Enhanced cell attachment to anorganic bone mineral in the presence of a synthetic peptide related to collagen

Advances in implants and bone graft types for lumbar spinal fusion surgery

The increasing prevalence of spinal disorders worldwide necessitates advanced treatments, particularly interbody fusion for severe cases that are unresponsive to non-surgical interventions. This procedure, especially 360° lumbar interbody fusion, employs an interbody cage, pedicle screw-and-rod instrumentation, and autologous bone graft (ABG) to enhance spinal stability and promote fusion. Despite significant advancements, a persistent 10% incidence of non-union continues to result in compromised patient outcomes and escalated healthcare costs. Innovations in lumbar stabilisation seek to mimic the properties of natural bone, with evolving implant materials like titanium (Ti) and polyetheretherketone (PEEK) and their composites offering new prospects. Additionally, biomimetic cages featuring precisely engineered porosities and interconnectivity have gained traction, as they enhance osteogenic differentiation, support osteogenesis, and alleviate stress-shielding. However, the limitations of ABG, such as harvesting morbidities and limited fusion capacity, have spurred the exploration of sophisticated solutions involving advanced bone graft substitutes. Currently, demineralised bone matrix and ceramics are in clinical use, forming the basis for future investigations into novel bone graft substitutes. Bioglass, a promising newcomer, is under investigation despite its observed rapid absorption and the potential for foreign body reactions in preclinical studies. Its clinical applicability remains under scrutiny, with ongoing research addressing challenges related to burst release and appropriate dosing. Conversely, the well-documented favourable osteogenic potential of growth factors remains encouraging, with current efforts focused on modulating their release dynamics to minimise complications. In this evidence-based narrative review, we provide a comprehensive overview of the evolving landscape of non-degradable spinal implants and bone graft substitutes, emphasising their applications in lumbar spinal fusion surgery. We highlight the necessity for continued research to improve clinical outcomes and enhance patient well-being.

The Osteogenic Peptide P-15 for Bone Regeneration: A Narrative Review of the Evidence for a Mechanism of Action

Bone regeneration is a complex multicellular process involving the recruitment and attachment of osteoprogenitors and their subsequent differentiation into osteoblasts that deposit extracellular matrixes. There is a growing demand for synthetic bone graft materials that can be used to augment these processes to enhance the healing of bone defects resulting from trauma, disease or surgery. P-15 is a small synthetic peptide that is identical in sequence to the cell-binding domain of type I collagen and has been extensively demonstrated in vitro and in vivo to enhance the adhesion, differentiation and proliferation of stem cells involved in bone formation. These events can be categorized into three phases: attachment, activation and amplification. This narrative review summarizes the large body of preclinical research on P-15 in terms of these phases to describe the mechanism of action by which P-15 improves bone formation. Knowledge of this mechanism of action will help to inform the use of P-15 in clinical practice as well as the development of methods of delivering P-15 that optimize clinical outcomes.

Peptide Enhanced Bone Graft Substitute Presents Improved Short-Term Increase in Bone Volume and Construct Stiffness Compared to Iliac Crest Autologous Bone in an Ovine Lumbar Interbody Fusion Model

STUDY DESIGN

Preclinical ovine model.

OBJECTIVE

To assess the in vivo efficacy and safety of the P-15 L bone graft substitute and compare its performance to autologous iliac crest bone graft (ICBG) for lumbar interbody fusion indications.

METHODS

Thirty skeletally mature sheep underwent lumbar interbody fusion surgery. Half of the sheep received autologous ICBG and the other half the peptide enhanced bone graft substitute (P-15 L). Following termination at 1, 3, and 6 months after surgery, the operated segments were analyzed using micro computed tomography (µCT), histology, and destructive mechanical testing. Additional systemic health monitoring was performed for the P-15 L group.

RESULTS

One month after surgery, there was only minor evidence of bone remodeling and residual graft material could be clearly observed within the cage. There was active bone remodeling between 1 and 3 months after surgery. At 3 months after surgery significantly denser and stiffer bone was found in the P-15 L group, whereas at 6 months, P-15 L and ICBG gave similar fusion results. The P-15 L bone graft substitute did not have any adverse effects on systemic health.

CONCLUSIONS

The drug device combination P-15 L was demonstrated to be effective and save for lumbar interbody fusion as evidenced by this ovine model. Compared to autologous ICBG, P-15 L seems to expedite bone formation and remodeling but in the longer-term fusion results were similar.

Does the use of i-FACTOR bone graft affect bone healing in those undergoing periacetabular osteotomy (PAO) for developmental dysplasia of the hip (DDH)? A retrospective study

The aims of this study were to compare, in patients with and without the use of i-FACTOR bone graft during periacetabular osteotomy (PAO) surgery for developmental dysplasia of the hip (DDH), (i) bone healing at six-weeks post-operatively (ii) rate of complications. This was a retrospective review of case records. Participants were people aged 15-50 years undergoing rectus-sparing minimally invasive PAO surgery for DDH. Group 1: patients with i-FACTOR, Group 2: No i-FACTOR. The primary outcome was the rate of bone healing on radiographs at 6 weeks. The likelihood of bone healing was compared using logistic regression with Generalised Estimating Equations (GEE) and expressed as odds ratios (95% confidence intervals (CIs; P < 0.05)). The occurrence of complications was extracted from surgical records. The i-FACTOR group had 3-times greater odds of partial/full union than those without [adjusted odds ratio (95% CIs, P-value)]: [3.265 (1.032 to 10.330, P = 0.044)]. The i-FACTOR group had 89% partial/full union at 6-weeks, compared to 69% of the non-i-FACTOR group. Half of the patients had leaking of bone graft in the i-FACTOR group versus 10% in the non-i-FACTOR group, 26% of the i-FACTOR group and 12% of the non-i-FACTOR group had neuropraxia of the lateral femoral cutaneous nerve (LFCN). Complication rates were low, and similar between groups. However, the rate of LFCN neuropraxia and bone graft leakage was higher in the i-FACTOR. These findings should be confirmed in a future prospective randomised clinical trial and include outcomes such as pain and quality of life.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Rat model of an autologous cancellous bone graft

Autologous cancellous bone (ACB) grafting is the "gold standard" treatment for delayed bone union. However, small animal models for such grafts are lacking. Here, we developed an ACB graft rat model. Anatomical information regarding the iliac structure was recorded from five rat cadavers (10 ilia). Additionally, 5 and 25 rats were used as controls and ACB graft models, respectively. A defect was created in rat femurs and filled with ACB. Post-graft neo-osteogenic potential was assessed by radiographic evaluation and histological analysis. Iliac bone harvesting yielded the maximum amount of cancellous bone with minimal invasiveness, considering the position of parailiac nerves and vessels. The mean volume of cancellous bone per rat separated from the cortical bone was 73.8 ± 5.5 mm³. Bone union was evident in all ACB graft groups at 8 weeks, and new bone volume significantly increased every 2 weeks (P < 0.001). Histological analysis demonstrated the ability of ACB grafts to act as a scaffold and promote bone union in the defect. In conclusion, we established a stable rat model of ACB grafts by harvesting the iliac bone. This model can aid in investigating ACB grafts and development of novel therapies for bone injury.

Review on material parameters to enhance bone cell function in vitro and in vivo

Bone plays critical roles in support, protection, movement, and metabolism. Although bone has an innate capacity for regeneration, this capacity is limited, and many bone injuries and diseases require intervention. Biomaterials are a critical component of many treatments to restore bone function and include non-resorbable implants to augment bone and resorbable materials to guide regeneration. Biomaterials can vary considerably in their biocompatibility and bioactivity, which are functions of specific material parameters. The success of biomaterials in bone augmentation and regeneration is based on their effects on the function of bone cells. Such functions include adhesion, migration, inflammation, proliferation, communication, differentiation, resorption, and vascularization. This review will focus on how different material parameters can enhance bone cell function both in vitro and in vivo.

Cost-Effectiveness of Peptide Enhanced Bone Graft i-Factor versus Use of Local Autologous Bone in Anterior Cervical Discectomy and Fusion Surgery

Study Design

We conducted decision analytical modeling using a Markov model to determine the ICER of i-factor compared to autograft in ACDF surgery.

Objective

The efficacy and safety of traditional anterior cervical discectomy and fusion (ACDF) surgery has improved with the introduction of new implants and compounds. Cost-effectiveness of these innovations remains an often-overlooked aspect of this effort. To evaluate the cost-effectiveness of i-FACTOR compared to autograft for patients undergoing ACDF surgery.

Methods

The patient cohort was extracted from a prospective, multicenter randomized control trial (RCT) from twenty-two North American centers. Patients randomly received either autograft (N = 154) or i-Factor (N = 165). We analyzed various real-world scenarios, including inpatient and outpatient surgical settings as well as private versus public insurances. Two primary outcome measures were assessed: cost and utility. In the base-case analysis, both health and societal system costs were evaluated. Health-related utility outcome was expressed in quality-adjusted life years (QALYs). Cost-effectiveness was expressed as an incremental cost-effectiveness ratio (ICER).

Results

In all scenarios, i-FACTOR reduced costs within the first year by 1.4% to 2.1%. The savings proved to be incremental over time, increasing to 3.7% over an extrapolated 10 years. The ICER at 90 days was $13,333 per QALY and became negative ("dominated") relative to the control group within one year and onwards. In a threshold sensitivity analysis, the cost of i-FACTOR could theoretically be increased 70-fold and still remain cost-effective.

Conclusion

The novel i-FACTOR is not only cost-effective compared to autograft in ACDF surgery but is the dominant economic strategy.

Collagen Structure-Function Mapping Informs Applications for Regenerative Medicine

Type I collagen, the predominant protein of vertebrates, assembles into fibrils that orchestrate the form and function of bone, tendon, skin, and other tissues. Collagen plays roles in hemostasis, wound healing, angiogenesis, and biomineralization, and its dysfunction contributes to fibrosis, atherosclerosis, cancer metastasis, and brittle bone disease. To elucidate the type I collagen structure-function relationship, we constructed a type I collagen fibril interactome, including its functional sites and disease-associated mutations. When projected onto an X-ray diffraction model of the native collagen microfibril, data revealed a matrix interaction domain that assumes structural roles including collagen assembly, crosslinking, proteoglycan (PG) binding, and mineralization, and the cell interaction domain supporting dynamic aspects of collagen biology such as hemostasis, tissue remodeling, and cell adhesion. Our type III collagen interactome corroborates this model. We propose that in quiescent tissues, the fibril projects a structural face; however, tissue injury releases blood into the collagenous stroma, triggering exposure of the fibrils' cell and ligand binding sites crucial for tissue remodeling and regeneration. Applications of our research include discovery of anti-fibrotic antibodies and elucidating their interactions with collagen, and using insights from our angiogenesis studies and collagen structure-function model to inform the design of super-angiogenic collagens and collagen mimetics.

Clinical effectiveness of anorganic bovine-derived hydroxyapatite matrix/cell-binding peptide grafts for regeneration of periodontal defects: a systematic review and meta-analysis

Aim: To ascertain clinical effectiveness of anorganic bovine-derived hydroxyapatite matrix/cell-binding peptide (ABM/P-15) for regeneration of periodontal defects. Materials & methods: Electronic databases (National Library of Medicine [Medline by PubMed], Cochrane Library [Wiley], CINAHL [EBSCO] and Medline [EBSCO]) were systematically searched up to December 2019. Randomized controlled clinical trials comparing ABM/P-15 grafts to conventional surgery for intrabony and gingival recession defects were included and evaluated intrabony defects including clinical attachment level (CAL), probing depth and gingival recession. Results: A significant gain in CAL (1.37 mm), and reduction in probing depth (1.22 mm) were shown by ABM/P-15 grafts than open flap debridement (p < 0.00001). The subgroup analysis also showed better results for ABM/P-15 grafts in CAL gain for intrabony defects. For furcation and gingival recession defects, no significant difference was seen. Conclusion: The adjunct use of ABM/P-15 grafts in conventional periodontal surgery is useful for periodontal regeneration of intrabony defects.

Autogenous Tooth Bone Graft and Simvastatin Combination Effect on Bone Healing

OBJECTIVE

Autogenous tooth bone grafts (ATGM) are materials prepared from extracted teeth and have been used for bone augmentation. These graft materials are known to have similar structures and components to bone grafts. In this sense, this study aimed to evaluate all the tooth layers mixed with simvastatin without any demineralization process effect on bone formation.

METHODS

In 60 Wistar albino rats, a standardized 6.0 m-diameter critical size bone defect was created in their calvarium. The study consists of 1 control and 4 experimental groups. In the control group (12 rats), the defects were left empty. The defects were grafted only with ATGM in Group 1, with ATGM mixed with simvastatin in Group 2, autogenous bone graft mixed with simvastatin in Group 3, and with xenogenic bone graft mixed with simvastatin in Group 4. The animals were sacrificed at the 7th and 28th days after operation.

RESULTS

PCR, micro CT and histological results show that bone formation was enhanced in the experimental groups in comparison to the control group. Group 1 and Group 2 had similar bone formation rate when compared to Group 3 and Group 4 at the 28th day after operation.

CONCLUSION

This study concludes that mineralized teeth may be used for defect reconstruction without any demineralization process. Autogenous mineralized tooth bone graft should be mixed with simvastatin for bone regeneration like other grafts.

Peptides and pseudopeptide ligands: a powerful toolbox for the affinity purification of current and next-generation biotherapeutics

Following the consolidation of therapeutic proteins in the fight against cancer, autoimmune, and neurodegenerative diseases, recent advancements in biochemistry and biotechnology have introduced a host of next-generation biotherapeutics, such as CRISPR-Cas nucleases, stem and car-T cells, and viral vectors for gene therapy. With these drugs entering the clinical pipeline, a new challenge lies ahead: how to manufacture large quantities of high-purity biotherapeutics that meet the growing demand by clinics and biotech companies worldwide. The protein ligands employed by the industry are inadequate to confront this challenge: while featuring high binding affinity and selectivity, these ligands require laborious engineering and expensive manufacturing, are prone to biochemical degradation, and pose safety concerns related to their bacterial origin. Peptides and pseudopeptides make excellent candidates to form a new cohort of ligands for the purification of next-generation biotherapeutics. Peptide-based ligands feature excellent target biorecognition, low or no toxicity and immunogenicity, and can be manufactured affordably at large scale. This work presents a comprehensive and systematic review of the literature on peptide-based ligands and their use in the affinity purification of established and upcoming biological drugs. A comparative analysis is first presented on peptide engineering principles, the development of ligands targeting different biomolecular targets, and the promises and challenges connected to the industrial implementation of peptide ligands. The reviewed literature is organized in (i) conventional (α-)peptides targeting antibodies and other therapeutic proteins, gene therapy products, and therapeutic cells; (ii) cyclic peptides and pseudo-peptides for protein purification and capture of viral and bacterial pathogens; and (iii) the forefront of peptide mimetics, such as β-/γ-peptides, peptoids, foldamers, and stimuli-responsive peptides for advanced processing of biologics.

Comparing bone tissue engineering efficacy of HDPSCs, HBMSCs on 3D biomimetic ABM-P-15 scaffolds in vitro and in vivo

Human bone marrow mesenchymal stem cells (HBMSCs) has been the gold standard for bone regeneration. However, the low proliferation rate and long doubling time limited its clinical applications. This study aims to compare the bone tissue engineering efficacy of human dental pulp stem cells (HDPSCs) with HBMSCs in 2D, and 3D anorganic bone mineral (ABM) coated with a biomimetic collagen peptide (ABM-P-15) for improving bone-forming speed and efficacy in vitro and in vivo. The multipotential of both HDPSCs and HBMSCs have been compared in vitro. The bone formation of HDPSCs on ABM-P-15 was tested using in vivo model. The osteogenic potential of the cells was confirmed by alkaline phosphatase (ALP) and immunohistological staining for osteogenic markers. Enhanced ALP, collagen, lipid droplet, or glycosaminoglycans production were visible in HDPSCs and HBMSCs after osteogenic, adipogenic and chondrogenic induction. HDPSC showed stronger ALP staining compared to HBMSCs. Confocal images showed more viable HDPSCs on both ABM-P-15 and ABM scaffolds compared to HBMSCs on similar scaffolds. ABM-P-15 enhanced cell attachment/spreading/bridging formation on ABM-P-15 scaffolds and significantly increased quantitative ALP specific activities of the HDPSCs and HBMSCs. After 8 weeks in vivo implantation in diffusion chamber model, the HDPSCs on ABM-P-15 scaffolds showed extensive high organised collagenous matrix formation that was positive for COL-I and OCN compared to ABM alone. In conclusion, the HDPSCs have a higher proliferation rate and better osteogenic capacity, which indicated the potential of combining HDPSCs with ABM-P-15 scaffolds for improving bone regeneration speed and efficacy.

Randomized double blind clinical trial of ABM/P-15 versus allograft in noninstrumented lumbar fusion surgery

BACKGROUND CONTEXT

Due to poor bone stock in the elderly, a noninstrumented fusion is commonly performed in Scandinavia when instability is present. Allograft bone is often used as graft extender with consequent low fusion rates. The use of 15 amino acid residue (ABM/P-15) has shown superior fusion rates in dental and cervical spinal surgery but no clinical studies have been conducted in noninstrumented lumbar fusion surgery.

PURPOSE

To evaluate patient reported outcomes (PROs) and the intertransverse fusion rate in noninstrumented posterolateral fusion with either ABM/P-15 or allograft.

STUDY DESIGN

Double-blind randomized clinical trial.

PATIENT SAMPLE

Patients 60 years or older with degenerative spondylolisthesis undergoing decompression and noninstrumented posterolateral fusion.

OUTCOME MEASURES

Visual analog scales for back and leg pain, Oswestry Disability Index and EuroQoL-5D.

METHODS

One hundred one patients were enrolled in the study and randomized 1:1 to either ABM/P-15 (mixed 50/50, 5cc/level) or allograft bone (30 g/level), both mixed with local bone graft. PROs were collected at baseline and at 12 and 24 months after surgery. The patients underwent 1-year postoperative fine cut computed tomography-scans (0.9 mm) with reconstructions, independently evaluated by three reviewers. Fusion status was concluded by consensus of two of the three as "fusion" or "no fusion."

RESULTS

There were 49 patients available for analysis in both cohorts. The two groups were similar in terms of sex distribution, age, and number of levels fused. The fusion rate was significantly higher in the ABM/P-15 group with 50% fused compared with 20% in the allograft group. PROs at baseline and at all follow-up time points were similar between the two groups.

CONCLUSIONS

Patients undergoing noninstrumented posterolateral fusion augmented with ABM/P-15 had a statistically significantly higher fusion rate compared with allograft when evaluated with postoperative fine cut computed tomography-scans (0.9 mm) with reconstructions. However, this did not translate to better clinical outcomes.

Evaluation of New Bone Formation Using Autogenous Tooth Bone Graft Combined with Platelet-Rich Fibrin in Calvarial Defects

The purpose of the present study was to evaluate the contributions of autogenous tooth bone graft (ATBG) combined with platelet-rich fibrin (PRF) on new bone formation and bone morphogenetic protein (BMP)-2 in rabbit calvarial defects. Twelve male New Zealand rabbits were used in this study. Three circular bone defects were prepared in each rabbit with a drill. These defects were divided into 3 groups: control, treated with ATBG, and treated with ATBG+PRF. The animals were sacrificed at 28 days. Samples were evaluated by histomorphometric analyses and total augmented area, new bone area and bone density were calculated. In addition, expression of BMP-2 was determined by immunohistochemical staining. The total augmented area, new bone area and bone density were significantly greater in the ATBG group than in the control group (P <0.05). Also, these values were significantly higher in the ATBG+PRF group than the ATBG group (P <0.05). Test groups demonstrated significantly increased BMP-2 levels compared with the control group (P <0.05). The present study suggested that ATBG combined with PRF significantly increased the new bone formation and enhanced bone healing in cranial defects.

Comparison of synthetic bone graft ABM/P-15 and allograft on uninstrumented posterior lumbar spine fusion in sheep

BACKGROUND

Spinal fusion is a commonly used procedure in spinal surgery. To ensure stable fusion, bone graft materials are used. ABM/P-15 (commercial name i-Factor™ Flex) is an available synthetic bone graft material that has CE approval in Europe. This peptide has been shown to improve bone formation when used in devices with fixation or on bone defects. However, the lack of external stability and large graft size make posterolateral lumbar fusion (PLF) a most challenging grafting procedure. This prospective randomized study was designed to evaluate early spinal fusion rates using an anorganic bovine-derived hydroxyapatite matrix (ABM) combined with a synthetic 15 amino acid sequence (P-15)-ABM/P-15 bone graft, and compared with allograft in an uninstrumented PLF model in sheep. The objective of this study was to assess fusion rates when using ABM/P-15 in uninstrumented posterolateral fusion in sheep.

METHODS

Twelve Texas/Gotland mixed breed sheep underwent open PLF at 2 levels L2/L3 and L4/L5 without fixation instruments. The levels were randomized so that sheep received an ABM graft either with or without P15 coating. Sheep were euthanized after 4.5 months and levels were harvested and evaluated with a micro-CT scanner and qualitative histology. Fusion rates were assessed by 2D sections and 3D reconstruction images and fusion was defined as intertransverse bridging.

RESULTS

There was 68% fusion rate in the allograft group and an extensive migration of graft material was noticed with a fusion rate of just 37% in the ABM/P-15 group. Qualitative histology showed positive osteointegration of the material and good correlation to scanning results.

CONCLUSIONS

In this PLF fusion model, ABM/P15 demonstrated the ability to migrate when lacking external stability. Due to this migration, reported fusion rates were significantly lower than in the allograft group. The use of ABM/P15 as i-Factor™ Flex may be limited to devices with fixation and bone defects.

ISASS Recommendations and Coverage Criteria for Bone Graft Substitutes used in Spinal Surgery

Autologous bone graft remains the gold standard by which bone graft substitutes are compared in spine fusion surgery. The utilization of bone graft substitutes, either as (1) an extender for spinal fusion constructs or (2) an alternative to minimize morbidity while maximizing outcomes, is changing. Moreover, current procedures technology (CPT) code 20939 became effective in 2018 defining bone marrow aspirate for bone grafting, spine surgery only. Changes in the complex landscape of grafting materials have prompted ISASS to provide category guidance for bone graft substitutes by comparing and contrasting US regulatory pathways, mechanisms of action, and supportive clinical evidence for these bone grafting materials.

Enhanced adhesion and proliferation of bone marrow mesenchymal stem cells on β‑tricalcium phosphate modified by an affinity peptide

Mesenchymal stem cells (MSCs) are often used in orthopedic tissue engineering, and bone marrow-derived mesenchymal stem cells (BMSCs) are currently considered the gold standard. One of the most important issues in MSC-based tissue engineering therapy is the low number of MSCs in pathological tissues. Achieving efficient recruitment of MSCs to defective or damaged tissues in vivo has been a difficult hurdle. The aim of the present study was to construct a biomaterial that can effectively recruit BMSCs to facilitate the repair of pathological tissues. So functional β-tricalcium phosphate (β-TCP) was synthesized using the BMSC affinity peptide DPIYALSWSGMA (DPI) adsorbed onto β-TCP through an adsorption/freeze-drying strategy. C57BL/6 mouse-derived BMSCs were seeded onto the DPI peptide-modified β-TCP (β-TCP-DPI); in vitro experiments demonstrated that β-TCP-DPI enhanced BMSC adhesion and proliferation compared with unmodified β-TCP. Results from the present study indicated that functional β-TCP may be used as an ideal scaffold in tissue engineering and in regenerative medicine.

Bone regeneration strategies: Engineered scaffolds, bioactive molecules and stem cells current stage and future perspectives

Bone fractures are the most common traumatic injuries in humans. The repair of bone fractures is a regenerative process that recapitulates many of the biological events of embryonic skeletal development. Most of the time it leads to successful healing and the recovery of the damaged bone. Unfortunately, about 5-10% of fractures will lead to delayed healing or non-union, more so in the case of co-morbidities such as diabetes. In this article, we review the different strategies to heal bone defects using synthetic bone graft substitutes, biologically active substances and stem cells. The majority of currently available reviews focus on strategies that are still at the early stages of development and use mostly in vitro experiments with cell lines or stem cells. Here, we focus on what is already implemented in the clinics, what is currently in clinical trials, and what has been tested in animal models. Treatment approaches can be classified in three major categories: i) synthetic bone graft substitutes (BGS) whose architecture and surface can be optimized; ii) BGS combined with bioactive molecules such as growth factors, peptides or small molecules targeting bone precursor cells, bone formation and metabolism; iii) cell-based strategies with progenitor cells combined or not with active molecules that can be injected or seeded on BGS for improved delivery. We review the major types of adult stromal cells (bone marrow, adipose and periosteum derived) that have been used and compare their properties. Finally, we discuss the remaining challenges that need to be addressed to significantly improve the healing of bone defects.

Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature.

SUMMARY OF BACKGROUND DATA

Ever since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results.

METHODS

A Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes.

RESULTS

A total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes.

CONCLUSIONS

There is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.

In vivo evaluation of biofunctionalized implant surfaces with a synthetic peptide (P-15) and its impact on osseointegration. A preclinical animal study

OBJECTIVES

The overall aim of the study was to investigate a biofunctionalized implant surface with electrochemically deposition of hydroxyapatite and the synthetic peptide (P-15) and its effect on osseointegration.

MATERIAL AND METHODS

Three modified implant types of ANKYLOS^® C/X implants were used; (1) machined implants used as negative control (M, n = 20), (2) implants with the FRIADENT^® plus surface (grit blasted and acid-etched) used as positive control (P, n = 20), and (3) implants with a biomimetic surface consisting of hydroxyapatite and the synthetic 15 aminoacids containing peptide P-15 (BP, n = 40). The implants were randomly inserted in the mandibles of 10 beagle dogs following 4 months after tooth extraction (P1-P4). Three animals were sacrificed 2 and 7 days after implant insertion, respectively, and four animals were sacrificed 6 months post implant insertion. Bone-to-implant contacts (BICs) were analyzed via histomorphometrical analyses at five different region of interests (ROIs); two at the middle part on either side of the implant (ROI 1/4), two at the apical part of the implant at each side (ROI 2/3), and one at the tip of the implant (ROI 5).

RESULTS

All implant surfaces showed a high level of osseointegration and osteoconductivity. The cumulative implant survival rate (CSR) was 93.8%, 100% in the M, 85% in the P, and 95% in the BP group. No statistical difference in BICs at ROI 1/4, 2/3, and 5 could be shown between implant types following 2 and 7 days of healing. BIC values increased in all groups over time. After 6 months of healing the BP group showed superiority in BIC in ROI 2/3 (73.2 ± 15.6%) compared to the P (48.3 ± 10.6%) and M group (66.3 ± 30.2%) with a significant difference between BP and P (P = 0.002).

CONCLUSION

It is hypothesized, that the surface biofunctionalization improves peri-implant bone formation and remodeling, leading to an increased bone-to implant contact. However, within the limitations of the study set-up no benefit in the early phase of osseointegration could be established for dental implants with P-15 containing surface in this study.

Effects of P-15 Peptide Coated Hydroxyapatite on Tibial Defect Repair In Vivo in Normal and Osteoporotic Rats

This study assessed the efficacy of anorganic bone mineral coated with P-15 peptide (ABM/P-15) on tibia defect repair longitudinally in both normal and osteoporotic rats in vivo. A paired design was used. 24 Norwegian brown rats were divided into normal and osteoporotic groups. 48 cylindrical defects were created in proximal tibias bilaterally. Defects were filled with ABM/P-15 or left empty. Osteoporotic status was assessed by microarchitectural analysis. Microarchitectural properties of proximal tibial defects were evaluated at 4 time points. 21 days after surgery, tibias were harvested for histology and histomorphometry. Significantly increased bone volume fraction, surface density, and connectivity were seen in all groups at days 14 and 21 compared with day 0. Moreover, the structure type of ABM/P-15 group was changed toward typical plate-like structure. Microarchitectural properties of ABM/P-15 treated newly formed bones at 21 days were similar in normal and osteoporotic rats. Histologically, significant bone formation was seen in all groups. Interestingly, significantly increased bone formation was seen in osteoporotic rats treated with ABM/P-15 indicating optimized healing potential. Empty defects showed lower healing potential in osteoporotic bone. In conclusion, ABM/P-15 accelerated bone regeneration in osteoporotic rats but did not enhance bone regeneration in normal rats.

Autogenous fresh demineralized tooth graft prepared at chairside for dental implant

BACKGROUND

This study aimed to evaluate the clinical usefulness of autogenous fresh demineralized tooth (auto-FDT) graft prepared at the chairside for alveolar bone grafting during dental implant surgery.

METHODS

In total, 38 patients requiring both tooth extraction (for endodontic or periodontal reasons or third molar extraction) and alveolar bone regeneration for dental implant placement were included. Within 2 h after clean extraction, the teeth were prepared at the chairside to serve as bone graft material. In the same sitting, blocks or chips of this graft material were used to reconstruct defects at the osteotomy site simultaneously with or before implant placement. Twelve months after prosthesis fabrication and placement, the clinical findings and implant success rates were evaluated. Histological studies were randomly conducted for selected cases.

RESULTS

Clinical evaluation showed favorable wound healing with minimal complications and good bone support for the implants. No implant was lost after 12 months of function following prosthetic rehabilitation. Histological examination revealed new bone formation induced by the graft material.

CONCLUSIONS

Chairside preparation of autogenous fresh demineralized teeth after extraction can be a useful alternative to the use of autogenous bone or other graft materials for the immediate reconstruction of alveolar bone defects to facilitate subsequent implant placement.

Prospective analysis of a new bone graft in lumbar interbody fusion: results of a 2- year prospective clinical and radiological study

Background

This study examined the efficacy and safety of bone graft material ABM/P-15 (iFACTOR) for use in posterior lumbar interbody fusion. ABM/P-15 has been used safely for more than a decade in dental applications.

Methods

Forty patients underwent PLIF surgery, with each patient as control. Assessments up to 24 months included radiographs, CT scan, VAS, and ODI. Primary success criteria were fusion and safety.

Results

Intra-cage bridging bone occurred earlier with ABM/P-15 than autograft (97.73% vs. 59.09% at 6 months). On average pain decreased 29 points and function improved 43 points. Radio dense material outside the disk space occurred more frequently with ABM/P-15 than autograft, without clinical consequence.

Conclusions

This study suggests that ABM/P-15 has equal or greater efficacy at 6 and 12 months. Pain improvements exceeded success criteria at all time points. Functional improvement exceeded success criteria at all time points.

Clinical Relevance

This study explores the safety and efficacy of an osteobiologic peptide enhanced bone graft material as a viable alternative to autograft and its attendant risks.

Efficacy of a small cell-binding peptide coated hydroxyapatite substitute on bone formation and implant fixation in sheep

Cylindrical critical size defects were created at the distal femoral condyles bilaterally of eight female adult sheep. Titanium implants with 2-mm concentric gaps were inserted and the gaps were filled with one of the four materials: allograft; a synthetic 15-amino acid cell-binding peptide coated hydroxyapatite (ABM/P-15); hydroxyapatite + βtricalciumphosphate+ Poly-Lactic-Acid (HA/βTCP-PDLLA); or ABM/P-15+HA/βTCP-PDLLA. After nine weeks, bone-implant blocks were harvested and sectioned for micro-CT scanning, push-out test, and histomorphometry. Significant bone formation and implant fixation could be observed in all four groups. Interestingly, the microarchitecture of the ABM/P-15 group was significantly different from the control group. Tissue volume fraction and thickness were significantly greater in the ABM/P-15 group than in the allograft group. Bone formation and bone ingrowth to porous titanium implant were not significantly different among the four groups. The ABM/P-15 group had similar shear mechanical properties on implant fixation as the allograft group. Adding HA/βTCP-PDLLA to ABM/P-15 did not significantly change these parameters. This study revealed that ABM/P-15 had significantly bone formation in concentric gap, and its enhancements on bone formation and implant fixation were at least as good as allograft. It is suggested that ABM/P-15 might be a good alternative biomaterial for bone implant fixation in this well-validated critical-size defect gap model in sheep. Nevertheless, future clinical researches should focus on prospective, randomized, controlled trials in order to fully elucidate whether ABM/P-15 could be a feasible candidate for bone substitute material in orthopedic practices.

AB, Taba Jr. M, Palioto DB, Grisi MFM, Souza SLS. Treatment of Intrabony Defects with Anorganic Bone Matrix/P-15 or Guided Tissue Regeneration in Patients with Aggressive Periodontitis

Intrabony periodontal defects present a particular treatment problem, especially in patients with generalized aggressive periodontitis (G-AgP). Regenerative procedures have been indicated for this clinical situation. The aim of this study was to compare treatment outcomes of intrabony periodontal defects with either anorganic bone matrix/cell binding peptide (ABM/P-15) or guided tissue regeneration (GTR) in patients with G-AgP. Fifteen patients, with two intrabony defects ≥3 mm deep, were selected. Patients were randomly allocated to be treated with ABM/P-15 or GTR. At baseline and at 3 and 6 months after surgery, clinical and radiographic parameters and IL-1β and IL-6 gingival fluid concentrations were recorded. There was a significant probing pocket depth reduction (p<0.001) for both groups (2.27 ± 0.96 mm for ABM/P-15 group and 2.57 ± 1.06 mm for GTR group). Clinical attachment level gain (1.87 ± 0.94 mm for ABM/P-15 group and 2.09 ± 0.88 mm for GTR group) was also observed. There were no statistically significant differences in clinical parameters between the groups. The radiographic bone fill was more expressive in ABM/P-15 group (2.49 mm) than in GTR group (0.73 mm). In subtraction radiographs, the areas representing gain in density were 93.16% of the baseline defect for ABM/P-15 group versus 62.03% in GRT group. There were no statistically significant differences in inter-group and intra-group comparisons with regards to IL-1β and IL-6 quantification. Treatment of intrabony periodontal defects in patients with G-AgP with ABM/P-15 and GTR improved significantly the clinical outcomes. The use of ABM/P-15 promoted a better radiographic bone fill.

Improvement of osteogenic potential of biphasic calcium phosphate bone substitute coated with synthetic cell binding peptide sequences

Purpose

The aim of this study was to evaluate the improvement of osteogenic potential of biphasic calcium phosphate (BCP) bone substitute coated with synthetic cell-binding peptide sequences in a standardized rabbit sinus model.

Methods

Standardized 6-mm diameter defects were created bilaterally on the maxillary sinus of ten male New Zealand white rabbits, receiving BCP bone substitute coated with synthetic cell binding peptide sequences on one side (experimental group) and BCP bone substitute without coating (control group) on the other side. Histologic and histomorphometric analysis of bone formation was carried out after a healing period of 4 or 8 weeks.

Results

Histological analysis revealed signs of new bone formation in both experimental groups (4- and 8-week healing groups) with a statistically significant increase in bone formation in the 4-week healing group compared to the control group. However, no statistically significant difference in bone formation was found between the 8-week healing group and the control group.

Conclusions

This study found that BCP bone substitute coated with synthetic cell-binding peptide sequences enhanced osteoinductive potential in a standardized rabbit sinus model and its effectiveness was greater in the 4-week healing group than in the 8-week healing group.

In vitro and in vivo studies of ePTFE vascular grafts treated with P15 peptide

The purpose of this study is to evaluate the effectiveness of P15 cell-binding peptide treated ePTFE vascular grafts in vitro and in vivo. The P15 peptide was covalently immobilized onto ePTFE vascular grafts by an atmospheric plasma coating method. In vitro cell growth properties were studied using primary human umbilical vein endothelial cells (HUVECs) and primary human umbilical artery smooth muscle cells (HUASMCs). X-ray photoelectron spectroscopy and amino-acid analysis were used to analyze the surface characteristics of the peptide treated and untreated grafts. The cell growth study showed that the P15 peptide effectively promoted the adhesion and proliferation of endothelial cells. 700% more endothelial cells were proliferated on the P15-treated ePTFE grafts compared to the untreated ePTFE controls. In contrast, the P15 peptide was significantly less effective for promoting the adhesion and proliferation of smooth muscle cells than endothelial cells; only about 100% more smooth muscle cells proliferated on the P15-treated samples compared to the untreated control samples. The sheep model was used in the in vivo study. The amount of neointimal hyperplasia present at the arterial and venous sides of the anastomosis and the degree of endothelialization on the luminal surface of the grafts were assessed. Four P15-treated grafts and two control grafts were implanted as arteriovenous grafts between the femoral artery and vein or the carotid artery and jugular vein in two sheep (n = 6). The in vivo study showed that the thickness of the neointimal hyperplasia of untreated grafts was 3-times thicker than that of P15-treated grafts (P < 0.05) at the venous side of the anastomosis. P15-treated grafts also had a higher degree of endothelialization on the graft lumen.

Comparative study on the cellular activities of osteoblast-like cells and new bone formation of anorganic bone mineral coated with tetra-cell adhesion molecules and synthetic cell binding peptide

Purpose

We have previously reported that tetra-cell adhesion molecule (T-CAM) markedly enhanced the differentiation of osteoblast-like cells grown on anorganic bone mineral (ABM). T-CAM comprises recombinant peptides containing the Arg-Gly-Asp (RGD) sequence in the tenth type III domain, Pro-His-Ser-Arg-Asn (PHSRN) sequence in the ninth type III domain of fibronectin (FN), and the Glu-Pro-Asp-Ilu-Met (EPDIM) and Tyr-His (YH) sequence in the fourth fas-1 domain of βig-h3. Therefore, the purpose of this study was to evaluate the cellular activity of osteoblast-like cells and the new bone formation on ABM coated with T-CAM, while comparing the results with those of synthetic cell binding peptide (PepGen P-15).

Methods

To analyze the cell viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed, andto analyze gene expression, northernblot was performed. Mineral nodule formations were evaluated using alizarin red stain. The new bone formations of each group were evaluated using histologic observation and histomorphometrc analysis.

Results

Expression of alkaline phosphatase mRNA was similar in all groups on days 10 and 20. The highest expression of osteopontin mRNA was observed in the group cultured with ABM/P-15, followed by those with ABM/T-CAM and ABM on days 20 and 30. Little difference was seen in the level of expression of collagen type I mRNA on the ABM, ABM/T-CAM, and ABM/P-15 cultured on day 20. There were similar growth and proliferation patterns for the ABM/T-CAM and ABM/P-15. The halo of red stain consistent with Ca²⁺ deposition was wider and denser around ABM/T-CAM and ABM/P-15 particles than around the ABM particles. The ABM/T-CAM group seemed to have bone forming bioactivity similar to that of ABM/P-15. A complete bony bridge was seen in two thirds of the defects in the ABM/T-CAM and ABM/P-15 groups.

Conclusions

ABM/T-CAM, which seemed to have bone forming bioactivity similar to ABM/P-15, was considered to serve as effective tissue-engineered bone graft material.

Cooperative effects in differentiation and proliferation between PDGF-BB and matrix derived synthetic peptides in human osteoblasts

Background

Enhancing osteogenic capabilities of bone matrix for the treatment of fractures and segmental defects using growth factors is an active area of research. Recently, synthetic peptides like AC- 100, TP508 or p-15 corresponding to biologically active sequences of matrix proteins have been proven to stimulate bone formation. The platelet-derived growth factor (PDGF) BB has been identified as an important paracrine factor in early bone healing. We hypothesized that the combined use of PDGF-BB with synthetic peptides could result in an increase in proliferation and calcification of osteoblast-like cells.

Methods

Osteoblast-like cell cultures were treated with PDGF and synthetic peptides, singly and as combinations, and compared to non-treated control cell cultures. The cultures were evaluated at days 2, 5, and 10 in terms of cell proliferation, calcification and gene expression of alkaline phosphate, collagen I and osteocalcin.

Results

Experimental findings revealed that the addition of PDGF, p-15 and TP508 and combinations of PDGF/AC-100, PDGF/p-15 and PDGF/TP508 resulted in an increase in proliferating osteoblasts, especially in the first 5 days of cultivation. Proliferation did not significantly differ between single factors and factor combinations (p > 0.05). The onset of calcification in osteoblasts occurred earlier and was more distinct compared to the corresponding control or PDGF stimulation alone. Significant difference was found for the combined use of PDGF/p-15 and PDGF/AC-100 (p < 0.05).

Conclusions

Our findings indicate that PDGF exhibits cooperative effects with synthetic peptides in differentiation and proliferation. These cooperative effects cause a significant early calcification of osteoblast-like cells (p < 0.05). We suggest the combination of synthetic peptides and PDGF as a potential clinical approach for accelerating bone healing or coating osteosynthesis materials.

Evaluation of an anorganic bovine-derived mineral with P-15 hydrogel bone graft: preliminary study in a rabbit cranial bone model

OBJECTIVES

The present investigation aimed to assess the bone-regenerative potential of two formulations of anorganic bovine-derived mineral bound to a P-15 (ABM/P-15) bone graft - the particulate and the hydrogel forms - in a delayed healing rabbit cranial defect model.

MATERIAL AND METHODS

Ten adult male New Zealand White rabbits were used to create two 8 mm transcortical cranial defects per rabbit and each one received randomly the test material (ABM/P-15 carboxymethyl cellulose (CMC)-hydrogel graft), the standard control material (ABM/P-15 particulate graft) or remained empty as a negative control. The defects were allowed to heal for 2 and 4 weeks. Qualitative and quantitative histological outcomes were assessed on undecalcified sections.

RESULTS

In the defects grafted with the test material, at both time points, there was a marked random migration of the bone substitute particles. As a consequence, the space maintenance provision was lost and new bone formation was reduced compared with the control particulate graft material. The histomorphometric analysis showed that the control material attained better results, with an average of 13.8 ± 1.9% and 18.2 ± 4.4% of new bone at 2 and 4 weeks, compared with 8.5 ± 2.4% and 13 ± 2.9% for the test material. These differences were significant at 2 weeks (P ≤ 0.05), but not at 4 weeks (P>0.05). Additionally, there was a significant difference in the total area of mineralized tissue (new bone plus particles), favoring the standard control over the test material: 43.2 ± 14.4% vs. 14.2 ± 5.3% at 2 weeks and 56.9 ± 4.2% vs. 24.2 ± 9.6% at 4 weeks, respectively.

CONCLUSIONS

The test ABM/P-15 CMC-hydrogel graft material behaved in this animal model by migration of the graft particles, what determined an unpredictable osseoconduction and, consequently, a decreased quality and quantity of bone regeneration as compared with the osseopromotive behavior exhibited by the standard particulate form of the ABM/P-15 control graft. It is therefore suggested to restrain the application of the hydrogel graft form in non-contained anatomical bone defects.

Construction of Biomimetic Environments with A Synthetic Peptide Analogue of Collagen

The flow of chemical and mechanical signals among cells, and between cells and their environment plays a crucial role in cell differentiation and morphogenesis. In tissues, type I collagen serves as the template for cell anchorage and migration, and it mediates the flux of regulatory signals via highly specific receptors. Cells respond to mechanical cues by secreting growth factors and remodeling their surrounding matrix in an exquisitely orchestrated spatial and temporal program of matrix turnover and organization. Cellular tractional forces contribute to the organization and orientation of the newly synthesized matrix, establishing the template for subsequent morphogenesis. The junction between cells and collagen plays a key role in cell differentiation, morphogenesis and tissue remodeling. An optimal biomimetic environment would emulate this pathway for the exchange of stimuli. To achieve this goal, we have constructed templates which place cells in apposition to P-15, a synthetic peptide ligand for collagen receptors. These environments prompted 3-D colony formation, induced increased osteogenic differentiation, and the deposition of highly oriented and organized matrix by human dermal and gingival fibroblasts and by osteoblast like HOS cells. These observations support our concept for biomimetic environments for tissue engineering.

Small peptide (P-15) bone substitute efficacy in a rabbit cancellous bone model

P-15 is a synthetic 15-amino acid residue identical to the cell binding domain of type I collagen. P-15 can be adsorbed onto anorganic bovine bone mineral (ABM) and will enhance cell attachment and subsequent cell activation. Although ABM/P-15 has been studied as a bone graft substitute in the oral cavity, its use in orthopedic models has been limited. Thus, this study investigated the efficacy of ABM/P-15 treatment in a rabbit model of long bone cancellous healing. Defects were created in the distal femurs and proximal medial tibiae of rabbits and were filled with either ABMP/P-15 suspended in hydrogel, ABM alone suspended in hydrogel, hydrogel carrier alone, or no graft material. Rabbits were sacrificed at 1, 2, 4, or 8 weeks postsurgery, and the femurs and tibiae were harvested. Histomorphometric analyses indicated that defects treated with ABM/P-15 had significantly larger areas of new bone formation than the other three treatments at 2 and 8 weeks postsurgery. ABM/P-15 treated defects also had significantly more bone growth than defects left empty or filled with ABM alone at 4 weeks postsurgery. Furthermore, histological examination did not reveal acute inflammatory infiltrate cells in any of the treatment conditions. These results are consistent with the findings of ABM/P-15 use in human oral-maxillofacial studies and in large animal spine fusion models.

Ridge preservation with acellular dermal matrix and anorganic bone matrix cell-binding peptide P-15 after tooth extraction in humans

BACKGROUND

Preventing ridge collapse with the extraction of maxillary anterior teeth is vital to an esthetic restorative result. Several regenerative techniques are available and are used for socket preservation. The aim of this study is to analyze by clinical parameters the use of acellular dermal matrix (ADM) and anorganic bovine bone matrix (ABM) with synthetic cell-binding peptide P-15 to preserve alveolar bone after tooth extraction.

METHODS

Eighteen patients in need of extraction of maxillary anterior teeth were selected and randomly assigned to the test group (ADM plus ABM/P-15) or the control group (ADM only). Clinical measurements were recorded initially and at 6 months after ridge-preservation procedures.

RESULTS

In the clinical measurements (external vertical palatal measurement [EVPM], external vertical buccal measurement [EVBM], and alveolar horizontal measurement [AHM]) the statistical analysis showed no difference between test and control groups initially and at 6 months. The intragroup analysis, after 6 months, showed a statistically significant reduction in the measurements for both groups. In the comparison between the two groups, the differences in the test group were as follows: EVPM = 0.83 ± 1.53 mm; EVBM = 1.20 ± 2.02 mm; and AHM = 2.53 ± 1.81 mm. The differences in the control group were as follows: EVPM = 0.87 ± 1.13 mm; EVBM = 1.50 ± 1.15 mm; and AHM = 3.40 ± 1.39 mm. The differences in EVPM and EVBM were not statistically significant; however, in horizontal measurement (AHM), there was a statistically significant difference (P<0.05).

CONCLUSION

The results of this study show that ADM used as membrane associated with ABM/P-15 can be used to reduce buccal-palatal dimensions compared to ADM alone for preservation of the alveolar ridge after extraction of anterior maxillary teeth.

Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model

A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies.

Synthesis, characterization, and remodeling of weight-bearing allograft bone/polyurethane composites in the rabbit

The process of bone healing requires the restoration of both anatomy and physiology, and there is a recognized need for innovative biomaterials that facilitate remodeling throughout this complex process. While porous scaffolds with a high degree of interconnectivity are known to accelerate cellular infiltration and new bone formation, the presence of pores significantly diminishes the initial mechanical properties of the materials, rendering them largely unsuitable for load-bearing applications. In this study, a family of non-porous composites has been fabricated by reactive compression molding of mineralized allograft bone particles (MBPs) with a biodegradable polyurethane (PUR) binder, which is synthesized from a polyester polyol and a lysine-derived polyisocyanate. At volume fractions exceeding the random close-packing limit, the particulated allograft component presented a nearly continuous osteoconductive pathway for cells into the interior of the implant. By varying the molecular weight of the polyol and manipulating the surface chemistry of the MBP via surface demineralization, compressive modulus and strength values of 3-6 GPa and 107-172 MPa were achieved, respectively. When implanted in bilateral femoral condyle plug defects in New Zealand White rabbits, MBP/PUR composites exhibited resorption of the allograft and polymer components, extensive cellular infiltration deep into the interior of the implant, and new bone formation at 6 weeks. While later in vivo timepoints are necessary to determine the ultimate fate of the MBP/PUR composites, these observations suggest that allograft bone/polymer composites have potential for future development as weight-bearing devices for orthopedic applications.

The bone formation capabilities of the anorganic bone matrix-synthetic cell-binding peptide 15 grafts in an animal periodontal model: a histologic and histomorphometric study in dogs

BACKGROUND

The aim of this study is to verify the regenerative potential of particulate anorganic bone matrix-synthetic peptide-15 (ABM-P-15) in class III furcation defects associated or not with expanded polytetrafluoroethylene membranes.

METHODS

Class III furcation defects were produced in the mandibular premolars (P2, P3, and P4) of six dogs and filled with impression material. The membranes and the bone grafts were inserted into P3 and P4, which were randomized to form the test and control groups, respectively; P2 was the negative control group. The animals were sacrificed 3 months post-treatment.

RESULTS

Histologically, the complete closure of class III furcation defects was not observed in any of the groups. Partial periodontal regeneration with similar morphologic characteristics among the groups was observed, however, through the formation of new cementum, periodontal ligament, and bone above the notch. Histologic analysis showed granules from the bone graft surrounded by immature bone matrix and encircled by newly formed tissue in the test group. The new bone formation area found in the negative control group was 2.28 + or - 2.49 mm(2) and in the test group it was 6.52 + or - 5.69 mm(2), which showed statistically significant differences for these groups considering this parameter (Friedman test P <0.05). There was no statistically significant difference among the negative control, control, and test groups for the other parameters.

CONCLUSIONS

The regenerative potential of ABM-P-15 was demonstrated through new bone formation circumscribing and above the graft particles. The new bone also was accompanied by the formation of new cementum and periodontal ligament fibers.

Comparison of cellular response to anorganic bone matrix/cell binding peptide and allogenic cranial bone after sinus augmentation in rhesus monkeys

This study compared cellular responses of maxillary sinuses after augmentation with anorganic bovine-derived hydroxyapatite matrix linked to the cell binding polypeptide P-15 (ABM/P-15) or PepGen P-15 and allogenic freeze-dried cranial bone slabs. Five adult Macaque fascicularis monkeys were used. On one side, the floor of the sinus was augmented with ABM/P-15, while the other side was augmented with 2 cranial bone slabs. Trephine bone biopsies were obtained 6, 12, and 24 weeks postgrafting. Animals were sacrificed 8 months after grafting. Soft X-ray microradiography was used to determine bone density. The volume fraction (Vv) of regenerated bone, the number of mesenchymal cells, and the numbers of proliferating cell nuclear antigen (PCNA)- and alkaline phosphatase-positive cells at different augmentation sites were measured and compared. Basal bone heights were calculated at surgery and compared with total heights of the augmented sinus floors 8 months postgrafting. Bone formation, number of mesenchymal cells, PCNA index, and alkaline phosphatase index were significantly higher for the ABM/P-15 side than for the allogenic bone-augmented side. Both sides ended with a significant increase in bone height. The PCNA index decreased significantly over time (P < .05), while the alkaline phosphatase index increased significantly (P < .05) over time on both sides. Both graft materials have led to significant augmentation of the floor of the maxillary sinus with new bone; however, new bone formation and maturation were faster on the ABM/P-15 sites.

Physicochemical characterization of biomaterials commonly used in dentistry as bone substitutes--comparison with human bone

The present work focuses on the physicochemical characterization of selected mineral-based biomaterials that are frequently used in dental applications. The selected materials are commercially available as granules from different biological origins: bovine, porcine, and coralline. Natural and calcined human bone were used for comparison purposes. Besides a classical rationalization of chemical composition and crystallinity, a major emphasis was placed on the measurement of various morphostructural properties such as particle size, porosity, density, and specific surface area. Such properties are crucial to acquiring a full interpretation of the in vivo performance. The studied samples exhibited distinct particle sizes (between 200 and 1000 microm) and shapes. Mercury intrusion revealed not only that the total sample porosity varied considerably (33% for OsteoBiol, 50% for PepGen P-15, and 60% for BioOss) but also that a significant percentage of that porosity corresponded to submicron pores. Biocoral was not analyzed by this technique as it possesses larger pores than those of the porosimeter upper limit. The density values determined for the calcined samples were close to the theoretical values of hydroxyapatite. However, the values for the collagenated samples were lower, in accordance with their lower mineral content. The specific surface areas ranged from less than 1 m(2)/g (Biocoral) up to 60 m(2)/g (BioOss). The chemical and phase composition of most of the samples, the exception being Biocoral (aragonite), were hydroxyapatite based. Nonetheless, the samples exhibited different organic material content as a consequence of the distinct heat treatments that each had received.

Organic / inorganic bioactive materials Part I: Synthesis, structure and in vitro assessment of collagen/silicocarnotite biocoatings

The silicocarnotite, as an inorganic part of the coatings, has been synthesized using a polystep sol-gel method. The chemical composition of the prepared silicocarnotite sol is described as 58.12 CaO, 29.42 P2O5, 12.45 SiO2 (wt%), where Ca/P+Si = 1,67. The acid soluble type I collagen, as an organic part of the obtained coatings, was mixed with silicocarnotite powder in a weight ratio of 25:75 and 75:25 weight ratio without cross-linkage. The acidity of the obtained mixture was readjust with 25% NH4OH to pH = 9.0. The mixture was then dried at 37°C for 12 h.

The growth of B-type carbonate containing hydroxyapatite (B-type CO3HA) in which CO3 2+→PO4 3− on the surface of collagen/silicocarnotite coatings soaked in 1.5 simulated body fluid (1.5 SBF) was observed. The nucleation of B-type CO3HA was estimated on the obtained coatings after 3 days immersion in 1.5 SBF. The negatively charged carboxylate groups from the collagen surface may be responsible for the HA deposition. This was confirmed by the “red shift” of carboxylate groups of collagen molecules in the FTIR spectra. After soaking in 1.5 SBF, the morphology of prepared coatings and HA formation was observed by SEM.

ABM/P-15 modulates proliferation and mRNA synthesis of growth factors of periodontal ligament cells

OBJECTIVE

Periodontal regeneration is histologically defined as regeneration of the tooth supporting structures, including alveolar bone, periodontal ligament, and cementum. Cells in the remaining periodontal tissues need optimal conditions if they are to perform their functions in the regeneration process. The present study is an investigation of the molecular effects of ABM/P-15 on human periodontal ligament cells (PDL) in vitro.

MATERIAL AND METHODS

PDL cells obtained from healthy subjects were used for in vitro experiments. Cell proliferation, morphology, and mineralization using Von kossa staining were evaluated. mRNA expressions for transforming growth factor-beta (TGF-beta), insulin-like growth factor-I (IGF-I), basic fibroblast growth factor (b-FGF), vascular endothelial growth factor (VEGF), bone morphogenic protein-2 (BMP-2), platelet-derived growth factor (PDGF), and type 1 collagen (COL1) were assessed on days 3 and 7 using RT-PCR.

RESULTS

ABM/P-15 enhanced proliferation of cultured PDL cells. It increased the mRNA expression of TGF-beta and BMP-2 in cultured PDL cells on days 3 and 7. IGF-I and b-FGF mRNA expressions showed a slight decrease, while PDGF expression was observed to have increased on day 3. VEGF and COL1 mRNA expressions were found not to be different on days 3 and 7. No differences were observed in the mineralization properties of cultured PDL cells treated with or without ABM/P-15.

CONCLUSIONS

Based on the results of this in vitro study, it may be concluded that ABM/P-15 enhanced the regenerative capacity of PDL by regulating specific gene expressions of cells during early wound healing.

The induction of bone formation by coral-derived calcium carbonate/hydroxyapatite constructs

The spontaneous induction of bone formation in heterotopic rectus abdominis and orthotopic calvarial sites by coral-derived biomimetic matrices of different chemical compositions was investigated in a long-term study in the non-human primate Papio ursinus. Coral-derived calcium carbonate constructs were converted to hydroxyapatite by hydrothermal exchange. Limited conversion produced hydroxyapatite/calcium carbonate (HA/CC) constructs of 5% and 13% hydroxyapatite. Rods of 20 mm in length and 7 mm in diameter were implanted in heterotopic rectus abdominis sites; discs 25 mm in diameter were implanted in orthotopic calvarial defects of six adult non-human primates P. ursinus. Heterotopic samples also included fully converted hydroxyapatite replicas sintered at 1100 degrees C. To further enhance spontaneous osteoinductive activity, fully converted hydroxyapatite replicas were coated with the synthetic peptide P15 known to increase the adhesion of fibroblasts to anorganic bovine mineral. Bone induction was assessed at 60, 90 and 365 days by histological examination, alkaline phosphatase and osteocalcin expression, as well as by the expression of BMP-7, GDF-10 and collagen type IV mRNAs. Induction of bone occurred in the concavities of the matrices at all time points. At 365 days, bone marrow was evident in the P15-coated and uncoated implants. Resorption of partially converted calcium carbonate/hydroxyapatite was apparent, as well as remodeling of the newly formed bone. Northern blot analyses of samples from heterotopic specimens showed high levels of expression of BMP-7 and collagen type IV mRNA in all specimen types at 60 days, correlating with the induction of the osteoblastic phenotype in invading fibrovascular cells. Orthotopic specimens showed prominent bone formation across the different implanted constructs. The concavities of the matrices biomimetize the remodeling cycle of the osteonic primate cortico-cancellous bone and promote the ripple-like cascade of the induction of bone formation. This study demonstrates for the first time that partially converted HA/CC constructs also induce spontaneous differentiation of bone, albeit only seen one year post-implantation.