The effect of Emdogain and platelet-derived growth factor on the osteoinductive potential of hydroxyapatite tricalcium phosphate

Combination of enamel matrix derivative and hyaluronic acid inhibits lipopolysaccharide-induced inflammatory response on human epithelial and bone cells

Objectives

The aim of this study was to evaluate the in vitro effect of enamel matrix derivative (EMD) and hyaluronic acid (HA) and their synergistic combination on lipopolysaccharides (LPS)-induced inflammation in human keratinocytes and osteoblasts.

Material and methods

Cells were challenged with LPS (1 μg/ml) and cultured in the following treatment groups with EMD (30 mg/ml) and HA (30 mg/ml): LPS, EMD, HA, EMD + HA, EMD + LPS, HA + LPS, and EMD + HA + LPS. Cell viability, inflammatory cytokine expression, and cell migration were determined using colorimetric assay, quantitative real-time polymerase chain reaction (qPCR), and scratch wound healing assay, respectively.

Results

Cell viability was decreased when exposed to LPS compared to the controls. Overall, LPS treatment expressed upregulation on inflammatory cytokine tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6). EMD and HA reduced up to 3.0-fold the cytokine expression caused by LPS (p < 0.05). EMD and HA statistically induced higher migration in osteoblasts and keratinocytes, respectively. Migration was impaired by LPS, whereas it significantly increased after addition of EMD and HA.

Conclusions

EMD and HA are advantageous biomaterials that individually generate strong directional migratory keratinocyte and osteoblast response. Their combination also enhances cell viability, and anti-inflammatory and migratory abilities to promote healing specially under LPS inflammatory stimulus. Future in vivo and animal research is necessary to further characterize the effect of EMD and HA on periodontal regeneration.

Clinical relevance

The use of EMD in conjunction with HA resulted in a reduction of inflammation and improvement of tissue healing at wound sites. Both biomaterials combined may potentially improve the effectiveness of bone regeneration in periodontal bone defects, pointing to the potential clinical relevance of both materials in regenerative periodontal surgery.

The Role of Growth Factors in Bioactive Coatings

With increasing obesity and an ageing population, health complications are also on the rise, such as the need to replace a joint with an artificial one. In both humans and animals, the integration of the implant is crucial, and bioactive coatings play an important role in bone tissue engineering. Since bone tissue engineering is about designing an implant that maximally mimics natural bone and is accepted by the tissue, the search for optimal materials and therapeutic agents and their concentrations is increasing. The incorporation of growth factors (GFs) in a bioactive coating represents a novel approach in bone tissue engineering, in which osteoinduction is enhanced in order to create the optimal conditions for the bone healing process, which crucially affects implant fixation. For the application of GFs in coatings and their implementation in clinical practice, factors such as the choice of one or more GFs, their concentration, the coating material, the method of incorporation, and the implant material must be considered to achieve the desired controlled release. Therefore, the avoidance of revision surgery also depends on the success of the design of the most appropriate bioactive coating. This overview considers the integration of the most common GFs that have been investigated in in vitro and in vivo studies, as well as in human clinical trials, with the aim of applying them in bioactive coatings. An overview of the main therapeutic agents that can stimulate cells to express the GFs necessary for bone tissue development is also provided. The main objective is to present the advantages and disadvantages of the GFs that have shown promise for inclusion in bioactive coatings according to the results of numerous studies.

Osteoinductivity and biomechanical assessment of a 3D printed demineralized bone matrix-ceramic composite in a rat spine fusion model

We recently developed a recombinant growth factor-free bone regenerative scaffold composed of stoichiometric hydroxyapatite (HA) ceramic particles and human demineralized bone matrix (DBM) particles (HA-DBM). Here, we performed the first pre-clinical comparative evaluation of HA-DBM relative to the industry standard and established positive control, recombinant human bone morphogenetic protein-2 (rhBMP-2), using a rat posterolateral spinal fusion model (PLF). Female Sprague-Dawley rats underwent bilateral L4-L5 PLF with implantation of the HA-DBM scaffold or rhBMP-2. Fusion was evaluated using radiography and blinded manual palpation, while biomechanical testing quantified the segmental flexion-extension range-of-motion (ROM) and stiffness of the fused segments at 8-weeks postoperatively. For mechanistic studies, pro-osteogenic gene and protein expression at 2-days and 1-, 2-, and 8-weeks postoperatively was assessed with another cohort. Unilateral fusion rates did not differ between the HA-DBM (93%) and rhBMP-2 (100%) groups; however, fusion scores were higher with rhBMP-2 (p = 0.008). Both treatments resulted in significantly reduced segmental ROM (p < 0.001) and greater stiffness (p = 0.009) when compared with non-operated controls; however, the degree of stabilization was significantly higher with rhBMP-2 treatment relative to the HA-DBM scaffold. In the mechanistic studies, PLGA and HA scaffolds were used as negative controls. Both rhBMP-2 and HA-DBM treatments resulted in significant elevations of several osteogenesis-associated genes, including Runx2, Osx, and Alp. The rhBMP-2 treatment led to significantly greater early, mid, and late osteogenic markers, which may be the mechanism in which early clinical complications are seen. The HA-DBM scaffold also induced osteogenic gene expression, but primarily at the 2-week postoperative timepoint. Overall, our findings show promise for this 3D-printed composite as a recombinant growth factor-free bone graft substitute for spinal fusion. STATEMENT OF SIGNIFICANCE: Despite current developments in bone graft technology, there remains a significant void in adequate materials for bone regeneration in clinical applications. Two of the most efficacious bone graft options are the gold-standard iliac crest bone graft and recombinant human-derived bone morphogenetic protein-2 (rhBMP-2), available commercially as Infuse™. Although efficacious, autologous graft is associated with donor-site morbidity, and Infuse™ has known side effects related to its substantial host inflammatory response, possibly associated with a immediate, robust osteoinductive response. Hence, there is a need for a bone graft substitute that provides adequate osteogenesis without associated adverse events. This study represents a significant step in the design of off-the-shelf growth factor-free devices for spine fusion.

In vivo studies on osteoinduction: A systematic review on animal models, implant site, and type and postimplantation investigation

Musculoskeletal diseases involving loss of tissue usually require management with bone grafts, among which autografts are still the gold standard. To overcome autograft disadvantages, the development of new scaffolds is constantly increasing, as well as the number of in vivo studies evaluating their osteoinductivity in ectopic sites. The aim of the present systematic review is to evaluate the last 10 years of osteoinduction in vivo studies. The review is focused on: (a) which type of animal model is most suitable for osteoinduction evaluation; (b) what are the most used types of scaffolds; (c) what kind of post-explant evaluation is most used. Through three websites (www.pubmed.com, www.webofknowledge.com and www.embase.com), 77 in vivo studies were included. Fifty-eight studies were conducted in small animal models (rodents) and 19 in animals of medium or large size (rabbits, dogs, goats, sheep, and minipigs). Despite the difficulty in establishing the most suitable animal model for osteoinductivity studies, small animals (in particular mice) are the most utilized. Intramuscular implantation is more frequent than subcutis, especially in large animals, and synthetic scaffolds (especially CaP ceramics) are preferred than natural ones, also in combination with cells and growth factors. Paraffin histology and histomorphometric evaluations are usually employed for postimplantation analyses.

Tissue reactions after simultaneous alveolar ridge augmentation with biphasic calcium phosphate and implant insertion--histological and immunohistochemical evaluation in humans

OBJECTIVES

Simultaneous lateral augmentation and implant placement is considered as standard procedure in deficient edentulous ridges in oral implantology. Histological studies monitoring osteogenesis after application of alloplastic bone substitutes in humans are scarce. Bone formation upon simultaneous augmentation with biphasic calcium phosphate (BCP) and implantation was histologically investigated after 6 months in situ. The results of this secondary analysis are reported tempting to ascribe specific observations to uneventful submerged healing or compromised healing of soft tissues including occurrence of dehiscences and premature graft exposure.

MATERIALS AND METHODS

Histology of biopsies from lateral, crestal bone augmentations using alloplastic BCP comprising seven sites with compromised, prematurely exposed healing and six sites with uneventful submerged healing was investigated for expression of osteogenic, osteoclastogenic, and angiogenic differentiation markers.

RESULTS

Histology revealed alkaline phosphatase (ALP)-positive osteoblasts and immunoreactivity for osteogenic markers osteocalcin and collagen type I in biopsies with submerged healing, while inflammatory infiltrates and accumulations of multinucleated giant cells around BCP granules were observed in compromised sites. All specimens presented adequate vessel density. Multinucleated giant cells showed inconsistent staining for the osteoclast marker tartrate-resistant acid phosphatase (TRAP).

CONCLUSIONS

The histological findings of this study indicate an osteoconductive nature of the BCP applied. Premature exposure of the bone substitute reduced new bone formation and may bear a risk for inflammatory and foreign body reactions.

CLINICAL RELEVANCE

A predictable appositional bone formation in simultaneously augmented sites using BCP is linked to an uneventful healing process.