Protease-activated receptor-2 promotes osteogenesis in skeletal mesenchymal stem cells at the expense of adipogenesis: Involvement of interleukin-6

• Published in: Bone Reports Vol. 15; p. 101113
• Main Authors: Sanaei, R., Kularathna, P.K., Taghavi, N., Hooper, J.D., Pagel, C.N., Mackie, E.J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-12-2021; Elsevier
• Subjects: Adipogenesis; Full Length; Interleukin-6; Lineage determination; Mesenchymal stem cells; Osteoblast; Protease-activated receptor-2; Osteoblast; Lineage determination; Protease-activated receptor-2; Adipogenesis; Interleukin-6; Mesenchymal stem cells
• ISSN: 2352-1872; 2352-1872
• DOI: 10.1016/j.bonr.2021.101113

Bone marrow mesenchymal stem cells (MSCs) give rise to osteoblasts and adipocytes, with an inverse relationship between the two. The MSCs from protease-activated receptor-2 knockout (PAR2 KO) mice have a reduced capacity to generate osteoblasts. Here we describe the observation that PAR2 KO osteoblastic cultures generate more adipocytes than wildtype (WT) cultures. Osteoblasts from PAR2 KO mice expressed lower levels of osteoblastic genes (Runx2, Col1a1 and Bglap), and higher levels of the adipocytic gene Pparg than WT osteoblasts. Bone marrow stromal cells from PAR2 KO mice generated fewer osteoblastic colonies (assessed by staining for alkaline phosphatase activity and mineral deposition) and more adipocytic (Oil Red-O positive) colonies than cultures from WT mice. Similarly, cultures of the bone marrow stromal cell line (Kusa 4b10) in which PAR2 was knocked down (F2rl1 KD), were less osteoblastic and more adipocytic than vector control cells. Putative regulators of PAR2-mediated osteogenesis and suppression of adipogenesis were identified in an RNA-sequencing (RNA-seq) investigation; these include C1qtnf3, Gpr35, Grem1, Snorc and Tcea3, which were more highly expressed, and Cnr1, Enpep, Hmgn5, Il6 and Ramp3 which were expressed at lower levels, in control than in F2rl1 KD cells. Interleukin-6 (IL-6) levels were higher in medium harvested from F2rl1 KD cells than from control cells, and a neutralising anti-IL-6 antibody reduced the number of adipocytes in F2rl1 KD cultures to that of control cultures. Thus, PAR2 appears to be a mediator of the reciprocal relationship between osteogenesis and adipogenesis, with IL-6 having a regulatory role in these PAR2-mediated effects.
•PAR2 promotes osteogenic differentiation of MSCs at the expense of adipogenesis.•PAR2 deficiency increases secretion of IL-6 by MSCs during early differentiation.•Elevated IL-6 secretion stimulates adipogenesis with no effect on osteogenesis.•Ten genes have been identified as putative novel mediators of PAR2 effects on MSCs.