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

Prostaglandin E 2 (PGE 2) 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 PGE 2 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 PGE 2 and assessed for expression of genes involved in PGE 2 , anabolic, and catabolic signaling. In 2D, PGE 2 had a rapid (1 h) and sustained (24 h) effect on many PGE 2 signaling genes, a rapid stimulatory effect on Il6 , and a sustained inhibitory effect on Tnfrsf11b and Bglap. Comparing culture environment without PGE 2 , 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 PGE 2 in 3D. With increasing PGE 2 , 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 PGE 2 signaling in bone, was not responsible for the PGE 2 -induced gene expression changes in osteocytes. In summary, osteocytes are highly responsive to PGE 2 when cultured in an in vitro 3D hydrogel model suggesting that autocrine and paracrine PGE 2 signaling in osteocytes may play a role in bone homeostasis. • A 3D degradable hydrogel promotes a mature osteocyte phenotype in IDG-SW3 cells. • IDG-SW3-derived osteocytes are highly sensitive to PGE 2 in 3D hydrogel culture. • In 3D, increasing PGE 2 concentration leads to an anabolic response in osteocytes. • The EP4 receptor does not mediate PGE 2 -induced changes in osteocyte gene expression. [ABSTRACT FROM AUTHOR]