Effect of grafting BMP2-derived peptide to nanoparticles on osteogenic and vasculogenic expression of stromal cells

Biomimetic Fabrication and Osteogenic Effects of E7BMP-2 Peptide Coassembly Microspheres Based α-Tricalcium Phosphate with Silk Fibroin

The repair and reconstruction of bone defects remain a challenge in orthopedics. Inadequate mechanical qualities, poor biocompatibility, and insufficient osteoconductivity are some of the issues facing current bone healing materials. Better materials that can replicate the composition and functionality of natural bone, promote quick and full healing, and reduce the likelihood of rejection and infection are desperately needed. Bone tissue engineering, combining biomaterial scaffolds and pro-osteogenic drugs, provides support in the repair and regeneration of bone defects. The development of an effective scaffold for bone defect repair is an urgent clinical need. The present study investigates the feasibility of using microspheres based on α-tricalcium phosphate and fibroin as an osteoconductive matrix and a carrier for controlled local delivery of the E7BMP-2 peptide, in which the E7 domain confers a calcium chelation property, while the BMP-2 mimicking peptide induces bone formation. We prepared α-tricalcium phosphate/silk fibroin (α-TCP/SF) microspheres through a high voltage electric field based on the protocol of α-TCP/SF bone cement slurry. This α-TCP/SF microspheres-based system was designed for delivery vehicles of the modified BMP-2 peptide by the E7 domain to realize sustainable and steady release of the peptide. In vitro cell tests and the experimental model of cranial bone defects in rats were used to investigate the pro-osteogenic benefits. The results demonstrated that the E7BMP-2 peptide-bound microspheres functioned as a sustained release system for the peptide and enhanced osteogenic differentiation of bone marrow mesenchymal stem cells in rat calvarial defects. Additionally, toxicity studies showed that microspheres have good biocompatibility and safety. Thus, these E7BMP-2 peptide-bound α-TCP/SF microspheres provide a promising therapeutic strategy for the treatment of bone defects.

Peptidomimetic inhibitor of L-plastin reduces osteoclastic bone resorption in aging female mice

L-plastin (LPL) was identified as a potential regulator of the actin-bundling process involved in forming nascent sealing zones (NSZs), which are precursor zones for mature sealing zones. TAT-fused cell-penetrating small molecular weight LPL peptide (TAT- MARGSVSDEE, denoted as an inhibitory LPL peptide) attenuated the formation of NSZs and impaired bone resorption in vitro in osteoclasts. Also, the genetic deletion of LPL in mice demonstrated decreased eroded perimeters and increased trabecular bone density. In the present study, we hypothesized that targeting LPL with the inhibitory LPL peptide in vivo could reduce osteoclast function and increase bone density in a mice model of low bone mass. We injected aging C57BL/6 female mice (36 weeks old) subcutaneously with the inhibitory and scrambled peptides of LPL for 14 weeks. Micro-CT and histomorphometry analyses demonstrated an increase in trabecular bone density of femoral and tibial bones with no change in cortical thickness in mice injected with the inhibitory LPL peptide. A reduction in the serum levels of CTX-1 peptide suggests that the increase in bone density is associated with a decrease in osteoclast function. No changes in bone formation rate and mineral apposition rate, and the serum levels of P1NP indicate that the inhibitory LPL peptide does not affect osteoblast function. Our study shows that the inhibitory LPL peptide can block osteoclast function without impairing the function of osteoblasts. LPL peptide could be developed as a prospective therapeutic agent to treat osteoporosis.

The effect of BMP-mimetic peptide tethering bioinks on the differentiation of dental pulp stem cells (DPSCs) in 3D bioprinted dental constructs

The goal of this study was to use 3D bioprinting technology to create a bioengineered dental construct containing human dental pulp stem cells (hDPSCs). To accomplish this, we first developed a novel bone morphogenetic protein (BMP) peptide-tethering bioink formulation and examined its rheological properties, its printability, and the structural stability of the bioprinted construct. Second, we evaluated the survival and differentiation of hDPSCs in the bioprinted dental construct by measuring cell viability, proliferation, and gene expression, as well as histological and immunofluorescent analyses. Our results showed that the peptide conjugation into the gelatin methacrylate-based bioink formulation was successfully performed. We determined that greater than 50% of the peptides remained in the bioprinted construct after three weeks in vitro cell culture. Human DPSC viability was >90% in the bioprinted constructs immediately after the printing process. Alizarin Red staining showed that the BMP peptide construct group exhibited the highest calcification as compared to the growth medium, osteogenic medium, and non-BMP peptide construct groups. In addition, immunofluorescent and quantitative reverse transcription-polymerase chain reaction analyses showed robust expression of dentin sialophosphoprotein and osteocalcin in the BMP peptide dental constructs. Together, these results strongly suggested that BMP peptide-tethering bioink could accelerate the differentiation of hDPSCs in 3D bioprinted dental constructs.

Synthetic cementum protein 1-derived peptide regulates mineralization in vitro and promotes bone regeneration in vivo

The use of recombinant proteins has revolutionized the development of biologic pharmaceuticals; however, they are not free of complications. Some have very high molecular weight, some demonstrate in vivo instability, and the high cost of producing them remains a major problem. On the other hand, it has been shown that peptides derived from active domains keep their biologic activity and can trigger events, such as osteogenesis and bone regeneration. Small peptides are advantageous because of their ease of synthesis and handling and their low immunogenic activity. The purpose of this study was to investigate the functions of a synthetic peptide, cementum protein 1-peptide1 (CEMP-1-p1), both in vitro and in vivo. Our results show that CEMP-1-p1 significantly enhanced the proliferation and differentiation of human periodontal ligament cells toward a mineralizing-like phenotype, as evidenced by increasing alkaline phosphatase (ALP)-specific activity and osterix, runt-related transcription factor (RUNX)-2, integrin binding sialoprotein, bone morphogenetic protein-2, osteocalcin, and cementum protein (CEMP)-1 expression at mRNA and protein levels. In vivo assays performed through standardized critical-size calvarial defects in rats treated with CEMP-1-p1 resulted in newly formed bone after 30 and 60 d. These data demonstrate that CEMP-1-p1 is an effective bioactive peptide for bone tissue regeneration. The application of this bioactive peptide may lead to implementing new strategies for the regeneration of bone and other mineralized tissues.-Correa, R., Arenas, J., Montoya, G., Hoz, L., López, S., Salgado, F., Arroyo, R., Salmeron, N., Romo, E., Zeichner-David, M., Arzate, H. Synthetic cementum protein 1-derived peptide regulates mineralization in vitro and promotes bone regeneration in vivo.

Effects of a self-assembling peptide as a scaffold on bone formation in a defect

Spinal fusion and bone defect after injuries, removal of bone tumors, and infections need to be repaired by implantation. In an aging society, recovery from these procedures is often difficult. In this study, we found that injection of SPG-178 leads to expression of several bone marker genes and mineralization in vitro, and revealed a significantly higher degree of newly formed bone matrix with use of SPG-178 in vivo. MC3T3-E1 cells were used to evaluate osteoblast differentiation promoted by SPG-178. To analyze gene expression, total RNA was isolated from MC3T3-E1 cells cultured for 7 and 14 days with control medium or SPG-178 medium. Among the several bone marker genes examined, SPG-178 significantly increased the mRNA levels for ALP, BMP-2 and Osteocalcin, OPN, BSP and for the Osterix. Ten-week-old female Wistar rats were used for all transplantation procedures. A PEEK cage was implanted into a bony defect (5 mm) within the left femoral mid-shaft, and stability was maintained by an external fixator. The PEEK cages were filled with either a SPG-178 hydrogel plus allogeneic bone chips (n = 4) or only allogeneic bone chips (n = 4). The rats were then kept for 56 days. Newly formed bone matrix was revealed inside the PEEK cage and there was an increased bone volume per total volume with the cage filled with SPG-178, compared to the control group. SPG-178 has potential in clinical applications because it has several benefits. These include its favorable bone conduction properties its ability to act as a support for various different cells and growth factors, its lack of infection risk compared with materials of animal origin such as ECM, and the ease with which it can be used to fill defects with complex shapes and combined with a wide range of other materials.

Fabrication of a biomimetic ZeinPDA nanofibrous scaffold impregnated with BMP-2 peptide conjugated TiO2 nanoparticle for bone tissue engineering

A biomimetic Zein polydopamine based nanofiber scaffold was fabricated to deliver bone morphogenic protein-2 (BMP-2) peptide conjugated titanium dioxide nanoparticles in a sustained manner for investigating its osteogenic differentiation potential. To prolong its retention time at the target site, BMP-2 peptide has been conjugated to titanium dioxide nanoparticles owing to its high surface to volume ratio. The effect of biochemical cues from BMP-2 peptide and nanotopographical stimulation of electrospun Zein polydopamine nanofiber were examined for its enhanced osteogenic expression of human fetal osteoblast cells. The sustained delivery of bioactive signals, improved cell adhesion, mineralization, and differentiation could be attributed to its highly interconnected nanofibrous matrix with unique material composition. Further, the expression of osteogenic markers revealed that the fabricated nanofibrous scaffold possess better cell-biomaterial interactions. These promising results demonstrate the potential of the composite nanofibrous scaffold as an effective biomaterial substrate for bone regeneration.

Loading of BMP-2-related peptide onto three-dimensional nano-hydroxyapatite scaffolds accelerates mineralization in critical-sized cranial bone defects

Extrusion free-forming, as a rapid prototyping technique, is extensively applied in fabricating ceramic material in bone tissue engineering. To improve the osteoinductivity of nano-hydroxyapatite (nHA) scaffold fabricated by extrusion free-forming, in this study, we incorporated a new peptide (P28) and optimized the superficial microstructure after shaping by controlling the sintering temperature. P28, a novel bone morphogenic protein 2 (BMP-2)-related peptide, was designed in this study. Analysis of the structure, physicochemical properties and release kinetics of P28 from nHA sintered at temperatures ranging from 1000 °C to 1400 °C revealed that nHA sintered at 1000 °C had higher porosity, preferable pore size and better capacity to control P28 release than that sintered at other temperatures. Moreover, the nHA scaffold sintered at 1000 °C with P28 showed improved adhesion, proliferation and osteogenic differentiation of MC3T3-E1 cells compared with scaffolds lacking P28 or BMP-2. In vivo, nHA scaffolds sintered at 1000 °C with P28 or BMP-2 induced greater bone regeneration in critical-sized rat cranial defects at 6 and 12 weeks post-implantation compared with scaffolds lacking P28 or BMP-2. Thus, nHA scaffolds sintered at 1000 °C and loaded with P28 may be excellent biomaterials for bone tissue engineering. Copyright © 2016 John Wiley & Sons, Ltd.

The preosteoblast response of electrospinning PLGA/PCL nanofibers: effects of biomimetic architecture and collagen I

Constructing biomimetic structure and incorporating bioactive molecules is an effective strategy to achieve a more favorable cell response. To explore the effect of electrospinning (ES) nanofibrous architecture and collagen I (COL I)-incorporated modification on tuning osteoblast response, a resorbable membrane composed of poly(lactic-co-glycolic acid)/poly(caprolactone) (PLGA/PCL; 7:3 w/w) was developed via ES. COL I was blended into PLGA/PCL solution to prepare composite ES membrane. Notably, relatively better cell response was delivered by the bioactive ES-based membrane which was fabricated by modification of 3,4-dihydroxyphenylalanine and COL I. After investigation by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle measurement, and mechanical test, polyporous three-dimensional nanofibrous structure with low tensile force and the successful integration of COL I was obtained by the ES method. Compared with traditional PLGA/PCL membrane, the surface hydrophilicity of collagen-incorporated membranes was largely enhanced. The behavior of mouse preosteoblast MC3T3-E1 cell infiltration and proliferation on membranes was studied at 24 and 48 hours. The negative control was fabricated by solvent casting. Evaluation of cell adhesion and morphology demonstrated that all the ES membranes were more favorable for promoting the cell adhesion and spreading than the casting membrane. Cell Counting Kit-8 assays revealed that biomimetic architecture, surface topography, and bioactive properties of membranes were favorable for cell growth. Analysis of β1 integrin expression level by immunofluorescence indicated that such biomimetic architecture, especially COL I-grafted surface, plays a key role in cell adhesion and proliferation. The real-time polymerase chain reaction suggested that both surface topography and bioactive properties could facilitate the cell adhesion. The combined effect of biomimetic architecture with enhanced surface activity by 3,4-dihydroxyphenylalanine-assisted modification and COL I incorporation of PLGA/PCL electrospun membranes could successfully fill osteogenic defects and allow for better cell proliferation and differentiation.

The influence of tissue microenvironment on stem cell-based cartilage repair

Mesenchymal stem/progenitor cells and induced pluripotent stem cells have become viable cell sources for prospective cell-based cartilage engineering and tissue repair. The development and function of stem cells are influenced by the tissue microenvironment. Specifically, the local tissue microenvironment can dictate how stem cells integrate into the existing tissue matrix and how successfully they can restore function to the damaged area in question. This review focuses on the microenvironmental features of articular cartilage and how they influence stem cell-based cartilage tissue repair. Also discussed are current tissue-engineering strategies used in combination with cell-based therapies, all of which are designed to mimic the natural properties of cartilage tissue in order to achieve a better healing response.

BMP-2 Derived Peptide and Dexamethasone Incorporated Mesoporous Silica Nanoparticles for Enhanced Osteogenic Differentiation of Bone Mesenchymal Stem Cells

Bone morphogenetic protein-2 (BMP-2), a growth factor that induces osteoblast differentiation and promotes bone regeneration, has been extensively investigated in bone tissue engineering. The peptides of bioactive domains, corresponding to residues 73-92 of BMP-2 become an alternative to reduce adverse side effects caused by the use of high doses of BMP-2 protein. In this study, BMP-2 peptide functionalized mesoporous silica nanoparticles (MSNs-pep) were synthesized by covalently grafting BMP-2 peptide on the surface of nanoparticles via an aminosilane linker, and dexamethasone (DEX) was then loaded into the channel of MSNs to construct nanoparticulate osteogenic delivery systems (DEX@MSNs-pep). The in vitro cell viability of MSNs-pep was tested with bone mesenchymal stem cells (BMSCs) exposure to different particle concentrations, revealing that the functionalized MSNs had better cytocompatibility than their bare counterparts, and the cellular uptake efficiency of MSNs-pep was remarkably larger than that of bare MSNs. The in vitro results also show that the MSNs-pep promoted osteogenic differentiation of BMSCs in terms of the levels of alkaline phosphatase (ALP) activity, calcium deposition, and expression of bone-related protein. Moreover, the osteogenic differentiation of BMSCs can be further enhanced by incorporating of DEX into MSNs-pep. After intramuscular implantation in rats for 3 weeks, the computed tomography (CT) images and histological examination indicate that this nanoparticulate osteogenic delivery system induces effective osteoblast differentiation and bone regeneration in vivo. Collectively, the BMP-2 peptide and DEX incorporated MSNs can act synergistically to enhance osteogenic differentiation of BMSCs, which have potential applications in bone tissue engineering.

Vascularization in bone tissue engineering constructs

Vascularization of large bone grafts is one of the main challenges of bone tissue engineering (BTE), and has held back the clinical translation of engineered bone constructs for two decades so far. The ultimate goal of vascularized BTE constructs is to provide a bone environment rich in functional vascular networks to achieve efficient osseointegration and accelerate restoration of function after implantation. To attain both structural and vascular integration of the grafts, a large number of biomaterials, cells, and biological cues have been evaluated. This review will present biological considerations for bone function restoration, contemporary approaches for clinical salvage of large bone defects and their limitations, state-of-the-art research on the development of vascularized bone constructs, and perspectives on evaluating and implementing novel BTE grafts in clinical practice. Success will depend on achieving full graft integration at multiple hierarchical levels, both between the individual graft components as well as between the implanted constructs and their surrounding host tissues. The paradigm of vascularized tissue constructs could not only revolutionize the progress of BTE, but could also be readily applied to other fields in regenerative medicine for the development of new innovative vascularized tissue designs.

Drug release kinetics, cell uptake, and tumor toxicity of hybrid VVVVVVKK peptide-assembled polylactide nanoparticles

An exciting approach to tumor delivery is encapsulation of the drug in self-assembled polymer-peptide nanoparticles. The objective of this work was to synthesize a conjugate of low molecular weight polylactide (LMW PLA) and V6K2 peptide and investigate self-assembly, drug release kinetics, cell uptake and toxicity, drug pharmacokinetics, and tumor cell invasion with Doxorubicin (DOX) or paclitaxel (PTX). The results for PLA-V6K2 self-assembled NPs were compared with those of polyethylene glycol stabilized PLA (PLA-EG) NPs. The size of PLA-V6K2 and PLA-EG NPs was 100 ± 20 and 130 ± 50 nm, respectively, with polydispersity index of 1.04 and 1.14. The encapsulation efficiency of DOX in PLA-V6K2 and PLA-EG NPs was 44 ± 9% and 55 ± 5%, respectively, and that of PTX was >90 for both NP types. The release of DOX and PTX from PLA-V6K2 was slower than that of PLA-EG, and the release rate was relatively constant with time. Based on molecular dynamic simulation, the less hydrophobic DOX was distributed in the lactide core as well as the peptide shell, while the hydrophobic PTX was localized mainly to the lactide core. PLA-V6K2 NPs had significantly higher cell uptake by 4T1 mouse breast carcinoma cells compared to PLA-EG NPs, which was attributed to the electrostatic interactions between the peptide and negatively charged moieties on the cell membrane. PLA-V6K2 NPs showed no toxicity to marrow stromal cells. DOX-loaded PLA-V6K2 NPs showed higher toxicity to 4T1 cells and the DNA damage response, and apoptosis was delayed compared to the free DOX. DOX or PTX encapsulated in PLA-V6K2 NPs significantly reduced invasion of 4T1 cells compared to those cells treated with the drug in PLA-EG NPs. Invasion of 4T1 cells treated with DOX in PLA-V6K2 and PLA-EG NPs was 5 ± 1% and 30 ± 5%, respectively, and that of PTX was 11 ± 2% and 40 ± 7%. The AUC of DOX in PLA-V6K2 NPs was 67% and 21% higher than those of free DOX and PLA-EG NPs, respectively. DOX-loaded PLA-V6K2 NPs injected in C3HeB/FeJ mice inoculated with MTCL syngeneic breast cancer cells displayed higher tumor toxicity than PLA-EG NPs and lower host toxicity than the free DOX. Cationic PLA-V6K2 NPs with higher tumor toxicity than the PLA-EG NPs are potentially useful in chemotherapy.