Microtia: epidemiology and genetics

Long-Term Morphological and Microarchitectural Stability of Tissue-Engineered, Patient-Specific Auricles In Vivo

Current techniques for autologous auricular reconstruction produce substandard ear morphologies with high levels of donor-site morbidity, whereas alloplastic implants demonstrate poor biocompatibility. Tissue engineering, in combination with noninvasive digital photogrammetry and computer-assisted design/computer-aided manufacturing technology, offers an alternative method of auricular reconstruction. Using this method, patient-specific ears composed of collagen scaffolds and auricular chondrocytes have generated auricular cartilage with great fidelity following 3 months of subcutaneous implantation, however, this short time frame may not portend long-term tissue stability. We hypothesized that constructs developed using this technique would undergo continued auricular cartilage maturation without degradation during long-term (6 month) implantation. Full-sized, juvenile human ear constructs were injection molded from high-density collagen hydrogels encapsulating juvenile bovine auricular chondrocytes and implanted subcutaneously on the backs of nude rats for 6 months. Upon explantation, constructs retained overall patient morphology and displayed no evidence of tissue necrosis. Limited contraction occurred in vivo, however, no significant change in size was observed beyond 1 month. Constructs at 6 months showed distinct auricular cartilage microstructure, featuring a self-assembled perichondrial layer, a proteoglycan-rich bulk, and rounded cellular lacunae. Verhoeff's staining also revealed a developing elastin network comparable to native tissue. Biochemical measurements for DNA, glycosaminoglycan, and hydroxyproline content and mechanical properties of aggregate modulus and hydraulic permeability showed engineered tissue to be similar to native cartilage at 6 months. Patient-specific auricular constructs demonstrated long-term stability and increased cartilage tissue development during extended implantation, and offer a potential tissue-engineered solution for the future of auricular reconstructions.

Genome-wide association study identifies multiple susceptibility loci for craniofacial microsomia

Craniofacial microsomia (CFM) is a rare congenital anomaly that involves immature derivatives from the first and second pharyngeal arches. The genetic pathogenesis of CFM is still unclear. Here we interrogate 0.9 million genetic variants in 939 CFM cases and 2,012 controls from China. After genotyping of an additional 443 cases and 1,669 controls, we identify 8 significantly associated loci with the most significant SNP rs13089920 (logistic regression P=2.15 × 10(-120)) and 5 suggestive loci. The above 13 associated loci, harboured by candidates of ROBO1, GATA3, GBX2, FGF3, NRP2, EDNRB, SHROOM3, SEMA7A, PLCD3, KLF12 and EPAS1, are found to be enriched for genes involved in neural crest cell (NCC) development and vasculogenesis. We then perform whole-genome sequencing on 21 samples from the case cohort, and identify several novel loss-of-function mutations within the associated loci. Our results provide new insights into genetic background of craniofacial microsomia.

Epidemiologic characteristics and time trend in the prevalence of anotia and microtia in China

BACKGROUND

Previous studies have shown an inconsistent time trend on the prevalence of anotia and microtia. Little has been reported on the epidemiologic characteristics of anotia and microtia in the Chinese population.

METHODS

Data from 1996-2007 were obtained from the Chinese Birth Defects Monitoring Network in China. Birth prevalence of anotia and microtia were assessed according to demographic characteristics and annual time trend. Poisson regression was used to calculate crude and adjusted prevalence ratios (APRs) and 95% confidence intervals (CIs) for selected demographic characteristics and subgroups of anotia and microtia.

RESULTS

A total of 1933 cases with anotia/microtia were identified among 6,308,594 live births, stillbirths, and terminations of pregnancy, yielding a rate of 3.06 per 10,000 births. Isolated anotia/microtia had a prevalence of 2.25 per 10,000 births, whereas among nonisolated cases, the prevalence was 0.81 per 10,000 births. The prevalence rates of anotia/microtia increased significantly during 1996-2007 (p < 0.05). Birth prevalence of isolated anotia/microtia was significantly higher among western births (APR, 1.24; 95% CI, 1.10-1.40), mothers residing in urban areas (APR, 1.29; 95% CI, 1.15-1.46), mothers more than 35 years of age (APR, 1.26; 95% CI, 1.01-1.57), and males (APR, 1.38; 95% CI, 1.24-1.53). No significant associations were observed between nonisolated anotia/microtia and geographic areas, maternal residence, and infant sex (except for maternal age).

CONCLUSION

An increasing trend of the birth prevalence of anotia and microtia is observed in China. Higher prevalence risk of isolated anotia and microtia is found among western births, mothers residing in urban areas, older mothers, and males.

Roles of GASP-1 and GDF-11 in Dental and Craniofacial Development

PURPOSE

Growth and differentiation factor-11 (GDF-11) is a TGF-β family member that plays important regulatory roles in development of multiple tissues which include axial skeletal patterning, palatal closure, and tooth formation. Proteins that have been identified as GDF-11 inhibitors include GDF-associated serum protein-1 (GASP-1) and GASP-2. Recently, we found that mice genetically engineered to lack both Gasp1 and Gdf11 have an increased frequency of cleft palate. The goal of this study was to investigate the roles of GDF-11 and its inhibitors, GASP-1 and GASP-2, during dental and craniofacial development and growth.

METHODS

Mouse genetic studies were used in this study. Homozygous knockout mice for Gasp1 (Gasp1^-/- ) and Gasp2 (Gasp2^-/- ) were viable and fertile, but Gdf11 homozygous knockout (Gdf11^-/- ) mice died within 24 hours after birth. The effect of either Gasp1 or Gasp2 deletion in Gdf11^-/- mice during embryogenesis was evaluated in Gasp1^-/-;Gdf11^-/- and Gasp2^-/-;Gdf11^-/- mouse embryos at 18.5 days post-coitum (E18.5). For the analysis of adult tissues, we used Gasp1^-/-;Gdf11^+/- and Gasp2^-/-;Gdf11^+/- mice to evaluate the potential haploinsufficiency of Gdf11 in Gasp1^-/- and Gasp2^-/- mice.

RESULTS

Although Gasp2 expression decreased after E10.5, Gasp1 expression was readily detected in various ectodermal tissues at E17.5, including hair follicles, epithelium in nasal cavity, retina, and developing tooth buds. Interestingly, Gasp1^-/- ;Gdf11^-/- mice had abnormal formation of lower incisors: tooth buds for lower incisors were under-developed or missing. Although Gdf11^+/- mice were viable and had mild transformations of the axial skeleton, no specific defects in the craniofacial development have been observed in Gdf11^+/- mice. However, loss of Gasp1 in Gdf11^+/- mice occasionally resulted in small and abnormally shaped auricles.

CONCLUSIONS

These findings suggest that both GASP-1 and GDF-11 play important roles in dental and craniofacial development both during embryogenesis and in adult tissues.

The image variations in mastoid segment of facial nerve and sinus tympani in congenital aural atresia by HRCT and 3D VR CT

OBJECTIVE

To find the variations of middle ear structures including the spatial pattern of mastoid segment of facial nerve and the shapes of the sinus tympani in patients with congenital aural atresia (CAA) by using the high-resolution (HR) CT and 3D volume rendered (VR) CT images.

METHODS

HRCT was performed in 25 patients with congenital aural atresia including six bilateral atresia patients (n=25, 21 males, 4 females, mean age 13.8 years, range 6-19). Along the long axis of the posterior semicircular canal ampulla, the oblique axial multiplanar reconstruction (MPR) was set to view the depiction of the round window and the mastoid segment of facial nerve. Volumetric rending technique was used to demonstrate the morphologic features. HRCT and 3D VR findings in atresia ears were compared with those in 19 normal ears of the unilateral ears of atresia patients.

RESULTS

On the basic plane, the horizontal line distances between the mastoid segment of the facial nerve and the round window (h-RF) in atresia ears significantly decreased compared to the control ears (P<0.05). There was a significant negative correlation between the sinus tympani area (a-ST) and the distance between the horizontal lines of FN and RW midpoint (h-RF) (P<0.05). The mean area of sinus tympani in atresia group is larger (P<0.05). The shapes of the sinus tympani were classified into three categories: the cup-shaped, the pear-shaped and the boot-shaped. Area measurement indicated that the boot-shaped sinus tympani was a special variation with a large area, which only appears in CAA group. There were a significant difference between the area of the boot-shaped group and the other two groups (P<0.05). The morphologic differences of ST and other middle ear structures can also be observed visually in 3D VR CT images.

CONCLUSION

HRCT and 3D VR CT could help a better understanding of different kinds of variations in mastoid segment of facial nerve and sinus tympani in CAA ears. And it may further help surgeons to make the correct decision for hearing rehabilitation.

The prevalence of preauricular sinus and associated factors in a nationwide population-based survey of South Korea

OBJECTIVE

To investigate the prevalence of preauricular sinus (PAS) using data from a government-centered survey in South Korea and to reveal the relationship between the occurrence of PAS and associated factors.

PATIENTS

Data obtained during July 2008 to December 2012 were analyzed. Annually, 10,000 to 12,000 individuals are selected from a panel to represent the population using a multistage clustered and stratified random sampling method based on the National Census Data. A total of 56,592 individuals participated in the survey (25,586 male and 31,006 female).

INTERVENTION

After completion of the otolaryngologic questionnaires, the auricle was examined to check for malformation and PAS in those older than 1 year. Next, an otolaryngologist conducted a physical examination of the head and neck using videoassisted endoscopy.

MAIN OUTCOME MEASURE

Physical examination.

RESULTS

One thousand one hundred thirty-two individuals had PAS representing the overall prevalence of 1.91% in South Korea, with 79.08% of cases occurring unilaterally. Female participants had a significantly higher prevalence than male (p < 0.001), and a significant decrease with age was observed in both male and female populations (p < 0.001). A higher proportion of PAS was found in individuals with external ear anomaly (p < 0.001) and not associated with abnormal otoendoscopic findings such as tympanic membrane perforation, cholesteatomatous condition including retraction pocket, and middle ear effusion.

CONCLUSION

A large-scale government-centered survey demonstrates a high prevalence, female dominance, and age-related decrease of PAS in South Korea.

Biochemical properties of tissue-engineered cartilage

OBJECTIVE

Microtia is treated with rib cartilage sculpting and staged procedures; though aesthetically pleasing, these constructs lack native ear flexibility. Tissue-engineered (TE) elastic cartilage may bridge this gap; however, TE cartilage implants lead to hypertrophic changes with calcification and loss of flexibility. Retaining flexibility in TE cartilage must focus on increased elastin, maintained collagen II, decreased collagen X, with prevention of calcification. This study compares biochemical properties of human cartilage to TE cartilage from umbilical cord mesenchymal stem cells (UCMSCs). Our goal is to establish a baseline for clinically useful TE cartilage.

METHODS

Discarded cartilage from conchal bowl, microtic ears, preauricular tags, rib, and TE cartilage were evaluated for collagen I, II, X, calcium, glycosaminoglycans, elastin, and fibrillin I and III. Human UCMSCs were chondroinduced on 2D surfaces and 3D D,L-lactide-co-glycolic acid (PLGA) fibers.

RESULTS

Cartilage samples demonstrated similar staining for collagens I, II, and X, elastin, and fibrillin I and III, but differed from rib. TE pellets and PLGA-supported cartilage were similar to auricular samples in elastin and fibrillin I staining. TE samples were exclusively stained for fibrillin III. Only microtic samples demonstrated calcium staining.

CONCLUSIONS

TE cartilage expressed similar levels of elastin, fibrillin I, and collagens I and X when compared to native cartilage. Microtic cartilage demonstrated elevated calcium, suggesting this abnormal tissue may not be a viable cell source for TE cartilage. TE cartilage appears to recapitulate the embryonic development of fibrillin III, which is not expressed in adult tissue, possibly providing a strategy to control TE elastic cartilage phenotype.

Ectopic external auditory canal and ossicular formation in the oculo-auriculo-vertebral spectrum

Ear abnormalities in oculo-auricular-vertebral spectrum commonly present with varying degrees of external and middle ear atresias, usually in the expected locations of the temporal bone and associated soft tissues, without ectopia of the external auditory canal. We present the unique imaging of a 4-year-old girl with right hemifacial microsomia and ectopic location of an atretic external auditory canal, terminating in a hypoplastic temporomandibular joint containing bony structures with the appearance of auditory ossicles. This finding suggests an early embryological dysfunction involving Meckel's cartilage of the first branchial arch.

Auricular reconstruction of congenital microtia: personal experience in 225 cases

Microtia is a congenital disease with various degrees of severity, ranging from the presence of rudimentary and malformed vestigial structures to the total absence of the ear (anotia). The complex anatomy of the external ear and the necessity to provide good projection and symmetry make this reconstruction particularly difficult. The aim of this work is to report our surgical technique of microtic ear correction and to analyse the short and long term results. From 2000 to 2013, 210 patients affected by microtia were treated at the Maxillo-Facial Surgery Division, Head and Neck Department, University Hospital of Parma. The patient population consisted of 95 women and 115 men, aged from 7 to 49 years. A total of 225 reconstructions have been performed in two surgical stages basing of Firmin's technique with some modifications and refinements. The first stage consists in fabrication and grafting of a three-dimensional costal cartilage framework. The second stage is performed 5-6 months later: the reconstructed ear is raised up and an additional cartilaginous graft is used to increase its projection. A mastoid fascial flap together with a skin graft are then used to protect the cartilage graft. All reconstructions were performed without any major complication. The results have been considered satisfactory by all patients starting from the first surgical step. Low morbidity, the good results obtained and a high rate of patient satisfaction make our protocol an optimal choice for treatment of microtia. The surgeon's experience and postoperative patient care must be considered as essential aspects of treatment.

[Microtia-atresia: clinical, genetic and genomic aspects]

Mexico has a prevalence of microtia of 7.37/10,000 (newborns), 3 times higher than the prevalence reported in other populations (USA 2-3/10,000). Microtia is defined as a congenital malformation of the external ear characterized by a small auricular lobe with an abnormal shape. It is more often unilateral and on the right side. Males are more frequently affected than females. It can occur as an isolated defect or can be associated with other abnormalities such as stenosis of the external auditory canal. In three of the main pediatric hospitals in Mexico, microtia is among the most important causes of attendance in the Genetics Department. Microtia-atresia must be considered as a major malformation with important repercussions in hearing function requiring multidisciplinary medical care in order to limit the disability associated and to provide genetic counseling. Its etiology is complex. Only in a minor number of cases it has been possible to identify a main genetic component (as in monogenic presentations) or a main environmental cause (as in fetal alcohol syndrome or pregestational diabetes). In most cases this malformation is multifactorial. Due to the relevance that the frequency of microtia atresia has in different health services in Mexico, it is important that all medical professionals are aware of its clinical, molecular and inherited characteristics.

Understanding the molecular mechanisms of human microtia via a pig model of HOXA1 syndrome

Microtia is a congenital malformation of the outer ears. Although both genetic and environmental components have been implicated in microtia, the genetic causes of this innate disorder are poorly understood. Pigs have naturally occurring diseases comparable to those in humans, providing exceptional opportunity to dissect the molecular mechanism of human inherited diseases. Here we first demonstrated that a truncating mutation in HOXA1 causes a monogenic disorder of microtia in pigs. We further performed RNA sequencing (RNA-Seq) analysis on affected and healthy pig embryos (day 14.25). We identified a list of 337 differentially expressed genes (DEGs) between the normal and mutant samples, shedding light on the transcriptional network involving HOXA1. The DEGs are enriched in biological processes related to cardiovascular system and embryonic development, and neurological, renal and urological diseases. Aberrant expressions of many DEGs have been implicated in human innate deformities corresponding to microtia-associated syndromes. After applying three prioritizing algorithms, we highlighted appealing candidate genes for human microtia from the 337 DEGs. We searched for coding variants of functional significance within six candidate genes in 147 microtia-affected individuals. Of note, we identified one EVC2 non-synonymous mutation (p.Asp1174Asn) as a potential disease-implicating variant for a human microtia-associated syndrome. The findings advance our understanding of the molecular mechanisms underlying human microtia, and provide an interesting example of the characterization of human disease-predisposing variants using pig models.

Summary: A pig model of HOXA1 syndrome provides novel insight into the molecular mechanisms of human microtia.

Phenotypic sub-grouping in microtia using a statistical and a clinical approach

The clinical presentation of microtia varies widely from minimal morphological abnormalities to complete absence of the ear. In this study we sought to identify and characterize sub-groups of microtia using a statistical and a clinical approach. Photographs of 86 ears were classified in relation to all the external ear components. We used cluster analysis and rater's clinical opinion to identify groups with similar phenotypes in two separate analyses. We used Cramer's Phi coefficient of association to assess the similarity among the clinician's groupings as well as among the statistical sub-phenotypic groups and each of the clinician's groupings. The cluster analysis initially divided the 86 ears into a more and a less severe group. The less severe group included two sub-groups that included ears classified as normal and a group that had very few anomalous components. The group of 48 more affected ears all had abnormalities of the helix crus; antihelix-stem, -superior crus and -inferior crus; and antitragus. These were further divided into 4 sub-phenotypes. There was a moderate degree of association among the raters' groupings (Cramer's Phi: 0.64 to 0.73). The statistical and clinical groupings had a lower degree of association (Cramer's Phi: 0.49 to 0.58). Using standardized characterization of structural abnormalities of the ear we identified six distinct phenotypic groups; correlations with clinicians' groupings were moderate. These clusters may represent groups of ear malformations associated with the same etiology, similar time of insult or target cell population during embryonic development. The results will help inform investigations on etiology.

Johnson-McMillin Microtia Syndrome: New Additional Family

Microtia is a congenital anomaly that is found with different prevalence among various populations. The exact etiology of ear anomalies is still unknown. We describe a new additional family with this rare disorder; Johnson-McMillin syndrome (JMS) where mother, son, and distant grandmother have multiple features of JMS in the form of microtia, facial asymmetry, ear malformation, hearing defect, and hypotrichosis. Variable presentations in this family could be referred to phenotype variation supporting an autosomal dominant pattern of inheritance. We observed that the mother was very sad and suffered from feelings of guilt. We found that she had isolated herself from family and community out of fear of being stigmatized and hurt. We concluded that the occurrence of microtia is of public health importance, adhering to traditional marriage customs in Egypt increases women's risk of giving birth to a disabled child, yet the mothers are blamed and shamed for their children's birth defects by their husbands, families, and communities, while the fathers are not stigmatized.

Sociodemographic and hispanic acculturation factors and isolated anotia/microtia

BACKGROUND

It has been observed in several studies that infants with anotia/microtia are more common among Hispanics compared with other racial/ethnic groups. We examined the association between selected Hispanic ethnicity and acculturation factors and anotia/microtia in the National Birth Defects Prevention Study.

METHODS

We examined data from mothers of 351 infants with isolated anotia/microtia and 8435 unaffected infants from the National Birth Defects Prevention Study with an expected delivery date from 1997 to 2007. Sociodemographic, maternal, and acculturation factors (e.g., age, maternal education, household income, body mass index, gestational diabetes, folic acid, smoking, alcohol intake, study center, parental birthplace, and years lived in the United States, maternal language) were assessed as overall risk factors and also as risk factors among subgroups of Hispanics (United States- and foreign-born) versus non-Hispanic whites.

RESULTS

Compared with non-Hispanic whites, both United States- and foreign-born Hispanic mothers demonstrated substantially higher odds of delivering infants with anotia/microtia across nearly all strata of sociodemographic and other maternal factors (adjusted odds ratios range: 2.1-11.9). The odds of anotia/microtia was particularly elevated among Hispanic mothers who emigrated from Mexico after age five (adjusted odds ratios = 4.88; 95% confidence interval = 2.93-8.11) or who conducted the interview in Spanish (adjusted odds ratios = 4.97; 95% confidence interval = 3.00-8.24).

CONCLUSION

We observed that certain sociodemographic and acculturation factors are associated with higher risks of anotia/microtia among offspring of Hispanic mothers.

Genome-wide scan reveals LEMD3 and WIF1 on SSC5 as the candidates for porcine ear size

The quantitative trait loci (QTL) for porcine ear size was previously reported to mainly focus on SSC5 and SSC7. Recently, a missense mutation, G32E, in PPARD in the QTL interval on SSC7 was identified as the causative mutation for ear size. However, on account of the large interval of QTL, the responsible gene on SSC5 has not been identified. In this study, an intercross population was constructed from the large-eared Minzhu, an indigenous Chinese pig breed, and the Western commercial Large White pig to examine the genetic basis of ear size diversity. A GWAS was performed to detect SNPs significantly associated with ear size. Thirty-five significant SNPs defined a 10.78-Mb (30.14–40.92 Mb) region on SSC5. Further, combining linkage disequilibrium and haplotype sharing analysis, a reduced region of 3.07-Mb was obtained. Finally, by using a selective sweep analysis, a critical region of about 450-kb interval containing two annotated genes LEMD3 and WIF1 was refined in this work. Functional analysis indicated that both represent biological candidates for porcine ear size, with potential application in breeding programs. The two genes could also be used as novel references for further study of the mechanism underlying human microtia.

Genome-wide linkage study suggests a susceptibility locus for isolated bilateral microtia on 4p15.32-4p16.2

Microtia is a congenital deformity where the external ear is underdeveloped. Genetic investigations have identified many susceptibility genes of microtia-related syndromes. However, no causal genes were reported for isolated microtia, the main form of microtia. We conducted a genome-wide linkage analysis on a 5-generation Chinese pedigree with isolated bilateral microtia. We identified a suggestive linkage locus on 4p15.32-4p16.2 with parametric LOD score of 2.70 and nonparametric linkage score (Zmean) of 12.28 (simulated occurrence per genome scan equal to 0.46 and 0.47, respectively). Haplotype reconstruction analysis of the 4p15.32-4p16.2 region further confined the linkage signal to a 10-Mb segment located between rs12505562 and rs12649803 (9.65-30.24 cM; 5.54-15.58 Mb). Various human organ developmental genes reside in this 10-Mb susceptibility region, such as EVC, EVC2, SLC2A9, NKX3-2, and HMX1. The coding regions of three genes, EVC known for cartilage development and NKX3-2, HMX1 involved in microtia, were selected for sequencing with 5 individuals from the pedigree. Of the 38 identified sequence variants, none segregates along with the disease phenotype. Other genes or DNA sequences of the 10-Mb region warrant for further investigation. In conclusion, we report a susceptibility locus of isolated microtia, and this finding will encourage future studies on the genetic basis of ear deformity.

Microtia in the Netherlands: clinical characteristics and associated anomalies

BACKGROUND

In Europe there have been few detailed reports on the clinical characteristics of microtia patient populations. The objective of the present study is to contribute to our insight of microtia in Europe by examining the Dutch microtia population treated in the University Medical Center Utrecht (UMCU) with regards to its clinical features and associated anomalies. In addition, an overview of the literature is provided for thorough comparison.

METHODS

A retrospective chart review was performed for all microtia patients referred to the UMCU for reconstructive surgery of the auricle over the period 1990-2012. Previous studies were identified by a systematic search of the electronic literature databases PubMed and Embase. In a subsequent meta-analysis the results from the literature review were pooled by geographical region to facilitate comparison.

RESULTS

A total of 204 microtia patients were referred for reconstructive surgery during 1990-2012. This group was characterized by a male predominance of 60.8%. Unilateral disease was observed in 91.7% of patients, affecting the right auricle in 66.3%. In unilateral patients lobule type microtia was seen in 59.9%, (small) concha type in 34.4% and anotia in 5.7%. The more frequent anomalies associated with microtia were atresia of the acoustic meatus (76.0%), preauricular skin tags (30.5%), hemifacial microsomia (27.5%), facial nerve paralysis (8.3%) and congenital heart disease (2.5%). Familial occurrence of microtia was reported for 2.0% of UMCU patients and for 10.0% of patients in the literature.

CONCLUSION

The clinical characteristics of microtia in the Netherlands correspond to those reported for other patient populations in the literature. Most congenital anomalies associated with microtia in Dutch patients belong to the Oculo-Auriculo-Vertebral Spectrum. The considerable degree of familial microtia observed in the literature points to a substantial genetic component in the etiology of the condition.

The genetics of auricular development and malformation: new findings in model systems driving future directions for microtia research

Microtia is a term used to describe a wide array of phenotypic presentations of the outer ear. Although the majority of the cases are isolated in nature, much of our understanding of the causes of microtia has been driven by the identification of genes underlying syndromic forms where the anomaly co-presents with various other craniofacial and extra-craniofacial structural defects. In this review we discuss recent findings in mice deficient in Hoxa2, a key regulator of branchial arch patterning, which has necessitated a revision to the canonical model of pinna morphogenesis. The revised model will likely impact current classification schemes for microtia and, as we argue in this review, the interpretation of the developmental basis for various auricular malformations. In addition, we highlight recent studies in other mammalian species that are providing the first clues as to possible causes of at least some isolated anomalies and thus should now accelerate the search for the more elusive genetic contributions to the many isolated and non-syndromic cases of microtia. These findings, together with the application of new genome-level sequencing technologies and more thorough quantitative assessment of available mutant mouse resources, promise an exciting future for genetic studies in microtia.

Auricular reconstruction for microtia: A review of available methods

Several surgical techniques have been described for auricular reconstruction. Autologous reconstruction using costal cartilage is the most widely accepted technique of microtia repair. However, other techniques have certain indications and should be discussed with patients and families when planning for an auricular reconstruction. In the present review, the authors discuss the main surgical techniques for auricular reconstruction including autologous costal cartilage graft, Medpor (Stryker, USA) implant and prosthetic reconstruction. To further elaborate on the advantages and disadvantages of each technique, the authors invited leaders in this field, Dr Nagata, Dr Park, Dr Reinisch and Dr Wilkes, to comment on their own technique and provide examples of their methods.

Clinical care in craniofacial microsomia: a review of current management recommendations and opportunities to advance research

Craniofacial microsomia (CFM) is a complex condition associated with microtia, mandibular hypoplasia, and preauricular tags. It is the second most common congenital facial condition treated in many craniofacial centers and requires longitudinal multidisciplinary patient care. The purpose of this article is to summarize current recommendations for clinical management and discuss opportunities to advance clinical research in CFM.

HOXA2 haploinsufficiency in dominant bilateral microtia and hearing loss

Microtia is a rare, congenital malformation of the external ear that in some cases has a genetic etiology. We ascertained a three-generation family with bilateral microtia and hearing loss segregating as an autosomal dominant trait. Exome sequencing of affected family members detected only seven shared, rare, heterozygous, nonsynonymous variants, including one protein truncating variant, a HOXA2 nonsense change (c.703C>T, p.Q235*). The HOXA2 variant was segregated with microtia and hearing loss in the family and was not seen in 6,500 individuals sequenced by the NHLBI Exome Sequencing Project or in 218 control individuals sequenced in this study. HOXA2 has been shown to be critical for outer and middle ear development through mouse models and has previously been associated with autosomal recessive bilateral microtia. Our data extend these conclusions and define HOXA2 haploinsufficiency as the first genetic cause for autosomal-dominant nonsyndromic microtia.

High-fidelity tissue engineering of patient-specific auricles for reconstruction of pediatric microtia and other auricular deformities

Introduction

Autologous techniques for the reconstruction of pediatric microtia often result in suboptimal aesthetic outcomes and morbidity at the costal cartilage donor site. We therefore sought to combine digital photogrammetry with CAD/CAM techniques to develop collagen type I hydrogel scaffolds and their respective molds that would precisely mimic the normal anatomy of the patient-specific external ear as well as recapitulate the complex biomechanical properties of native auricular elastic cartilage while avoiding the morbidity of traditional autologous reconstructions.

Methods

Three-dimensional structures of normal pediatric ears were digitized and converted to virtual solids for mold design. Image-based synthetic reconstructions of these ears were fabricated from collagen type I hydrogels. Half were seeded with bovine auricular chondrocytes. Cellular and acellular constructs were implanted subcutaneously in the dorsa of nude rats and harvested after 1 and 3 months.

Results

Gross inspection revealed that acellular implants had significantly decreased in size by 1 month. Cellular constructs retained their contour/projection from the animals' dorsa, even after 3 months. Post-harvest weight of cellular constructs was significantly greater than that of acellular constructs after 1 and 3 months. Safranin O-staining revealed that cellular constructs demonstrated evidence of a self-assembled perichondrial layer and copious neocartilage deposition. Verhoeff staining of 1 month cellular constructs revealed de novo elastic cartilage deposition, which was even more extensive and robust after 3 months. The equilibrium modulus and hydraulic permeability of cellular constructs were not significantly different from native bovine auricular cartilage after 3 months.

Conclusions

We have developed high-fidelity, biocompatible, patient-specific tissue-engineered constructs for auricular reconstruction which largely mimic the native auricle both biomechanically and histologically, even after an extended period of implantation. This strategy holds immense potential for durable patient-specific tissue-engineered anatomically proper auricular reconstructions in the future.

Vasoactive exposures during pregnancy and risk of microtia

BACKGROUND

Little is known about the etiology of nonsyndromic microtia. This study investigated the hypothesis that microtia is caused by vascular disruption.

METHODS

The study analyzed data from the population-based National Birth Defects Prevention Study (NBDPS) for deliveries between 1997 and 2005. Four hundred eleven nonsyndromic cases of microtia, with or without additional defects, were compared to 6560 nonmalformed infants with respect to maternal exposures to vasoactive medications and smoking during the periconceptional period and conditions that have previously been associated with vascular events (multiple gestation, maternal history of type 1, type 2, or gestational diabetes, and hypertension). Odds ratios (ORs) were estimated with multivariable models, controlling for the effects of race/ethnicity, education, periconceptional folic acid use, and study center.

RESULTS

Risk estimates for vasoactive medications and smoking were not meaningfully increased. Maternal type 1/2 diabetes was diagnosed before or during the index pregnancy in 4% and 1% of cases, respectively, compared to 1% and 0.05% of controls; the adjusted OR for these two groups combined was 7.2 (95% confidence interval [CI], 3.9-13.1). Gestational diabetes was observed for 9% of cases and 6% of controls; the OR was moderately elevated (OR, 1.4; 95% CI, 0.9-2.0). ORs were also increased for multiple gestations (OR, 2.5; 95% CI, 1.5-4.2) and pre-existing hypertension (OR, 1.6; 95% CI, 1.0-2.5).

CONCLUSIONS

Because ORs were only elevated for diabetes and not for vasoactive exposures or other potential vascular events, findings suggest that some microtia occurrences may be part of the diabetic embryopathy rather than manifestations of vascular disruption. Birth Defects Research (Part A), 2013. © 2012 Wiley Periodicals, Inc.