発生中および除神経された味蕾におけるβ-カテニンの発現と活性化(Expression and activation of β-catenin in developing and denervated taste buds)

出生後発育期間または神経除去後期間の味蕾における活性化β-カテニンの発現の発現機構を明らかにすることを目的として、マウス味蕾におけるβ-カテニン、Wnt10b、Wnt5aおよびWntのレセプターであるFrizzled(Fzd)の発現パターンを調べた。これらパターンはin situハイブリダイゼーションおよび免疫組織化学法を用いて測定した。活性化β-カテニンの細胞質内の蓄積および核内への移行をソニックヘッジホッグ(Shh)免疫反応性基底細胞および味蕾内細胞において観察し、WntおよびそのレセプターであるFzd-1および-3の細胞内挙動を追跡した。これらの結果から、発生および再生の初期段階におけるβ-カテニン転写増大が基底細胞および未熟細胞の味蕾細胞への分化を促進すること、およびマウス味蕾細胞におけるWnt10bおよびFzd-1および-3はWnt/β-カテニン経路を構成し、その経路がβ-カテニンを活性化して、発生および再生の初期段階におけるβ-カテニン遺伝子の発現を上方調節する役割を持つことが示唆された。出生後発育期間または神経除去後期間の味蕾における活性化β-カテニンの発現の発現機構を明らかにすることを目的として、マウス味蕾におけるβ-カテニン、Wnt10b、Wnt5aおよびWntのレセプターであるFrizzled(Fzd)の発現パターンを調べた。これらパターンはin situハイブリダイゼーションおよび免疫組織化学法を用いて測定した。活性化β-カテニンの細胞質内の蓄積および核内への移行をソニックヘッジホッグ(Shh)免疫反応性基底細胞および味蕾内細胞において観察し、WntおよびそのレセプターであるFzd-1および-3の細胞内挙動を追跡した。これらの結果から、発生および再生の初期段階におけるβ-カテニン転写増大が基底細胞および未熟細胞の味蕾細胞への分化を促進すること、およびマウス味蕾細胞におけるWnt10bおよびFzd-1および-3はWnt/β-カテニン経路を構成し、その経路がβ-カテニンを活性化して、発生および再生の初期段階におけるβ-カテニン遺伝子の発現を上方調節する役割を持つことが示唆された

Expression and Role of IL-1β Signaling in Chondrocytes Associated with Retinoid Signaling during Fracture Healing

The process of fracture healing consists of an inflammatory reaction and cartilage and bone tissue reconstruction. The inflammatory cytokine interleukin-1β (IL-1β) signal is an important major factor in fracture healing, whereas its relevance to retinoid receptor (an RAR inverse agonist, which promotes endochondral bone formation) remains unclear. Herein, we investigated the expressions of IL-1β and retinoic acid receptor gamma (RARγ) in a rat fracture model and the effects of IL-1β in the presence of one of several RAR inverse agonists on chondrocytes. An immunohistochemical analysis revealed that IL-1β and RARγ were expressed in chondrocytes at the fracture site in the rat ribs on day 7 post-fracture. In chondrogenic ATDC5 cells, IL-1β decreases the levels of aggrecan and type II collagen but significantly increased the metalloproteinase-13 (Mmp13) mRNA by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. An RAR inverse agonist (AGN194310) inhibited IL-1β-stimulated Mmp13 and Ccn2 mRNA in a dose-dependent manner. Phosphorylated extracellular signal regulated-kinases (pERK1/2) and p-p38 mitogen-activated protein kinase (MAPK) were increased time-dependently by IL-1β treatment, and the IL-1β-induced p-p38 MAPK was inhibited by AGN194310. Experimental p38 inhibition led to a drop in the IL-1β-stimulated expressions of Mmp13 and Ccn2 mRNA. MMP13, CCN2, and p-p38 MAPK were expressed in hypertrophic chondrocytes near the invaded vascular endothelial cells. As a whole, these results point to role of the IL-1β via p38 MAPK as important signaling in the regulation of the endochondral bone formation in fracture healing, and to the actions of RAR inverse agonists as potentially relevant modulators of this process

Sonic Hedgehog Regulates Bone Fracture Healing

Bone fracture healing involves the combination of intramembranous and endochondral ossification. It is known that Indian hedgehog (Ihh) promotes chondrogenesis during fracture healing. Meanwhile, Sonic hedgehog (Shh), which is involved in ontogeny, has been reported to be involved in fracture healing, but the details had not been clarified. In this study, we demonstrated that Shh participated in fracture healing. Six-week-old Sprague–Dawley rats and Gli-CreERT2; tdTomato mice were used in this study. The right rib bones of experimental animals were fractured. The localization of Shh and Gli1 during fracture healing was examined. The localization of Gli1 progeny cells and osterix (Osx)-positive cells was similar during fracture healing. Runt-related transcription factor 2 (Runx2) and Osx, both of which are osteoblast markers, were observed on the surface of the new bone matrix and chondrocytes on day seven after fracture. Shh and Gli1 were co-localized with Runx2 and Osx. These findings suggest that Shh is involved in intramembranous and endochondral ossification during fracture healing

Sonic Hedgehog Signaling and Tooth Development

Sonic hedgehog (Shh) is a secreted protein with important roles in mammalian embryogenesis. During tooth development, Shh is primarily expressed in the dental epithelium, from initiation to the root formation stages. A number of studies have analyzed the function of Shh signaling at different stages of tooth development and have revealed that Shh signaling regulates the formation of various tooth components, including enamel, dentin, cementum, and other soft tissues. In addition, dental mesenchymal cells positive for Gli1, a downstream transcription factor of Shh signaling, have been found to have stem cell properties, including multipotency and the ability to self-renew. Indeed, Gli1-positive cells in mature teeth appear to contribute to the regeneration of dental pulp and periodontal tissues. In this review, we provide an overview of recent advances related to the role of Shh signaling in tooth development, as well as the contribution of this pathway to tooth homeostasis and regeneration