Cleft lip and cleft palate in Esrp1 knockout mice is associated with alterations in epithelial-mesenchymal crosstalk.

Cleft lip is one of the most common human birth defects. However, there remain a limited number of mouse models of cleft lip that can be leveraged to characterize the genes and mechanisms that cause this disorder. Crosstalk between epithelial and mesenchymal cells underlies formation of the face and palate, but the basic molecular events mediating this crosstalk remain poorly understood. We previously demonstrated that mice lacking the epithelial-specific splicing factor Esrp1 have fully penetrant bilateral cleft lip and palate. In this study, we further investigated the mechanisms leading to cleft lip as well as cleft palate in both existing and new Esrp1 mutant mouse models. These studies included a detailed transcriptomic analysis of changes in ectoderm and mesenchyme in Esrp1-/- embryos during face formation. We identified altered expression of genes previously implicated in cleft lip and/or palate, including components of multiple signaling pathways. These findings provide the foundation for detailed investigations using Esrp1 mutant disease models to examine gene regulatory networks and pathways that are essential for normal face and palate development - the disruption of which leads to orofacial clefting in human patients.

Comprehensive Long-Term Outcomes Following Mandibular Distraction Osteogenesis.

OBJECTIVE: To describe long-term outcomes and complications following mandibular distraction osteogenesis (MDO) in a diverse patient cohort. DESIGN: Cross-sectional study. SETTING: Single tertiary-care pediatric center. PATIENTS: Forty-eight patients previously undergoing MDO with minimum 4-year follow-up. MAIN OUTCOME MEASURES: Respiratory outcomes, feeding patterns, dental development, motor/sensory nerve function, temporo-mandibular joint function, and postsurgical scarring. RESULTS: Forty-six patients with a median age of 7 years were evaluated. Of 20 nonsyndromic patients, none required additional airway procedures, none required continuous positive airway pressure (CPAP) during sleep, and 19 (95%) fed exclusively by mouth. Among 26 syndromic patients, 7 (27%) required CPAP and 8 (31%) were tube fed. Permanent first molar differences were seen in the majority of subjects; patterns of damage interfering with function were more common in syndromic (13/28, 46%) compared to nonsyndromic (5/24, 21%; P = .014) subjects. MDO prior to age two was associated with more frequent and worse dental damage (P = .001). Inferior alveolar nerve and marginal mandibular nerve function were fully intact in 37 (80%) and 39 (85%) of patients, respectively. Three patients (6%), all with associated genetic syndromes, demonstrated severe nerve impairment. By the Vancouver scar scale, ≥ 80% of surgical scars were rated in the most favorable category for each quality assessed. Temporomandibular joint dysfunction was rare. CONCLUSIONS: MDO shows highly favorable long-term respiratory, feeding, nerve, and scar outcomes in nonsyndromic patients, although permanent molar changes not precluding tooth viability are commonly seen. Patients with associated syndromes demonstrate respiratory and feeding benefits, but higher rates of dental and nerve abnormalities.

Postoperative Changes in the Upper Airway Following Mandibular Distraction Osteogenesis in Pediatric Hemifacial Microsomia.

BACKGROUND: Patients with hemifacial microsomia (HFM) may undergo unilateral mandibular distraction osteogenesis (MDO) before skeletal maturity in an effort to improve facial symmetry. Mandibular distraction osteogenesis's effect on airway volumes have been studied in the past, though to our knowledge, none have accounted for the effect of head and neck posture on airway morphology. This study aimed to tackle this shortcoming, using imaging to analyze the upper airway of patients with HFM before and after surgical intervention with MDO. METHODS/DESCRIPTION: The authors retrospectively reviewed patients with a diagnosis of unilateral HFM whom underwent unilateral MDO with an oblique vector at age 4 to 14 years at a single institution from 2004 to 2019. Patients with pre- and post-MDO three-dimensional computed tomography scans of the upper airway within 12 months of distractor placement and removal, respectively, were included. Head and neck postures were determined by craniocervical, pitch, roll, and yaw angles. Pre- and post-operative pharyngeal airway volumes, pharyngeal surface area, minimum retropalatal cross-sectional areas (RP CSA) and retroglossal (RG) CSA and associated anteroposterior distances were measured using Mimics 22.0 (Materialise; Leuven, Belgium). Comparison was done using Kruskal-Wallis tests and linear mixed-effects models controlling for head and neck postures. RESULTS: Ten patients met inclusion criteria. Mean age at pre-distractor placement computed tomography scan was 99 ±â€Š35 months, and mean duration between pre- and post-surgery scans was 220 ±â€Š90 days. Head and neck posture were found to be significant predictors of all airway dimensions. After controlling for significant factors with fixed effects linear modeling, surface area was found to be significantly smaller in patients after MDO by 189.48 mm2 (F[10.8] = -3.47, P = 0.0053), compared to their preoperative measurements. Surgery was not a significant predictor of changes in airway volume (F[11.6] = 0.52, P = 0.61), minimum RP CSA (F[12.2] =  -0.64, P = 0.53), minimum RG CSA (F[12.6] =  -1.64, P = 0.13), RP anteroposterior distance (F[14.0] = 0.30, P = 0.77), or RG anteroposterior distance (F[20.0] =  -0.04, P = 0.97). CONCLUSIONS: Oblique vector MDO in patients with HFM is associated only with statistically significant changes in the surface area of the upper airway, and is not associated with statistically significant changes in dimensions like volume, CSA, or anteroposterior dimension. This is an important finding, as it may guide discussions surrounding risk/benefit ratio for MDO in childhood.

Degree of Sagittal Suture Fusion, Cephalic Index, and Head Shape in Nonsyndromic Sagittal Craniosynostosis.

BACKGROUND: Sagittal craniosynostosis may present with complete or partial fusion of the sagittal suture, but relationships between degree of sagittal suture fusion and head shape are currently poorly described. The aim of this study was to characterize sagittal suture fusion patterns and determine associations with head shape in a cohort of patients with nonsyndromic sagittal craniosynostosis. METHODS: Patients with nonsyndromic sagittal craniosynostosis at a tertiary care center with available computed tomography imaging were included in this study. The anterior and posterior distances of sagittal suture patency were measured along 3-dimensional parietal bones. Degree of sagittal suture fusion was compared to head shape characteristics, including cephalic index (CI), frontal bossing, and occipital bulleting. RESULTS: Ninety patients (69 male) were included in this retrospective study. The sagittal suture was on average 85.6±20.1% fused, and 45 (50.0%) patients demonstrated complete fusion of the sagittal suture. CI was associated with increased degree of fusion for the anterior one-half (ρ=0.26, P =0.033) and anterior one-third (ρ=0.30, P =0.012) of the sagittal suture. Complete fusion of the anterior one-third of the sagittal suture predicted higher CI (ß=13.86, SE=6.99, z =-0.25, P =0.047). Total degree of sagittal suture fusion was not predictive of CI or head shape in any analysis. CONCLUSIONS: Decreased fusion of the anterior one-third of the sagittal suture, but not total suture, may paradoxically predict increased severity of scaphocephaly as quantified by CI in nonsyndromic sagittal craniosynostosis.

The Roles of Indian Hedgehog Signaling in TMJ Formation.

The temporomandibular joint (TMJ) is an intricate structure composed of the mandibular condyle, articular disc, and glenoid fossa in the temporal bone. Apical condylar cartilage is classified as a secondary cartilage, is fibrocartilaginous in nature, and is structurally distinct from growth plate and articular cartilage in long bones. Condylar cartilage is organized in distinct cellular layers that include a superficial layer that produces lubricants, a polymorphic/progenitor layer that contains stem/progenitor cells, and underlying layers of flattened and hypertrophic chondrocytes. Uniquely, progenitor cells reside near the articular surface, proliferate, undergo chondrogenesis, and mature into hypertrophic chondrocytes. During the past decades, there has been a growing interest in the molecular mechanisms by which the TMJ develops and acquires its unique structural and functional features. Indian hedgehog (Ihh), which regulates skeletal development including synovial joint formation, also plays pivotal roles in TMJ development and postnatal maintenance. This review provides a description of the many important recent advances in Hedgehog (Hh) signaling in TMJ biology. These include studies that used conventional approaches and those that analyzed the phenotype of tissue-specific mouse mutants lacking Ihh or associated molecules. The recent advances in understanding the molecular mechanism regulating TMJ development are impressive and these findings will have major implications for future translational medicine tools to repair and regenerate TMJ congenital anomalies and acquired diseases, such as degenerative damage in TMJ osteoarthritic conditions.

IGF-1-mediated osteoblastic niche expansion enhances long-term hematopoietic stem cell engraftment after murine bone marrow transplantation.

The efficiency of hematopoietic stem cell (HSC) engraftment after bone marrow (BM) transplantation depends largely on the capacity of the marrow microenvironment to accept the transplanted cells. While radioablation of BM damages osteoblastic stem cell niches, little is known about their restoration and mechanisms governing their receptivity to engraft transplanted HSCs. We previously reported rapid restoration and profound expansion of the marrow endosteal microenvironment in response to marrow radioablation. Here, we show that this reorganization represents proliferation of mature endosteal osteoblasts which seem to arise from a small subset of high-proliferative, relatively radio-resistant endosteal cells. Multiple layers of osteoblasts form along the endosteal surface within 48 hours after total body irradiation, concomitant with a peak in marrow cytokine expression. This niche reorganization fosters homing of the transplanted hematopoietic cells to the host marrow space and engraftment of long-term-HSC. Inhibition of insulin-like growth factor (IGF)-1-receptor tyrosine kinase signaling abrogates endosteal osteoblast proliferation and donor HSC engraftment, suggesting that the cytokine IGF-1 is a crucial mediator of endosteal niche reorganization and consequently donor HSC engraftment. Further understanding of this novel mechanism of IGF-1-dependent osteoblastic niche expansion and HSC engraftment may yield clinical applications for improving engraftment efficiency after clinical HSC transplantation.

Intra-amniotic transient transduction of the periderm with a viral vector encoding TGFß3 prevents cleft palate in Tgfß3(-/-) mouse embryos.

Cleft palate is a developmental defect resulting from the failure of embryonic palatal shelves to fuse with each other at a critical time. Immediately before and during palatal fusion (E13-E15 in mice), transforming growth factor ß3 (TGFß3) is expressed in the palatal shelf medial edge epithelium (MEE) and plays a pivotal role in palatal fusion. Using Tgfß3(-/-) mice, which display complete penetrance of the cleft palate phenotype, we tested the hypothesis that intra-amniotic gene transfer could be used to prevent cleft palate formation by restoring palatal midline epithelial function. An adenoviral vector encoding Tgfß3 was microinjected into the amniotic sacs of mouse embryos at successive developmental stages. Transduced Tgfß3(-/-) fetuses showed efficient recovery of palatal fusion with mesenchymal confluence following injection at E12.5 (100%), E13.5 (100%), E14.5 (82%), and E15.5 (75%). Viral vectors injected into the amniotic sac transduced the most superficial and transient peridermal cell layer but not underlying basal epithelial cells. TGFß3 transduction of the peridermdal cell layer was sufficient to induce adhesion, fusion, and disappearance of the palatal shelf MEE in a cell nonautonomous manner. We propose that intra-amniotic gene transfer approaches have therapeutic potential to prevent cleft palate in utero, especially those resulting from palatal midline epithelial dysfunction.

Treatment of large calvarial defects with bone transport osteogenesis: a preclinical sheep model.

BACKGROUND: Bone transport osteogenesis (BTO), distraction of a free portion of bone across a defect, offers an autologous solution to large cranial defects that may allow treatment without permanent hardware implantation. This study establishes a sheep model to evaluate the feasibility and distraction kinetics of BTO. METHODS: Subtotal cranial defects (3.5 × 3.5 cm) were created in 10 young adult sheep and a transport segment (3.5 × 2 cm) traversed the defect at varying distraction rates (0, 0.5, 1.0, and 1.5 mm/day) using semi-buried cranial distractors. After a 6-week consolidation period, sheep were euthanized and the resultant bone was analyzed by CT, histology, and mechanical testing. RESULTS: Gross examination, histology, and 3D CT revealed that control animals had fibrous nonunion whereas distraction animals had ossified defects with fibrous nonunion at the distal docking site. There was one premature consolidation in the 0.5 mm/day group. The volume of bony regenerate in the 0.5, 1.0, and 1.5 mm/day distraction rate groups was statistically indistinct (P = 0.16). The mean flexural moduli (MPa) of non-decalcified samples from the control cranium, transport segment, and bone regenerate were found to be 4.50 ± 4.9, 6.17 ± 2.1, and 4.14 ± 4.8, respectively (P = 0.24). CONCLUSIONS: This experiment provides proof of concept for BTO for large calvarial defects in a sheep model. Distraction at a rate of 0.5 mm per day may place individuals at higher risk for premature consolidation, but distraction rates did not have significant effects on regenerate quantity or quality. Future work will include the use of curvilinear distraction devices for 3-dimensional contour.

Orthognathic Considerations of Maxillary and Mandibular Asymmetry at Skeletal Maturity in Patients with Cleft Lip and Palate.

BACKGROUND: Improving occlusion and aesthetics is the primary objective of orthognathic surgery for patients with cleft lip and palate (CLP). However, these patients often suffer from horizontal, vertical, and rotational asymmetry in addition to maxillary retrusion. This study aims to describe maxillary and mandibular asymmetry in patients with CLP undergoing orthognathic surgery and analyze its anatomic basis. METHODS: Patients with isolated CLP undergoing CT imaging prior to orthognathic surgery were retrospectively reviewed. Maxillary and mandibular positioning and dimensional symmetry were evaluated. Incidence of clinically significant asymmetry, correlations between areas of asymmetry, and associations with clinical history were analyzed. RESULTS: Fifty-eight patients, with mean age 17 years were analyzed, including 32 patients with unilateral CLP and 26 with bilateral CLP. Twenty (34%) patients demonstrated chin deviation ≥4mm and 21 (36%) had a ≥5% discrepancy in mandibular ramus lengths. Horizontal occlusal plane cant of ≥2° was seen in 20 (34%) maxillae and 28 (48%) mandibles, with dental arch yaw ≥2° noted in 32 (55%) of both maxillae and mandibles. Chin deviation correlated with maxillary cant, discrepancy in ramus length, discrepancy in mandibular body length, and discrepancy in condylar volume (p<0.05). Bilateral and unilateral CLP did not show significantly different asymmetry on any measure (p>0.05). CONCLUSIONS: Both maxillary and mandibular asymmetry is common in skeletally mature patients with CLP and frequently results in notable chin deviation. Preoperative three-dimensional imaging and virtual surgical planning of orthognathic surgery aid in recognition of facial asymmetries and reveal opportunities to optimize results in this population.

Long-Term Outcomes and Growth Analysis of Costochondral Grafts for Hemifacial Microsomia: 24-Year Experience of a Single Surgeon.

BACKGROUND: Costochondral grafts (CCGs) can be used in mandibular reconstruction of Kaban-Pruzansky IIB/III hemifacial microsomia (HFM). Their growth is variable, occasionally necessitating secondary surgery. This study examined one surgeon's 24-year experience to better quantify long-term outcomes and surgical care required in CCG reconstruction of HFM mandibles. METHODS: Serial three-dimensional computed tomography scans, from preoperative to most recent, were analyzed in patients with minimum four years of clinical follow-up following CCG reconstruction. Graft/ramus height, length, volume, bilateral mandibular body length, and chin deviation were measured. Changes in measurements were analyzed at preoperative, immediate postoperative, most recent imaging prior to secondary surgery, and most recent imaging overall. Growth rates per measure were calculated utilizing scans after CCG, but before secondary surgery. RESULTS: Thirteen patients were analyzed. Median clinical follow-up was 10.0 (5.1) years. One patient developed temporomandibular joint ankylosis secondary to stacked-graft malposition, which was repaired without further complications. CCG reconstruction led to immediate improvement in graft/ramus height (p=0.03), length (p=0.002), and volumetric symmetry (p=0.02). No difference was found between graft and native ramus height (p=0.4) and length measures (p=0.5), while graft volume and affected mandibular body grew significantly more slowly. By latest imaging, 63% of patients required secondary surgery, including distraction osteogenesis and/or orthognathic surgery due to differential graft/hemimandible growth behavior. By most recent clinical follow-up, this proportion increased to 93%. CONCLUSION: CCGs provide significant short-term mandibular and facial symmetry improvement in HFM IIB/III. Long-term analysis reveals frequent undergrowth requiring secondary intervention to promote and maintain symmetry.

Associations between the timing of tongue reduction surgery, (Epi)genotype, and dentoskeletal development in patients with Beckwith-Wiedemann syndrome.

Tongue reduction surgery is often pursued to manage the adverse effects of macroglossia in patients with Beckwith-Wiedemann syndrome (BWS). This study characterized dental outcomes in patients with BWS based on surgical timing and molecular diagnosis. A retrospective study was designed to include patients with BWS over the age of two who had clinical or radiographic documentation of dental development. Patients were grouped by history of tongue reduction surgery and surgical timing (early: <12 months). One hundred three patients were included (55 no tongue reduction, 18 early, 30 late). Patients who underwent late surgery had lower odds of class I occlusion (OR 0.11, 95% CI 0.02-0.58, p = 0.009) and higher odds of anterior open bite (OR 7.5, 95% CI 1.14-49.4, p = 0.036). Patients with clinical diagnoses and negative molecular testing had anterior open bite less frequently than patients with imprinting center 2 loss of methylation and paternal uniparental isodisomy of 11p15.5 (p = 0.009). Compared to reference values, patients who had tongue reductions had an increased mandibular plane angle (32.0 ± 4.5° versus 36.9 ± 5.0°, p = 0.001), indicative of hyperdivergent growth. The results of this study help to understand the complex nature of dentoskeletal growth in BWS and shed insight on how surgical timing and molecular diagnosis influence prognosis.

Radiographic Evidence of Dental Complications Following Mandibular Distraction Osteogenesis: Inverted-L versus Oblique Osteotomy.

INTRODUCTION: Patients with micrognathia undergoing mandibular distraction osteogenesis (MDO) for functional and aesthetic improvement are at significant risk for dental complications. This study investigates association of two osteotomy patterns-oblique and inverted-L-with risk to developing dentition. METHODS: Our senior orthodontist performed a retrospective review of dental radiographs of patients undergoing MDO with confirmed oblique or inverted-L osteotomies between 2012 and 2022. Images were assessed for evidence of missing, damaged, or displaced teeth, and proportion of affected hemimandibles by injury type and median number of affected teeth per hemimandible were compared between groups using appropriate statistical methodology. RESULTS: Analysis included 44 patients (23 oblique, 21 inverted-L) and 85 hemimandibles (45 and 40). Mean age at surgery was 3.1±4.6 years, and mean time to imaging was 4.9±4.1 years; there was no difference between groups (p=0.23, p=0.34, respectively). Oblique osteotomy was associated with greater odds of missing teeth (OR 13.3, p<0.001), damaged teeth (OR 3.2, p=0.02), and any dental injury (OR 39.9, p<0.001) compared to inverted-L, as well as greater number of missing teeth (ß=0.6, p<0.01), damaged teeth (ß=0.3, p=0.02), and total number of affected teeth (ß=0.9, p<0.001). There was no difference in incidence (p=0.5) or number (p=0.4) of displaced teeth between groups. CONCLUSION: Inverted-L osteotomies were associated with fewer dental complications as compared to oblique osteotomy at all ages studied. While longer-term follow up and prospective data are needed prior to making definitive recommendations, this data is helpful to surgeons as they plan MDO.

Phenotype profile of a genetic mouse model for Muenke syndrome.

PURPOSE: The Muenke syndrome mutation (FGFR3 (P250R)), which was discovered 15 years ago, represents the single most common craniosynostosis mutation. Muenke syndrome is characterized by coronal suture synostosis, midface hypoplasia, subtle limb anomalies, and hearing loss. However, the spectrum of clinical presentation continues to expand. To better understand the pathophysiology of the Muenke syndrome, we present collective findings from several recent studies that have characterized a genetically equivalent mouse model for Muenke syndrome (FgfR3 (P244R)) and compare them with human phenotypes. CONCLUSIONS: FgfR3 (P244R) mutant mice show premature fusion of facial sutures, premaxillary and/or zygomatic sutures, but rarely the coronal suture. The mice also lack the typical limb phenotype. On the other hand, the mutant mice display maxillary retrusion in association with a shortening of the anterior cranial base and a premature closure of intersphenoidal and spheno-occipital synchondroses, resembling human midface hypoplasia. In addition, sensorineural hearing loss is detected in all FgfR3 (P244R) mutant mice as in the majority of Muenke syndrome patients. It is caused by a defect in the mechanism of cell fate determination in the organ of Corti. The mice also express phenotypes that have not been previously described in humans, such as reduced cortical bone thickness, hypoplastic trabecular bone, and defective temporomandibular joint structure. Therefore, the FgfR3 (P244R) mouse provides an excellent opportunity to study disease mechanisms of some classical phenotypes of Muenke syndrome and to test novel therapeutic strategies. The mouse model can also be further explored to discover previously unreported yet potentially significant phenotypes of Muenke syndrome.

The Muenke syndrome mutation (FgfR3P244R) causes cranial base shortening associated with growth plate dysfunction and premature perichondrial ossification in murine basicranial synchondroses.

Muenke syndrome caused by the FGFR3(P250R) mutation is an autosomal dominant disorder mostly identified with coronal suture synostosis, but it also presents with other craniofacial phenotypes that include mild to moderate midface hypoplasia. The Muenke syndrome mutation is thought to dysregulate intramembranous ossification at the cranial suture without disturbing endochondral bone formation in the skull. We show in this study that knock-in mice harboring the mutation responsible for the Muenke syndrome (FgfR3(P244R)) display postnatal shortening of the cranial base along with synchondrosis growth plate dysfunction characterized by loss of resting, proliferating and hypertrophic chondrocyte zones and decreased Ihh expression. Furthermore, premature conversion of resting chondrocytes along the perichondrium into prehypertrophic chondrocytes leads to perichondrial bony bridge formation, effectively terminating the postnatal growth of the cranial base. Thus, we conclude that the Muenke syndrome mutation disturbs endochondral and perichondrial ossification in the cranial base, explaining the midface hypoplasia in patients.

Computer-aided Surgical Planning and Osteosynthesis Plates for Bimaxillary Orthognathic Surgery: A Study of 14 Consecutive Patients.

Computer-aided surgical planning has become popular for planning orthognathic surgery (OS) as it saves surgeons' time and effort. A recent advancement has been the utilization of patient-specific cutting guides and osteosynthesis. The purpose of this study is to report the postoperative bimaxillary position utilizing custom plates for both jaws versus custom plates used in the maxilla only in 23 consecutive patients. Methods: All patients who underwent bimaxillary OS in 2017-2018 with preoperative computed tomography (CT) scan, postoperative day 1 CT scan, and at least 6 months follow-up were included in the study. Group 1 utilized maxillary preprinted plates (maxilla only). Group 2 utilized bimaxillary preprinted plates (maxillomandibular). Eight cephalometric landmarks to evaluate the movements were chosen. The ranges of the angle between the sella/nasion plane and the nasion/A plane (SNA), the angle between the sella/nasion plane and the nasion/B plane (SNB), and the angle created by the A point' nasion' and B point' which measures the relative position of maxilla to mandible, were analyzed to assess the angular change. Mean-squared displacement and the SD of the distances were used to assess movement in space. Results: Twenty-three patients (nine in group 1 and 14 in group 2) met the inclusion criteria. Results showed interarch relationships using custom plates for both jaws with ANB 0.4 compared to ANB 1.4 for maxillary custom plates only. Mandibular landmarks showed greater variation, and the t test study revealed the right mandibular first molar landmark showing the greatest variation (P = 0.03). Conclusions: Custom osteosynthesis plates for OS show good accuracy for the maxilla and higher variation in the mandible. Further studies will determine the margin of error that cannot be corrected with postoperative orthodontics.

Engineering of a periodontal ligament construct: cell and fibre alignment induced by shear stress.

AIM: We report an in vitro technique to establish alignment of collagen fibres and cells within a three-dimensional tissue equivalent that mimics the natural periodontal ligament (PDL) using a novel custom-designed bioreactor. MATERIAL AND METHODS: Shear stress was applied to the tissue equivalent prepared with collagen solution and seeded with human PDL cells. Stress-strain dynamics and the alignment of collagen fibres and PDL cells in tissue equivalents were analysed. RESULTS: Shear stress aligned collagen fibres and PDL cells in a direction parallel to the principle strain vector. PDL cells and Collagen fibres aligned in strained tissue equivalents with higher uniformity than in unstrained tissue equivalents. CONCLUSIONS: The cell and fibre alignment of the engineered PDL was precisely guided by mechanical shear stress along the direction of principal strain vector using a custom-designed bioreactor, suggesting that the enhanced functional property of engineered PDL constructs could be achieved with this technique.

Influence of Monobloc/Le Fort III Surgery on the Developing Posterior Maxillary Dentition and Its Resultant Effect on Orthognathic Surgery.

BACKGROUND: Timing of frontofacial surgery for the syndromic craniosynostosis as it relates to various surgical risks has not been adequately studied. The purpose of this study was to investigate posterior dental complications of midface advancement in patients with syndromic craniosynostosis undergoing surgery at different ages and the effects on subsequent orthognathic surgery. METHODS: A retrospective chart review of patients with syndromic craniosynostosis treated with midface advancement (monobloc or Le Fort III) from 1999 to 2018 was carried out. Patient demographics, records, and imaging studies were reviewed. A subanalysis of those patients who were also treated with orthognathic surgery from 2014 to 2018 with imaging studies available for analysis was also performed. RESULTS: Thirty-seven patients met the inclusion criteria. Sixty-four percent of the patients had radiographic evidence of maxillary molar dental abnormality. Older age at the time of surgery was significantly associated with a lower odds of sustaining dental injury (OR, 0.55; p = 0.034). The odds of damaging second or third maxillary molars was significantly higher with a younger age at the time of surgery (p = 0.021 and p = 0.034). The odds of sustaining dental injury increased moving posteriorly, showing the risk of abnormal pattern of M3 greater than M2 greater than M1. Advanced age at the time of surgery was significantly associated with decreased odds of dental injury (OR, 0.55; p = 0.034). CONCLUSIONS: Damage to the developing permanent maxillary molars may affect orthodontic management, mastication, and potentially maxillary development. Delaying frontofacial surgery until development of the permanent maxillary dentition should be considered if other indications do not mandate earlier intervention.

Metopic craniosynostosis due to mutations in GLI3: A novel association.

We report on the novel association of trigonocephaly and polysyndactyly in two unrelated patients due to mutations within the last third (exon 14) and first third (exon 6) of the GLI3 gene, respectively. GLI3 acts as a downstream mediator of the Sonic hedgehog signal-transduction pathway which is essential for early development; and plays a role in cell growth, specialization, and patterning of structures such as the brain and limbs. GLI3 mutations have been identified in patients with Pallister-Hall, Grieg cephalopolysyndactyly syndrome (GCPS), postaxial polydactyly type A1, preaxial polydactyly type IV, and in one patient with acrocallosal syndrome (ACLS). Furthermore, deletions including the GLI3 gene have been reported in patients with features of GCPS and ACLS. To date, trigonocephaly has not been associated with abnormalities of GLI3 and craniosynostosis is not a feature of GCPS. However, Hootnick and Holmes reported on a father with polysyndactyly and son with trigonocephaly, polysyndactyly, and agenesis of the corpus callosum, considered GCPS thereafter. Guzzetta et al. subsequently described a patient with trigonocephaly, polysyndactyly, and agenesis of the corpus callosum postulating a diagnosis of GCPS, later considered ACLS. In retrospect, these two patients, evaluated prior to mutational analysis, and our patients, with confirmed mutations, likely fall within the GLI3 morphopathy spectrum and may provide a bridge to better understanding those patients with overlapping features of GCPS and ACLS. Based on this observation, we suggest GLI3 studies in patients presenting with this constellation of findings, specifically metopic craniosynostosis with polysyndactyly, in order to provide appropriate medical management and genetic counseling.

Novel ANKH mutation in a patient with sporadic craniometaphyseal dysplasia.

Craniometaphyseal dysplasia is caused by mutations in ANKH (ankylosis, progressive homolog [mouse]) in the majority of cases, and all of the reported mutations are single amino acid changes. Genomic DNA from an affected patient, his biological parents, and a sibling was amplified and ANKH was sequenced. The affected patient had a complex heterozygous mutation in exon 7 (c.936T > C, c.938C > G, c.942_953delTGGTTGACGGAA), predicting p.Try290Gln and p.Trp292_Glu295del. We studied the effect of the predicted mutation on the subcellular distribution of ANKH protein. Immunofluorescent labeling of COS-7 cells transduced with normal or mutant Ank (murine progressive ankylosis), showed that normal Ank localized to both the plasma membrane and cytoplasm, whereas mutant Ank was detected only in the cytoplasmic compartment. We propose that this craniometaphyseal dysplasia mutation causes a loss of ANKH protein expression and activity in the plasma membrane as a result of aberrant intracellular protein trafficking.

Dura in the pathogenesis of syndromic craniosynostosis: fibroblast growth factor receptor 2 mutations in dural cells promote osteogenic proliferation and differentiation of osteoblasts.

Mutations in fibroblast growth factor receptor 2 (FGFR2), a transmembrane receptor expressed in suture mesenchyme, osteogenic fronts, and dura, have been implicated in the etiopathogenesis of craniosynostosis syndromes. The C278F- and P253R-FGFR2 mutations result in Crouzon and Apert syndromes, respectively. The dura mater plays a critical role in the formation and maintenance of cranial sutures. However, its role in syndromic craniosynostosis remains unclear. This study examines the influence of FGFR2 mutations in dural cells on osteoblast proliferation and differentiation. Primary cultures of dural cells and osteoblasts were established, and adenoviral-FGFR2 constructs were prepared by subcloning mutant (C278F and P253R) FGFR2 constructs into adenovirus. Dural cells were infected with adenovirus, and dural protein expression was confirmed by immunostaining. Infected dural cells were cocultured with osteoblasts using a transwell system for 7 days. Dural cells infected with null adenovirus served as the negative control. In separate cultures, osteoblasts were directly infected with the adenoviral-FGFR2 constructs. Osteoblast proliferation was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and differentiation was analyzed by alkaline phosphatase assay, histochemical staining, and gene expression studies. Osteoblasts directly infected with the Crouzon (C278F-FGFR2) mutation demonstrated an increase in cell proliferation (P < 0.05). Osteoblasts directly infected with the Apert (P253R-FGFR2) mutation demonstrated an increase in alkaline phosphatase activity. In coculture experiments, osteoblasts cocultured with Crouzon-transformed dural cells demonstrated increased cell proliferation (P < 0.05), whereas osteoblasts cocultured with Apert-transformed dural cells showed an increase in alkaline phosphatase activity (P < 0.05). In addition, osteogenic gene expression (alkaline phosphatase, osteopontin, and runx2) were up-regulated in osteoblasts cocultured with Apert-expressing dural cells. These experiments suggest that FGFR2 mutations in dural cells alter normal dural signaling. Apert mutations promote osteodifferentiation, whereas Crouzon mutations result in enhanced cell proliferation. These mutations may induce craniosynostosis in part through the influence of mutation-induced constitutive signaling in the dura, with subsequent enhancement of dural-mediated osteogenesis.