Small molecule-mediated tribbles homolog 3 promotes bone formation induced by bone morphogenetic protein-2

Jiabing Fan,Mian Guo,Benjamin M Wu,Dan C S Im,Soyon Kim,Tara L Aghaloo,Zhong-Kai Cui,Joan Pi-Anfruns,Min Lee

doi:10.1038/s41598-017-07932-z

Abstract

Although bone morphogenetic protein-2 (BMP2) has demonstrated extraordinary potential in bone formation, its clinical applications require supraphysiological milligram-level doses that increase postoperative inflammation and inappropriate adipogenesis, resulting in well-documented life-threatening cervical swelling and cyst-like bone formation. Recent promising alternative biomolecular strategies are toward promoting pro-osteogenic activity of BMP2 while simultaneously suppressing its adverse effects. Here, we demonstrated that small molecular phenamil synergized osteogenesis and bone formation with BMP2 in a rat critical size mandibular defect model. Moreover, we successfully elicited the BMP2 adverse outcomes (i.e. adipogenesis and inflammation) in the mandibular defect by applying high dose BMP2. Phenamil treatment significantly improves the quality of newly formed bone by inhibiting BMP2 induced fatty cyst-like structure and inflammatory soft-tissue swelling. The observed positive phenamil effects were associated with upregulation of tribbles homolog 3 (Trib3) that suppressed adipogenic differentiation and inflammatory responses by negatively regulating PPARγ and NF-κB transcriptional activities. Thus, use of BMP2 along with phenamil stimulation or Trib3 augmentation may be a promising strategy to improve clinical efficacy and safety of current BMP therapeutics.

Highlights

Mandibular bone defects are commonly caused by traumatic injury, infection, congenital deformity, and secondary treatment of varying pathologies such as tumor resection and drug-induced osteonecrosis, leading to undesirable effects on oral function and appearance[1]
The cystic structure induced by Bone morphogenetic protein 2 (BMP2) at 30 μg or higher presented low osseous matrix production filled with fatty marrow as observed by hematoxylin and eosin (H&E), Masson’s trichrome, osteocalcin (OCN) and PicroSirius red stain (Fig. 1f–h and Supplementary Fig. 1a)
We investigated the role of Tribbles homologs family members (Trib)[3] in phenamil + BMP2 mediated mesenchymal stem cell differentiation in vitro. Human bone marrow mesenchymal stem cells (hBMSCs) were transduced with Trib[3] siRNA or control siRNA and treated with phenamil (20 μM) and/

Summary

Introduction

Mandibular bone defects are commonly caused by traumatic injury, infection, congenital deformity, and secondary treatment of varying pathologies such as tumor resection and drug-induced osteonecrosis, leading to undesirable effects on oral function and appearance[1]. The premature release of such high dose BMP2 from conventional collagen carriers may lead to numerous side effects such as ectopic bone formation, inflammatory soft tissue swelling, or osteoclastic bone resorption[10,11,12]. Phenamil treatment has high potential to effectively complement the BMP activity to maximize osteogenesis without exogenous application of supraphysiological BMP doses while inhibiting BMP-induced adverse outcomes (i.e. adipogenesis and inflammation). We will determine if phenamil can maximize BMP2 induced bone formation in critical-sized large mandibular bone defects created in rats. We will apply high dose BMP2 to induce adverse cyst-like bone formation and inflammation in the mandibular defect model and will test whether phenamil can inhibit BMP2 induced fatty cyst-like structure and inflammatory soft-tissue swelling. We will determine whether the positive phenamil effects in the combinatorial treatment of phenamil + BMP2 are through increased Trb[3] expression in vitro cell culture and in vivo early mandibular implantation

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Discussion

Conclusion