The role of autonomously secreted PGE2 and its autocrine/paracrine effect on bone matrix mineralization at the different stages of differentiating MC3T3-E1 cells

17β-Estradiol (E2) Activates Matrix Mineralization through Genomic/Nongenomic Pathways in MC3T3-E1 Cells

Estrogen plays an important role in osteoporosis prevention. We herein report the possible novel signaling pathway of 17β-estradiol (E2) in the matrix mineralization of MC3T3-E1, an osteoblast-like cell line. In the culture media-containing stripped serum, in which small lipophilic molecules such as steroid hormones including E2 were depleted, matrix mineralization was significantly reduced. However, the E2 treatment induced this. The E2 effects were suppressed by ICI182,780, the estrogen receptor (ER)α, and the ERβ antagonist, as well as their mRNA knockdown, whereas Raloxifene, an inhibitor of estrogen-induced transcription, and G15, a G-protein-coupled estrogen receptor (GPER) 1 inhibitor, had little or no effect. Furthermore, the E2-activated matrix mineralization was disrupted by PMA, a PKC activator, and SB202190, a p38 MAPK inhibitor, but not by wortmannin, a PI3K inhibitor. Matrix mineralization was also induced by the culture media from the E2-stimulated cell culture. This effect was hindered by PMA or heat treatment, but not by SB202190. These results indicate that E2 activates the p38 MAPK pathway via ERs independently from actions in the nucleus. Such activation may cause the secretion of certain signaling molecule(s), which inhibit the PKC pathway. Our study provides a novel pathway of E2 action that could be a therapeutic target to activate matrix mineralization under various diseases, including osteoporosis.

Bone mineralisation and glucose metabolism

Recent advancements in the bone biology field have identified a novel bone-metabolism axis. In this review, we highlight several novel studies that further our knowledge of new endocrine functions of bone; explore remaining unanswered questions; and discuss translational challenges in this complex era of bone biology research.

Gene Expression in MC3T3-E1 Cells Treated with Diclofenac and Methylprednisolone

Nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids (GCs) are often used to treat articular-skeletal disorders. The extended use of NSAIDs and GCs have adverse effects on bone metabolism, reducing bone quality and impairing fracture healing. In the present study, we used mouse pre-osteoblast cells MC3T3-E1 to demonstrate the effects of diclofenac (DF) and methylprednisolone (MP) on cell proliferation and gene expression. Cells were incubated with three doses of DF or MP: 0.5 µM, 5 µM, and 50 µM. MP decreased cell viability even after 24 h, but DF inhibited cell viability after only seven days of treatment. The cells were lysed after one, two, three, and seven days of treatment, and gene expression was analyzed by reverse transcription and quantitative PCR (RT-qPCR) assays. DF did not significantly affect the expression of the osteogenic marker genes. MP modified the expression of Osx, Runx, and Col1a1. We concluded that MP is a more potent inhibitor of mouse pre-osteoblast differentiation and viability than is DF. Our results suggest that prolonged DF treatment could be less harmful to osteoblasts than MP treatment.

The effects of prostaglandin E2 on gene expression of IDG-SW3-derived osteocytes in 2D and 3D culture

Prostaglandin E2 (PGE2) is a key signaling molecule produced by osteocytes in response to mechanical loading, but its effect on osteocytes is less understood. This work examined the effect of PGE2 on IDG-SW3-derived osteocytes in standard 2D culture (collagen-coated tissue culture polystyrene) and in a 3D degradable poly(ethylene glycol) hydrogel. IDG-SW3 cells were differentiated for 35 days into osteocytes in 2D and 3D cultures. 3D culture led to a more mature osteocyte phenotype with 100-fold higher Sost expression. IDG-SW3-derived osteocytes were treated with PGE2 and assessed for expression of genes involved in PGE2, anabolic, and catabolic signaling. In 2D, PGE2 had a rapid (1 h) and sustained (24 h) effect on many PGE2 signaling genes, a rapid stimulatory effect on Il6, and a sustained inhibitory effect on Tnfrsf11b and Bglap. Comparing culture environment without PGE2, osteocytes had higher expression of all four EP receptors and Sost but lower expression of Tnfrsf11b, Bglap, and Gja1 in 3D. Osteocytes were more responsive to PGE2 in 3D. With increasing PGE2, 3D led to increased Gja1 and decreased Sost expressions and a higher Tnfrsf11b/Tnfsf11 ratio, indicating an anabolic response. Further analysis in 3D revealed that EP4, the receptor implicated in PGE2 signaling in bone, was not responsible for the PGE2-induced gene expression changes in osteocytes. In summary, osteocytes are highly responsive to PGE2 when cultured in an in vitro 3D hydrogel model suggesting that autocrine and paracrine PGE2 signaling in osteocytes may play a role in bone homeostasis.

The effect of topical application of meloxicam on inflamed dental pulp

Background/purpose

Effective regulation of the inflammatory process is essential for pulp repair and regeneration. Meloxicam has anti-inflammatory activity in systemic administration. The purpose of this study is to observe effects of topically applied meloxicam on inflamed pulp and to explore its potential value in the treatment of pulpitis.

Materials and methods

The coronal pulp tissues of rat molars were stimulated with 10 mg/mL lipopolysaccharide (LPS group) and then treated with 500 μmol/L meloxicam (meloxicam group). The untreated pulp tissues were used as the control group. After 3 h of incubation in vitro, the gene expression of interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in each group was detected by real-time RT-PCR. The pulp tissues of each group were randomly subcutaneously implanted into nude mice, and 500 μmol/L meloxicam was injected into the subcutaneous pocket of the meloxicam group. Haematoxylin eosin staining, Masson staining and immunohistochemical staining were performed on samples after 3 days and 4 weeks retrieval, respectively.

Results

Compared with the LPS group, the mRNA expression levels of TNF-α and IL-6 of the meloxicam group were significantly reduced in vitro. The inflammatory response and cyclooxygenase-2 expression of the meloxicam group were decreased, and osteodentin-like tissue was generated in the pulp cross section of the meloxicam group in vivo.

Conclusion

The topical application of meloxicam inhibits the inflammatory response of inflamed pulp and further promotes the formation of osteodentin-like tissues but fails to induce the formation of the pulp–dentin complex. Topically applied meloxicam has the potential to regulate pulp inflammation.