Interrogating the osteogenic potential of implant surfaces in vitro: a review of current assays

The success of implantable devices relies heavily on their interaction with the host cells facilitating the osseointegration process. However, with so many new surface modifications, with subtly varying design parameters, in vitro assays can, with proper interpretation, provide valuable information for understanding cellular behavior. This review brings together pertinent in vitro experimental protocols available to researchers and discusses them in relationship to the development of the osteoblast phenotype during bone repair. Consideration is also paid to the influence of endothelial and macrophage cells that can substantially change osteogenic cell activity and thus can provide added value for predicting the osseointegration potential in vivo. Due to the diverse and heterogeneous nature of cell types available for culture use, this review concludes that there is no “gold standard” series of assays. Rather, we present guidance in the experimental design of in vitro assays to better identify those surfaces with promising osteogenic potential

Oral mucosal lamina propria-progenitor cells exert antibacterial properties via the secretion of osteoprotegerin and haptoglobin

The oral cavity possesses a diverse microflora, yet recurrent infections within healthy individuals are rare. Wound healing within the buccal mucosa is preferential, potentially because of the presence of oral mucosal lamina propria-progenitor cells (OMLP-PCs). In addition to their multipotency, OMLP-PCs demonstrate potent immunosuppressive properties. The present study investigated whether OMLP-PCs possess antibacterial properties, directly interacting with microorganisms and contributing to the maintenance of a balanced oral microflora. Gram-positive and -negative bacteria were cocultured with OMLP-PCs, buccal mucosal fibroblasts, or their respective conditioned media (CM). Bacterial growth was significantly inhibited when cocultured with OMLP-PCs or their CM. No antibacterial activity was apparent within the fibroblasts. Analysis of the OMLP-PC CM indicated constitutive secretion of osteoprotegerin (OPG) and haptoglobin (Hp). Exposure of the bacteria to OPG or Hp demonstrated their differential antibacterial properties, with neutralization/blocking studies confirming that the growth of Gram-positive bacteria was partially restored by neutralizing OPG within OMLP-PC CM; blocking Hp restored the growth of Gram-negative bacteria. The present study demonstrates, for the first time, the broad-spectrum antibacterial properties of OMLP-PCs. We report the direct and constitutive antibacterial nature of OMLP-PCs, with retention of this effect within the CM suggesting a role for soluble factors such as OPG and Hp. Knowledge of the immunomodulatory and antibacterial properties of these cells could potentially be exploited in the development of novel cell- or soluble factor-based therapeutics for the treatment of infectious diseases such as pneumonia or ailments such as chronic nonhealing wounds

Lipopolysaccharide alters decorin and biglycan synthesis in rat alveolar bone osteoblasts: Consequences for bone repair during periodontal disease

A prime pathogenic agent associated with periodontitis is lipopolysaccharide (LPS) derived from Porphyromonas gingivalis. This study investigated the effects of P. gingivalis LPS on osteoblasts, which are responsible for alveolar bone repair. Bone cells were obtained from explants of rat alveolar bone chips and cultured with 0-200 ng ml-1 of P. gingivalis LPS. Porphyromonas gingivalis LPS significantly increased cell proliferation and inhibited osteoblast differentiation, as judged by reduced alkaline phosphatase activity. Analysis of biglycan mRNA and protein levels indicated that P. gingivalis LPS significantly delayed the normally high expression of biglycan during the early stages of culture, which are associated with cell proliferation and early differentiation of progenitor cells. In the presence of P. gingivalis LPS, decorin expression by the alveolar bone cells was reduced during periods of culture relating to collagen fibrillogenesis and mineral deposition. Analysis of glycosaminoglycan chains conjugated to these proteoglycans suggested that in the presence of P. gingivalis LPS, dermatan sulfate persisted within the matrix. This study suggests that P. gingivalis LPS influences the expression and processing of decorin and biglycan in the matrix, altering alveolar bone cell activity and osteoblast phenotype development. The consequences of this altered expression in relation to hindering bone repair as part of the cycle of events during periodontal disease are discussed. © 2008 Eur J Oral Sci

An assessment of early colonisation of implant-abutment metal surfaces by single species and co-cultured bacterial periodontal pathogens

Objective Numerous studies have proposed that smooth metal surfaces reduce initial bacterial attachment in the establishment of an early biofilm formation. However, these studies have largely examined single bacterial species, which are not always relevant as pathogens identified as initiators of inflammatory peri-implantitis. This study investigated the adherence of four periodontally-relevant bacterial species to implant and abutment surfaces in current clinical use. Methods Discs of polished cobalt chromium (CoCr-polished) and milled titanium (Ti-milled), representing two clinically relevant surfaces, were prepared and surfaces were characterised. Bacterial species Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia and Aggregatibacter actinomycetemcomitans were cultured to mid-log or stationary growth phase. Co-cultures of P. gingivalis, F. nucleatum and P. gingivalis, F. nucleatum, Pr. intermedia were similarly prepared. Bacteria were inoculated onto discs for 2 h, stained with a live/dead fluorescent stain and percentage bacterial coverage was calculated by confocal microscopy and image analysis. Results CoCr-polished discs had smooth surfaces with gentle valley structures, whilst Ti-milled discs had sharp edged peaks. Both discs demonstrated a partial wetting ability capable of initiating bacterial adhesion. P. gingivalis, F. nucleatum and co-cultures, at both mid-log and stationary concentrations, demonstrated equally high coverage of both the smooth CoCr-polished and the rougher Ti-milled metal surfaces. Pr. intermedia and A. actinomycetemcomitans demonstrated lower surface coverage which was slightly higher for Ti-milled. Conclusion Variability was noted in the adherence potential for the respective periodontal pathogens examined. Particularly high adherence was noted for P. gingivalis and F. nucleatum, despite the manufacture of a smooth surface. Clinical significance Both surfaces studied may be used at implant-abutment junctions and both possess an ability to establish a bacterial biofilm containing a periodontally-relevant species. These surfaces are thus able to facilitate the apical migration of bacteria associated with peri-implantitis

Parameters controlling octadecyl phosphonic acid self-assembled monolayers on titanium dioxide for anti-fouling biomedical applications

Octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs) have demonstrated potential for deterring bacterial attachment to titanium, however the coating process is time consuming and uses toxic solvents. In this study, ODPA SAM quantity, quality, and structure were evaluated on titanium quartz crystal microbalance (QCM) sensors by varying solvent type (anisole or cyclopentyl methyl ether (CPME), environmentally friendly non-polar solvents); ODPA concentration (0.5 mM or 1 mM); and temperature (21 °C or 60 °C). Surfaces were characterised using QCM frequency and dissipation measurements and Sauerbrey mass calculations; X-ray photoelectron spectroscopy; water contact angle measurements; and temperature-programmed desorption mass spectrometry (TPD-MS). Anti-fouling ability was established against Staphylococcus aureus. Incubation in 0.5 mM ODPA in CPME at 21 °C rapidly formed uniform rigid ODPA SAMs as demonstrated by high Sauerbrey mass (≈285-290 ng/cm2), viscoelastic modelling, high atomic percentage surface phosphorus (1.1 %) and high water contact angles (117.6 ± 2.5°), consistent across the entire sample surface. High temperatures or the use of anisole resulted in suspected multilayer formation, which reduced bacterial attachment. TPD-MS confirmed covalent bonding of ODPA SAMs on TiO2 at ≈ 110–120 °C and thermal stability below 300 °C. This study demonstrates the key parameters that control ODPA SAM formation on titanium and their future potential for biomedical applications

Effects of eight neuropsychiatric copy number variants on human brain structure

Many copy number variants (CNVs) confer risk for the same range of neurodevelopmental symptoms and psychiatric conditions including autism and schizophrenia. Yet, to date neuroimaging studies have typically been carried out one mutation at a time, showing that CNVs have large effects on brain anatomy. Here, we aimed to characterize and quantify the distinct brain morphometry effects and latent dimensions across 8 neuropsychiatric CNVs. We analyzed T1-weighted MRI data from clinically and non-clinically ascertained CNV carriers (deletion/duplication) at the 1q21.1 (n = 39/28), 16p11.2 (n = 87/78), 22q11.2 (n = 75/30), and 15q11.2 (n = 72/76) loci as well as 1296 non-carriers (controls). Case-control contrasts of all examined genomic loci demonstrated effects on brain anatomy, with deletions and duplications showing mirror effects at the global and regional levels. Although CNVs mainly showed distinct brain patterns, principal component analysis (PCA) loaded subsets of CNVs on two latent brain dimensions, which explained 32 and 29% of the variance of the 8 Cohen’s d maps. The cingulate gyrus, insula, supplementary motor cortex, and cerebellum were identified by PCA and multi-view pattern learning as top regions contributing to latent dimension shared across subsets of CNVs. The large proportion of distinct CNV effects on brain morphology may explain the small neuroimaging effect sizes reported in polygenic psychiatric conditions. Nevertheless, latent gene brain morphology dimensions will help subgroup the rapidly expanding landscape of neuropsychiatric variants and dissect the heterogeneity of idiopathic conditions

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Is there anything to be gained by augmenting the implant surface?

Titanium implants are widely considered as a great success story in dentistry, with a 95% survival rate after five years. However, a vast amount of research continues to augment the titanium surface for better osseointegration. This paper sets out to define our current research goals for implant dentistry and to consider the scientific merits of approaches to surface modifications

Dental pulp stem cells: what, where, how?

International Journal of Paediatric Dentistry 2009; 19: 61-70 It is now accepted that progenitor/stem cells reside within the post-natal dental pulp. Studies have identified several niches of multipotent mesenchymal progenitor cells, known as dental pulp stem cells, which have a high proliferative potential for self-renewal. These progenitor stem cells are now recognized as being vital to the dentine regeneration process following injury. Understanding the nature of these progenitor/stem cell populations in the pulp is important in determining their potentialities and development of isolation or recruitment strategies for use in regeneration and tissue engineering. Characterization of these cells, and determination of their potentialities in terms of specificity of regenerative response, may help direct new clinical treatment modalities. Such novel treatments may involve controlled direct recruitment of the cells in situ and possible seeding of stem cells at sites of injury for regeneration or use of the stem cells with appropriate scaffolds for tissue engineering solutions. Such approaches may provide an innovative and novel biologically based new generation of clinical materials and/or treatments for dental disease. This study aimed to review the body of knowledge relating to stem cells and to consider the possibility of these cell populations, and related technology, in future clinical applications