Arch Defects Research Articles

Retinoic acid is required for endodermal pouch morphogenesis and not for pharyngeal endoderm specification

Because tissues from all three germ layers contribute to the pharyngeal arches, it is not surprising that all major signaling pathways are involved in their development. We focus on the role of retinoic acid (RA) signaling because it has been recognized for quite some time that alterations in this pathway lead to craniofacial malformations. Several studies exist that describe phenotypes observed upon RA perturbations in pharyngeal arch development; however, these studies did not address whether RA plays multiple roles at distinct time points during development. Here, we report the resulting phenotypes in the hindbrain, the neural crest-derived tissues, and the pharyngeal endoderm when RA synthesis is disrupted during zebrafish gastrulation and pharyngeal arch morphogenesis. Our results demonstrate that RA is required for the post-gastrulation morphogenesis and segmentation of endodermal pouches, and that loss of RA does not affect the length of the pharyngeal ectoderm or medial endoderm along the anterior-posterior axis. We also provide evidence that RA is not required for the specification of pharyngeal pouch endoderm and that the pharyngeal endoderm consists of at least two different cell populations, of which the pouch endoderm is sensitive to RA and the more medial pharyngeal endoderm is not. These results demonstrate that the developmental processes underlying pharyngeal arch defects differ depending on when RA signaling is disturbed during development.

A novel nonsense mutation in the EYA1 gene associated with branchio‐oto‐renal/branchiootic syndrome in an Afrikaner kindred

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by the associations of hearing loss, branchial arch defects and renal anomalies. Branchiootic (BO) syndrome is a related disorder that presents without the highly variable characteristic renal anomalies of BOR syndrome. Dominant mutations in the human homologue of the Drosophila eyes absent gene (EYA1) are frequently the cause of both BOR and BO syndromes. We report a South African family of Afrikaner descent with affected individuals presenting with pre-auricular abnormalities and either hearing loss or bilateral absence of the kidneys. Genetic analysis of the pedigree detected a novel EYA1 heterozygous nonsense mutation in affected family members but not in unaffected family members or a random DNA panel. Through mutational analysis, we conclude that this particular mutation is the cause of BOR/BO syndrome in this family as a result of a truncation of the EYA1 protein that ablates the critical EYA homologous region. To the best of our knowledge, this is the first case of BOR/BO syndrome reported in Africa or in those of the Afrikaner descent.

Selective management of the left ventricular outflow tract for repair of interrupted aortic arch with ventricular septal defect: Management of left ventricular outflow tract obstruction

Left ventricular outflow tract obstruction remains an early and late complication after repair of interrupted aortic arch and ventricular septal defect. We reviewed our experience with the selective management of the infundibular septum during primary repair to address left ventricular outflow tract obstruction. From 1991 through 2001, all 27 patients presenting with interrupted aortic arch/ventricular septal defect and posterior deviation of the infundibular septum were analyzed. Fifteen patients with the smallest subaortic areas underwent myectomy or myotomy of the infundibular septum concomitant with interrupted aortic arch/ventricular septal defect repair. Patients undergoing myectomy-myotomy (Group I) had significantly smaller subaortic diameter indexes (0.83 +/- 0.16 cm/m2) when compared with those who had only interrupted aortic arch/ventricular septal defect repair (group 2: 0.99 +/- 0.13 cm/m2, P = .012). Two hospital deaths occurred in group 1, and 1 occurred in group 2. No late deaths occurred. No patient in group 2 required reoperation. Six group 1 patients required 9 reoperations for left ventricular outflow tract obstruction. Five patients underwent resection of a new subaortic membrane. Only 1 patient had recurrent muscular left ventricular outflow tract obstruction. Three patients required a second reoperation, primarily related to aortic valve stenosis. Interrupted aortic arch/ventricular septal defect with posterior malalignment of the infundibular septum can be repaired with low mortality in the neonatal period. Tailored to the degree of subaortic narrowing, resection or incision of the infundibular septum at the time of primary repair was very effective in preventing or prolonging the interval to recurrent left ventricular outflow tract obstruction compared with the published data. However, reoperation for left ventricular outflow tract obstruction, often related to the development of a new and discrete subaortic membrane or valvar stenosis, is still required in a subset of patients.

Effects of genetic background on cardiovascular and placental anomalies in the Ts16 mouse

To investigate the genetic contribution to phenotypic variability in aneuploidy, we generated mice with trisomy 16 (Ts16) by mating [Rb(6.16)24Lub x Rb(16.17)7Bnr]F1 males with females from four inbred strains, BALB/cJ, C3H/HeJ,C57BL/6J, and DBA/2J. Among the four Ts16 strains generated, there were no significant differences in survival,weight,or length relative to euploid controls at either embryonic day (E) 14.5 or E17.5. All Ts16 fetuses exhibited gross morphological abnormalities that were not strain-specific in occurrence or frequency. There was gross disorganization of the placenta with an increased area of spongiotrophoblast invading the labyrinth and a range of limited trophoblast cell invasion in all Ts16 fetuses relative to euploid controls. Interestingly, at E10.5, we observed pharyngeal arch artery (PAA) anomalies exclusively on the C3H/HeJ background. In contrast, at E17.5, in addition to ventricular and atrioventricular septal defects, a high frequency of aortic arch defects were detected in all Ts16 fetuses, regardless of genetic background. Taken together, the cardiovascular findings indicate that in the presence of three copies of murine chromosome 16 the development of PAA defects is strongly influenced by genetic background while the development of aortic arch anomalies in the absence of preexisting PAA anomalies, is not. These results provide the foundation for studying genomic-based pathological conditions in the Ts16 murine model by analyzing strain-specific differences in gene expression.

Application of graded dendritic vein graft in the treatment of hand injuries

目的 探讨手掌严重碾挫伤应用血管移植手术方法的选择.方法对12例手掌碾挫伤伴血管损伤的患者,采用树枝状浅表静脉倒转后多级移植修复缺损的手掌动脉,同时对缺损皮肤一期行植皮或皮瓣修复.结果术后12例创面全部Ⅰ期愈合,手指血循环好.术后随访3～22个月,手功能评定[1]:优5例,良4例,可2例,差1例,优良率为75%.手掌恢复了良好的外形和功能,能完成手指的捏、握、对掌和对指功能.结论对严重的手掌毁损伤,利用树枝状静脉移植修复缺损的血管,能获得较好的手功能和外形。

Tethered Spinal Cord with Double Spinal Lipomas

Although lumbosacral lipoma is reported to occur in 4-8 of 100,000 patients, and 66% of lipomyelomeningoceles in young patients are accompanied by hypertrophic filum terminale, it is very rare to find two isolated spinal lipomas simultaneously. A 3 month-old baby girl was admitted to the hospital for a protruding, non-tender, soft, subcutaneous 2.5 cm mass of the lumbosacral area that had been present since birth. Simple radiography showed a spinal posterior arch defect from L3 to L5, and magnetic resonance imaging (MRI) demonstrated two isolated spinal lipomas, a transitional type from L3 to L5, and a terminal type below S1 without dural defect. The cornus medullaris was severely tethered descending to the S1, but there was no cerebellar or brain stem herniation on the MRI. We suggest that the presence of a combined spinal lipoma should be a point for careful differentiation in an infant with spinal lipoma.

Os odontoideum with bipartite atlas and segmental instability: a case report

We report on the case of a 15-year-old adolescent who presented with a transient paraplegia and hyposensibility of the upper extremities after sustaining a minor hyperflexion trauma to the cervical spine. Neuroimaging studies revealed atlantoaxial dislocation and ventral compression of the rostral spinal cord with increased cord signal at C1/C2 levels caused by an os odontoideum, as well as anterior and posterior arch defects of the atlas. The patient underwent closed reduction and posterior atlantoaxial fusion. We describe the association of an acquired instability secondary to an os odontoideum with an anteroposterior spondyloschisis of the atlas and its functional result after 12 months. The rare coincidence of both lesions indicates a multiple malformation of the upper cervical spine and supports the theory of an embryologic genesis of os odontoideum.

A randomized, double-blind, placebo-controlled pilot trial of triiodothyronine in neonatal heart surgery

This study was undertaken to evaluate the effect of triiodothyronine replacement on the early postoperative course of neonates undergoing aortic arch reconstruction. We performed a randomized, double-blind, placebo-controlled trial of triiodothyronine supplementation in neonates undergoing either a Norwood procedure or two-ventricle repair of interrupted aortic arch and ventricular septal defect. Patients were assigned to receive a continuous infusion of triiodothyronine (0.05 micro/kg/h) or placebo for 72 hours after cardiopulmonary bypass. Primary end points were a composite clinical outcome score and cardiac index at 48 postoperative hours. We enrolled 42 patients (triiodothyronine n = 22, placebo n = 20). Baseline characteristics were similar in the treatment groups. Study drug was discontinued prematurely because of hypertension (n = 1) and ectopic atrial tachycardia (n = 1), both cases in the triiodothyronine group. Free and total triiodothyronine levels were higher in the triiodothyronine group than in the placebo group at 24, 48, and 72 postoperative hours (P < .001). The median clinical outcome scores were 2.0 (range 0-4) with triiodothyronine and 2.0 (range 0-7) with placebo (P = .046). Compared with those in the placebo group, neonates assigned to triiodothyronine had shorter median time to negative fluid balance (2.0 vs 2.5 days, P = .027). Cardiac index values were 2.11 +/- 0.64 L/min x m2 with triiodothyronine and 2.05 +/- 0.72 L/min x m2 with placebo (P = .81). Heart rate and diastolic blood pressure were not influenced by triiodothyronine supplementation, but systolic blood pressure was higher in the triiodothyronine group (P < .001). No serious adverse events were attributed to triiodothyronine administration. Triiodothyronine supplementation was safe and resulted in more rapid achievement of negative fluid balance after aortic arch reconstruction. Cardiac index at 48 hours was not significantly improved.

Loss of Gbx2 results in neural crest cell patterning and pharyngeal arch artery defects in the mouse embryo

Several syndromes characterized by defects in cardiovascular and craniofacial development are associated with a hemizygous deletion of chromosome 22q11 in humans and involve defects in pharyngeal arch and neural crest cell development. Recent efforts have focused on identifying 22q11 deletion syndrome modifying loci. In this study, we show that mouse embryos deficient for Gbx2 display aberrant neural crest cell patterning and defects in pharyngeal arch-derived structures. Gbx2 −/− embryos exhibit cardiovascular defects associated with aberrant development of the fourth pharyngeal arch arteries including interrupted aortic arch type B, right aortic arch, and retroesophageal right subclavian artery. Other developmental abnormalities include overriding aorta, ventricular septal defects, cranial nerve, and craniofacial skeletal patterning defects. Recently, Fgf8 has been proposed as a candidate modifier for 22q11 deletion syndromes. Here, we demonstrate that Fgf8 and Gbx2 expression overlaps in regions of the developing pharyngeal arches and that they interact genetically during pharyngeal arch and cardiovascular development.

Anomalous Left Coronary Artery, Ventricular Septal Defect, and Double Aortic Arch

Anomalous origin of the left coronary artery from the pulmonary artery generally occurs in isolation. We report an infant diagnosed with double aortic arch and ventricular septal defect who was found to have an anomalous origin of the left coronary artery from the pulmonary artery at surgery. Successful ventricular septal defect repair, division of the arch, and aortic reimplantation of the left coronary artery was performed. This article describes a combination of lesions previously not described, highlights the altered presentation when multiple lesions coexist, discusses the propensity to miss the anomalous coronary, and reviews the literature that demonstrates the consequences of overlooking this defect.

An abused five-month-old girl: Hangman’s fracture or congenital arch defect?

Hangman’s fractures are a rare finding in childhood. In case of suspected or proven child abuse, differentiation with a congenital defect of the posterior arch of C2 is essential. We present the case of a 5-month-old girl, who had a history of being physically abused by one of her caretakers. On the lateral view of the cervical spine, a defect of the posterior elements of C2 and an anterolisthesis of C2 on C3 was seen. CT scan showed a bilateral defect in the posterior elements of C2. No soft-tissue swelling of hematoma was noted. MRI showed a normal signal intensity of the intervertebral disc C2-C3. No haematoma was noted. Clinical examination revealed a slight head lag and local tenderness; there were no neurological deficits. This case shows that the differentiation between a congenital C2 arch defect and a hangman’s fracture is precarious. In this case the findings on MRI and CT scan were interpreted as a congenital posterior arch defect (spondylolysis).

Transposition of medial descending branch of the femoral lateral circumflex artery for repair of superficial palmar arch defect

目的 探讨应用旋股外侧动脉内侧降支移植修复掌浅弓缺损的可行性.方法通过对旋股外侧动脉内侧降支的应用解剖学研究,1999年5月-2004年2月,对8例手掌严重损伤致掌浅弓缺损的患者,切取上述血管移植重建掌浅动脉弓,血管切取长度为9～15cm.结果术后患者手指及移植皮瓣全部成活,手功能恢复满意,血管供区血液循环无影响,肌力正常.结论旋股外侧动脉内侧降支,与掌浅弓有十分相似的解剖学结构,且解剖位置恒定,切取方便.该血管最佳适应证是修复掌浅弓缺损和同时伴有皮肤软组织缺损。

Sonic hedgehog is required for cardiac outflow tract and neural crest cell development

The Hedgehog signaling pathway is critical for a significant number of developmental patterning events. In this study, we focus on the defects in pharyngeal arch and cardiovascular patterning present in Sonic hedgehog ( Shh) null mouse embryos. Our data indicate that, in the absence of Shh, there is general failure of the pharyngeal arch development leading to cardiac and craniofacial defects. The cardiac phenotype results from arch artery and outflow tract patterning defects, as well as abnormal development of migratory neural crest cells (NCCs). The constellation of cardiovascular defects resembles a severe form of the human birth defect syndrome tetralogy of Fallot with complete pulmonary artery atresia. Previous studies have demonstrated a role for Shh in NCC survival and proliferation at later stages of development. Our data suggest that SHH signaling does not act directly on NCCs as a survival factor, but rather acts to restrict the domains that NCCs can populate during early stages (e8.5–10.5) of cardiovascular and craniofacial development.

Maxillary Reconstruction with the Free Fibula Flap

The objective of this study was to evaluate the outcomes of using the free fibula flap in the reconstruction of maxillary defects. Thirty-four consecutive cases of maxillary reconstruction with the free fibula flap were reviewed. All clinical data were analyzed, including primary diseases, types of maxillary defect, free fibula flap design, perioperative complications, and follow-up results. The main postoperative functional indices, including oral diet, speech, type of dental restoration, and aesthetic results, were evaluated. Of the 34 patients who underwent maxillary reconstruction with the free fibula flap, the primary diseases were malignant tumor in 20 patients, benign tumor in 11 patients, and trauma in three patients. Free fibula flap transfer was successful in all cases. Postoperative complications occurred in five patients. Recipient-site wound infection occurred in two patients and donor-site wound dehiscence occurred in three patients. One patient with donor-site wound dehiscence had postoperative lameness. The oral and nasal cavities were separated well by the flap in all patients. The patients were able to take food orally and had no problems with speech intelligibility. Osseointegrated implants were placed in four patients, and complete conventional prostheses were applied in 19 patients. Excellent cosmetic results were obtained in 22 patients. Alveolar arch defects can be reconstructed successfully using free fibula flaps. This procedure also allows for dental implant rehabilitation, which can improve the patient's appearance and oral function and enhance the overall quality of life. The fibula free flap transfer has a high success rate and low perioperative complication rate, making it an ideal choice for maxillary defect reconstruction.

Vangl2 Acts via RhoA Signaling to Regulate Polarized Cell Movements During Development of the Proximal Outflow Tract

Loop-tail (Lp) mice develop double outlet right ventricle and aortic arch defects, and the defects are caused by mutations in the Vangl2 gene. Vangl2 mRNA is found in the outflow tract myocardium, including the myocardializing cells that migrate into the outflow tract cushions. Analysis of muscularization of the outflow tract septum showed that this process is compromised in Lp/Lp fetuses. Vangl2 is a component of the noncanonical Wnt, planar cell polarity (PCP) pathway that signals via RhoA. We therefore looked for evidence of polarization in myocardializing cells. In wild-type fetuses, myocardializing cells extend lamellipodia and filopodia into the cushion tissue and reorganize their actin cytoskeleton from a cortical form to stress fibers; behaviors that are characteristic of polarized cells. In contrast, Lp/Lp littermates do not extend lamellipodia or filopodia into the cushion tissue, and their actin remains in a cortical form, suggesting that polarized cell migration of myocardializing cells is inhibited in Lp/Lp. Several other components of the PCP pathway are also localized in the outflow tract myocardium. In wild-type fetuses, the myocardializing cells coexpress RhoA and one of its downstream mediators, ROCK1. RhoA expression is disrupted in Lp/Lp, and is lost from the myocardial-cushion tissue interface, including the presumptive myocardializing cells. These data suggest that Vangl2 is required for the polarization and movement of myocardializing cells into the outflow tract cushions, and that RhoA and ROCK1 are downstream mediators of the PCP signaling pathway in the developing outflow tract.

Effects of genetic background on cardiovascular anomalies in the Ts16 mouse

To investigate the genetic contribution to phenotypic variability in aneuploidy, we generated mice with trisomy 16 (Ts16) by mating [Rb(6.16)24Lub x Rb(16.17)7Bnr]F1 males with females from four inbred strains, BALB/cJ, C3H/HeJ, C57BL/6J, and DBA/2J. Among the four Ts16 strains that were generated, there were no significant differences in survival, weight, or length relative to euploid control littermates at either embryonic day (E) 14.5 or E17.5. All Ts16 fetuses at E14.5 had edema that ranged from mild to severe, increased amniotic fluid volume, and a thickened neck. At E17.5, Ts16 fetuses exhibited two distinct phenotypes, one with an edematous morphology and the other runt-like. None of these gross morphological abnormalities was strain-specific either in occurrence or frequency. At E10.5, there were pharyngeal arch artery (PAA) anomalies in all Ts16 embryos on the C3H/HeJ background, but none in trisomics on the other three backgrounds. However, at E17.5, there was in addition to ventricular and atrioventricular septal defects, a high frequency of aortic arch defects in Ts16 fetuses, irrespective of genetic background. Taken together, these findings indicate that there are at least two mechanistic responses to the presence of three copies of mouse chromosome 16 in the modeling of the cardiovascular system: one, development of PAA defects, is strongly influenced by genetic background; but the second, development of aortic arch anomalies in the absence of preexisting PAA anomalies, is not.

Lateral advancement flaps in obstructive sleep apnea

Objectives: Palatal and pharyngeal soft tissue laxity and redundancy contribute to upper airway obstruction and obstructive sleep apnea. Hypertrophic tonsils exacerbate the condition. Uvulopalatopharyngoplasty with-or-without tonsillectomy is the procedure of choice to correct the disorder. In some instances, however, excision of the excess lateral soft tissues creates a faucial arch defect that cannot be closed primarily. We present our technique using laterally-advanced full-thickness pharyngeal muscular-mucosal flaps to achieve tension-free closure of the tonsillar fossae. Methods: Open lateral wall defects in the oropharynx heal by secondary intention. Drawbacks with this approach include excess scar tissue deposition, contracture of the fauces, and decreased mobility of the pharyngeal arch, which contribute to a poor surgical result. Coincidentally, too tight a closure causes the same result. To avoid these complications, we undermine the lateral free edge of the posterolateral pharyngeal wall to include a thick cuff of muscle and overlying mucosa. The thickest flaps expose the prevertebral fascia. The flaps can be elevated unilaterally or bilaterally. The blood supply is random, primarily based on terminal branches of the ascending pharyngeal arteries, arising inferiorly. The venous plexus is sufficiently dense to provide adequate vascular drainage. Results: The vascular integrity and elasticity of the pharyngeal musculature permits medially based lateral soft tissue advancement sufficient to allow reapproximation to the palatoglossus. Defects approaching 50% of the flap’s length have been closed. Conclusion: In complex cases, primary, tension-free closure of the faucial arch using soft tissue advancement flaps from the posterior pharynx reduces the likelihood of infection and scar contracture, facilitates healing, and improves surgical results.

Developmental toxicity of mixtures: the water disinfection by-products dichloro-, dibromo- and bromochloro acetic acid in rat embryo culture

The chlorination of drinking water results in production of numerous disinfection by-products (DBPs). One of the important classes of DBPs is the haloacetic acids. We have previously shown that the haloacetic acids (HAs), dichloro (DCA), dibromo (DBA) and bromochloro (BCA) acetic acid are developmentally toxic in mouse whole embryo culture. Human exposure to these contaminants in drinking water would involve simultaneous exposure to all three HAs. This study explores the question of developmental toxicity interactions between these compounds. Gestational day (GD) 9.5 rat embryos were exposed to various concentrations of the three HAs (singly or in combination) for 48 h and then evaluated for dysmorphology. The embryonic effects from exposure to the single compounds and mixtures were evaluated using developmental score (DEVSC) as the parameter of comparison. Concentrations of individual compounds and mixtures were chosen (based on a dose-additivity model) which were predicted to produce scores 10 or 20% lower than control levels. Evaluations were performed on all possible combinations of the three HAs. The HAs were dysmorphogenic and resulted in primarily rotation and heart defects and to a lesser extent prosencephalic, visceral arch, and eye defects. The percent anomalies in the rat were comparable to those previously published for the mouse at comparable toxicant concentration. There was a low incidence of neural tube defects in the rat following exposure to the HAs. The rat neural tube appeared less sensitive to the HAs than did the mouse resulting in a higher rate of neural tube dysmorphology in the mouse. Following exposures to BCA and DBA, alone and in combination, there was a significant incidence of delayed embryonic caudal development with apparent normal development anterior to the second visceral arch. The developmental scores for embryos exposed to combinations of the three compounds, when compared to scores for embryos exposed to the single compounds, indicated that the dose-additivity model adequately predicted the observed toxicity and that the developmental toxicity of these water disinfection by-products appears to be additive in whole embryo culture (WEC).

Full spectrum of malformations in velo-cardio-facial syndrome/DiGeorge syndrome mouse models by altering Tbx1 dosage.

Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is associated with de novo hemizygous 22q11.2 deletions and is characterized by malformations attributed to abnormal development of the pharyngeal arches and pouches. The main physical findings include aortic arch and outflow tract heart defects, thymus gland hypoplasia or aplasia and craniofacial anomalies. The disorder varies greatly in expressivity; while some patients are mildly affected with learning disabilities and subtle craniofacial malformations, others die soon after birth with major cardiovascular defects and thymus gland aplasia. In addition to the main clinical features, many other findings are associated with the disorder such as chronic otitis media and hypocalcemia. Tbx1, a gene encoding a T-box transcription factor, which is hemizygously deleted on chromosome 22q11.2, was found to be a strong candidate for the equivalent of human VCFS/DGS in mice. Mice hemizygous for a null allele of Tbx1 had mild malformations, while homozygotes had severe malformations in the affected structures; neither precisely modeling the syndrome. Interestingly, bacterial artificial chromosome (BAC) transgenic mice overexpressing human TBX1 and three other transgenes, had similar malformations as VCFS/DGS patients. By employing genetic complementation studies, we demonstrate that altered TBX1 dosage and not overexpression of the other transgenes is responsible for most of the defects in the BAC transgenic mice. Furthermore, the full spectrum of VCFS/DGS malformations was elicited in a Tbx1 dose dependent manner, thus providing a molecular basis for the pathogenesis and varied expressivity of the syndrome.

Inactivation of mouse Twisted gastrulation reveals its role in promoting Bmp4 activity during forebrain development.

Twisted gastrulation (Tsg) is a secreted protein that regulates Bmp signaling in the extracellular space through its direct interaction with Bmp/Dpp and Chordin (Chd)/Short gastrulation (Sog). The ternary complex of Tsg/Chd/Bmp is cleaved by the metalloprotease Tolloid (Tld)/Xolloid (Xld). Studies in Drosophila, Xenopus and zebrafish suggest that Tsg can act both as an anti-Bmp and as a pro-Bmp. We have analyzed Tsg loss-of-function in the mouse. Tsg homozygous mutants are viable but of smaller size and display mild vertebral abnormalities and osteoporosis. We provide evidence that Tsg interacts genetically with Bmp4. When only one copy of Bmp4 is present, a requirement of Tsg for embryonic development is revealed. Tsg-/-;Bmp4+/- compound mutants die at birth and display holoprosencephaly, first branchial arch and eye defects. The results show that Tsg functions to promote Bmp4 signaling during mouse head development.