The effects of tissue-non-specific alkaline phosphatase gene therapy on craniosynostosis and craniofacial morphology in the FGFR2C342Y/+ mouse model of Crouzon craniosynostosis.

OBJECTIVES: Craniosynostosis, the premature fusion of cranial bones, has traditionally been described as a disease of increased bone mineralization. However, multiple mouse models of craniosynostosis display craniosynostosis simultaneously with diminished cranial bone volume and/or density. We propose an alternative hypothesis that craniosynostosis results from abnormal tissue mineralization through the downregulation of tissue-non-specific alkaline phosphatase (TNAP) enzyme downstream of activating mutations in FGFRs. MATERIAL AND METHODS: Neonatal Crouzon (FGFRC342Y/+) and wild-type (FGFR+/+) mice were injected with lentivirus to deliver a recombinant form of TNAP. Mice were sacrificed at 4 weeks postnatal. Serum was collected to test for alkaline phosphatase (AP), phosphorus, and calcium levels. Craniofacial bone fusion and morphology were assessed by micro-computed tomography. RESULTS: Injection with the TNAP lentivirus significantly increased serum AP levels (increased serum AP levels are indicative of efficient transduction and production of the recombinant protein), but results were variable and dependent upon viral lot and the litter of mice injected. Morphological analysis revealed craniofacial form differences for inferior surface (p=0.023) and cranial height (p=0.014) regions between TNAP lentivirus-injected and vehicle-injected Crouzon mice. With each unit increase in AP level, the odds of lambdoid suture fusion decreased by 84.2% and these results came close to statistical significance (p=0.068). CONCLUSION: These results suggest that TNAP deficiency may mediate FGFR2-associated craniosynostosis. Future studies should incorporate injection of recombinant TNAP protein, to avoid potential side effects and variable efficacy of lentiviral gene delivery.

Effect of excessive methionine on the development of the cranial growth plate in newborn rats.

OBJECTIVE: Methionine is an essential amino acid and pivotal for normal growth and development. However, previous animal studies have shown that excessive maternal intake of methionine causes growth restrictions, organ damages, and abnormal growth of the mandible in newborn animals. However, the effect of excessive methionine on the development of the cranial growth plate is unknown. This study investigated histological alterations of the cranial growth plate induced by high methionine administration in newborn rats. DESIGN: Twenty pregnant dams were divided into a control and an experimental group. The controls received a diet for rats and the experimental group was fed from the 18th gestational day with a special manufactured high methionine diet for rats. The high methionine diet was maintained until the end of the lactation phase (day 20). The offspring of both groups were killed at day 10 or 20 postnatally and their spheno-occipital synchondroses were collected for histological analysis. RESULTS: The weight of the high-dose methionine treated experimental group was considerably reduced in comparison to the control group at day 10 and 20 postnatally. The cartilaginous area of the growth plate and the height of the proliferative zone were markedly reduced at postnatal day 10 in the experimental group. CONCLUSIONS: In summary, the diet-induced hypermethioninemia in rat dams resulted in growth retardations and histomorphological changes of the spheno-occipital synchondrosis, an important craniofacial growth centre in newborns. This finding may elucidate facial dysmorphoses reported in patients suffering from hypermethioninemia.

Effects and noneffects of personal environmental experimentation on postnatal craniofacial growth.

Genetic makeup, as well as various environmental factors, such as gravity, temperature, disease, trauma, inflammation, radiation, and chemicals, may affect skeletal growth sites and centers, thereby causing faulty growth of bone(s). The degree of the subsequent deformity will depend not only on the type, intensity, extent, and chronology of the noxious agent but also on the site and its particular susceptibility and growth activity. Over the years, I conceived, designed, initiated, and carried out a series of experiments in regard to bone(s), in both young and adult animals. Eventually, I directed my efforts principally toward local surgical experimentation as it related to both normal and abnormal gross postnatal craniofacial growth. Because of the wide variety of different structures, their interrelated individualities, and the challenges presented in both its richness of sites of growth and complexity, the skull proved to be a most unusual source of study. The purpose of this selective, organized, and limited review, analysis, and summary of personally conducted experiments is to relate certain aspects of growth with change and nonchange to age, sites, rates, factors, and mechanisms. In many instances, there are correlations between basic research findings and clinical practice. There is no such similar report in the literature. This retrospective study brings it all together.

Light maxillary expansion forces with the magnetic expansion device. A preliminary investigation.

An active maxillary magnetic expansion device (MED) was developed to be used clinically. The aim was to show the effects of light and continuous forces producing less traumatic stimulation of maxillary sutural growth than a conventional rapid maxillary expansion device. In this study, two different types of appliances were used on six patients between 7 years 4 months and 16 years 2 months: the first type was bonded, the other one used bands. For better appreciation, four implants were placed on each patient: two apically between central and lateral incisors, and two between second premolars and molars. A standardized radiographic technique was used to take occlusal radiographs, and postero-anterior and lateral headplates. The results varied according to the age and the appliance used. The skeletal effect with the banded MED was between 16 and 77 per cent, and for the bonded MED 0 and 25 per cent in comparison to the overall expansion. It seems that 250-500 g of continuous magnetic forces can produce dental and skeletal movements in a light force expansion concept, but further studies with larger samples are needed to make firm conclusions.