Abstract
Bone morphogenetic proteins (BMPs) are believed to be the most potent osteoinductive factors. However, BMPs are highly pleiotropic molecules and their supra-physiological high dose requirement leads to adverse side effects and inefficient bone formation. Thus, there is a need to develop alternative osteoinductive growth factor strategies that can effectively complement BMP activity. In this study, we intrinsically stimulated BMP signaling in adipose derived stem cells (ASCs) by downregulating noggin, a potent BMP antagonist, using an RNAi strategy. ASCs transduced with noggin shRNA significantly enhanced osteogenic differentiation of cells. The potency of endogenous BMPs was subsequently enhanced by stimulating ASCs with exogenous BMPs at a significantly reduced dose. The level of mineralization in noggin shRNA treated ASCs when treated with BMP-2 was comparable to that of control shRNA treated cell treated with 10-fold more BMP-2. The complementary strategy of noggin suppression + BMP-2 to enhance osteogenesis was further confirmed in 3D in vitro environments using scaffolds consisting of chitosan (CH), chondroitin sulfate (CS), and apatite layer on their surfaces designed to slowly release BMP-2. This finding supports the novel therapeutic potential of this complementary strategy in bone regeneration.
Highlights
Skeletal defects caused by traumas, diseases and accidents remain a major healthcare challenge
This study investigates whether noggin suppression and simultaneous treatment with Bone morphogenetic proteins (BMPs)-2 can enhance osteogenic differentiation of mesenchymal cells using adipose derived stem cells (ASCs)
Noggin knockdown in ASCs Noggin suppression in ASCs was induced using noggin-targeted short hairpin RNA (shRNA) lentiviral particles via RNAi-mediated knockdown. Quantitative real-time polymerase chain reaction (qRTPCR) analysis demonstrated that ASCs transduced with noggintargeted shRNA decreased transcription level of noggin gene to 1.7- and 3.3-fold compared to cells transduced with control shRNA in the presence and absence of BMP-2, respectively (Fig. 1)
Summary
Skeletal defects caused by traumas, diseases and accidents remain a major healthcare challenge. Autologous bone grafts remain the gold standard for skeletal reconstruction, their applications are limited by donor site availability and associated complications such as donor site morbidity [1]. Tissue engineering approaches are promising alternative strategies to regenerate bone involving sophisticated osteoconductive matrices, osteogenic precursor cells, and appropriate osteoinductive growth factors [2],[3]. Bone morphogenetic proteins (BMP) are considered the most potent osteoinductive factors and have been extensively used in clinical practice [4],[5]. While BMP-2 has demonstrated extraordinary potential in bone formation, their clinical applications require supraphysiological milligram-level doses, leading to undesired ectopic bone and cyst formation [6,7,8]. There is a need to develop alternative strategies that can effectively complement BMP activity
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