Glypican-based drug releasing titania implants to regulate BMP2 bioactivity as a potential approach for craniosynostosis therapy

Craniofacial therapy: advanced local therapies from nano-engineered titanium implants to treat craniofacial conditions

Nano-engineering-based tissue regeneration and local therapeutic delivery strategies show significant potential to reduce the health and economic burden associated with craniofacial defects, including traumas and tumours. Critical to the success of such nano-engineered non-resorbable craniofacial implants include load-bearing functioning and survival in complex local trauma conditions. Further, race to invade between multiple cells and pathogens is an important criterion that dictates the fate of the implant. In this pioneering review, we compare the therapeutic efficacy of nano-engineered titanium-based craniofacial implants towards maximised local therapy addressing bone formation/resorption, soft-tissue integration, bacterial infection and cancers/tumours. We present the various strategies to engineer titanium-based craniofacial implants in the macro-, micro- and nano-scales, using topographical, chemical, electrochemical, biological and therapeutic modifications. A particular focus is electrochemically anodised titanium implants with controlled nanotopographies that enable tailored and enhanced bioactivity and local therapeutic release. Next, we review the clinical translation challenges associated with such implants. This review will inform the readers of the latest developments and challenges related to therapeutic nano-engineered craniofacial implants.

Role of glypican-1 in regulating multiple cellular signaling pathways

Glypican-1 (GPC1) is one of the six glypican family members in humans. It is composed of a core protein with three heparan sulfate chains and attached to the cell membrane by a glycosyl-phosphatidylinositol anchor. GPC1 modulates various signaling pathways including fibroblast growth factors (FGF), vascular endothelial growth factor-A (VEGF-A), transforming growth factor-β (TGF-β), Wnt, Hedgehog (Hh), and bone morphogenic protein (BMP) through specific interactions with pathway ligands and receptors. The impact of these interactions on signaling pathways, activating or inhibitory, is dependent upon specific GPC1 domain interaction with pathway components, as well as cell surface context. In this review, we summarize the current understanding of the structure of GPC1, as well as its role in regulating multiple signaling pathways. We focus on the functions of GPC1 in cancer cells and how new insights into these signaling processes can inform its translational potential as a therapeutic target in cancer.

Advancing of titanium medical implants by surface engineering: recent progress and challenges

Introduction:Titanium (Ti) and their alloys are used as main implant materials in orthopedics and dentistry for decades having superior mechanical properties, chemical stability and biocompatibility. Their rejections due lack of biointegration and bacterial infection are concerning with considerable healthcare costs and impacts on patients. To address these limitations, conventional Ti implants need improvements where the use of surface nanoengineering approaches and the development of a new generation of implants are recognized as promising strategies.Areas covered:This review presents an overview of recent progress on the application of surface engineering methods to advance Ti implants enable to address their key limitations. Several promising surface engineering strategies are presented and critically discussed to generate advanced surface properties and nano-topographies (tubular, porous, pillars) able not only to improve their biointegration, antibacterial performances, but also to provide multiple functions such as drug delivery, therapy, sensing, communication and health monitoring underpinning the development of new generation and smart medical implants.Expert opinion:Recent advances in cell biology, materials science, nanotechnology and additive manufacturing has progressively influencing improvements of conventional Ti implants toward the development of the next generation of implants with improved performances and multifunctionality. Current research and development are in early stage, but progressing with promising results and examples of moving into in-vivo studies an translation into real applications.

Titania nanotube-based protein delivery system to inhibit cranial bone regeneration in Crouzon model of craniosynostosis

BACKGROUND

Craniosynostosis is a developmental disorder characterized by the premature fusion of skull sutures, necessitating repetitive, high-risk neurosurgical interventions throughout infancy. This study used protein-releasing Titania nanotubular implant (TNT/Ti) loaded with glypican 3 (GPC3) in the cranial critical-sized defects (CSDs) in Crouzon murine model (Fgfr2c342y/+ knock-in mutation) to address a key challenge of delaying post-operative bone regeneration in craniosynostosis.

MATERIALS AND METHODS

A 3 mm wide circular CSD was created in two murine models of Crouzon syndrome: (i) surgical control (CSDs without TNT/Ti or any protein, n=6) and (ii) experimental groups with TNT/Ti loaded with GPC3, further subdivided into the presence or absence of chitosan coating (on nanotubes) (n=12 in each group). The bone volume percentage in CSDs was assessed 90 days post-implantation using micro-computed tomography (micro-CT) and histological analysis.

RESULTS

Nano-implants retrieved after 90 days post-operatively depicted well-adhered, hexagonally arranged, and densely packed nanotubes with average diameter of 120±10 nm. The nanotubular architecture was generally well-preserved. Compared with the control bone volume percentage data (without GPC3), GPC3-loaded TNT/Ti without chitosan coating displayed a significantly lower volume percent in cranial CSDs (P<0.001). Histological assessment showed relatively less bone regeneration (healing) in GPC3-loaded CSDs than control CSDs.

CONCLUSION

The finding of inhibition of cranial bone regeneration by GPC3-loaded TNT/Ti in vivo is an important advance in the novel field of minimally-invasive craniosynostosis therapy and holds the prospect of altering the whole paradigm of treatment for affected children. Future animal studies on a larger sample are indicated to refine the dosage and duration of drug delivery across different ages and both sexes with the view to undertake human clinical trials.

Signaling Mechanisms Underlying Genetic Pathophysiology of Craniosynostosis

Craniosynostosis, is the premature fusion of one or more cranial sutures which is the second most common cranial facial anomalies. The premature cranial sutures leads to deformity of skull shape and restricts the growth of brain, which might elicit severe neurologic damage. Craniosynostosis exhibit close correlations with a varieties of syndromes. During the past two decades, as the appliance of high throughput DNA sequencing techniques, steady progresses has been made in identifying gene mutations in both syndromic and nonsyndromic cases, which allow researchers to better understanding the genetic roles in the development of cranial vault. As the enrichment of known mutations involved in the pathogenic of premature sutures fusion, multiple signaling pathways have been investigated to dissect the underlying mechanisms beneath the disease. In addition to genetic etiology, environment factors, especially mechanics, have also been proposed to have vital roles during the pathophysiological of craniosynostosis. However, the influence of mechanics factors in the cranial development remains largely unknown. In this review, we present a brief overview of the updated genetic mutations and environmental factors identified in both syndromic and nonsyndromic craniosynostosis. Furthermore, potential molecular signaling pathways and its relations have been described.

Extensive phenotyping of the orofacial and dental complex in Crouzon syndrome

OBJECTIVES

Fibroblast growth factor receptor 2 (FGFR2) ^C342Y/+ mutation is a known cause of Crouzon syndrome that is characterised by craniosynostosis and midfacial hypoplasia. Our aim was to conduct extensive phenotyping of the maxillary, mandibular and dental morphology associated with this mutation.

MATERIALS AND METHODS

Morphometric data were obtained from 40 mice, representing two genotypes (Crouzon and wild-type) and two sexes (males and females) (n=10 in each group). Dental analysis further categorised the first molars into the two jaws (maxillary and mandibular) (n=20 in each group). Maxillary, mandibular and dental morphology was compared by analysing 23 linear landmark-based dimensions in three-dimensional micro-computed tomography reconstructions.

RESULTS

Compared with wild-type, Crouzon (FGFR2^C342Y/+) maxillae were significantly shorter in maximum height, anterior and posterior lengths and middle width, but larger in posterior width (p<0.05 for height; p<0.001 for other comparisons). In the Crouzon mandible, the ascending and descending heights, effective and mandibular lengths, and intercoronoid and intercondylar widths were significantly shorter, whereas intergonial width was larger (p<0.01 for intercondylar width; p<0.001 for other comparisons). Crouzon teeth were significantly smaller mesiodistally, but larger in crown height (p<0.001 for each comparison). All Crouzon mice presented with bifid mandibular condyles and a quarter presented with expansive bone lesions in the mandibular incisor alveolus.

CONCLUSIONS

Our findings of hypoplasia in all three planes in Crouzon maxillae and mandibles, together with the presence of bifid mandibular condyles and expansive bone lesions, may be relevant to maxillofacial surgery and orthodontics. Beyond skeletal effects, the FGFR2^C342Y/+ mutation is now implicated in affecting tooth development. This study's skeletal phenomics data also provides baseline data against which the effect of various treatments can now be assessed.