Effect of cross-linked vs non-cross-linked collagen membranes on bone: A systematic review.

The aim of this study was to conduct a systematic review to compare the clinical outcomes of two different resorbable collagen membranes in terms of regenerated bone volume, postoperative complications and membrane degradation during bone regeneration procedures. Randomized controlled trials (RCT) or controlled trials (CT) that compared both techniques were reviewed on four electronic databases up to December 2015, a manual search was performed on the bibliography of the collected articles and the authors were contacted for additional references if undetected on the electronic and manual search. Membrane exposure was evaluated as a dichotomous outcome and the statistical unit was the membrane. The results were presented as relative risk (RR) with a 95% confidence interval. Eight RCTs and one CT were included in this study. The majority of the studies depicted a bone augmentation area, which ranged from 46.15% to 94.6% for the non-cross-link membranes and from 44% to 92.6% for the cross-link membranes at the 4-6 month re-entry surgery. From a total of 289 patients, a forest plot concerning the membrane exposure was constructed using the obtained RR of the included studies. The overall RR was 1.43 (95% CI: 0.85-2.39) with no statistically significant differences between the two groups, although with a marginal tendency towards higher exposure in the cross-link membrane group. This systematic review suggests the different membranes present themselves as appropriate for bone regeneration procedures, although cross-link membranes present higher rates of postoperative complications. However, more RCT with higher sample sizes are needed to evaluate the different membranes. The suggested lack of clinical differences between the compared membranes suggest that further cost-benefit ratio, tissue integration and postoperative complication oriented studies should be performed so that clinicians can take a patient-centred, evidence-based decision.

Transcription factor and bone marrow stromal cells in osseointegration of dental implants.

Titanium implants are widely used in dental clinics and orthopaedic surgery. However, bone formation surrounding the implant is relatively slow after inserting the implant. The current study assessed the effects of bone marrow stromal cells (BMSCs) with forced expression of special AT-rich sequence-binding protein 2 (SATB2) on the osseointegration of titanium implants. To determine whether SATB2 overexpression in BMSCs can enhance the osseointegration of implants, BMSCs were infected with the retrovirus encoding Satb2 (pBABE-Satb2) and were locally applied to bone defects before implanting the titanium implants in the mouse femur. Seven and twenty-one days after implantation, the femora were isolated for immunohistochemical (IHC) staining, haematoxylin eosin (H&E) staining, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), and micro-computed tomography (µCT) analysis. IHC staining analysis revealed that SATB2-overexpressing BMSCs were intensely distributed in the bone tissue surrounding the implant. Histological analysis showed that SATB2-overexpressing BMSCs significantly enhanced new bone formation and bone-to-implant contact 3 weeks after implantation. Real-time qRT-PCR results showed that the local delivery of SATB2-overexpressing BMSCs enhanced expression levels of potent osteogenic transcription factors and bone matrix proteins in the implantation sites. µCT analysis demonstrated that SATB2-overexpressing BMSCs significantly increased the density of the newly formed bone surrounding the implant 3 weeks post-operatively. These results conclude that local delivery of SATB2-overexpressing BMSCs significantly accelerates osseointegration of titanium implants. These results provide support for future pharmacological and clinical applications of SATB2, which accelerates bone regeneration around titanium implants.

Structure and function of RGD peptides involved in bone biology.

This review focuses on recent papers that describe the involvement of the RGD sequence in bone biology and incorporate the use of synthetic RGD peptides to develop new drugs or control the bioactivity of materials used for bone regeneration. Because in vivo bone function is completely dependent on angiogenesis and vessels, the present publication is focused on physiology, pathophysiology and therapeutics of RGD peptides dedicated to bone cells and endothelial systems. It appears that alphavbeta3, alphavbeta5 and alphaIIbbeta3 are the integrins most reported to be involved in bone function and RGD sequence binding. The specificity of RGD peptides depends on backbone conformation, orientations of the charged side chains of Arg and Asp residues, and hydrophobic moieties flanking the Asp residue. Despite of recent progress in integrins and RGD peptide structures and function, future work should focus on integrin selectivity of RGD-based agents, model structure and activity-selectivity relationships.