Fibronectin and Craniofacial Surgery

Lamellipodia-Mediated Osteoblast Haptotaxis Guided by Fibronectin Ligand Concentrations on a Multiplex Chip

Skull morphogenesis is a complex, dynamic process involving two different germ layers and progressing to the coordinated, directional growth of individual bones. The mechanisms underlying directional growth toward the apex are not completely understood. Here, a microfluidic chip-based approach is utilized to test whether calvarial osteoblast progenitors undergo haptotaxis on a gradient of Fibronectin1 (FN1) via lamellipodia. Mimicking the embryonic cranial mesenchyme's FN1 pattern, FN1 gradients is established in the chip using computer modeling and fluorescent labeling. Primary mouse calvarial osteoblast progenitors are plated in the chip along an array of segmented gradients of adsorbed FN1. The study performs single-cell tracking and measures protrusive activity. Haptotaxis is observed at an intermediate FN1 concentration, with an average directional migration index (yFMI) of 0.07, showing a significant increase compared to the control average yFMI of -0.01. A significant increase in protrusive activity is observed during haptotaxis. Haptotaxis is an Arp2/3-dependent, lamellipodia-mediated process. Calvarial osteoblast progenitors treated with the Arp2/3 (Actin Related Protein 2/3 complex) inhibitor CK666 show significantly diminished haptotaxis, with an average yFMI of 0.01. Together, these results demonstrate haptotaxis on an FN1 gradient as a new mechanism in the apical expansion of calvarial osteoblast progenitors during development and shed light on the etiology of calvarial defects.

A child with Apert syndrome and Sturge-Weber syndrome: could fibronectin or the RAS/MAPK signaling pathway be the connection?

BACKGROUND

Apert syndrome is one of the most common craniosynostosis syndrome caused by mutation in genes encoding fibroblast growth factor receptor 2 (FGFR2). Craniosynostosis, midfacial hypoplasia, and syndactyly/symphalangism are features of this syndrome. Sturge-Weber syndrome (SWS) on the other hand is a congenital neurocutaneous disorder characterized by facial port-wine stains (PWSs) and leptomeningeal vascular capillary malformations. In 2013, the causative mutation underlying SWS (p.R183Q somatic activating mutation in the guanine nucleotide-binding protein alpha-q (GNAQ) gene) was identified. This mutation increases downstream signaling along the RAS/MAPK pathway, resulting in increased cell proliferation. The interaction between FGFR and the RAS/MAPK signaling pathway was proposed in recent years. Elevated synthesis of fibronectin in the calvaria of patients with Apert syndrome and increased fibronectin gene expression in port wine-derived fibroblasts of patients with Sturge-Weber disease have also been reported.

CASE PRESENTATION

We report a unique case of Apert and Sturge-Weber syndromes occurring in the same patient. The child was noted to demonstrate features suggestive of Apert syndrome at birth, including brachycephaly, midface hypoplasia, and syndactyly. In addition, a left-sided facial port wine stain in the forehead was noted. Magnetic resonance imaging (MRI) of the brain was performed and confirmed the diagnosis of Sturge-Weber syndrome by demonstrating the presence of left sided leptomeningeal vascular capillary malformation and left-sided cerebral hemiatrophy.

CONCLUSION

To the best of our knowledge, there has been no prior described case of Apert and Sturge-Weber syndromes occurring in the same patient. This case report identifies an area of potential research on fibronectin and derangement of the RAS/MAPK signaling pathway in relation to Apert syndrome and Sturge-Weber syndrome. In view of the rare concurrence of Apert and Sturge-Weber syndromes, the underlying pathogenesis is thought to be multifactorial, one of which may be related to either increased fibronectin gene expression or derangement of the RAS/MAPK signaling pathway.

New biomaterials versus traditional techniques: advances in cleft palate reconstruction

PURPOSE OF REVIEW

Cleft lip and palate still remains one of the most common congenital anomalies, and consequently surgical correction of these anomalies is still commonplace. Despite numerous existing surgical techniques having good outcomes, it is still recognized that the morbidity of certain surgical procedures and success rates regarding outcomes can be improved. The purpose of this review is to evaluate new literature and techniques compared with the time tested procedures that are commonly used.

RECENT FINDINGS

As technology continues to advance, the understanding of details regarding biochemical pathways responsible for the development of cleft defects and also the efficacy of biomaterials that can be used in their correction are being discovered and better understood. Many studies have been conducted in both animal and human study participants that further the understanding of these questions. The efficacy and benefit of newly devised biomaterials seems to indicate that these biomaterials are a viable adjunct and often an alternative in the treatment of cleft palate patients.

SUMMARY

In this review of recent literature, the discussion begins with a review of the more traditional and widely accepted iliac crest bone grafting and then evolves into a discussion of several animal and human studies to delineate the progress being made in this field. The literature exploring the details regarding biochemical pathways and cellular mediators that are involved in cleft formation, as well as biomaterials used in surgical repair are evaluated. The findings in the literature suggest that there is a bright future in better understanding the cause of cleft formation on a molecular level and associated attempts that can be made in altering some of these factors along with discovering new biomaterials that can be a useful adjunct to existing techniques.