rhBMP6 in autologous blood coagulum is a preferred osteoinductive device to rhBMP2 on bovine collagen sponge in the rat ectopic bone formation assay

Osteoinductive BMPs require a suitable delivery system for treating various pathological conditions of the spine and segmental bone defects. INFUSE, the only commercially available BMP-based osteoinductive device, consisting of rhBMP2 on bovine absorbable collagen sponge (ACS) showed major disadvantages due to serious side effects. A novel osteoinductive device, OSTEOGROW, comprised of rhBMP6 dispersed within autologous blood coagulum (ABC) is a promising therapy for bone regeneration, subjected to several clinical trials for diaphysial bone repair and spinal fusion. In the present study, we have examined the release dynamics showing that the ABC carrier provided a slower, more steady BMP release in comparison to the ACS. Rat subcutaneous assay was employed to evaluate cellular events and the time course of ectopic osteogenesis. The host cellular response to osteoinductive implants was evaluated by flow cytometry, while dynamics of bone formation and maintenance in time were evaluated by histology, immunohistochemistry and micro CT analyses. Flow cytometry revealed that the recruitment of lymphoid cell populations was significantly higher in rhBMP6/ABC implants, while rhBMP2/ACS implants recruited more myeloid populations. Furthermore, rhBMP6/ABC implants more efficiently attracted early and committed progenitor cells. Dynamics of bone formation induced by rhBMP2/ACS was characterized by a delayed endochondral ossification process in comparison to rhBMP6/ABC implants. Besides, rhBMP6/ABC implants induced more ectopic bone volume in all observed time points in comparison to rhBMP2/ACS implants. These results indicate that OSTEOGROW was superior to INFUSE due to ABC's advantages as a carrier and rhBMP6 superior efficacy in inducing bone.

Calcium phosphate ceramics combined with rhBMP6 within autologous blood coagulum promote posterolateral lumbar fusion in sheep

Posterolateral spinal fusion (PLF) is a procedure used for the treatment of degenerative spine disease. In this study we evaluated Osteogrow-C, a novel osteoinductive device comprised of recombinant human Bone morphogenetic protein 6 (rhBMP6) dispersed in autologous blood coagulum with synthetic ceramic particles, in the sheep PLF model. Osteogrow-C implants containing 74-420 or 1000-1700 µm ceramic particles (TCP/HA 80/20) were implanted between L4-L5 transverse processes in sheep (Ovis Aries, Merinolaandschaf breed). In the first experiment (n = 9 sheep; rhBMP6 dose 800 µg) the follow-up period was 27 weeks while in the second experiment (n = 12 sheep; rhBMP6 dose 500 µg) spinal fusion was assessed by in vivo CT after 9 weeks and at the end of the experiment after 14 (n = 6 sheep) and 40 (n = 6 sheep) weeks. Methods of evaluation included microCT, histological analyses and biomechanical testing. Osteogrow-C implants containing both 74-420 and 1000-1700 µm ceramic particles induced radiographic solid fusion 9 weeks following implantation. Ex-vivo microCT and histological analyses revealed complete osseointegration of newly formed bone with adjacent transverse processes. Biomechanical testing confirmed that fusion between transverse processes was complete and successful. Osteogrow-C implants induced spinal fusion in sheep PLF model and therefore represent a novel therapeutic solution for patients with degenerative disc disease.

The Zagreb Skull Collection-The unique identified collection of human skulls from fetuses to centenarians

Skull anatomy and development have been extensively studied due to their significance in evolutionary biology, forensic anthropology, and clinical medicine. Bone collections are an indispensable resource for conducting such anthropological and anatomical studies. However, worldwide there are only few skull collections containing specimens covering the entire fetal and postnatal period. Herein we describe the Zagreb Skull Collection, an identified collection comprising more than 1100 skulls and skull bone sets from the early fetal period to centenarians. The Zagreb Skull Collection consists of two main parts: the unique Collection of Skull Bones containing 386 sets of separated skull bones from the early fetal period to adulthood and the Collection of Skulls containing 742 skulls (age range 4-101 years). The collection was the core source for numerous anatomical studies on the development, postnatal changes, and anatomical variations of the skull. However, the Zagreb Skull Collection is still an underexploited resource for anthropological, forensic, and anatomical studies with translatability to contemporary clinical practice.

Comparison of synthetic ceramic products formulated with autologous blood coagulum containing rhBMP6 for induction of bone formation

PURPOSE

Osteogrow, an osteoinductive device containing recombinant human Bone Morphogenetic Protein 6 (rhBMP6) in autologous blood coagulum, is a novel therapeutic solution for bone regeneration. This study aimed to evaluate different commercially available calcium phosphate synthetic ceramic particles as a compression-resistant matrix (CRM) added to Osteogrow implants to enhance their biomechanical properties.

METHODS

Osteogrow implants with the addition of Vitoss, ChronOs, BAM, and Dongbo ceramics (Osteogrow-C, where C stands for ceramics) were evaluated in the rodent subcutaneous ectopic bone formation assay. Osteogrow-C device was prepared as follows: rhBMP6 was added to blood, and blood was mixed with ceramics and left to coagulate. Osteogrow-C was implanted subcutaneously in the axillary region of Sprague-Dawley rats and the outcome was analyzed 21 days following implantation using microCT, histology, morphometric analyses, and immunohistochemistry.

RESULTS

Osteogrow-C implants with all tested ceramic particles induced the formation of the bone-ceramic structure containing cortical bone, the bone between the particles, and bone at the ceramic surfaces. The amount of newly formed bone was significant in all experimental groups; however, the highest bone volume was measured in Osteogrow-C implants with highly porous Vitoss ceramics. The trabecular number was highest in Osteogrow-C implants with Vitoss and ChronOs ceramics while trabeculae were thicker in implants containing BAM and Dongbo ceramics. The immunological response and inflammation were comparable among ceramic particles evaluated in this study.

CONCLUSION

Osteogrow-C bone regenerative device was effective with a broad range of commercially available synthetic ceramics providing a promising therapeutic solution for the regeneration of long bone fracture nonunion, large segmental defects, and spinal fusion surgeries.

Zoledronate Bound to Ceramics Increases Ectopic Bone Volume Induced by rhBMP6 Delivered in Autologous Blood Coagulum in Rats

Autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (ABC) with synthetic ceramics is a novel therapeutic solution for bone repair. The aim of this study was to investigate whether the application of Zoledronate (ZOL) with ABGS might enhance the properties of newly formed bone. The effect of ZOL on bone induction was tested in a rat subcutaneous implant model. ZOL bound to synthetic ceramics was added into ABGS implants, and the quantity, quality, and longevity of the induced bone were assessed by micro-CT, histomorphometry, and histology over a period of 365 days. Local use of ZOL in the ABGS implants with ceramics had no influence on the bone volume (BV) on day 14 but subsequently significantly increased BV on days 35, 50, 105, 140, and 365 compared to the control implants. Locally applied ZOL had a similar effect in all of the applied doses (2–20 µg), while its systemic use on stimulating the BV of newly induced bone by ABGS depended on the time of application. BV was increased when ZOL was applied systemically on day 14 but had no effect when applied on day 35. The administration of ZOL bound to ceramics in ABGS increased and maintained the BV over a period of one year, offering a novel bone tissue engineering strategy for treating bone defects and spinal fusions.

A novel autologous bone graft substitute containing rhBMP6 in autologous blood coagulum with synthetic ceramics for reconstruction of a large humerus segmental gunshot defect in a dog: The first veterinary patient to receive a novel osteoinductive therapy

Background

Management of large segmental defects is one of the most challenging issues in bone repair biology. Autologous bone graft substitute (ABGS) containing rhBMP6 within autologous blood coagulum (ABC) with synthetic ceramics is a novel biocompatible therapeutic solution for bone regeneration.

Case presentation

A 2-year old dog was brought to the veterinary clinics due to pain and bleeding from the right front leg after being unintendedly hit by a gunshot. Radiological examination revealed a large, 3 cm long multisegmental defect of the humerus on the right front leg with a loss of anatomical structure in the distal portion of the bone. The defect was treated surgically and an external fixator was inserted to ensure immobilization. Complete lack of bone formation 3 months following surgery required a full reconstruction of the defect site with a novel ABGS (rhBMP6 in ABC with ceramic particles) to avoid front leg amputation. The healing was then followed for the next 16 months. The callus formation was observed on x-ray images 2 months following ABGS implantation. The bone segments progressively fused together leading to the defect rebridgment allowing removal of the external fixator by 4 months after the reconstruction surgery. At the end of the observation period, the function of the leg was almost fully restored while analyses of the humeral CT sections revealed restoration and cortices rebridgment with a renewal of uniform medullary canal including structural reconstruction of the distal humerus.

Conclusion

This large humeral gunshot segmental defect of the front leg in a dog was saved from amputation via inducing bone regeneration using a novel ABGS osteoinductive device containing BMP6 in ABC.

Autologous bone graft substitute containing rhBMP6 within autologous blood coagulum and synthetic ceramics of different particle size determines the quantity and structural pattern of bone formed in a rat subcutaneous assay

Bone morphogenetic proteins (BMPs) are potent osteoinductive agents for bone tissue engineering. In order to define optimal properties of a novel autologous bone graft substitute (ABGS) containing rhBMP6 within the autologous blood coagulum (ABC) and ceramic particles as a compression resistant matrix (CRM), we explored the influence of their amount, chemical composition and particle size on the quantity and quality of bone formation in the rat subcutaneous assay. Tested ceramic particles included tricalcium phosphate (TCP), hydroxyapatite (HA) and biphasic calcium phosphate ceramic (BCP), containing TCP and HA in 80/20 ratio of different particle sizes (small 74-420 μm, medium 500-1700 μm and large 1000-4000 μm). RhBMP6 was either mixed with ABC or lyophilized on CRM prior to use with ABC. The experiments were terminated on day 21 and implants were analysed by microCT, histology and histomorphometry. Addition of CRM to ABGS containing rhBMP6 in ABC significantly increased the amount of newly formed bone and the optimal CRM/ABC ratio was found to be around 100 mg/500 μL. MicroCT analyses revealed that all tested ABGS formulations induced an extensive new bone formation and there were no differences between the two methods of rhBMP6 application as determined by the bone volume. However, the particle size played a significant role in the quantity and quality of newly formed bone. ABGS containing small particles induced new bone forming a dense trabecular network, cortical bone at the rim, bone and bone marrow in apposition to and in between ceramic particles. ABGS containing medium and large particles also resulted in new bone on the surface of particles as well as inside the pores. Histomorphometric analysis revealed that the ceramics particle size correlated with the quality of trabecular pattern of newly formed bone, bone/bone marrow ratio as observed in apposition and between particles, and the ratio between the cortical and trabecular bone. By employing rat subcutaneous implant assay, we showed for the first time that the size of synthetic ceramics particles affected the osteogenesis as defined by both the quantity and quality of ectopic bone.

Evaluation of synthetic ceramics as compression resistant matrix to promote osteogenesis of autologous blood coagulum containing recombinant human bone morphogenetic protein 6 in rabbit posterolateral lumbar fusion model

Posterolateral lumbar fusion (PLF) is a commonly performed surgical procedure for the treatment of pathological conditions of the lumbosacral spine. In the present study, we evaluated an autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (ABC) and synthetic ceramics used as compression resistant matrix (CRM) in the rabbit PLF model. In the pilot PLF rabbit experiment, we tested four different CRMs (BCP 500-1700 μm, BCP 1700-2500 μm and two different TCP in the form of slabs) which were selected based on achieving uniform ABC distribution. Next, ABGS implants composed of 2.5 mL ABC with 0.5 g ceramic particles (TCP or BCP (TCP/HA 80/20) of particle size 500-1700 μm) and 125 μg rhBMP6 (added to blood or lyophilized on ceramics) were placed bilaterally between transverse processes of the lumbar vertebrae (L5-L6) following exposition and decortication in 12 New Zealand White Rabbits observed for 7 weeks following surgery. Spinal fusion outcome was analysed by μCT, palpatory segmental mobility testing and selected specimens were either tested biomechanically (three-point bending test) and/or processed histologically. The total fusion success rate was 90.9% by both μCT analyses and by palpatory segmental mobility testing. The volume of newly formed bone between experimental groups with TCP or BCP ceramics and the different method of rhBMP6 application was comparable. The newly formed bone and ceramic particles integrated with the transverse processes on histological sections resulting in superior biomechanical properties. The results were retrospectively found superior to allograft devitalized mineralized bone as a CRM as reported previously in rabbit PLF. Overall, this novel ABGS containing rhBMP6, ABC and the specific 500-1700 μm synthetic ceramic particles supported new bone formation for the first time and successfully promoted posterolateral lumbar fusion in rabbits.

Synthetic ceramic macroporous blocks as a scaffold in ectopic bone formation induced by recombinant human bone morphogenetic protein 6 within autologous blood coagulum in rats

PURPOSE

We have recently developed an autologous bone graft substitute (ABGS) containing recombinant human bone morphogenetic protein 6 (rhBMP6) in autologous blood coagulum (ABC) that induces new bone formation in vivo. In order to improve biomechanical properties of the implant, compression resistant matrix (CRM) consisting of synthetic ceramics in the form of macroporous cylinders was added to the ABGS and we evaluated the biomechanical properties and the quantity and quality of bone formation following subcutaneous implantation in rats.

METHODS

ABGS implants containing rhBMP6 in ABC with cylindrical ceramic blocks were implanted subcutaneously (n = 6 per time point) in the axillary region of Sprague-Dawley rats and removed at specified time points (7, 14, 21, 35, and 50 days). The quantity and quality of newly formed bone were analyzed by microCT, histology, and histomorphometric analyses. Biomechanical properties of ABGS formulations were determined by employing the cut test.

RESULTS

MicroCT analyses revealed that ABGS implants induced formation of new bone within ceramic blocks. Histological analysis revealed that on day seven following implantation, the endochondral ossification occupied the peripheral part of implants. On days 14 and 21, newly formed bone was present both around the ceramic block and through the pores inside the block. On both days 35 and 50, cortical bone encircled the ceramic block while inside the block, bone covered the ceramic surface surrounding the pores. Within the osseous circles, there were few trabeculae and bone marrow containing adipocytes. ABGS containing cylindrical ceramic blocks were more rigid and had significantly increased stiffness compared with implants containing ceramic particles as CRM.

CONCLUSION

We demonstrated that macroporous ceramic blocks in a form of cylinders are promising CRMs with good handling and enhanced biomechanical properties, supporting bone formation with ABGS containing rhBMP6 within autologous blood coagulum. Hence, ABGS containing ceramic blocks should be tested in preclinical models including diaphyseal segmental defects and non-unions in larger animals.