression starts in mesenchymal progenitors, continues in the round and flat chondrocyte stages at high levels, and ceases just prior to the hypertrophic chondrocyte stage. Sox9 is important in mesenchymal progenitors for their differentiation into chondrocytes, but its functions post-differentiation have not been determined. To investigate Sox9 function in chondrocytes, we deleted mouse Sox9 at two different steps after chondrocyte differentiation. Sox9 inactivation in round chondrocytes resulted in a loss of Col2a1 expression and in apoptosis. Sox9 inactivation in flat chondrocytes caused immediate terminal maturation without hypertrophy and with excessive apoptosis. Inactivation of Sox9 in the last few cell layers resulted in the absence of Col10a1 expression, suggesting that continued expression of Sox9 just prior to hypertrophy is necessary for chondrocyte hypertrophy. SOX9 knockdown also caused apoptosis of human chondrosarcoma SW1353 cells. These phenotypes were associated with reduced Akt phosphorylation. Forced phosphorylation of Akt by Pten inactivation partially restored Col10a1 expression and cell survival in Sox9 floxdel/floxdel mouse chondrocytes, suggesting that phosphorylated Akt mediates chondrocyte survival and hypertrophy induced by Sox9. When the molecular mechanism of Sox9-induced Akt phosphorylation was examined, we found that expression of the PI3K subunit Pik3ca (p110) was decreased in Sox9 floxdel/floxdel mouse chondrocytes. Sox9 binds to the promoter and enhances the transcriptional activities of Pik3ca. Thus, continued expression of Sox9 in differentiated chondrocytes is essential for subsequent hypertrophy and sustains chondrocyte-specific survival mechanisms by binding to the Pik3ca promoter, inducing Akt phosphorylation.

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Section: Discussionsupporting

confidence: 51%

Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

et al. 2011

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“…Of note, we observed that insulin alone promoted more intense deposition of cartilaginous matrix than either TGF-β3 or a combination of insulin/TGF-β3 did, indicating that insulin plays a more important role than TGF-β3 in inducing the synthesis and deposition of glycosaminoglycans. In agreement, activation of the direct downstream factor of insulin, AKT, has been reported to enhance the chondrogenic differentiation of chondroprogenitor cells or stem cells [Kita et al, 2008;Hara et al, 2015], whereas the chemical inhibition of AKT completely repressed chondrogenic differentiation of stem cells [Hara et al, 2015]. The effect of insulin was apparently independent of TGF-β3 signaling, because there was no alteration in Smad phosphorylation or in the expression of CCN2, a direct target gene of TGF-β3, after insulin treatment.…”

Section: Discussionsupporting

confidence: 57%

Antagonistic Effects of Insulin and TGF-β3 during Chondrogenic Differentiation of Human BMSCs under a Minimal Amount of Factors

Hara

Ono

Yoshioka

et al. 2016

Cells Tissues Organs

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Growth factors are crucial regulators of cell differentiation towards tissue and organ development. Insulin and transforming growth factor-β (TGF-β) have been used as the major factors for chondrogenesis in vitro, by activating the AKT and Smad signaling pathways. Previous reports demonstrated that AKT and Smad3 have a direct interaction that results in the inhibition of TGF-β-mediated cellular responses. However, the result of this interaction between AKT and Smad3 during the chondrogenesis of human bone marrow-derived stem/progenitor cells (hBMSCs) is unknown. In this study, we performed functional analyses by inducing hBMSCs into chondrogenesis with insulin, TGF-β3 or in combination, and found that TGF-β3, when applied concomitantly with insulin, significantly decreases an insulin-induced increase in mRNA levels of the master regulator of chondrogenesis, SOX9, as well as the regulators of the 2 major chondrocyte markers, ACAN and COL2A1. Similarly, the insulin/TGF-β3-treated group presented a significant decrease in the deposition of cartilage matrix as detected by safranin O staining of histological sections of hBMSC micromass cultures when compared to the group stimulated with insulin alone. Intracellular analysis revealed that insulin-induced activation of AKT suppressed Smad3 activation in a dose-dependent manner. Accordingly, insulin/TGF-β3 significantly decreased the TGF-β3-induced increase in mRNA levels of the direct downstream factor of TGF-β/Smad3, CCN2/CGTF, compared to the group stimulated with TGF-β3 alone. On the other hand, insulin/TGF-β3 stimulation did not suppress insulin-induced expression of the downstream targets TSC2 and DDIT4/REDD1. In summary, insulin and TGF-β3 have antagonistic effects when applied concomitantly, with a minimal number of factors. The application of an insulin/TGF-β3 combination without further supplementation should be used with caution in the chondrogenic differentiation of hBMSCs.

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“…Likewise, in a temporal analysis of the alterations caused by AA/b-GP during MC3T3-E1 differentiation [Zambuzzi et al, 2008b], we observed down-regulation of the ERK 1/2 and PI3K/Akt pathways followed by the activation of GSK3b. Previous reports have associated inhibition of the PI3K pathway with differentiation in B16 melanoma cells [Buscà et al, 1996], human promyelocytic HL60 leukemia cells [Peiretti et al, 2001], and the myogenic cell line C2C12 [Viñ als et al, 2002], as well as in chondrocyte terminal differentiation [Kita et al, 2008]. On the other hand, PI3K/Akt/GSK3b signaling pathway is one of the key players in the signaling of potent anabolic factors in bone.…”

Section: Discussionmentioning

confidence: 98%

Profiling the changes in signaling pathways in ascorbic acid/β‐glycerophosphate‐induced osteoblastic differentiation

Chaves‐Neto¹,

Queiroz²,

Milani³

et al. 2011

J of Cellular Biochemistry

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Despite numerous reports on the ability of ascorbic acid and β-glycerophosphate (AA/β-GP) to induce osteoblast differentiation, little is known about the molecular mechanisms involved in this phenomenon. In this work, we used a peptide array containing specific consensus sequences (potential substrates) for protein kinases and traditional biochemical techniques to examine the signaling pathways modulated during AA/β-GP-induced osteoblast differentiation. The kinomic profile obtained after 7 days of treatment with AA/β-GP identified 18 kinase substrates with significantly enhanced or reduced phosphorylation. Peptide substrates for Akt, PI3K, PKC, BCR, ABL, PRKG1, PAK1, PAK2, ERK1, ERBB2, and SYK showed a considerable reduction in phosphorylation, whereas enhanced phosphorylation was observed in substrates for CHKB, CHKA, PKA, FAK, ATM, PKA, and VEGFR-1. These findings confirm the potential usefulness of peptide microarrays for identifying kinases known to be involved in bone development in vivo and in vitro and show that this technique can be used to investigate kinases whose function in osteoblastic differentiation is poorly understood.

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PI3K/Akt signaling as a key regulatory pathway for chondrocyte terminal differentiation

Cited by 103 publications

References 50 publications

Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

Antagonistic Effects of Insulin and TGF-β3 during Chondrogenic Differentiation of Human BMSCs under a Minimal Amount of Factors

Profiling the changes in signaling pathways in ascorbic acid/β‐glycerophosphate‐induced osteoblastic differentiation

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