Activated protein C (APC) can increase bone anabolism via a protease-activated receptor (PAR)1/2 dependent mechanism

Abstract

Activated Protein C (APC) is an anticoagulant with strong cytoprotective properties that has been shown to promote wound healing. In this study APC was investigated for its potential orthopedic application using a Bone Morphogenetic Protein 2 (rhBMP-2) induced ectopic bone formation model. Local co-administration of 10 mg rhBMP-2 with 10 mg or 25 mg APC increased bone volume at 3 weeks by 32% (N.S.) and 74% (p < 0.01) compared to rhBMP-2 alone. This was associated with a significant increase in CD31þ and TRAPþ cells in tissue sections of ectopic bone, consistent with enhanced vascularity and bone turnover. The actions of APC are largely mediated by its receptors endothelial protein C receptor (EPCR) and protease-activated receptors (PARs). Cultured preosteoblasts and bone nodule tissue sections were shown to express PAR1/2 and EPCR. When pre-osteoblasts were treated with APC, cell viability and phosphorylation of ERK1/2, Akt, and p38 were increased. Inhibition with PAR1 and sometimes PAR2 antagonists, but not with EPCR blocking antibodies, ameliorated the effects of APC on cell viability and kinase phosphorylation. These data indicate that APC can affect osteoblast viability and signaling, and may have in vivo applications with rhBMP-2 for bone repair. ß

Downregulation of Proteinase‐Activated Receptor‐2, Interleukin‐17, and Other Proinflammatory Genes by Subantimicrobial Doxycycline Dose in a Rat Periodontitis Model

“…PAR family is composed of four members (PAR 1 , PAR 2 , PAR 3 , and PAR 4 ) distributed by several types of body cells. Because of a direct association with chronic inflammatory diseases such as arthritis and periodontitis, PAR 2 is the one most commonly studied 27 , 28 . In rats, Holzhausen et al 29 demonstrated that topical application of PAR 2 agonist induced significant ABL and gingival granulocyte infiltration.…”

The regulators of G protein signaling RGS16 and RGS18 inhibit protease‐activated receptor 2/Gi/o signaling through distinct interactions with Gα in live cells

“…To determine whether PAR2 protein is endogenously expressed in Neuro2a cells, RT-qPCR was performed using a PAR2-specific primer set (Fig. PAR2 mRNA levels in Neuro2a cells were similar to those of cells endogenously expressing PAR2, including 293T, HeLa, and MG63 [20][21][22]. PAR2 mRNA levels in Neuro2a cells were similar to those of cells endogenously expressing PAR2, including 293T, HeLa, and MG63 [20][21][22].…”

Regulation of long‐term repopulating hematopoietic stem cells by EPCR/PAR1 signaling

“…Interestingly, EPCR expression in the BM is not limited to LT-HSCs, as preosteoblasts and osteoblasts also functionally express EPCR. 131,132 EPCR expression by osteoblasts might also participate in bone turnover, as aPC stimulates osteoblast proliferation via EPCR 132 and administration of aPC together with bone morphogenetic protein 2 in mice induced ectopic bone formation with higher rates of osteoclast differentiation and vascularization, all implicated in bone-remodeling processes. 131 Further evidence linking hemostatic regulation with bone physiology demonstrated that long-term oral anticoagulant therapy in children is associated with osteopenia and a risk of future development of osteoporosis, 133 possibly indicating the need for balanced production of anticoagulant factors and normal bone turnover.…”