MBCP biphasic calcium phosphate granules and tissucol fibrin sealant in rabbit femoral defects: the effect of fibrin on bone ingrowth

Biomaterials for Guided Tissue Regeneration and Guided Bone Regeneration: A Review

This review aims to provide an overview of the types of membranes, bone substitutes, and mucosal substitutes used for GTR and GBR and briefly explores recent innovations for tissue regeneration and their future perspectives. Since this is a narrative review, no systematic search, meta-analysis, or statistical analysis was conducted. Using biomaterials for GTR and GBR provides a reduction in postoperative morbidity, as it contributes to less invasive clinical procedures, serving as an alternative to autogenous grafts. Moreover, randomized clinical trials (RCTs) and systematic reviews are essential for the evaluation of new biomaterials. These studies provide more robust evidence and help guide clinical practice in the selection of safer and more effective biomaterials, allowing for the personalization of treatment protocols for each patient.

Fibrin-konjac glucomannan-black phosphorus hydrogel scaffolds loaded with nasal ectodermal mesenchymal stem cells accelerated alveolar bone regeneration

BACKGROUND

Effective treatments for the alveolar bone defect remain a major concern in dental therapy. The objectives of this study were to develop a fibrin and konjac glucomannan (KGM) composite hydrogel as scaffolds for the osteogenesis of nasal mucosa-derived ectodermal mesenchymal stem cells (EMSCs) for the regeneration of alveolar bone defect, and to investigate the osteogenesis-accelerating effects of black phosphorus nanoparticles (BPNs) embedded in the hydrogels.

METHODS

Primary EMSCs were isolated from rat nasal mucosa and used for the alveolar bone recovery. Fibrin and KGM were prepared in different ratios for osteomimetic hydrogel scaffolds, and the optimal ratio was determined by mechanical properties and biocompatibility analysis. Then, the optimal hydrogels were integrated with BPNs to obtain BPNs/fibrin-KGM hydrogels, and the effects on osteogenic EMSCs in vitro were evaluated. To explore the osteogenesis-enhancing effects of hydrogels in vivo, the BPNs/fibrin-KGM scaffolds combined with EMSCs were implanted to a rat model of alveolar bone defect. Micro-computed tomography (CT), histological examination, real-time quantitative polymerase chain reaction (RT-qPCR) and western blot were conducted to evaluate the bone morphology and expression of osteogenesis-related genes of the bone regeneration.

RESULTS

The addition of KGM improved the mechanical properties and biodegradation characteristics of the fibrin hydrogels. In vitro, the BPNs-containing compound hydrogel was proved to be biocompatible and capable of enhancing the osteogenesis of EMSCs by upregulating the mineralization and the activity of alkaline phosphatase. In vivo, the micro-CT analysis and histological evaluation demonstrated that rats implanted EMSCs-BPNs/fibrin-KGM hydrogels exhibited the best bone reconstruction. And compared to the model group, the expression of osteogenesis genes including osteopontin (Opn, p < 0.0001), osteocalcin (Ocn, p < 0.0001), type collagen (Col , p < 0.0001), bone morphogenetic protein-2 (Bmp2, p < 0.0001), Smad1 (p = 0.0006), and runt-related transcription factor 2 (Runx2, p < 0.0001) were all significantly upregulated.

CONCLUSIONS

EMSCs/BPNs-containing fibrin-KGM hydrogels accelerated the recovery of the alveolar bone defect in rats by effectively up-regulating the expression of osteogenesis-related genes, promoting the formation and mineralisation of bone matrix.

Effect of fibrin glue on the healing efficacy of deproteinized bovine bone and autologous bone in critical-sized calvarial defects in rats

OBJECTIVES

In order to verify the hypothesis that fibrin glue (FG) is able to seal the area of bone grafting and facilitate bone regeneration.

MATERIALS AND METHODS

Twenty-one Sprague-Dawley rats with critical-sized calvarial bone defects were randomly assigned to three groups: (A) co-administrated deproteinized bovine bone (DBB) and autologous bone grafts with FG [fibrin ( +)], (B) co-administrated DBB and autologous bone grafts without FG [fibrin ( -)], and (C) no graft as control. Four weeks and 8 weeks later, micro-CT analysis and histomorphometric analysis were carried out to evaluate following parameters: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp), percentage of new bone area (Pe.NB), average thickness of bone defect (Th.BD), average thickness of basal bone (Th.BB), and percentage of new bone in center of the skull defect (Pe.NBc).

RESULTS

BV/TV, Tb.Th, and Tb.N in fibrin ( -) group were significantly higher than that of fibrin ( +) group (p = 0.008, 0.000, 0.007, respectively) and control group (p = 0.004, 0.001, and 0.007, respectively) at 8 weeks. Pe.NB in fibrin ( -) group (33.67 ± 11.72%) was significantly higher than that of fibrin ( +) group (12.33 ± 3.21%) (p = 0.038) and control group (9.66 ± 8.50%) (p = 0.045) at 8 weeks. Pe.NBc in fibrin ( -) group (12.05 ± 3.91%) was significantly higher than that of fibrin ( +) group (4.79 ± 1.21%) (p = 0.005) and control group (0.00 ± 0.00%) (p = 0.000) at 4 weeks.

CONCLUSIONS

Administration of both DBB and autograft stimulates calvarial bone defect regeneration, while combination of FG does not additionally accelerate new bone formation.

CLINICAL RELEVANCE

The use of fibrin to cement traditional bone graft materials in oral clinical practice requires caution.

Physical/Chemical Properties and Resorption Behavior of a Newly Developed Ca/P/S-Based Bone Substitute Material

Properly regulating the resorption rate of a resorbable bone implant has long been a great challenge. This study investigates a series of physical/chemical properties, biocompatibility and the behavior of implant resorption and new bone formation of a newly developed Ca/P/S-based bone substitute material (Ezechbone^® Granule CBS-400). Experimental results show that CBS-400 is comprised majorly of HA and CSD, with a Ca/P/S atomic ratio of 54.6/39.2/6.2. After immersion in Hank’s solution for 7 days, the overall morphology, shape and integrity of CBS-400 granules remain similar to that of non-immersed samples without showing apparent collapse or disintegration. With immersion time, the pH value continues to increase to 6.55 after 7 days, and 7.08 after 14 days. Cytotoxicity, intracutaneous reactivity and skin sensitization tests demonstrate the good biocompatibility features of CBS-400. Rabbit implantation/histological observations indicate that the implanted granules are intimately bonded to the surrounding new bone at all times. The implant is not merely a degradable bone substitute, but its resorption and the formation of new cancellous bone proceed at the substantially same pace. After implantation for 12 weeks, about 85% of the implant has been resorbed. The newly-formed cancellous bone ratio quickly increases to >40% at 4 weeks, followed by a bone remodeling process toward normal cancellous bone, wherein the new cancellous bone ratio gradually tapers down to about 30% after 12 weeks.

Porcine Collagen-Bone Composite Induced Osteoblast Differentiation and Bone Regeneration In Vitro and In Vivo

Due to autogenous bone limitations, some substitute bone grafts were developed. Collagenated porcine graft (CPG) is able to regenerate new bone, although the number of studies is insufficient, highlighting the need for future studies to better understand the biomaterial. In order to understand better CPG′s possible dental guided bone regeneration indications, the aim of this work was to determine CPG′s biological capacity to induce osteoblast differentiation in vitro and guided bone regeneration in vivo, whilst being compared with commercial hydroxyapatite and beta tricalcium phosphate (HA/β-TCP) and porcine graft alone. Cell cytotoxicity (WST-1), alkaline phosphatase activity (ALP), and real-time polymerase chain reaction (qPCR) were assessed in vitro. Critical size defects of New Zealand white rabbits were used for the in vivo part, with critical size defect closures and histological analyses. WST-1 and ALP indicated that CPG directly stimulated a greater proliferation and confluency of cells with osteoblastic differentiation in vitro. Gene sequencing indicated stable bone formation markers, decreased resorption makers, and bone remodeling coupling factors, making the transition from osteoclast to osteoblast expression at the end of seven days. CPG resulted in the highest new bone regeneration by osteoconduction in critical size defects of rabbit calvaria at eight weeks. Nonetheless, all biomaterials achieved nearly complete calvaria defect closure. CPG was found to be osteoconductive, like porcine graft and HA/β-TCP, but with higher new bone formation in critical size defects of rabbit calvaria at eight weeks. CPG can be used for different dental guided bone regeneration procedures; however, further studies are necessary.

Dental alloplastic bone substitutes currently available in Korea

As dental implant surgery and bone grafts were widely operated in Korean dentist, many bone substitutes are commercially available, currently. For commercially used in Korea, all bone substitutes are firstly evaluated by the Ministry of Health and Welfare (MOHW) for safety and efficacy of the product. After being priced, classified, and registration by the Health Insurance Review and Assessment Service (HIRA), the post-application management is obligatory for the manufacturer (or representative importer) to receive a certificate of Good Manufacturing Practice by Ministry of Food and Drug Safety. Currently, bone substitutes are broadly classified into C group (bone union and fracture fixation), T group (human tissue), L group (general and dental material) and non-insurance material group in MOHW notification No. 2018-248. Among them, bone substitutes classified as dental materials (L7) are divided as xenograft and alloplastic bone graft. The purpose of this paper is to analyze alloplastic bone substitutes of 37 products in MOHW notification No. 2018-248 and to evaluate the reference level based on the ISI Web of Knowledge, PubMed, EMBASE (1980–2019), Cochrane Database, and Google Scholar using the criteria of registered or trademarked product name.

Physiochemical characteristics and bone/cartilage tissue engineering potentialities of protein-based macromolecules - A review

Protein-based macromolecules such as keratin, silk fibroin, collagen, gelatin, and fibrin have emerged as potential candidate materials with unique structural and functional characteristics. Despite many advantages, the development of tissue-engineered constructs that can match the biological context of real tissue matrix remains a challenge in tissue engineering (TE). The tissue-engineered constructs should also support vascularization. Protein-based macromolecules, in pristine or combine form, provide a promising platform to engineer constructs with unique design and functionalities which are highly essential for an appropriate stimulation and differentiation of cells in a specific TE approach. However, much work remains to be undertaken with particular reference to in-depth interactions between constructed cues and target host tissues. Thus, modern advancements are emphasizing to understand critiques and functionalization of protein-based macromolecule that organize not only cellular activities but also tissue regenerations. In this review, numerous physicochemical, functional, and structural characteristics of protein-based macromolecules such as keratin, silk fibroin, collagen, gelatin, and fibrin are discussed. This review also presents the hope vs. hype phenomenon for tissue engineering. Later part of the review focuses on different requisite characteristics and their role in TE. The discussion presented here could prove highly useful for the construction of scaffolds with requisite features.

Effects of Growth Factors From Platelet-Rich Fibrin on the Bone Regeneration

Platelet-rich fibrin (PRF) has simple manufacturing process without risk of immunologic rejection or infection by additional materials. This study was designed to investigate the effects of platelet-derived growth factors and transforming growth factors-β in PRF on the proliferation and differentiation of osteoblasts. The authors analyzed platelet-derived growth factors and transforming growth factors-β in normal human serum (NHS) and PRF by enzyme-linked immunosorbent assay quantitatively and those in PRF group were significantly increased when compared with NHS. After harvesting osteoblasts from iliac bone, the authors added 10% fetal bovine serum, 10% NHS, and 3% PRF to osteoblasts, respectively and incubated for 24, 48, 72 hours. For analysis of osteoblast proliferation and differentiation, the authors measured DNA synthesis by [3H]-thymidine isotope activity, protein synthesis by sulforhoamine B assay and those were increased according to elapsed time in all groups, but they were significantly increased in 3% PRF. The authors measured alkaline phosphatase activity of osteoblasts, it was increased according to elapsed to time in all groups, but significantly increased in 72 hours. In conclusion, application of PRF to bone defect sites may have an enhanced effect of bone regeneration with low risk of complications, and relatively simple manufacturing process.

A review of fibrin and fibrin composites for bone tissue engineering

Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.

Enhanced Osteogenic and Vasculogenic Differentiation Potential of Human Adipose Stem Cells on Biphasic Calcium Phosphate Scaffolds in Fibrin Gels

For bone tissue engineering synthetic biphasic calcium phosphate (BCP) with a hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ratio of 60/40 (BCP60/40) is successfully clinically applied, but the high percentage of HA may hamper efficient scaffold remodelling. Whether BCP with a lower HA/β-TCP ratio (BCP20/80) is more desirable is still unclear. Vascular development is needed before osteogenesis can occur. We aimed to test the osteogenic and/or vasculogenic differentiation potential as well as degradation of composites consisting of human adipose stem cells (ASCs) seeded on BCP60/40 or BCP20/80 incorporated in fibrin gels that trigger neovascularization for bone regeneration. ASC attachment to BCP60/40 and BCP20/80 within 30 min was similar (>93%). After 11 days of culture BCP20/80-based composites showed increased alkaline phosphatase activity and DMP1 gene expression, but not RUNX2 and osteonectin expression, compared to BCP60/40-based composites. BCP20/80-based composites also showed enhanced expression of the vasculogenic markers CD31 and VEGF189, but not VEGF165 and endothelin-1. Collagen-1 and collagen-3 expression was similar in both composites. Fibrin degradation was increased in BCP20/80-based composites at day 7. In conclusion, BCP20/80-based composites showed enhanced osteogenic and vasculogenic differentiation potential compared to BCP60/40-based composites in vitro, suggesting that BCP20/80-based composites might be more promising for in vivo bone augmentation than BCP60/40-based composites.

Combining mesenchymal stem cell sheets with platelet-rich plasma gel/calcium phosphate particles: a novel strategy to promote bone regeneration

Background

Promotion of bone regeneration is important for successful repair of bony defects. This study aimed to investigate whether combining bone marrow-derived mesenchymal stem cell (BMSC) sheets with platelet-rich plasma (PRP) gel/calcium phosphate particles could promote bone formation in the femoral bone defects of rats.

Methods

The proliferation and differentiation of BMSCs or BMSC sheets cultured with calcium phosphate particles and/or PRP were investigated in in vitro. In vivo, 36 2.5 × 5 mm bone defects were randomly divided into groups and treated with either BMSCs/PRP gel, calcium phosphate particles, PRP gel/calcium phosphate particles, a BMSC sheet/calcium phosphate particles, a BMSC sheet/PRP gel/calcium phosphate particles, or were left untreated (n = 6/group). A further 15 bone defects were treated with chloromethyl-benzamidodialkylcarbocyanine (CM-Dil)-labelled BMSC sheet/PRP gel/calcium phosphate particles and observed using a small animal in vivo fluorescence imaging system to trace the implanted BMSCs at 1 day, 3 days, 7 days, 2 weeks, and 4 weeks after surgery.

Results

The expression of collagen type I and osteocalcin genes of BMSCs or BMSC sheets treated with PRP and calcium phosphate particles was significantly higher than that of BMSCs or BMSC sheets treated with calcium phosphate particles or the controls (P <0.05). PRP can promote gene expression of collagen III and tenomodulin by BMSCs and in BMSC sheets. The VEGF, collagen I and osteocalcin gene expression levels were higher in the BMSC sheet than in cultured BMSCs (P <0.05). Moreover, alizarin red staining quantification, ALP quantification and calcein blue fluorescence showed the osteogenic potential of BMSCs treated with PRP and calcium phosphate particles The implanted BMSCs were detectable at 1 day, 3 days, 7 days, 2 weeks and 4 weeks after surgery by a small animal in vivo fluorescence imaging system and were visualized in the defect zones by confocal microscopy. At 4 weeks after implantation, the defects treated with the BMSC sheet/PRP gel/calcium phosphate particles showed significantly more bone formation than the other five groups.

Conclusions

Incorporation of an BMSC sheet into the PRP gel/calcium phosphate particles greatly promoted bone regeneration. These BMSC sheet and tissue engineering strategies offer therapeutic opportunities for promoting bone defect repair clinically.

A Novel Porcine Graft for Regeneration of Bone Defects

Bone regeneration procedures require alternative graft biomaterials to those for autogenous bone. Therefore, we developed a novel porcine graft using particle sizes of 250–500 μm and 500–1000 μm in rabbit calvarial bone defects and compared the graft properties with those of commercial hydroxyapatite (HA)/beta-tricalcium phosphate (β-TCP) over eight weeks. Surgery was performed in 20 adult male New Zealand white rabbits. During a standardized surgical procedure, four calvarial critical-size defects of 5 mm diameter and 3 mm depth were prepared. The defects were filled with HA/β-TCP, 250–500 μm or 500–1000 μm porcine graft, and control defects were not filled. The animals were grouped for sacrifice at 1, 2, 4, and 8 weeks post-surgery. Subsequently, sample blocks were prepared for micro-computed tomography (micro-CT) scanning and histological sectioning. Similar bone formations were observed in all three treatment groups, although the 250–500 μm porcine graft performed slightly better. Rabbit calvarial bone tissue positively responded to porcine grafts and commercial HA/β-TCP, structural analyses showed similar crystallinity and porosity of the porcine and HA/β-TCP grafts, which facilitated bone formation through osteoconduction. These porcine grafts can be considered as graft substitutes, although further development is required for clinical applications.

Tolerance and osteointegration of TricOs(TM)/MBCP(®) in association with fibrin sealant in mastoid obliteration after canal wall-down technique for cholesteatoma

CONCLUSION

The TricOs™/MBCP(®) and fibrin sealant composite was a convenient, effective, and well-tolerated material for mastoid cavity filling and immediate reconstruction of the external auditory meatus after cholesteatoma surgery with canal wall down (CWD).

OBJECTIVE

To assess the tolerance and osteointegration of a bone graft substitute, TricOs™/MBCP(®), in association with fibrin sealant for filling the mastoid cavity after cholesteatoma surgery using the CWD technique.

METHODS

In this prospective observational study 57 patients with cholesteatoma suitable for CWD were recruited from April 2006 to April 2008 and followed up for 1 year. The mastoid cavity was filled with TricOs™/MBCP(®) followed by immediate reconstruction of the external auditory meatus covered with fascia temporalis and/or cartilage. The main outcome was skin tolerance assessed by a novel weighted score emphasizing long-term results. The typical weighted reference score was 1.67; skin tolerance was considered acceptable if 75% of patients had a score ≤ 1.67. Secondary outcomes were otorrhea and/or otalgia, hearing, and osteointegration assessed through computed tomography scanning at 12 months.

RESULTS

Forty-one patients had a complete follow-up; 34 (82.3%) patients achieved the main end point with scores ≤ 1.67. Otorrhea decreased postoperatively. No otalgia interfering with daily tasks was reported. Ossicular reconstruction was carried out in 29 patients. Absence of cochlear toxicity was confirmed by unimpaired bone conduction. Preoperative and postoperative speech audiometry results were similar. No serious adverse events were observed. Osteointegration was satisfactory with hyperdensity or intermediate density in 95% of patients at 12 months.

Biphasic, triphasic and multiphasic calcium orthophosphates

Biphasic, triphasic and multiphasic (polyphasic) calcium orthophosphates have been sought as biomaterials for reconstruction of bone defects in maxillofacial, dental and orthopedic applications. In general, this concept is determined by advantageous balances of more stable (frequently hydroxyapatite) and more resorbable (typically tricalcium orthophosphates) phases of calcium orthophosphates, while the optimum ratios depend on the particular applications. Therefore, all currently known biphasic, triphasic and multiphasic formulations of calcium orthophosphate bioceramics are sparingly soluble in water and, thus, after being implanted they are gradually resorbed inside the body, releasing calcium and orthophosphate ions into the biological medium and, hence, seeding new bone formation. The available formulations have already demonstrated proven biocompatibility, osteoconductivity, safety and predictability in vitro, in vivo, as well as in clinical models. More recently, in vitro and in vivo studies have shown that some of them might possess osteoinductive properties. Hence, in the field of tissue engineering biphasic, triphasic and multiphasic calcium orthophosphates represent promising biomaterials to construct various scaffolds capable of carrying and/or modulating the behavior of cells. Furthermore, such scaffolds are also suitable for drug delivery applications. This review summarizes the available information on biphasic, triphasic and multiphasic calcium orthophosphates, including their biomedical applications. New formulations are also proposed.

Biocomposites and hybrid biomaterials based on calcium orthophosphates

The state-of-the-art of biocomposites and hybrid biomaterials based on calcium orthophosphates that are suitable for biomedical applications is presented in this review. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through successful combinations of the desired properties of matrix materials with those of fillers (in such systems, calcium orthophosphates might play either role), innovative bone graft biomaterials can be designed. Various types of biocomposites and hybrid biomaterials based on calcium orthophosphates, either those already in use or being investigated for biomedical applications, are extensively discussed. Many different formulations, in terms of the material constituents, fabrication technologies, structural and bioactive properties as well as both in vitro and in vivo characteristics, have already been proposed. Among the others, the nanostructurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using biocomposites and hybrid biomaterials based on calcium orthophosphates in the selected applications are highlighted. As the way from the laboratory to the hospital is a long one, and the prospective biomedical candidates have to meet many different necessities, this review also examines the critical issues and scientific challenges that require further research and development.

Biphasic bone substitute and fibrin sealant for treatment of benign bone tumours and tumour-like lesions

PURPOSE

Bone defects resulting from tumour resection or curettage are most commonly reconstructed with autologous bone graft which is associated with limited availability and donor site morbidity. Recent research has focussed on synthetic biomaterials as bone graft substitutes. The aim of this study was to assess the safety and efficiency of a bone substitute as an alternative for autologous bone in the treatment of benign bone tumours and tumour-like lesions.

METHODS

In the present study, a biphasic ceramic (60% HA and 40% β-TCP) combined with a fibrin sealant was used to reconstruct defects in 51 patients after curettage of benign bone tumours or tumour-like lesions. Patient age ranged from eight to 68 years (mean 29.7), defect size from 2 cm(3) to 35 cm(3) (mean 12.1), and time of follow-up from one to 56 months (mean 22.7).

RESULTS

Radiologic analysis showed complete bony defect consolidation in 50 of 51 patients after up to 56 months. No postoperative fractures were observed. Revision surgery had to be performed in one case. Histological analysis showed new bone formation and good biocompatibility and osseointegration of the implanted material.

CONCLUSION

In summary, the biphasic ceramic in combination with fibrin sealant was proven an effective alternative to autologous bone grafts eliminating the risk of donor site morbidity for the patient.

A review on endogenous regenerative technology in periodontal regenerative medicine

Periodontitis is a globally prevalent inflammatory disease that causes the destruction of the tooth-supporting apparatus and potentially leads to tooth loss. Currently, the methods to reconstitute lost periodontal structures (i.e. alveolar bone, periodontal ligament, and root cementum) have relied on conventional mechanical, anti-infective modalities followed by a range of regenerative procedures such as guided tissue regeneration, the use of bone replacement grafts and exogenous growth factors (GFs), and recently developed tissue engineering technologies. However, all current or emerging paradigms have either been shown to have limited and variable outcomes or have yet to be developed for clinical use. To accelerate clinical translation, there is an ongoing need to develop therapeutics based on endogenous regenerative technology (ERT), which can stimulate latent self-repair mechanisms in patients and harness the host's innate capacity for regeneration. ERT in periodontics applies the patient's own regenerative 'tools', i.e. patient-derived GFs and fibrin scaffolds, sometimes in association with commercialized products (e.g. Emdogain and Bio-Oss), to create a material niche in an injured site where the progenitor/stem cells from neighboring tissues can be recruited for in situ periodontal regeneration. The choice of materials and the design of implantable devices influence therapeutic potential and the number and invasiveness of the associated clinical procedures. The interplay and optimization of each niche component involved in ERT are particularly important to comprehend how to make the desired cell response safe and effective for therapeutics. In this review, the emerging opportunities and challenges of ERT that avoid the ex vivo culture of autologous cells are addressed in the context of new approaches for engineering or regeneration of functional periodontal tissues by exploiting the use of platelet-rich products and its associated formulations as key endogenous resources for future clinical management of periodontal tissue defects.

Reduction of bone resorption by the application of platelet-rich plasma (PRP) in bone grafting of the alveolar cleft

OBJECTIVE

We evaluated the effectiveness of platelet-rich plasma (PRP) on the regeneration of autogenous cancellous bone and marrow grafted in the alveolar cleft.

DESIGN

Twenty patients with alveolar clefts were examined; 6 were the control group and received cancellous bone and marrow grafts without PRP, while the remaining 14 comprised the PRP group and received grafts with PRP. Prior to surgery, 50 ml of blood was withdrawn and 5 ml of PRP gel produced through centrifugal separation. The bone graft mixed with PRP was then packed into the alveolar cleft. Postoperative bone density was assessed as the aluminium-equivalent value on occlusal X-ray films in a qualitative analysis. Quantitative evaluation of regenerated bone was made with computed tomography and panoramic radiographs at 1 month, 6 months and 1 year after surgery.

RESULTS

Satisfactory bone bridging formation was observed in all patients without any complications. The bone density of the PRP group was lower than that of the control group at 1 week, but the same after 1 month. The added PRP reduced the resorption of regenerated bone postoperatively.

CONCLUSION

Autogenous cancellous bone grafting with PRP, which significantly reduces postoperative bone resorption, is a reliable technique for alveolar bone grafting of cleft patients.

Biofunctionality of MBCP ceramic granules (TricOs) plus fibrin sealant (Tisseel) versus MBCP ceramic granules as a filler of large periprosthetic bone defects: an investigative ovine study

We aimed to quantify bone colonization toward an untreated titanium implant with primary stability following filling of the defect with micromacroporous biphasic calcium phosphate (MBCP) granules (TricOs) or MBCP granules mixed with fibrin sealant (Tisseel). Medial arthrotomy was performed on the knees of 20 sheep to create a bone defect (16 mm deep; 10 mm diameter), followed by anchorage of a titanium screw. Defects were filled with TricOs or TricOs-Tisseel granules, a perforated MBCP washer, a titanium washer and titanium screw. Sheep were euthanized at 3, 6, 12 and 26 weeks. From Week 12 onwards, the percentage of bone in contact with the 8 mm anchorage part of the screw increased in both groups, confirming its primary stability. At 26 weeks, whereas bone colonization was similar in both groups, biodegradation of ceramic was more rapid in the TricOs-Tisseel group (P = 0.0422). The centripetal nature of bone colonization was evident. Bone contact with the titanium implant surface was negligible. In conclusion, the use of a model that reproduces a large metaphyseal bone defect around a titanium implant with primary stability, filled with a mixture of either TricOs ceramic granules or TricOs granules mixed with Tisseel fibrin sealant, suggests that the addition of fibrin to TricOs enhances bone filling surgical technology.

Prevention of growth arrest by fibrin interposition into physeal injury

This study investigated the repair effects of fat and fibrin graft interposition through a proximal tibia transphyseal injury model and assessed the effectiveness of treatment to physeal injury with the fibrin. In this study, a unilateral growth plate injury was created in the right proximal tibia of 28 rats without any graft interposition; all left tibias were left untouched. In the other group of 28 rats, a bilateral physeal injury was made with the left tibia filled with autogenously adipose tissue and the right tibia filled with fibrin. To compare the malformed extents induced by different interventions, the length and the metaphyseal-diaphyseal angle of the tibia of three injured groups were examined. Further studies on bone density analysis and histological change were used to compare the bony bridge formation under different interventions. Results showed that the deformity angle and medial length of the tibia were significantly different between the grafted groups and nongrafted group at 4, 16, and 24 weeks postoperative (P<0.01). Results also showed no significant difference between fibrin-graft and fat-graft groups (P>0.05). Furthermore, the bone mineralization density of bony bridge induced by injury was significantly different between the grafted group and nongrafted group at 4, 16, and 24 weeks postoperative (P<0.01). Histological findings showed that bony repair after physeal injury was inhibited by both fibrin and fat interventions. We concluded that fibrin could be a substitute of adipose tissue in preventing the deformities induced by epiphyseal injury. Similar to autogenous fat, fibrin was found to alleviate limb shortness and prevent angular malformation by forming a scar instead of a bony bridge. The use of fibrin can help us to develop effective and compound intervention grafts to prevent skeletal deformity and regenerate normal cartilage tissue in the future.

Comparison of two bone substitute biomaterials consisting of a mixture of fibrin sealant (Tisseel) and MBCP (TricOs) with an autograft in sinus lift surgery in sheep

OBJECTIVES

The aim of this study was to assess the efficacy and safety of macroporous biphasic calcium phosphate (MBCP())/fibrin grafts (TricOs((R)))/(Tisseel((R))) for sinus lift augmentation in sheep. Autologous bone grafts were used as a positive control, and dental implants were placed to assess the efficiency of the composite.

MATERIALS AND METHODS

A total of 12 adult sheep (24 maxillary sinuses) were randomized to receive sinus lift augmentation with MBCP()/fibrin grafts obtained by either simultaneous or sequential addition of thrombin and fibrinogen to MBCP(), or autologous bone grafts. Six months post-sinus lift surgery, dental implants were placed. At 6 months post-sinus lift and 3 months after dental implant placement, the characteristics of newly formed bone and dental implant stability were assessed. The methods used were radiography, scanning electron microscopy, light microscopy, micro-CT analysis, radio frequency analysis (RFA), and image analysis.

RESULTS

There were no clinical adverse events in the post-operative period. New bone formation was similar for MBCP()/fibrin grafts and autografts at 21-20% and 20%, respectively, at 6 months, and at 34-35% and 35%, respectively, at 9 months. Implantability of dental implants was better at the time of placement with MBCP()/fibrin grafts than autografts at 81-88% and 69%, respectively. Three months after placement, RFA showed better implantability with MBCP()/fibrin grafts than with autografts at 75-82% and 71%, respectively. The bone contact measurements were around 50% for the three groups, without significant differences.

CONCLUSIONS

This study shows that following sinus lift augmentation in sheep, MBCP()/fibrin grafts support new bone formation that is comparable to autografts, while providing better support for the dental implants.

Applications and Degradation of Proteins Used as Tissue Engineering Materials

This article provides an up-to-date review on the applications of natural polymers, i.e., proteins, as materials for tissue engineering. Proteins are one of the important candidates for tissue engineering materials based on their superior biocompatibility, biodegradation, bioresorbability, and so on. However, their inferior mechanical properties limit their broad application. Currently-available proteins for application in tissue engineering or drug delivery systems, such as fibrin, collagen, zein, silk fibroin, keratin, casein and albumin, and the biodegradation of tissue-engineered substitutes based on proteins are presented. Techniques of scaffold fabrication are also mentioned. Problems and future possibilities for development of protein-based tissue-engineered substitutes are also introduced in this review.

Microporous nanofibrous fibrin-based scaffolds for bone tissue engineering

The fibrotic response of the body to synthetic polymers limits their success in tissue engineering and other applications. Though porous polymers have demonstrated improved healing, difficulty in controlling their pore sizes and pore interconnections has clouded the understanding of this phenomenon. In this study, a novel method to fabricate natural polymer/calcium phosphate composite scaffolds with tightly controllable pore size, pore interconnection, and calcium phosphate deposition was developed. Microporous, nanofibrous fibrin scaffolds were fabricated using sphere-templating methods. Composite scaffolds were created by solution deposition of calcium phosphate on fibrin surfaces or by direct incorporation of nanocrystalline hydroxyapatite (nHA). The SEM results showed that fibrin scaffolds exhibited a highly porous and interconnected structure. Osteoblast-like cells, obtained from murine calvaria, attached, spread and showed a polygonal morphology on the surface of the biomaterial. Multiple cell layers and fibrillar matrix deposition were observed. Moreover, cells seeded on mineralized fibrin scaffolds exhibited significantly higher alkaline phosphatase activity as well as osteoblast marker gene expression compared to fibrin scaffolds and nHA incorporated fibrin scaffolds (0.25 and 0.5g). All types of scaffolds were degraded both in vitro and in vivo. Furthermore, these scaffolds promoted bone formation in a mouse calvarial defect model and the bone formation was enhanced by addition of rhBMP-2.

Bone tissue formation in sheep muscles induced by a biphasic calcium phosphate ceramic and fibrin glue composite

Some biomaterials are able to induce ectopic bone formation in muscles of large animals. The osteoinductive potential of macro- micro-porous biphasic calcium phosphate (MBCP) ceramic granules with fibrin glue was evaluated by intramuscular implantation for 6 months in six adult female sheep. The MBCP granules were 1-2 mm in size and were composed of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) in a 60/40 ratio. The fibrin glue was composed of fibrinogen, thrombin and other biological factors. After 6 months of implantation in the dorsal muscles of sheep, the explants were rigid. Histology, back-scattered electron microscopy and micro-computed tomography of the implants indicated that approximately 12% of mineralized bone had formed in between the MBCP granules. The ectopic bone appeared well-mineralized with mature osteocytes and Haversian structures. In addition, the number and thickness of bone trabeculae formed in between the MBCP particles were similar to those measured in trabecular bone in sheep. The overall results therefore confirmed the formation of well-mineralized ectopic bone tissue after intramuscular implantation of MBCP/fibrin glue composites. These bone substitutes exhibiting osteoinductive properties could be used for the reconstruction of large bone defects.

The primacy of octacalcium phosphate collagen composites in bone regeneration

We have engineered a scaffold constructed of synthetic octacalcium phosphate (OCP) and porcine collagen sponge (OCP/Col), and reported that OCP/Col drastically enhanced bone regeneration. In this study, we investigated whether OCP/Col would enhance bone regeneration more than beta-tricalcium phosphate (beta-TCP) collagen composite (beta-TCP/Col) or hydroxyapatite (HA) collagen composite (HA/Col). Discs of OCP/Col, beta-TCP/Col, or HA/Col were implanted into critical-sized defects in rat crania and fixed at 4 or 12 weeks after implantation. The newly formed bone and the remaining granules of implants in the defect were determined by histomorphometrical analysis, and radiographic and histological examinations were performed. Statistical analysis showed that the newly formed bone by the implantation of OCP/Col was significantly more than that of beta-TCP/Col or HA/Col. In contrast, the remaining granules in OCP/Col were significantly lower than those in beta-TCP/Col or HA/Col. Bone regeneration by OCP/Col was based on secured calcified collagen and bone nucleation by OCP, whereas bone regeneration by beta-TCP/Col or HA/Col was initiated by poorly calcified collagen and osteoconductivity by beta-TCP or HA. This study showed that the implantation of OCP/Col in a rat cranial defect enhanced more bone regeneration than beta-TCP/Col and HA/Col.

Biodegradable Adhesive (LYDEX) with Hydroxyapatite Granules

A new biodegradable adhesive(LYDEX) which is based on Schiff base formation had developed. LYDEX is easy to control the setting time and degradation speed and it has no risk of infection. In the previous study, LYDEX showed high bonding strength and low cytotoxicity in vitro[1]. In the present study, good bone repair was seen in rat bone defect models, especially in rapidly degrading type. On the other hand, slowly degrading type kept its shape longer without excessive inflammation. In rabbit critical defect model with hydroxyapatite granules (HAs), more newly formed bone was seen in rapidly degrading group and hydroxyapatite group, in 3weeks. In 6weeks, more new bone was seen in slowly degrading type group, whereas, almost no new bone was seen in deep area of the fibrin group, in 12weeks. Direct bonding between HAs and bone was seen in HA group and LYDEX groups. These findings suggest that LYDEX with hydroxyapatite granules can be a promising bone substitute.

Staged-injection procedure to prevent cement leakage during vertebroplasty: an in vitro study

STUDY DESIGN

Fibrin sealant (FS) combined with or without growth factor was used to improve the micro-architectural and biomechanical properties of vertebral body in osteoporotic ovine spine.

OBJECTIVE

To analyze the treatment effects of bovine bone morphogenetic protein (bBMP) combined with FS on osteopenic ovine vertebral architecture, bone mineral density, and biomechanics in vivo.

SUMMARY OF BACKGROUND DATA

Vertebroplasty and kyphoplasty were used to treat spinal osteoporosis. They can increase strength of vertebrae physically. However, each has specific disadvantages. bBMP could rapidly increasing bone formation and suppressing bone resorption, but little is known about its effect on ovariectomized-induced osteoporosis.

METHODS

Six sheep underwent ovariectomy and were placed on a low-calcium diet. Twelve months later, according to Ladin square design, L4-L6 vertebrae in all sheep were randomly assigned to 3 treatment groups: A (30 mg bBMP/1.5 mL FS), B (30 mg bBMP) and C (1.5 mL FS). All materials were injected into the assigned vertebra transpedicularly. Animals were killed 3 months after injection, and bone mineral density (BMD), biomechanics, and histomorphometry were assessed. Analysis of variance was used to determine effects of bBMP/FS (alpha = 0.05).

RESULTS

The BMD in Group 1 was 17.1% and 14.7% higher than that in Group 2 and Group 3, respectively. The micro-CT reconstruction analysis showed that the density and connectivity of trabecular bone in bBMP/FS treated vertebrae were higher than those in control groups. The mechanical properties (yield stress, ultimate stress, energy absorption, bone modulus) of the vertebrae were also significantly higher. In this study, local bBMP/FS treatment showed a positive trend in improving BMD, histomorphometric parameters, and mechanical strength of osteoporotic vertebra. Slow release of bBMP using FS appeared to be an effective method of protein delivery.

CONCLUSION

The use of bBMP/FS in the treatment of vertebral osteoporosis in an attempt to enhance bone strength merits further study.

Influence of calcium chloride and aprotinin in the in vivo biological performance of a composite combining biphasic calcium phosphate granules and fibrin sealant

Highly bioactive biomaterials have been developed to replace bone grafts in orthopedic revision and maxillofacial surgery for bone augmentation. A mouldable, self-hardening material can be obtained by combining TricOs Biphasic Calcium Phosphate Granules and Tissucol Fibrin Sealant. Two components, calcium chloride and antifibrinolytic agents (aprotinin), are essential for the stability of the fibrin clot. The ingrowth of cells in composites combining sealants without calcium chloride or with a low concentration of aprotinin was evaluated in vivo in an experiment on rabbits. Bone colonization was compared using TricOs alone or with the composite made from TricOs and the standard fibrin sealant. Without the addition of calcium chloride, the calcium ions released by the ceramic component interacted with the components of the sealant too late to stabilize the clot. With a low concentration of aprotinin, the degradation of the clot occurred more quickly, leading to the absence of a scaffold on which the bone cells could colonize the composite. Our results indicate that a stable fibrin scaffold is crucial for bone colonization. The low calcium chloride and low aprotinin groups have shown lower bone growth. Further studies will be necessary to determine the minimal amount of antifibrinolytic agent (aprotinin) necessary to allow the same level of osteogenic activity as the TricOs-fibrin glue composite.

Hybrid composites of calcium phosphate granules, fibrin glue, and bone marrow for skeletal repair

Synthetic bone substitutes, such as calcium phosphate ceramics, give good results in clinical applications. In order to adapt to surgical sites, bioceramics come in the form of blocks or granules, and are either dense or porous. Combining these bioceramics with fibrin glue provides a mouldable and self-hardening composite biomaterial with the biochemical properties of each component. Critical-sized defects in the femoral condyle of rabbits were filled with TricOs/fibrin glue/bone marrow hybrid/composite material. The TricOs granules (1-2 mm) were composed of hydroxyapatite and beta tricalcium phosphate (60/40 in weight). The fibrin glue was composed of fibrinogen, thrombin and other biological factors and mixed with MBCP granules either simultaneously or sequentially. Bone marrow was also added to the MBCP/fibrin composite prior to filling the defects. After 3, 6, 12, and 24 weeks of implantation, the newly-formed bone was analysed with histology, histomorphometry and mechanical tests. The newly-formed bone had grown centripetally. Simultaneous application of fibrin glue showed better results for mechanical properties than sequential application after 6 weeks. Around 40% of bone had formed after 24 weeks in the three groups. Although the addition of bone marrow did not improve bone formation, the MBCP/fibrin material could be used in clinical bone filling applications.

Osteogenic properties of calcium phosphate ceramics and fibrin glue based composites

Calcium phosphate (Ca-P) ceramics are currently used in various types of orthopaedic and maxillofacial applications because of their osteoconductive properties. Fibrin glue is also used in surgery due to its haemostatic, chemotactic and mitogenic properties and also as scaffolds for cell culture and transplantation. In order to adapt to surgical sites, bioceramics are shaped in blocks or granules and preferably in porous forms. Combining these bioceramics with fibrin glue provides a mouldable and self-hardening composite biomaterial. The aim of this work is to study the osteogenic properties of this composite material using two different animal models. The formation of newly formed bone (osteoinduction) and bone healing capacity (osteconduction) have been study in the paravertebral muscles of sheep and in critical sized defects in the femoral condyle of rabbits, respectively. The different implantations sites were filled with composite material associating Ca-P granules and fibrin glue. Ca-P granules of 1-2 mm were composed with 60% of hydroxyapatite and 40% of beta tricalcium phosphate in weight. The fibrin glue was composed of fibrinogen, thrombin and other biological factors. After both intramuscular or intraosseous implantations for 24 weeks and 3, 6, 12 and 24 weeks, samples were analyzed using histology and histomorphometry and mechanical test. In all cases, the newly formed bone was observed in close contact and around the ceramic granules. Depending on method of quantification, 6.7% (with BSEM) or 17% (with micro CT) of bone had formed in the sheep muscles and around 40% in the critical sized bone rabbit defect after 24 weeks. The Ca-P/fibrin material could be used for filling bone cavities in various clinical indications.

A novel poly(ethylene glycol)–fibrinogen hydrogel for tibial segmental defect repair in a rat model

The aim of this study is to investigate regeneration in a segmental bone defect using a novel fibrinogen-based hydrogel material. The use of hydrogels made from poly(ethylene glycol) (PEG) conjugated to fibrinogen for this purpose may be better to conventional fibrin-based materials as it offers an additional degree of control over the structural characteristics and biodegradation of the material. At the same time, it maintains some of the inherent biofunctionality of the fibrinogen molecule. PEGylated fibrinogen hydrogels with various degrees of proteolytic resistance based on PEG and fibrinogen composition were designed for slow, intermediate, and fast biodegradation. The hydrogels were implanted into 7-mm segmental rat tibial defects without additional osteoinductive factors with the rationale that the ingrowth matrix will displace the normal fibrin clot while sustaining a similar healing effect for a longer duration. Histological and X-ray results confirmed that the extent and distribution of newly formed bone in the defect after 5 weeks strongly parallels the biodegradation pattern of the implanted material. When compared to nonunions in animals treated with the fast-degrading implants and untreated control animals, the rats implanted with the intermediate-degrading material exhibited osteoneogenesis. This data supports the hypothesis that the perseverance of the PEGylated fibrinogen material can be synchronized with the optimal healing characteristics of a segmental osseous defect and that the consequent sustained release of fibrinogen fragments facilitates the osteogenic response at the injury site. The PEGylated fibrinogen material may, therefore, be a highly efficacious material for promoting the healing of bone defects and especially nonunion fractures.

The modulation of gene expression in osteoblasts by thrombin coated on biphasic calcium phosphate ceramic

For many years, fibrin sealants were associated with bone substitutes to promote bone healing. However, the osteoblastic response to fibrin sealant components remains poorly documented. In this study, MC3T3-E1 osteoblastic cells were cultured on biphasic calcium phosphate ceramic (MBCP) coated with Tissucol components (thrombin and fibrinogen). Analysis of osteoblastic differentiation markers by RT-PCR revealed that MBCP coated with Tissucol stimulated mRNA levels for osteocalcin and alkaline phosphatase (ALP). Of all the components of Tissucol, thrombin has been reported to affect osteoblastic behavior. Our results demonstrated that low thrombin concentrations (0.5-5 U/ml) stimulated mRNA levels for ALP, whereas high thrombin concentrations (50-100 U/ml) decreased mRNA levels for ALP and PTH/PTHrP receptor and also increased mRNA level for the osteoclastogenesis inhibitor OPG. As thrombin stimulated angiogenesis, we then wondered whether thrombin could influence the expression of angiogenic factors. Low thrombin concentrations were shown to up-regulate mRNA levels for VEGF-B and VEGF-R1, suggesting an autocrine/paracrine role for VEGF-B. Higher thrombin concentrations also up-regulated mRNA for VEGF-A and neuropilin-1. In conclusion, the association of MBCP with thrombin and fibrinogen appears to be a convenient scaffold for bone cell differentiation. Thrombin could also acts at the cellular level by increasing the angiogenic potential of osteoblasts as well as their responsiveness to thrombin and VEGF.