Characterization of a shorter recombinant polypeptide chain of bone morphogenetic protein 2 on osteoblast behaviour

A modular programmed biphasic dual-delivery system on 3D ceramic scaffolds for osteogenesis in vitro and in vivo

Single-factor delivery is the most common characteristic of bone tissue engineering techniques. However, bone regeneration is a complex process requiring multiple factors and specialized release mechanisms. Therefore, the development of a dual-delivery system allowing for programmed release kinetics would be highly desirable. Improvement of the molarity and versatility of the delivery system has rarely been studied. Herein, we report the development of a novel, modular programmed biphasic dual-release system (SCB), carrying a BMP2 and an engineered collagen I-derived recognition motif (Stath-DGEA), with a self-remodification feature on hydroxyapatite (HA)-based materials. The SCB system was loaded onto an additive manufactured (AM) scaffold in order to evaluate its bifactor osteogenic potential and its biphasic release behavior. Further, the biomechanical properties of the scaffold were studied by using the fluid-structure interaction (FSI) method. Section fluorescent labeling revealed that the HA scaffold has a relatively higher density and efficiency. Additionally, the results of the release and inhibition experiment suggested that the SCB system could facilitate the sustained release of therapeutic levels of two factors during the initial stage of implantation, thereby exhibiting a rapid high-dose release pattern at a specific time point during the second stage. The FSI prediction model indicated that the scaffold provides an excellent biomimetic mechanical and fluid dynamic microenvironment to promote osteogenesis. Our results indicated that incorporation of BMP2 with Stath-DGEA in the biphasic SCB system could have a synergetic effect in promoting the adhesion, proliferation, and differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro, under staged stimulations. Further, in vivo studies in both ectopic and orthotopic rat models showed that the SCB system loaded onto an AM scaffold could enhance osteointegration and osteoinduction throughout the osteogenic process. Thus, the novel synthetic SCB system described herein used on an AM scaffold provides a biomimetic extracellular environment that enhances bone regeneration and is a promising multifunctional, dual-release platform.

Inorganic Self-Assembled Bioactive Artificial Proto-Osteocells Inducing Bone Regeneration

Since the discovery of osteoinduction in the early 20th century, innovative biomaterials with osteoinductive potential have emerged as candidates for bone repair. Recently, artificial protocell models have demonstrated great potential for tissue regeneration. Herein, we developed artificial bioactive proto-osteocells by self-assembly of biodegradable biphasic-phosphate particles in the form of aqueous bone morphogenetic protein 2 (BMP2)-containing Pickering emulsions in corn oil to fulfill the release of BMP2 with controlled and local efficacy. These artificial proto-osteocells have the advantage of (1) being directly injected into the target location to avert reported side effects of BMP2, minimizing surgical complications, (2) exhibiting the capability of osteoinduction as shown in both in vitro and in vivo models, and (3) demonstrating calcific deposition locally by utilizing the biodegradable calcium phosphate shell. The efficiency of BMP2 within the artificial proto-osteocells showed 25 times greater bone-inducing potential when compared to the control. This study demonstrates for the first time a new strategy toward utilizing material-based artificial proto-osteocells to tackle medical issues in bone tissue repair and regeneration.

Bone Morphogenetic Protein-Based Therapeutic Approaches

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the transforming growth factor (TGF)-β family of ligands and exert most of their effects through the canonical effectors Smad1, 5, and 8. Appropriate regulation of BMP signaling is critical for the development and homeostasis of numerous human organ systems. Aberrations in BMP pathways or their regulation are increasingly associated with diverse human pathologies, and there is an urgent and growing need to develop effective approaches to modulate BMP signaling in the clinic. In this review, we provide a wide perspective on diseases and/or conditions associated with dysregulated BMP signal transduction, outline the current strategies available to modulate BMP pathways, highlight emerging second-generation technologies, and postulate prospective avenues for future investigation.

Postoperative Complications Associated With rhBMP2 Use in Posterior/Posterolateral Lumbar Fusion

STUDY DESIGN

Retrospective database review.

OBJECTIVE

Posterior/posterolateral lumbar fusion (PLF) is an effective treatment for a variety of spinal disorders; however, variations in surgical technique have different complication profiles. The aim of our study was to quantify the frequency of various complications in patients undergoing PLF with and without human recombinant bone morphogenetic protein 2 (rhBMP2).

METHODS

We queried the orthopedic subset of the Medicare database (PearlDiver) between 2005 and 2011 for patients undergoing PLF procedures with and without rhBMP2. Complication and reoperation rates were analyzed within 1 year of the index procedure. Complications assessed include: acute renal failure, deep vein thrombosis, dural tear, hematoma, heterotopic ossification, incision and drainage, cardiac complications, nervous system complications, osteolysis, pneumonia, pseudarthrosis, pulmonary embolism, radiculopathy, respiratory complications, sepsis, urinary retention, urinary tract infection, mechanical, and wound complications. Chi-square analysis was used to calculate the complication differences between the groups.

RESULTS

Our data revealed higher overall complication rates in patients undergoing PLF with rhBMP2 versus no_rhBMP2 (76.9% vs 68.8%, P < .05). Stratified by gender, rhBMP2 males had higher rates of mechanical complications, pseudarthrosis, and reoperations compared with no_rhBMP2 males (P < .05), whereas rhBMP2 females had higher rates of pseudarthrosis, urinary tract infection, and urinary retention compared with no_rhBMP2 females (P < .05).

CONCLUSION

Our data revealed higher overall complication rates in PLF patients given rhBMP2 compared with no_rhBMP2. Furthermore, our data suggests that rhBMP2-associated complications may be gender specific.

A Survey of Strategies to Modulate the Bone Morphogenetic Protein Signaling Pathway: Current and Future Perspectives

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the TGF-β family of ligands and are unequivocally involved in regulating stem cell behavior. Appropriate regulation of canonical BMP signaling is critical for the development and homeostasis of numerous human organ systems, as aberrations in the BMP pathway or its regulation are increasingly associated with diverse human pathologies. In this review, we provide a wide-perspective on strategies that increase or decrease BMP signaling. We briefly outline the current FDA-approved approaches, highlight emerging next-generation technologies, and postulate prospective avenues for future investigation. We also detail how activating other pathways may indirectly modulate BMP signaling, with a particular emphasis on the relationship between the BMP and Activin/TGF-β pathways.