Calcium phosphate scaffold and bone marrow for bone reconstruction in irradiated area: a dog study

Cell therapy: A potential solution for the healing of bone cavities

Aim

To Explore whether the use of autologous BMMNCs as a cell therapy technique will improve the healing of bone cavities in vivo.

Methodology

After achieving proper anesthesia, mononuclear cells were isolated from iliac crest's bone marrow aspirates (BMMNCs). Then access cavity, root canal preparation, and filling were done in third and fourth premolars, followed by amalgam coronal restoration. After that, a flap was reflected and a standardized bone cavity was drilled, the related root-ends were resected and retrocavity was drilled and filled with MTA. Before repositioning the flap, the bone cavity was filled with the desired filling material according to its corresponding group (n = 8): CollaCote group; where collagen scaffold was used, MNC group; in which CollaCote® loaded with isolated BMMNCs were applied, Biogen group; in which BIO-GEN® graft material was applied and finally Control group; where the bone cavities were left empty to heal spontaneously. Evaluations of healing of the bone cavities were done radiographically and histologically.

Results

The MNC group induced the best healing potential with statistical significant difference from other groups.

Conclusion

cell therapy utilizing autologous BMMNCs looks to beat the conventional therapies and convey a significant improvement in the healing of the bone cavity in vivo.

Bone marrow cell extract promotes the regeneration of irradiated bone

Mandibular osteoradionecrosis is a severe side effect of radiotherapy after the treatment of squamous cell carcinomas of the upper aerodigestive tract. As an alternative to its treatment by micro-anastomosed free-flaps, preclinical tissular engineering studies have been developed. Total bone marrow (TBM) associated with biphasic calcium phosphate (BCP) significantly enhanced bone formation in irradiated bone. One mechanism, explaining how bone marrow cells can help regenerate tissues like this, is the paracrine effect. The bone marrow cell extract (BMCE) makes use of this paracrine mechanism by keeping only the soluble factors such as growth factors and cytokines. It has provided significant results in repairing various tissues, but has not yet been studied in irradiated bone reconstruction. The purpose of this study was to evaluate the effect of BMCE via an intraosseous or intravenous delivery, with a calcium phosphate scaffold, in irradiated bone reconstruction.

Twenty rats were irradiated on their hind limbs with a single 80-Gy dose. Three weeks later, surgery was performed to create osseous defects. The intraosseous group (n = 12) studied the effect of BMCE in situ, with six combinations (empty defect, BCP, TBM, BCP-TBM, lysate only, BCP-lysate). After four different combinations of implantation (empty defect, BCP, TBM, BCP-TBM), the intravenous group (n = 8) received four intravenous injections of BMCE for 2 weeks. Five weeks after implantation, samples were explanted for histological and scanning electron microscopy analysis. Lysate immunogenicity was studied with various mixed lymphocyte reactions.

Intravenous injections of BMCE led to a significant new bone formation compared to the intraosseous group. The BCP-TBM mixture remained the most effective in the intraosseous group. However, intravenous injections were more effective, with TBM placed in the defect, with or without biomaterials. Histologically, highly cellularized bone marrow was observed in the defects after intravenous injections, and not after an in situ use of the lysate. The mixed lymphocyte reactions did not show any proliferation after 3, 5, or 7 days of lysate incubation with lymphocytes from another species.

This study evaluated the role of BMCE in irradiated bone reconstruction. There were significant results arguing in favor of BMCE intravenous injections. This could open new perspectives to irradiated bone reconstruction.

Biphasic calcium phosphate ceramics for bone reconstruction: A review of biological response

Autologous bone graft is considered as the gold standard in bone reconstructive surgery. However, the quantity of bone available is limited and the harvesting procedure requires a second surgical site resulting in severe complications. Due to these limits, scientists and clinicians have considered alternatives to autologous bone graft. Calcium phosphates (CaPs) biomaterials including biphasic calcium phosphate (BCP) ceramics have proven efficacy in numerous clinical indications. Their specific physico-chemical properties (HA/TCP ratio, dual porosity and subsequent interconnected architecture) control (regulate/condition) the progressive resorption and the bone substitution process. By describing the most significant biological responses reported in the last 30years, we review the main events that made their clinical success. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

STATEMENT OF SIGNIFICANCE

Nowadays, BCPs are definitely considered as the gold standard of bone substitutes in bone reconstructive surgery. Among the numerous clinical studies in literature demonstrating the performance of BCP, Passuti et al. and Randsford et al. studies largely contributed to the emergence of the BCPs. It could be interesting to come back to the main events that made their success and could explain their large adhesion from scientists to clinicians. This paper aims to review the most significant biological responses reported in the last 30years, of these BCP-based materials. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

Porous Li-containing biphasic calcium phosphate scaffolds fabricated by three-dimensional plotting for bone repair

A well designed Li-BCP scaffolds by 3D plotting possessed an elaborate pore structure, porosity and interconnection for bone repair application.

Fabrication, Properties and Applications of Dense Hydroxyapatite: A Review

In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes.

Development of a cyclosporin-A-induced immune tolerant rat model to test marrow allograft cell type effects on bone repair

Bone repair is an important concept in tissue engineering, and the ability to repair bone in hypotrophic conditions such as that of irradiated bone, represents a challenge for this field. Previous studies have shown that a combination of bone marrow and (BCP) was effective to repair irradiated bone. However, the origin and role played by each cell type in bone healing still remains unclear. In order to track the grafted cells, the development of an animal model that is immunotolerant to an allograft of bone marrow would be useful. Furthermore, because the immune system interacts with bone turnover, it is of critical importance to demonstrate that immunosuppressive drugs do not interfere with bone repair. After a preliminary study of immunotolerance, cyclosporin-A was chosen to be used in immunosuppressive therapy. Ten rats were included to observe qualitative and quantitative bone repair 8 days and 6 weeks after the creation of bone defects. The defects were filled with an allograft of bone marrow alone or in association with BCP under immunosuppressive treatment (cyclosporin-A). The results showed that there was no significant interaction of cyclosporin-A with osseous regeneration. The use of this new immunotolerant rat model of bone marrow allograft in future studies will provide insight on how the cells within the bone marrow graft contribute to bone healing, especially in irradiated conditions.

Evaluation of new bone formation in irradiated areas using association of mesenchymal stem cells and total fresh bone marrow mixed with calcium phosphate scaffold

The consequences of the treatment of the squamous cell carcinomas of the upper aerodigestive tract (bone removal and external radiation therapy) are constant. Tissue engineering using biphasic calcium phosphate (BCP) and mesenchymal stem cells (MSC) is considered as a promising alternative. We previously demonstrated the efficacy of BCP and total fresh bone marrow (TBM) in regenerating irradiated bone defect. The aim of this study was to know if adding MSC to BCP + TBM mixture could improve the bone formation in irradiated bone defects. Twenty-four Lewis 1A rats received a single dose of 20 Gy to the hind limbs. MSC were sampled from non-irradiated donors and amplified in proliferative, and a part in osteogenic, medium. 3 weeks after, defects were created on femurs and tibias, which were filled with BCP alone, BCP + TBM, BCP + TBM + uncommitted MSC, or BCP + TBM + committed MSC. 3 weeks after, samples were removed and prepared for qualitative and quantitative analysis. The rate of bone ingrowth was significantly higher after implantation of BCP + TBM mixture. The adding of a high concentration of MSC, committed or not, didn't improve the bone regeneration. The association BCP + TBM remains the most efficient material for bone substitution in irradiated areas.

Bone marrow aspirate concentrate and platelet-rich plasma enhanced bone healing in distraction osteogenesis of the tibia

BACKGROUND

During lower limb lengthening, poor bone regeneration is a devastating complication. Several local or systemic applications have been used to promote osteogenesis, and biologic stimulations are gaining attention, but their utility has not been proven in this setting.

QUESTIONS/PURPOSES

In patients undergoing bilateral tibial lengthening, we compared those receiving an osteotomy site injection of autologous bone marrow aspirate concentrate (BMAC) plus platelet-rich plasma (PRP) with those not receiving such an injection in terms of external fixator index (time in external fixation divided by amount of lengthening), full weightbearing index (time until a patient was permitted to do full weightbearing divided by amount of lengthening), four cortical healing indexes (time until each cortical union divided by amount of lengthening), and callus shape and type.

METHODS

Twenty-two patients (44 tibias) undergoing bilateral tibial lengthening enrolled in this randomized trial. Two patients were excluded, one due to insufficient radiographic evaluation and one who was lost to followup, leaving 20 patients (40 segments) for inclusion. Ten patients (20 segments) received BMAC combined with PRP injection (treatment group) and 10 patients (20 segments) received no injection (control group). All patients underwent stature lengthening for familial short stature with the lengthening over nail technique. Autologous BMAC combined with PRP was injected at the tibial osteotomy site at the end of the index surgery. Mean distraction rates were similar between groups (0.75 mm/day in the treatment group versus 0.72 mm/day in the control group; p = 0.24). Full weightbearing was permitted when we observed radiographic evidence of healing at two cortices; this assessment was made by the surgeon who was blinded to the treatment each patient received. Minimum followup was 24 months (mean, 28 months; range, 24-34 months).

RESULTS

There was no difference in mean external fixator index between groups. However, mean cortical healing indexes (anterior/posterior/medial/lateral) were 1.14/0.81/0.96/0.88 months/cm in the treatment group and 1.47/1.26/1.42/1.22 months/cm in the control group (all p < 0.001), showing faster healing in the treatment group at each cortex. Full weightbearing was permitted earlier in the treatment group than in the control group (index: 0.99 months/cm and 1.38 months/cm, respectively, p < 0.001). Callus shape and type were not different between groups.

CONCLUSIONS

Autologous BMAC combined with PRP injection at the osteotomy site helped improve bone healing in distraction osteogenesis of the tibia, although the effect size was small.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Direct 3D powder printing of biphasic calcium phosphate scaffolds for substitution of complex bone defects

The 3D printing technique based on cement powders is an excellent method for the fabrication of individual and complex bone substitutes even in the case of large defects. The outstanding bone remodeling capacity of biphasic calcium phosphates (BCPs) containing hydroxyapatite (HA) as well as tricalcium phosphate (TCP) in varying ratios makes the adaption of powder systems resulting in BCP materials to this fabrication technique a desirable aim. This study presents the synthesis and characterization of a novel powder system for the 3D printing process, intended for the production of complexly shaped BCP scaffolds by a hydraulic setting reaction of calcium carbonate and TCP with phosphoric acid. The HA/TCP ratio in the specimens could be tailored by the calcium/phosphate ratio of the starting powder. The scaffolds could be fabricated with a dimensional accuracy of >96.5% and a minimal macro pore size of 300 µm. Independent of the phase composition the printed specimens showed a microporosity of approximately 68%, while the compressive strength strongly depended on the chemical composition and increased with rising TCP content in the scaffolds to a maximum of 1.81 MPa. Post-treatment of the scaffolds with a polylactic-co-glycolic acid-solution enhanced the mechanical properties by a factor of 8. In vitro studies showed that all BCP scaffolds were cytocompatible and enhanced the cell viability as well as the cell proliferation, as compared with pure TCP. Cell proliferation is even better on BCP when compared to HA and cell viability is in a similar range on these materials.

The association of hydrogel and biphasic calcium phosphate in the treatment of dehiscence-type peri-implant defects: an experimental study in dogs

Hydrogel polymers have many applications in regenerative medicine. The aim of this study in dogs was to investigate bone regeneration in dehiscence-type peri-implant defects created surgically and treated with (i) biphasic calcium phosphate (BCP) granules alone; (ii) a composite putty hydroxypropyl methylcellulose (HPMC)/BCP (MBCP/putty); and (iii) a polymer crosslinked membrane of silanized-HPMC (Si-HPMC/BCP) compared with empty controls. At 3 months, new bone formation was significantly more important in defects filled with HPMC/BCP or Si-HPMC/BCP compared with spontaneous healing in control (P = 0.032 and P = 0.046 respectively) and more substantial compared with BCP alone. Furthermore, new bone formation in direct contact with the implant surface was observed in all three groups treated with BCP. The addition of HPMC to the BCP granules may have enhanced the initial stability of the material within the blood clot in these large and complex osseous defects. The Si-HPMC hydrogel may also act as an occlusive membrane covering the BCP, which could improve the stability of the granules in the defect area. However, the crosslinking time of the Si-HPMC is too long for easy handling and the mechanical properties remain to be improved. The composite MBCP/putty appears to be a valuable bone-graft material in complex defects in periodontology and implantology. These encouraging results should now be confirmed in clinical studies.

The in vitro and in vivo effects of a low-molecular-weight fucoidan on the osteogenic capacity of human adipose-derived stromal cells

Human adipose-derived stromal cells (hASCs) may hold potential for bone tissue engineering. Osteogenic differentiation of these cells is crucial to bone formation. Low-molecular-weight fucoidan (LMWF) is a sulfated polysaccharide that potentiates several growth factors, including pro-angiogenic growth factors. To investigate whether hASC preconditioning with LMWF promoted bone repair, we compared the effects of LMWF and low-molecular-weight heparin on hASC phenotype and osteogenic differentiation. LMWF did not modify the stem-cell phenotype of hASCs but enhanced their osteogenic differentiation (formation of calcium deposits, increased activity and expression of alkaline phosphatase, and increased expression of osteopontin and runt-related transcription factor 2). However, when hASCs were exposed to LMWF before their adhesion to biphasic calcium phosphate particles and implantation in a bone-growth mouse model, no bone formation was apparent after 5 or 8 weeks, probably due to cell death. In conclusion, LMWF may hold promise for enhancing the osteogenic differentiation of hASCs before their implantation. However, concomitant vascularization would be required to enhance bone formation.

On the structural, mechanical, and biodegradation properties of HA/β-TCP robocast scaffolds

Hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composite scaffolds have shown great potential for bone-tissue engineering applications. In this work, ceramic scaffold with different HA/β-TCP compositions (pure HA, 60HA/40β-TCP, and 20HA/80β-TCP) were fabricated by a robotic-assisted deposition (robocasting) technique using water-based hydrogel inks. A systematic study was conducted to investigate the porosity, mechanical property, and degradation of the scaffolds. Our results indicate that, at a similar volume porosity, the mechanical strength of the sintered scaffolds increased with the decreasing rod diameter. The compressive strength of the fabricated scaffolds (porosity ≈ 25-80 vol %) varied between ∼3 and ∼50 MPa, a value equal or higher than that of human cancellous bone (2-12 MPa). Although there was a slight increase of Ca and P ions in water after 5 month, no noticeable degradation of the scaffolds in SBF or water was observed. Our findings from this work indicate that composite calcium phosphate scaffolds with customer-designed chemistry and architecture may be fabricated by a robotic-assisted deposition method.

In-vivo behavior of Si-hydroxyapatite/polycaprolactone/DMB scaffolds fabricated by 3D printing

Scaffolds made of polycaprolactone and nanocrystalline silicon-substituted hydroxyapatite have been fabricated by 3D printing rapid prototyping technique. To asses that the scaffolds fulfill the requirements to be considered for bone grafting applications, they were implanted in New Zealand rabbits. Histological and radiological studies have demonstrated that the scaffolds implanted in bone exhibited an excellent osteointegration without the interposition of fibrous tissue between bone and implants and without immune response after 4 months of implantation. In addition, we have evaluated the possibility of improving the scaffolds efficiency by incorporating demineralized bone matrix during the preparation by 3D printing. When demineralized bone matrix (DBM) is incorporated, the efficacy of the scaffolds is enhanced, as new bone formation occurs not only in the peripheral portions of the scaffolds but also within its pores after 4 months of implantation. This enhanced performance can be explained in terms of the osteoinductive properties of the DBM in the scaffolds, which have been assessed through the new bone tissue formation when the scaffolds are ectopically implanted.

Sol-gel method to fabricate CaP scaffolds by robocasting for tissue engineering

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol-gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and β-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2-12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 μm in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol-gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances.

Scaffold translation: barriers between concept and clinic

Translation of scaffold-based bone tissue engineering (BTE) therapies to clinical use remains, bluntly, a failure. This dearth of translated tissue engineering therapies (including scaffolds) remains despite 25 years of research, research funding totaling hundreds of millions of dollars, over 12,000 papers on BTE and over 2000 papers on BTE scaffolds alone in the past 10 years (PubMed search). Enabling scaffold translation requires first an understanding of the challenges, and second, addressing the complete range of these challenges. There are the obvious technical challenges of designing, manufacturing, and functionalizing scaffolds to fill the Form, Fixation, Function, and Formation needs of bone defect repair. However, these technical solutions should be targeted to specific clinical indications (e.g., mandibular defects, spine fusion, long bone defects, etc.). Further, technical solutions should also address business challenges, including the need to obtain regulatory approval, meet specific market needs, and obtain private investment to develop products, again for specific clinical indications. Finally, these business and technical challenges present a much different model than the typical research paradigm, presenting the field with philosophical challenges in terms of publishing and funding priorities that should be addressed as well. In this article, we review in detail the technical, business, and philosophical barriers of translating scaffolds from Concept to Clinic. We argue that envisioning and engineering scaffolds as modular systems with a sliding scale of complexity offers the best path to addressing these translational challenges.

Treatment of periodontal defects in dogs using an injectable composite hydrogel/biphasic calcium phosphate

An injectable composite silanized hydroxypropyl methyl cellulose/biphasic calcium phosphate (Si-HPMC/BCP) has been investigated in humans with promising results. The aim of this study was to evaluate his efficacy for treating periodontal defects (canine fenestration and premolar furcation) in dog models. At 3 months, we observed that bone formation around BCP particles in furcation model is more discernible but not statistically significant in defects filled with Si-HPMC/BCP compared to healing in control. We suggest that BCP particles sustain the bone healing process by osteoconduction, while the Si-HPMC hydrogel enhances intergranular cohesion and acts as an exclusion barrier. Furthermore, bone ingrowth is not so distinctive in superficial defects where the biomaterial appears unstable. These results with Si-HPMC/BCP are encouraging. In addition, this biomaterial is easy to use and simplifies the process of filling periodontal lesions. However, more researches are needed to improve the viscosity and hardness to adjust the material to the specificities of periodontal defects.

Calcium phosphate combination biomaterials as human mesenchymal stem cell delivery vehicles for bone repair

A new class of biomimetic, bioresorbable apatitic calcium phosphate cement (CPC) was recently developed. The handling characteristics, and the ability to harden at body temperature in the presence of physiological saline, make this material an attractive clinical bone substitute and delivery vehicle for therapeutic agents in orthopedic applications. The major challenge with the material is formulating an injectable paste with options for cell delivery, in order to regenerate new bone faster and with high quality. In this study, three different additives and/or viscosity modifiers (carboxymethylcellulose, silk, and alginate) were incorporated into a CPC matrix. Injectability, cell viability, cell proliferation, surface morphology, and gene expression for osteogenesis of hMSCs were all evaluated. Injectable CPC-gel composites with cell protection were achieved. The CPC modified with alginate provided the best results based on cell proliferation, ALP and collagen production, and osteogenic transcript increases (for ALP, type I collagen, BSP, and OP). Furthermore, osteogenic analysis indicated lineage-specific differentiation of hMSCs into osteogenic outcomes. The results suggest that CPC mixed with alginate can be used as a cell delivery vehicle for bone regeneration.

Alveolar ridge augmentation in irradiated rabbit mandibles

Oral carcinomas are frequently treated with a nonsegmental mandibulectomy plus radiotherapy. Improving the quality of life of these patients depends on the possibilities for dental rehabilitation. The aim of this study was to increase the alveolar ridge height. Twelve white New Zealand rabbits underwent surgery to produce a 11 x 9 x 7 mm(3) horizontal bicortical full-thickness defect at the alveolar ridge of the left mandible. Six were implanted with a composite associating resorbable collagen membrane filled with micro-macroporous biphasic calcium phosphate granules. After a daily radiation delivery schedule for 4 weeks, a total autologous bone marrow graft was injected percutaneously into the center of the implant. All animals were sacrificed at 16 weeks. Successful osseous colonization was observed in all implants. Significant ridge augmentation was observed (p = 0.0349) in the implanted group compared with the control group. This study contributed to producing an experimental model for oncological mandible defects in rabbits.

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.

Radiation effects on bone healing and reconstruction: interpretation of the literature

OBJECTIVE

Reconstructing irradiated mandibles with biomaterials is still a challenge but little investigated. We collected data that could help us understand studies in the field of regeneration with biomaterials and irradiated bone.

STUDY DESIGN

Systematic review of the literature.

RESULTS

Delay and duration of radiation delivery and total equivalent dose are the most variable parameters in the various studies, resulting in confusion when interpreting the literature. Most reproducible experiments show that radiation reduces osteogenic cell numbers, alters cytokine capacity, and delays and damages bone remodeling. Interindividual variations and how such changes become irreversible lesions are still uncertain. In the case of regeneration using biomaterials, most studies have addressed the question of reconstruction in previously irradiated bone. The results show that osseointegration is often possible, although the failure rate is higher. The sooner the implantation takes place after the end of the radiation, the higher the likelihood of failure. Few studies have focused on primary reconstruction followed by early irradiation, and most of the currently available engineering models would be altered by radiation. Good outcomes have been obtained with bone morphogenetic protein and with total bone marrow transplanation.

CONCLUSION

This review points out the difficulties in achieving reproducible experiments and interpreting literature in this underinvestigated field.

Bone formation in a rat calvarial defect model after transplanting autogenous bone marrow with beta-tricalcium phosphate

In the present study, we evaluated the osteogenic potential of an autogenous bone marrow graft combined with beta-tricalcium phosphate (beta-TCP) in a rat calvarial bone defect model. The bone marrow harvested from the tibia of 7-week-old rats was grafted autogenously in a calvarial defect together with beta-TCP (=BTG group, n=16) or without beta-TCP (=BG group, n=16). Groups of animals were also treated with beta-TCP alone (=TG group, n=16) and control animals (n=8) received no graft implanted into the defect. We then observed the process of bone formation by histology, enzyme histochemistry and immunohistochemistry. Five days after grafting, in the BTG and BG groups, cell proliferation and osteogenic differentiation were observed. From 5 to 10 days after surgery, active Runx2, osteopontin (OPN), and TRAP- positive cells appeared in the BTG and BG groups. New bone formation started in the defect in both the BTG and BG groups. At 30 days after grafting, the BTG group showed new bone development and replacement of beta-TCP to fill the bone defect. New bone formation in the BTG group was significantly greater than in the BG group (P<0.01). The TG group showed no marked bone formation in the defect. The combination graft of bone marrow with beta-TCP showed marked bone formation in rat calvarial defects. Our results indicate that the combination grafts of bone marrow with beta-TCP may be an effective technique for repairing bone defects Beta-TCPgraft (TG) group.

Reconstruction of irradiated bone segmental defects with a biomaterial associating MBCP+(R), microstructured collagen membrane and total bone marrow grafting: an experimental study in rabbits

The bone tissue engineering models used today are still a long way from any oncologic application as immediate postimplantation irradiation would decrease their osteoinductive potential. The aim of this study was to reconstruct a segmental critical size defect in a weight-bearing bone irradiated after implantation. Six white New Zealand rabbits were immediately implanted with a biomaterial associating resorbable collagen membrane EZ(R) filled and micro-macroporous biphasic calcium phosphate granules (MBCP+(R)). After a daily schedule of radiation delivery, and within 4 weeks, a total autologous bone marrow (BM) graft was injected percutaneously into the center of the implant. All the animals were sacrificed at 16 weeks. Successful osseous colonization was found to have bridged the entire length of the defects. Identical distribution of bone ingrowth and residual ceramics at the different levels of the implant suggests that the BM graft plays an osteoinductive role in the center of the defect. Periosteum-like formation was observed at the periphery, with the collagen membrane most likely playing a role. This model succeeded in bridging a large segmental defect in weight-bearing bone with immediate postimplantation fractionated radiation delivery. This has significant implications for the bone tissue engineering approach to patients with cancer-related bone defects.

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.

Bone Regeneration of Canine Skull Using Bone Marrow-Derived Stromal Cells and β-Tricalcium Phosphate

OBJECTIVE

The aim of this study was to regenerate high-quality cranial bone using tissue engineering techniques, with subsequent extension to clinical application. Our previous study with a 3-month observation period indicated that a composite scaffold composed primarily of beta-tricalcium phosphate (TCP) had the potential for cranial bone regeneration. In this study, we investigated whether bone marrow derived stromal cells (BSCs) could promote the regeneration of cranial bone as determined after 3 and 6 months.

STUDY DESIGN

The pilot study was conducted with 14 adult beagle dogs.

MATERIALS AND METHODS

Craniotomy was performed in the same manner used clinically. The bone defect (2 x 2 cm) was created at each canine temporoparietal region. The test animals were divided into three groups. In group I, the bone defect was closed by replacing the original free bone flap without filling the residual gaps. In group II, the gap was filled with a composite scaffold consisting of collagen coated beta-TCP and autologous bone fragments with fibrin glue. In group III, autologous cultured BSCs and the composite scaffold were used to fill the gap. The sites of craniotomy were analyzed with three-dimensional computed tomography and histologic examination 3 and 6 months after the operation.

RESULTS

Bone regeneration was observed in groups II and III, with more extensive formation in group III than in group II. In group I, bone regeneration was not observed.

CONCLUSION

This study showed that BSCs have the potential to promote cranial bone regeneration and confirmed the efficacy of a composite scaffold made of beta-TCP and autologous bone fragments with fibrin glue.

A comparison between bone reconstruction following the use of mesenchymal stem cells and total bone marrow in association with calcium phosphate scaffold in irradiated bone

The purpose of this study was to compare bone reconstruction using either mesenchymal stem cells (MSCs) or total bone marrow (TBM) in association with biphasic calcium phosphate (BCP) granules after irradiation in a rat model. Three weeks after an external irradiation of the hind limbs of rats, four bone defects were created per animal. The defects were filled with either BCP alone, or with a mixture of BCP and TBM, or with a mixture of BCP and MSCs (adipose-derived or bone marrow-derived MSCs). Three weeks after implantations, new-bone formation was assessed. Histological examination showed osteoconductive and osteointegrative properties of BCP in irradiated tissue. The BCP-TBM mixture significantly improved bone ingrowth (p<0.05). The BCP-MSCs mixtures did not provide new-bone formation over and above that induced by BCP alone. This gives grounds for suspecting that there is a link between this result and the cellular and vascular weakness observed in irradiated bone. The BCP-TBM mixture may have induced an increased vascularization of irradiated bone. This could be due to the presence of all components in TBM that were lacking in the BCP-MSCs mixtures. BCP associated with TBM appears to be the most efficient material for bone substitution in irradiated areas.

Intraosseous delivery of paclitaxel-loaded hydroxyapatitealginate composite beads delaying paralysis caused by metastatic spine cancer in rats

Object

Bone is frequently the first site and the only site of breast cancer at recurrence. Local control is important especially for metastatic spine cancer, because epidural spinal cord compression is significantly associated with the quality of life and survival of these patients. The authors have developed a local delivery system of paclitaxel in the form of hydroxyapatite-alginate composite beads. This study was conducted to clarify the therapeutic effect in a rat model of metastatic spine cancer.

Methods

Twenty-one rats with metastatic spine cancer were divided into 3 groups: a local treatment group (6 rats), a systemic treatment group (9 rats), and a control group (6 rats). The hind-limb motor function of the animals was monitored daily by using the Basso-Beattie-Bresnahan scale. The authors monitored the disease-free time and survival times. The log-rank test was used to define statistically significant differences between the 3 groups.

Results

The animals in the control group developed hind-limb paralysis at a mean of 10.8 days and died at a mean of 16.0 days. The animals treated with 2.4 wt% of paclitaxel-loaded hydroxyapatite-alginate composite beads (the local treatment group) showed a 140–150% increase in the disease-free time and survival time compared with that of the control group. Although an ~ 30-fold higher dosage of paclitaxel was administered, the therapeutic effect was not evident in the systemic treatment group.

Conclusions

Intraosseous delivery of paclitaxel-loaded hydroxyapatite-alginate composite beads delayed paralysis caused by metastatic spine cancer in rats. The results indicate that intraosseous chemotherapy may provide an effective local treatment of metastatic spine cancer.

Comparison of the effectiveness of autologous fibrin glue and macroporous biphasic calcium phosphate as carriers in the osteogenesis process with or without mesenchymal stem cells

BACKGROUND

Facial bone reconstruction has been a challenge for oral and maxillofacial surgeons for a long time. Recently, some studies have reported the use of stem cells in facial reconstruction to achieve osteogenesis. However, to ensure that stem cells remain in the recipient site, a biocompatible carrier is needed to transfer the stem cells. Fibrin glue has been shown to promote hemostasis in wound management and accelerate soft tissue healing, but the role of fibrin glue in bone regeneration remains debatable. The purpose of this study was to compare the effectiveness of autologous fibrin glue and macroporous biphasic calcium phosphate (MBCP) as carriers in the osteogenesis process with/without mesenchymal stem cells.

METHODS

Fifteen New Zealand white rabbits were used in this study. Mesenchymal stem cells were harvested from the iliac bone, and autologous fibrin glue was made from peripheral blood. Three cranial defects with a diameter of 6 mm were created over the cranial bone in each rabbit. The 15 animals were separated into 2 groups. The first group contained 12 rabbits. The grafted substances placed over the regions of defect were: (1) stem cells plus autologous fibrin glue; (2) stem cells plus MBCP; (3) defect alone as control. In the second group of 3 rabbits, the cranial defects were grafted with: (1) autologous fibrin glue alone; (2) MBCP alone; (3) defect alone as control. Rabbits were sacrificed at 1, 2 and 3 months post operation. Radiography and histology were used to detect bone formation.

RESULTS

Stem cells plus autologous fibrin glue induced more bone formation 2 months post operation and more mature bone was found 3 months post operation compared with the other groups. MBCP with or without stem cells showed moderate tissue reaction, including giant cell, histiocyte and eosinophil cell accumulation.

CONCLUSION

Using stem cells plus autologous fibrin glue as the carrier may accelerate new bone regeneration.

Biomaterials for tissue reconstruction and bone substitution of the ear, nose and throat, face and neck

The role of biomaterials has become more important in the last 30 years in otorhinolaryngology. Legal directives for their use and, more importantly, indications have been specified. Biomaterials are medical devices, designed for tissue substitution or reconstruction. Approval labeling is issued in the form of European Community certification and postmarketing medical device safety in Europe - completely independent from the US FDA's certification. The indications for biomaterials are generally similar to those of autografts. Their main advantage is that they limit the morbidity caused by autograft harvesting. The benefits are aesthetic, functional or both. The main indications are in otology, sinus surgery, cranio-maxillo-facial traumatology, osteosynthesis and orthognatic surgery, skeletal augmentation and anti-aging surgery, facial prosthetic rehabilitation and laryngology. The research fields are extremely varied (e.g., increased therapeutic properties, drug-delivery systems or tissue engineering). Increasingly, biomaterials are implanted and the surgical success of their use is dependent upon strict legal labeling and well-defined indications.

Biomatériaux de reconstruction et de comblement osseux en ORL et chirurgie cervicofaciale

INTRODUCTION

Position of medical devices has increased for last 30 years in otorhinolaryngology. Legal directive of use, main indications and perspectives are presented.

RESULTS AND DISCUSSION

Biomaterials are medical devices planned for tissue reconstruction or substitution. The approval labelling are planned in Europe by the European Community certification (marquage CE) and overseen by a postmarket medical device safety (matériovigilance), that are completely independent from the Food and Drug Administration certification. Indications of biomaterials are likely competitive to those of autografts; their advantage is to limit the morbidity due to autograft harvesting. Benefits are aesthetics, functional or complementary. Main indications are presented in otology, rhinology, face traumatology, laryngology, anti-aging surgery, implants and epithesis. Research fields are scanned (increased therapeutic properties, drug delivery systems, tissue engineering...).

CONCLUSION

Biomaterials are increasingly implanted in ENT surgery. The surgical success of their use require a strict legal label and well-defined indications.

Interactions of total bone marrow cells with increasing quantities of macroporous calcium phosphate ceramic granules

The biological properties of synthetic calcium phosphate bioceramics have made them the third choice of material for bone reconstructive surgery, after autologous bone and allografts. Nevertheless, bioceramics lack the osteogenic properties that would allow them to repair large bone defects. One strategy in bone tissue engineering consists of associating a synthetic scaffold with osteogenic cells. Mesenchymal stem cells (MSC) are usually isolated from bone marrow cultured for several weeks and seeded on to a small quantity of bioceramic. We have studied the association of total bone marrow cells, harvested from femurs of rats, with increasing amounts of calcium phosphate ceramic granules (50-250 mg). A cell viability test indicated that a little quantity of bioceramics granules (50 mg) was less detrimental for culturing 1 million nucleated cells from the whole bone marrow population. Cell morphology, viability, adhesion and differentiation were studied after different culture periods. Among the heterogeneous population of bone marrow cells, only a limited amount of cells attached and differentiated on the bioceramics. To explain the influence of the amount of synthetic scaffold on cell viability, media calcium concentrations were measured. Low cell viability could be explained by calcium phosphate precipitation leading to a decrease in calcium concentrations observed with relatively large amounts of scaffold. This study showed that the chemical stability of the ceramic plays a critical role in the viability of bone marrow cells.

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.