Interleukin pattern of Apert fibroblasts in vitro

Craniosynostosis: current conceptions and misconceptions

Cranial bones articulate in areas called sutures that must remain patent until skull growth is complete. Craniosynostosis is the condition that results from premature closure of one or more of the cranial vault sutures, generating facial deformities and more importantly, skull growth restrictions with the ability to severely affect brain growth. Typically, craniosynostosis can be expressed as an isolated event, or as part of syndromic phenotypes. Multiple signaling mechanisms interact during developmental stages to ensure proper and timely suture fusion. Clinical outcome is often a product of craniosynostosis subtypes, number of affected sutures and timing of premature suture fusion. The present work aimed to review the different aspects involved in the establishment of craniosynostosis, providing a close view of the cellular, molecular and genetic background of these malformations.

Unexpected artefacts and occult pathologies under CBCT

Purpose

To present the most frequent occult pathologies unexpectedly encountered via cone-beam computed tomography (CBCT), with particular reference to the diagnostic role of the dentist and that of the radiographer, with a view to clarifying where the diagnostic responsibility lies.

Material and methods

A narrative literature review on the most diffused occult pathologies under CBCT was conducted, with iconographical guide as an example for each category.

Results

The most frequent forms of unexpected pathologies encountered are: the presence of foreign bodies, airway anomaly, and the presence of radio-opacity or -transparency in the maxillofacial district.

Conclusions

The orthodontists must know that they are responsible to recognize these frequent, and potentially serious, pathologies of the head and neck. If the dentist feels unable to take on this responsibility, he or she should, however, be sure to have the scans read by a specialist radiologist.

Cleft palate only: current concepts

Cleft palate only (CPO) is one of the most common congenital malformations worldwide. The etiopathogenesis of CPO is not completely understood. Environmental factors, such as smoking, alcohol consumption, intake of drugs during pregnancy, advanced paternal age, have been demonstrated to be a risk of CPO, but conflicting results have also been published. Insufficient intake of folic acid during the pregnancy has been suggested to increase the risk for CPO. The demonstrated risk for siblings and the higher risk for monozygotic twins suggest a genetic etiopathogenesis for CPO. In some cases of CPO a prevalent mode of inheritance has been reported, but oligogenic models with reduced penetrance, and the risk related to environmental factors have also been proved. One of the first manifestations associated with CPO is difficulty with feeding. Aerophagia is a problem in these infants with CPO and requires more frequent burping and slower feeding. The inability to generate intraoral breath pressure due to nasal air emission in CPO children frequently manifests as articulation difficulties, particularly consonant weakness, and unintelligible speech. Hearing disorders are prevalent among individuals with CPO, as a result of chronic otitis media with effusion due to eustachian tube dysfunction. A multidisciplinary team is essential to manage the many aspects of CPO. In treating CPO, the reconstructive surgeon works in cooperation with otolaryngologists, dentists and orthodontists, speech pathologists, audiologists, geneticists, psychiatrists, maxillofacial surgeons, social workers, and prosthodontists. CPO can be considered a genetically complex disease, but new knowledge and new therapeutic approaches have greatly improved the quality of life of these children. Prenatal diagnosis is an important step in the treatment of this disease.

New insights in orofacial cleft: epidemiological and genetic studies on italian samples

Cleft of the lip and/or palate (CL±P) is the most common congenital craniofacial anomaly affecting around 1 in 700 live births worldwide. Clefts of the human face can be classified anatomically as cleft lip only (CL), cleft palate only (CP), cleft lip and palate (CLP) or a combined group of cleft lip with or without cleft palate (CL±P), based on differences in embryologic development. CL±P has a genetic base and several linkage and association analyses have been performed in order to obtain important information about the role of candidate genes in its onset; not less important are gene-environment interactions that play an increasing role in its aetiology. In CL±P, several loci have been seen associated with the malformation, and, in some cases, a specific gene mapping in a locus has also been identified as susceptibility factor. In CP, one gene has been found, but many more are probably involved. In this short review the genetic studies carried out on CL±P, and the interaction with environmental factors (alcohol, smoking, drugs) are discussed.

FGF2 effects in periosteal fibroblasts bearing the FGFR2 receptor Pro253 Arg mutation

AIM

A growing number of mutations mapped in the receptor gene for fibroblast growth factor have been implicated in several cranial development disorders including the Apert and Crouzon syndromes. The present paper investigated cellular mechanisms underlying Apert phenotype, by analyzing the effects of FGF2 in primary cultures of Apert periosteal fibroblasts carrying the FGFR2 Pro253Arg mutation.

RESULTS

FGF2 administration significantly decreased extracellular matrix production in mutant cells by stimulating degradative enzymatic activities. Gene expression analysis revealed that decorin and biglycan, two proteoglycans involved in collagen fibrillogenesis, were more expressed in mutant cells and down-regulated by FGF2. FGF2 receptor binding showed little differences in high affinity receptor counts between mutant and wild-type cells, while we showed for the first time that low affinity receptors are significantly fewer in mutant cells. Differences were found in Crouzon syndrome, where both high and low affinity receptor counts were up-regulated.

CONCLUSIONS

The different mutation and low affinity receptor regulation in mutant receptors support the hypothesis that the impact on the activity of the ligand-receptor complex could allow distinct modes of FGF2 activation in Apert and Crouzon syndromes, which interfere with the FGFR2 signalling cascade.

Apert and Crouzon syndromes: clinical findings, genes and extracellular matrix

Apert and Crouzon syndromes are well known craniostenosis. In the last 10 years several studies were performed to provide a better understanding of the etiology and pathogenesis of these diseases. Both have an autosomal dominant mode of transmission, and a mutation in the gene encoding for the fibroblast growth factor receptor 2 (FGFR2) is the cause in most patients. However, the fact that the same mutation can produce a wide range of phenotypic expression makes the mechanism of anomalous development more complex. The extracellular matrix (ECM) is composed of proteins, glycosaminoglycans, and cytokines that are secreted in an autocrine and paracrine manner and are able to modify the ECM. Fibroblast growth factors are complexed with heparan sulfate, a component of the ECM, before binding the FGFR2. Data exist about different expressions of cytokines and ECM macromolecule in craniostenosis-derived fibroblasts and osteoblasts. Changes in ECM composition could explain the altered osteogenic process and account for pathologic variations in cranial development in addition to the FGFR2 mutations.

Bad bones, absent smell, selfish testes: The pleiotropic consequences of human FGF receptor mutations

The discovery in 1994 that highly specific mutations of fibroblast growth factor (FGF) receptor 3 caused the most common form of human short-limbed dwarfism, achondroplasia, heralded a new era in FGF receptor (FGFR) biology. A decade later, the purpose of this review is to survey how the study of humans with FGFR mutations continues to provide insights into FGFR function in health and disease, and the clinical applications of these findings. Amongst the most interesting recent discoveries have been the description of novel phenotypes associated with FGFR1 and FGFR3 mutations; identification of fundamental differences in the cellular mechanisms of mutant FGFR2 and FGFR3 action; and the direct identification of FGFR2 and FGFR3 mutations in sperm. These clinical observations illustrate the pleiotropism of FGFR action and fuel ongoing efforts to understand the rich biology and pathophysiology of the FGF signalling system.

P253R fibroblast growth factor receptor-2 mutation induces RUNX2 transcript variants and calvarial osteoblast differentiation

Unregulated fibroblast growth factor 2 (FGF2) signaling caused by mutations in the fibroblast growth factor receptor (FGFR2) leads to human craniosynostosis such as the Apert syndrome. In an in vitro control model of calvarial osteoblasts from Apert patients carrying the FGFR2 P253R mutation, we studied the changes in cellular phenotype and evaluated the effects of FGF2. Compared with wild-type controls, osteocalcin mRNA was down-regulated in Apert osteoblasts, Runt-related transcription factor-2 (RUNX2) mRNA was differentially spliced, and FGF2 secretion was greater. Total protein synthesis, fibronectin and type I collagen secretion were up-regulated, while protease and glycosidase activities and matrix metalloproteinase-13 (MMP-13) transcription were decreased, suggesting an altered ECM turnover. Adding FGF2 increased protease and glycosidase activities and down-regulated fibronectin and type I collagen secretion in Apert osteoblasts. High affinity FGF2 receptors were up-regulated in Apert osteoblasts and analysis of signal transduction showed elevated levels of Grb2 tyrosine phosphorylation and the Grb2-p85 beta association, which FGF2 stimulation strongly reduced. All together these findings suggest increased constitutive receptor activity in Apert mutant osteoblasts and an autocrine loop involving the FGF2 pathway in modulation of Apert osteoblast behavior.

Fibroblast growth factor 2 induces increased calvarial osteoblast proliferation and cranial suture fusion

OBJECTIVE

Craniosynostosis has been associated with fibroblast growth factors (FGFs) and their receptors. The purpose of this study was to quantitatively determine the effect of FGF2 on rat calvarial osteoblasts and a rat cranial suture formation model.

DESIGN

Fetal rat calvarial osteoblasts were cultured with and without FGF2. Cell attachment and proliferation was determined by alamar Blue dye assay and cell morphology by toluidine-blue staining. In rat calvarial organ culture, postnatal day 15 rat calvariae with dura mater were placed in serum-free media with and without FGF2. A unique quantitative analysis of suture fusion was developed by obtaining measurements of suture bridging in histological serial sections at progressive stages of fusion.

RESULTS

Attachment for cells treated with FGF2 was similar to control. In contrast, proliferation was higher for cells treated with FGF2 while maintaining an osteoblastic morphology. After 5 days in organ culture, FGF2-treated posterior frontal sutures showed a dramatic increase in fusion, compared with untreated controls. This increased fusion was maintained throughout days 7 and 10 in culture. Also, fusion was enhanced on the dural side of the suture, as is normally observed in vivo, and the normal tissue architecture was maintained.

CONCLUSIONS

These results indicate that FGF2 can promote rat osteoblast attachment and normal cell morphology as well as induce cell proliferation. In calvarial organ culture, FGF2 treatment produced an enhanced suture fusion. These results provide further support for a critical role for FGF2 in cranial suture development. These studies also present a new quantitative approach to evaluating the effect of suture-perturbing growth factors on cranial suture fusion.

Basic fibroblast growth factor: effects on matrix remodeling, receptor expression, and transduction pathway in human periosteal fibroblasts with FGFR2 gene mutation

The Crouzon syndrome, which is associated with fibroblast growth factor receptor (FGFR2) mutations, is characterized by premature fusion of cranial sutures. We used an in vitro model of cultured periosteal fibroblasts from normal subjects and from Crouzon patients with FGFR2 mutation. We analyzed the matrix turnover rate and the effects of adding FGF2 by evaluating fibronectin synthesis and the activity of some proteolytic enzymes. To assess the role of some FGF signaling molecules involved in FGFR2 regulation, we studied Grb2 tyrosine phosphorylation and the phosphotyrosine proteins associated with Grb2. The iodinate FGF binding assay was performed to quantify FGFR expression. Compared with normal fibroblasts, fibronectin synthesis was decreased in Crouzon fibroblasts, and protease activities in cells and medium were enhanced, suggesting that excess fibronectin catabolism is present. Differences were more marked when FGF2 was added. Very few phosphoproteins were visible in anti-Grb2 immunoprecipitations from Crouzon fibroblasts, which showed a significant increase in the number of high-affinity and low-affinity FGF2 receptors. These results suggest that the abnormal genotype and the Crouzon cellular phenotype are related. To compensate the low levels of tyrosine phosphorylation, Crouzon cells might increase the numbers of FGFR2, thus increasing the cell surface binding sites for FGF2.

Induction of intracellular interleukin-1 beta signals via type II interleukin-1 receptor in human gingival fibroblasts

The type II interleukin-1 receptor (IL-1RII) has been thought to be incapable of transducing signals to cells because of its short intracellular domain, while type I IL-1 receptor (IL-1RI) does transduce signals. Since over-expression of IL-1RII has been demonstrated to inhibit cytokine production in the fibroblastic cell line, it has been proposed to use IL-1RII to prevent IL-1-induced inflammation in connective tissue. In this study, trace amounts of IL-1RII mRNA expression were detected in human gingival fibroblasts (HGFs), which are affected by cytokines in inflammatory periodontal disease. Cloning of the cDNA encoding IL-1RII expressed in HGFs revealed 3 amino acid substitutions in the extracellular domain, when compared with the 408 residues predicted from human B-cells. Over-expression of IL-1RII on HGFs by gene transfer down-regulated the expression of IL-1 beta mRNA and IL-6 mRNA in response to IL-1 beta stimulation, while the expression of IL-8 mRNA was not affected. In the IL-1RII-transfected HGFs, phosphorylation of 25- and 74-kDa proteins was up-regulated upon IL-1 beta stimulation in the transfected HGFs. The phosphorylation of these proteins was suppressed by the addition of a neutralizing antibody against IL-1RII. These results suggest that the IL-1RII may regulate HGFs expression of cytokine mRNA upon IL-1 beta stimulation, possibly by altering the IL-1RI-dependent signals.

Interleukin secretion, proteoglycan and procollagen alpha(1)(I) gene expression in Crouzon fibroblasts treated with basic fibroblast growth factor

The present study provides the first evidence that fibroblasts obtained from patients affected by Crouzon syndrome, a rare craniosynostosis, despite mutations in the high-affinity bFGF receptor retain their capacity to respond to bFGF. The growth factor reduces IL-1 secretion, downregulates biglycan and procollagen alpha(1)(I), and increases betaglycan expression. Since betaglycan is a co-receptor for bFGF signalling, an alternative signal transduction pathway is suggested in Crouzon fibroblasts, to explain the documented changes in ECM macromolecule production.

TGFbeta isoforms and decorin gene expression are modified in fibroblasts obtained from non-syndromic cleft lip and palate subjects

Interaction between extracellular matrix (ECM) and cytokines is thought to be crucial for palatal development. The localization of transforming growth factors (TGFalpha and TGFbeta isoforms) in craniofacial tissues suggests that they carry out multiple functions during development. In the present report, we studied TGFalpha, TGFbeta1, and TGFbeta3 expressions and their effects on ECM macromolecule production of normal and cleft palatal fibroblasts in vitro, to investigate the mechanisms by which the phenotypic modulation of fibroblasts occurs during the cleft palate process. The results indicated that, while TGFalpha mRNA was not evidenced in CLP or normal fibroblasts, a reduced TGFbeta1 hybridization signal was detected in CLP fibroblasts. In addition, these secreted more active TGFbeta3 than TGFbeta1, as evaluated in a biological assay. The CLP phenotype, which differed from the normal one because of its higher PG decorin expression and greater production of GAG and collagen, was further modified by the addition of growth factors. In fact, in CLP fibroblasts, TGFalpha and TGFbeta1 down-regulated PG decorin transcript, TGFbeta1 increased collagen and GAG in both cellular and extracellular compartments, and TGFbeta3 promoted secretory processes of cells. In conclusion, the data represent the first report in a human model in vitro that TGFbeta1 and beta3 are differently expressed and are correlated to the CLP phenotype. Thus, strength is given to the hypothesis that TGFbeta isoforms are the potential inducers of phenotypic expression in palatal fibroblasts during development and that an autocrine growth factor production mechanism may be responsible for the phenotypic modifications.

A regulatory role of fibroblast growth factor in the expression of decorin, biglycan, betaglycan and syndecan in osteoblasts from patients with Crouzon's syndrome

Bone development is controlled by the autocrine and/or paracrine effects of regulatory molecules. We previously showed that the phenotype of fibroblasts obtained from patients affected by Crouzon's syndrome, an autosomal dominant disease characterized by pathological skull bone development, differed from that of normal cells and was regulated by interleukin treatments. The changes in the relative concentrations of extracellular macromolecules (glycosaminoglycans-GAG, collagen and fibronectin) were associated with abnormal interleukin secretion that affected the microenvironment where the osteogenic processes take place. Mutations in human fibroblast growth factor receptors are now thought to be involved in Crouzon's syndrome. Since coactivation of interleukins and basic fibroblast growth factor (bFGF) is probably implicated in morphogenetic and osteogenic processes and heparan sulphate proteoglycans have a critical role in regulating bFGF activity, the phenotypes of normal and Crouzon osteoblasts were studied and the effects of bFGF on the expression of bFGF, procollagen alpha1 (I), and proteoglycan (PG) genes for biglycan, decorin, betaglycan and syndecan analyzed. Specific human cDNA probes were used to screen the relative levels of mRNA by Northern analysis. Spontaneous or bFGF-modulated release of interleukins was also assayed. The bFGF gene transcript was detected only in Crouzon osteoblasts. We showed for the first time that Crouzon osteoblasts, despite a mutation in the FGF receptor, still responded to exogenous bFGE In fact, the growth factor induced changes in the GAG profile and in the levels of mRNA coding for PG and procollagen alpha1 (I) and down-regulated heparan sulfate GAG chains. ELISA showed that bFGF-induced interleukin secretion differed in normal and Crouzon osteoblasts. The observed differences in PG core protein, procollagen alpha1 (I) and bFGF could be associated with the Crouzon bone phenotype and also should provide further understanding on the molecular basis of the diseased state of bone.