In vivo biological performance of composites combining micro-macroporous biphasic calcium phosphate granules and fibrin sealant

Adhesives for treatment of bone fractures: A review of the state-of-the art

Treatment of fractures remains challenging and carries a high economical burden to both patients and society. In order to prevent some of the complications, the use of bone adhesives has been proposed, but up to date, bone adhesives are not part of the current clinical practice. Early results of use of bone cements and bone glues are promising, focusing in the areas of highly fragmented fractures, fixation of long bone fractures, filling bone voids and defects, promoting osseointegration, preventing non-union while maintaining the reduction of fracture fixation. This review aims to describe the state-of-the-art of the development, properties and use of adhesives in fracture treatment.

Fibrin biopolymer as scaffold candidate to treat bone defects in rats

Background

Bone tissue repair remains a challenge in tissue engineering. Currently, new materials are being applied and often integrated with live cells and biological scaffolds. The fibrin biopolymer (FBP) proposed in this study has hemostatic, sealant, adhesive, scaffolding and drug-delivery properties. The regenerative potential of an association of FBP, biphasic calcium phosphate (BCP) and mesenchymal stem cells (MSCs) was evaluated in defects of rat femurs.

Methods

Adult male Wistar rats were submitted to a 5-mm defect in the femur. This was filled with the following materials and/or associations: BPC; FBP and BCP; FBP and MSCs; and BCP, FBP and MSCs. Bone defect without filling was defined as the control group. Thirty and sixty days after the procedure, animals were euthanatized and subjected to computed tomography, scanning electron microscopy and qualitative and quantitative histological analysis.

Results

It was shown that FBP is a suitable scaffold for bone defects due to the formation of a stable clot that facilitates the handling and optimizes the surgical procedures, allowing also cell adhesion and proliferation. The association between the materials was biocompatible. Progressive deposition of bone matrix was higher in the group treated with FBP and MSCs. Differentiation of mesenchymal stem cells into osteogenic lineage was not necessary to stimulate bone formation.

Conclusions

FBP proved to be an excellent scaffold candidate for bone repair therapies due to application ease and biocompatibility with synthetic calcium-based materials. The satisfactory results obtained by the association of FBP with MSCs may provide a more effective and less costly new approach for bone tissue engineering.

Infected tooth extraction, bone grafting, immediate implant placement and immediate temporary crown insertion in a patient with severe type-B hemophilia

Haemorrhagic disorders combined with soft tissue inflammation and infection may lead to severe bleeding complications before, during or after dental treatment. In selected cases, a combined therapeutic approach involving clinical therapies and systemic and local medication could improve the treatment outcomes and the patient's quality of life. This clinical case report, presents for the first time a successful combined approach, completed in a 38-year-old male patient with severe type-B haemophilia in which an infected tooth was extracted, an immediate implant was inserted, bone grafting was performed and early implant loading was successfully applied. In addition to the clinical therapy, medication was provided orally, systemically and locally, thus preventing the haemorrhagic complications and improving the patient's quality of life.

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.

Sodium-DNA for Bone Tissue Regeneration: An Experimental Study in Rat Calvaria

Surgical techniques in dental and maxillofacial surgery request fast bone tissue regeneration, so there is a significant need to improve therapy for bone regeneration. Several studies have recently underlined the importance of nucleotides and nucleosides to increase cell proliferation and activity; in particular, the ability of polydeoxyribonucleotide (PDRN) to induce growth and activity of human osteoblasts was demonstrated. Sodium-DNA is the deoxyribonucleic acid (DNA) extracted from the gonadic tissue of male sturgeon and then purified, depolymerized, and neutralized with sodium hydroxide. To date, there are no evidences about the use of Sodium-DNA for bone tissue regeneration. Consequently, our question is about the efficacy of Sodium-DNA in bone healing. For testing the role of Sodium-DNA in bone healing we used a rat calvarial defect model. Sodium-DNA at different concentrations used alone or in association with Fibrin and/or Bio-Oss was used for healing treatments and the bone healing process was evaluated by histomorphometric and immunohistochemical analyses. Our results suggested a positive effect of Sodium-DNA in bone regeneration, providing a useful protocol and a model for the future clinical evaluation of its osteogenic properties.

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.

A doxycycline inducible, adenoviral bone morphogenetic protein-2 gene delivery system to bone

We report the novel use of a tuneable, non-integrating viral gene delivery system to bone that can be combined with clinically approved biomaterials in an 'off-the-shelf' manner. Specifically, a doxycycline inducible Tet-on adenoviral vector (AdTetBMP-2) in combination with mesenchymal stromal cells (MSCs), fibrin and a biphasic calcium phosphate ceramic (MBCP®) was used to repair large bone defects in nude rats. Bone morphogenetic protein-2 (BMP-2) transgene expression could be effectively tuned by modification of the doxycycline concentration. The effect of adenoviral BMP-2 gene delivery upon bone healing was investigated in vivo in 4 mm critically sized, internally fixated, femoral defects. MSCs were transduced either by direct application of AdTetBMP-2 or by pre-coating MBCP granules with the virus. Radiological assessment scores post-mortem were significantly improved upon delivery of AdTetBMP-2. In AdTetBMP-2 groups, histological analysis revealed significantly more newly formed bone at the defect site compared with controls. Newly formed bone was vascularized and fully integrated with nascent tissue and implanted biomaterial. Improvement in healing outcome was achieved using both methods of vector delivery (direct application vs. pre-coating MCBP). Adenoviral delivery of BMP-2 enhanced bone regeneration achieved by the transplantation of MSCs, fibrin and MBCP in vivo. Importantly, our in vitro and in vivo data suggest that this can be achieved with relatively low (ng/ml) levels of the growth factor. Our model and novel gene delivery system may provide a powerful standardized tool for the optimization of growth factor delivery and release for the healing of large bone defects. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Use of granules of biphasic ceramic in rehabilitation of canal wall down mastoidectomy

The objective of this study is to evaluate the anatomical and functional results of rehabilitation of canal wall down (CWD) mastoidectomy using granules of biphasic ceramic. This is a study design retrospective in a tertiary referral centre Fifty-seven patients (59 ears) operated on between 2006 and 2010 of mastoid obliteration with granules of biphasic ceramic (TricOs, Maurepas, France) have been included (55 revisions and 4 first surgeries). Forty-six patients presented already a CWD mastoidectomy. The mean pre-operative bone conduction (BC) was 29 ± 3.4 dB (mean ± SEM) and mean air conduction (AC) was 57 ± 3.2 dB. Cholesteatoma was found in 33 cases. All but seven cases had post-operative otoscopy examination at 1, 3, 6 months, and 1 year postoperative with a CT scan and pure tone audiometry. Mean follow-up was 14 ± 1.8 months (3-35). At one-year follow-up (n = 52), 47 cases (90 %) presented well-healed external auditory canal. Five cases (10 %) of uncovered granules without sign of infection of external auditory canal skin were observed. Mean post-operative threshold was 25 ± 1.8 and 46 ± 1.9 dB for BC and AC , respectively (n = 47). CT scan (n = 42) showed no opacity suggesting residual disease within or behind obliteration. Mastoid obliteration with granules of biphasic ceramic is a safe and effective procedure that allows restoration of a near normal external auditory canal.

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.

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.

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.

Ceramic composites as matrices and scaffolds for drug delivery in tissue engineering

Ceramic composites and scaffolds are popular implant materials in the field of dentistry, orthopedics and plastic surgery. For bone tissue engineering especially CaP-ceramics or cements and bioactive glass are suitable implant materials due to their osteoconductive properties. In this review the applicability of these ceramics but also of ceramic/polymer composites for bone tissue engineering is discussed, and in particular their use as drug delivery systems. Overall, the high density and slow biodegradability of ceramics is not beneficial for tissue engineering purposes. To address these issues, macroporosity can be introduced often in combination with osteoinductive growth factors and cells. Ceramics are good carriers for drugs, in which release patterns are strongly dependent on the chemical consistency of the ceramic, type of drug and drug loading. Biodegradable polymers like polylactic acid, gelatin or chitosan are used as matrices for ceramic particles or as adjuvant to calcium phosphate cements. The use of these polymers can introduce a tailored biodegradation/drug release to the ceramic material.

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.

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.