Growth Factors, Carrier Materials, and Bone Repair

NIR light-facilitated bone tissue engineering

In the last decades, near-infrared (NIR) light has attracted considerable attention due to its unique properties and numerous potential applications in bioimaging and disease treatment. Bone tissue engineering for bone regeneration with the help of biomaterials is currently an effective means of treating bone defects. As a controlled light source with deeper tissue penetration, NIR light can provide real-time feedback of key information on bone regeneration in vivo utilizing fluorescence imaging and be used for bone disease treatment. This review provides a comprehensive overview of NIR light-facilitated bone tissue engineering, from the introduction of NIR probes as well as NIR light-responsive materials, and the visualization of bone regeneration to the treatment of bone-related diseases. Furthermore, the existing challenges and future development directions of NIR light-based bone tissue engineering are also discussed. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Preparation of Collagen/Hydroxyapatite Composites Using the Alternate Immersion Method and Evaluation of the Cranial Bone-Forming Capability of Composites Complexed with Acidic Gelatin and b-FGF

Bone-substitute materials are essential in dental implantology. We prepared collagen (Col)/hydroxyapatite (Hap)/acidic gelatin (AG)/basic fibroblast growth factor (b-FGF) constructs with enhanced bone-forming capability. The Col/Hap apatite composites were prepared by immersing Col sponges alternately in calcium and phosphate ion solutions five times, for 20 and 60 min, respectively. Then, the sponges were heated to 56 °C for 48 h. Scanning electron microscopy/energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses showed that the Col/Hap composites contained poorly crystalline Hap precipitates on the Col matrix. Col/Hap composite granules were infiltrated by AG, freeze-dried, and immersed in b-FGF solution. The wet quaternary constructs were implanted in rat cranial bone defects for 8 weeks, followed by soft X-ray measurements and histological analysis. Animal studies have shown that the constructs moderately increase bone formation in cranial bone defects. We found that an alternate immersion time of 20 min led to the greatest bone formation (p < 0.05). Constructs placed inside defects slightly extend the preexisting bone from the defect edges and lead to the formation of small island-like bones inside the defect, followed by disappearance of the constructs. The combined use of Col, Hap, AG, and b-FGF might bring about novel bone-forming biomaterials.

Transgenic PDGF-BB sericin hydrogel potentiates bone regeneration of BMP9-stimulated mesenchymal stem cells through a crosstalk of the Smad-STAT pathways

Silk as a natural biomaterial is considered as a promising bone substitute in tissue regeneration. Sericin and fibroin are the main components of silk and display unique features for their programmable mechanical properties, biocompatibility, biodegradability and morphological plasticity. It has been reported that sericin recombinant growth factors (GFs) can support cell proliferation and induce stem cell differentiation through cross-talk of signaling pathways during tissue regeneration. The transgenic technology allows the productions of bioactive heterologous GFs as fusion proteins with sericin, which are then fabricated into solid matrix or hydrogel format. Herein, using an injectable hydrogel derived from transgenic platelet-derived GF (PDGF)-BB silk sericin, we demonstrated that the PDGF-BB sericin hydrogel effectively augmented osteogenesis induced by bone morphogenetic protein (BMP9)-stimulated mesenchymal stem cells (MSCs) in vivo and in vitro, while inhibiting adipogenic differentiation. Further gene expression and protein-protein interactions studies demonstrated that BMP9 and PDGF-BB synergistically induced osteogenic differentiation through the cross-talk between Smad and Stat3 pathways in MSCs. Thus, our results provide a novel strategy to encapsulate osteogenic factors and osteoblastic progenitors in transgenic sericin-based hydrogel for robust bone tissue engineering.

In Vivo Bone Tissue Engineering Strategies: Advances and Prospects

Reconstruction of critical-sized bone defects remains a tremendous challenge for surgeons worldwide. Despite the variety of surgical techniques, current clinical strategies for bone defect repair demonstrate significant limitations and drawbacks, including donor-site morbidity, poor anatomical match, insufficient bone volume, bone graft resorption, and rejection. Bone tissue engineering (BTE) has emerged as a novel approach to guided bone tissue regeneration. BTE focuses on in vitro manipulations with seed cells, growth factors and bioactive scaffolds using bioreactors. The successful clinical translation of BTE requires overcoming a number of significant challenges. Currently, insufficient vascularization is the critical limitation for viability of the bone tissue-engineered construct. Furthermore, efficacy and safety of the scaffolds cell-seeding and exogenous growth factors administration are still controversial. The in vivo bioreactor principle (IVB) is an exceptionally promising concept for the in vivo bone tissue regeneration in a predictable patient-specific manner. This concept is based on the self-regenerative capacity of the human body, and combines flap prefabrication and axial vascularization strategies. Multiple experimental studies on in vivo BTE strategies presented in this review demonstrate the efficacy of this approach. Routine clinical application of the in vivo bioreactor principle is the future direction of BTE; however, it requires further investigation for overcoming some significant limitations.

Efficacy of regenerative medicine for alveolar cleft reconstruction: A systematic review and meta-analysis

Objective:

Objective: To analyze the efficacy and complications of regenerative medicine compared to autogenous bone graft for alveolar cleft reconstruction.

Method:

Method: Electronic search was done in PubMed, Scopus, Embase and Cochrane database for studies published until May 2021. No limitations were considered for the type of the included studies. The risk of bias (ROB) of the studies was assessed using the Cochrane Collaborations and NIH quality assessment tool. Meta-analyses were performed to assess the difference in the amount of bone formation and rate of complications. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for analyzing the level of the evidence.

Results:

Results: Among a total of 42 included studies, 21 studies used growth factors, 16 studies delivered cells, and five studies used biomaterials for bone regeneration of the alveolar cleft. Results showed no significant difference in the amount of bone formation between bone morphogenic protein-2 and iliac graft treated patients after six months (P=0.44) and 12 months (P=0.17) follow-up. Besides, higher swelling (OR=9.46,P<0.01) and less infection (OR=0.19,P=0.01) observed in BMP treated patients. Using stem cells can reduce the post-treatment pain (OR=0.04,P=0.01) but it has no significant impact on other complications (P>0.05). Using tissue engineering methods reduced the operation time (SD=1.06,P<0.01). GRADE assessment showed that results regarding the amount of bone formation volume after six and 12 months have low level of evidence.

Conclusion:

Conclusion: Tissue engineering methods can provide a comparable amount of bone formation as of the autogenous graft and reduce some of the complications, operation time and hospitalization duration.

Commercial Bone Grafts Claimed as an Alternative to Autografts: Current Trends for Clinical Applications in Orthopaedics

In the last twenty years, due to an increasing medical and market demand for orthopaedic implants, several grafting options have been developed. However, when alternative bone augmentation materials mimicking autografts are searched on the market, commercially available products may be grouped into three main categories: cellular bone matrices, growth factor enhanced bone grafts, and peptide enhanced xeno-hybrid bone grafts. Firstly, to obtain data for this review, the search engines Google and Bing were employed to acquire information from reports or website portfolios of important competitors in the global bone graft market. Secondly, bibliographic databases such as Medline/PubMed, Web of Science, and Scopus were also employed to analyse data from preclinical/clinical studies performed to evaluate the safety and efficacy of each product released on the market. Here, we discuss several products in terms of osteogenic/osteoinductive/osteoconductive properties, safety, efficacy, and side effects, as well as regulatory issues and costs. Although both positive and negative results were reported in clinical applications for each class of products, to date, peptide enhanced xeno-hybrid bone grafts may represent the best choice in terms of risk/benefit ratio. Nevertheless, more prospective and controlled studies are needed before approval for routine clinical use.