Single-Access Fetal Endoscopy (SAFE) for myelomeningocele in sheep model I: amniotic carbon dioxide gas approach

Evolution and Variations of the Ovine Model of Spina Bifida

Spina bifida is the most common congenital anomaly of the central nervous system and the first non-fatal fetal lesions to be addressed by fetal intervention. While research in spina bifida has been performed in rodent, nonhuman primate, and canine models, sheep have been a model organism for the disease. This review summarizes the history of development of the ovine model of spina bifida, previous applications, and translation into clinical studies. Initially used by Meuli et al. [Nat Med. 1995;1(4):342-7], fetal myelomeningocele defect creation and in utero repair demonstrated motor function preservation. The addition of myelotomy in this model can reproduce hindbrain herniation malformations, which is the leading cause of mortality and morbidity in humans. Since inception, the ovine models have been validated numerous times as the ideal large animal model for fetal repair, with both locomotive scoring and spina bifida defect scoring adding to the rigor of this model. The ovine model has been used to study different methods of myelomeningocele defect repair, the application of various tissue engineering techniques for neuroprotection and bowel and bladder function. The results of these large animal studies have been translated into human clinical trials including Management of Meningocele Study (MOMS) trial that established current standard of care for prenatal repair of spina bifida defects, and the ongoing trials including the Cellular Therapy for In Utero Repair of Myelomeningocele (CuRe) trial using a stem cell patch for repair. The advancement of these life savings and life-altering therapies began in sheep models, and this notable model continues to be used to further the field including current work with stem cell therapy.

Regenerative medicine: prenatal approaches

This two-paper Series focuses on recent advances and applications of regenerative medicine that could benefit paediatric patients. Innovations in genomic, stem-cell, and tissue-based technologies have created progress in disease modelling and new therapies for congenital and incurable paediatric diseases. Prenatal approaches present unique opportunities associated with substantial biotechnical, medical, and ethical obstacles. Maternal plasma fetal DNA analysis is increasingly adopted as a noninvasive prenatal screening or diagnostic test for chromosomal and monogenic disorders. The molecular basis for cell-free DNA detection stimulated the development of circulating tumour DNA testing for adult cancers. In-utero stem-cell, gene, gene-modified cell (and to a lesser extent, tissue-based) therapies have shown early clinical promise in a wide range of paediatric disorders. Fetal cells for postnatal treatment and artificial placenta for ex-utero fetal therapies are new frontiers in this exciting field.

Dural substitutes for spina bifida repair: past, present, and future

PURPOSE

The use of materials to facilitate dural closure during spina bifida (SB) repair has been a highly studied aspect of the surgical procedure. The overall objective of this review is to present key findings pertaining to the success of the materials used in clinical and pre-clinical studies. Additionally, this review aims to aid fetal surgeons as they prepare for open or fetoscopic prenatal SB repairs.

METHODS

Relevant publications centered on dural substitutes used during SB repair were identified. Important information from each article was extracted including year of publication, material class and sub-class, animal model used in pre-clinical studies, whether the repair was conducted pre-or postnatally, the bioactive agent delivered, and key findings from the study.

RESULTS

Out of 1,121 publications, 71 were selected for full review. We identified the investigation of 33 different patches where 20 and 63 publications studied synthetic and natural materials, respectively. From this library, 43.6% focused on clinical results, 36.6% focused on pre-clinical results, and 19.8% focused on tissue engineering approaches. Overall, the use of patches, irrespective of material, have shown to successfully protect the spinal cord and most have shown promising survival and neurological outcomes.

CONCLUSION

While most have shown significant promise as a therapeutic strategy in both clinical and pre-clinical studies, none of the patches developed so far are deemed perfect for SB repair. Therefore, there is an opportunity to develop new materials and strategies that aim to overcome these challenges and further improve the outcomes of SB patients.

Biodegradation of poly(L-lactic acid) and poly(ε-caprolactone) patches by human amniotic fluid in an in-vitro simulated fetal environment

Open spina bifida or myelomeningocele (MMC) is a devastating neurologic congenital defect characterized by primary failure of neural tube closure of the spinal column during the embryologic period. Cerebrospinal fluid leak caused by the MMC spinal defect in the developing fetus can result in a constellation of encephalic anomalies that include hindbrain herniation and hydrocephalus. The exposure of extruded spinal cord to amniotic fluid also poses a significant risk for inducing partial or complete paralysis of the body parts beneath the spinal aperture by progressive spinal cord damage in-utero. A randomized trial demonstrated that prenatal repair by fetal surgery, sometimes using patches, to cover the exposed spinal cord with a watertight barrier is effective in reducing the postnatal neurologic morbidity as evidenced by decreased incidence and severity of postnatal hydrocephalus and the reduced need for ventricular-peritoneal shunting. Currently, the use of inert or collagen-based patches are associated with high costs and inadequate structural properties. Specifically, the inert patches do not degrade after implantation, causing the need for a post-natal removal surgery associated with trauma for the newborn. Our present study is aimed towards in-vitro degradation studies of a newly designed patch, which potentially can serve as a superior alternative to existing patches for MMC repair. This novel patch was fabricated by blending poly(l-lactic acid) and poly(ε-caprolactone). The 16-week degradation study in amniotic fluid was focused on tracking changes in crystallinity and mechanical properties. An additional set of designed patches was exposed to phosphate-buffered saline (PBS), as a time-paired control. Crystallinity studies indicate the progress of hydrolytic degradation of the patch in both media, with a preference to bulk erosion in phosphate buffered saline and surface erosion in amniotic fluid. Mechanical testing results establish that patch integrity is not compromised up to 16 weeks of exposure either to body fluids analog (PBS) or to amniotic fluid.

Experience of 300 cases of prenatal fetoscopic open spina bifida repair: report of the International Fetoscopic Neural Tube Defect Repair Consortium

BACKGROUND

The multicenter randomized controlled trial Management of Myelomeningocele Study demonstrated that prenatal repair of open spina bifida by hysterotomy, compared with postnatal repair, decreases the need for ventriculoperitoneal shunting and increases the chances of independent ambulation. However, the hysterotomy approach is associated with risks that are inherent to the uterine incision. Fetal surgeons from around the world embarked on fetoscopic open spina bifida repair aiming to reduce maternal and fetal/neonatal risks while preserving the neurologic benefits of in utero surgery to the child.

OBJECTIVE

This study aimed to report the main obstetrical, perinatal, and neurosurgical outcomes in the first 12 months of life of children undergoing prenatal fetoscopic repair of open spina bifida included in an international registry and to compare these with the results reported in the Management of Myelomeningocele Study and in a subsequent large cohort of patients who received an open fetal surgery repair.

STUDY DESIGN

All known centers performing fetoscopic spina bifida repair were contacted and invited to participate in a Fetoscopic Myelomeningocele Repair Consortium and enroll their patients in a registry. Patient data entered into this fetoscopic registry were analyzed for this report. Fisher exact test was performed for comparison of categorical variables in the registry with both the Management of Myelomeningocele Study and a post-Management of Myelomeningocele Study cohort. Binary logistic regression analyses were used to assess the registry data for predictors of preterm birth at <30 weeks' gestation, preterm premature rupture of membranes, and need for postnatal cerebrospinal fluid diversion in the fetoscopic registry.

RESULTS

There were 300 patients in the fetoscopic registry, 78 in the Management of Myelomeningocele Study, and 100 in the post-Management of Myelomeningocele Study cohort. The 3 data sets showed similar anatomic levels of the spinal lesion, mean gestational age at delivery, distribution of motor function compared with upper anatomic level of the lesion in the neonates, and perinatal death. In the Management of Myelomeningocele Study (26.16±1.6 weeks) and post-Management of Myelomeningocele Study cohort (23.3 [20.2-25.6] weeks), compared with the fetoscopic registry group (23.6±1.4 weeks), the gestational age at surgery was lower (comparing fetoscopic repair group with the Management of Myelomeningocele Study; P<.01). After open fetal surgery, all patients were delivered by cesarean delivery, whereas in the fetoscopic registry approximately one-third were delivered vaginally (P<.01). At cesarean delivery, areas of dehiscence or thinning in the scar were observed in 34% of cases in the Management of Myelomeningocele Study, in 49% in the post-Management of Myelomeningocele Study cohort, and in 0% in the fetoscopic registry (P<.01 for both comparisons). At 12 months of age, there was no significant difference in the number of patients requiring treatment for hydrocephalus between those in the fetoscopic registry and the Management of Myelomeningocele Study.

CONCLUSION

Prenatal and postnatal outcomes up to 12 months of age after prenatal fetoscopic and open fetal surgery repair of open spina bifida are similar. Fetoscopic repair allows for having a vaginal delivery and eliminates the risk of uterine scar dehiscence, therefore protecting subsequent pregnancies of unnecessary maternal and fetal risks.

State of the art in translating experimental myelomeningocele research to the bedside

Myelomeningocele (MMC), the commonest type of spina bifida (SB), occurs due to abnormal development of the neural tube and manifest as failure of the complete fusion of posterior arches of the spinal column, leading to dysplastic growth of the spinal cord and meninges. It is associated with several degrees of motor and sensory deficits below the level of the lesion, as well as skeletal deformities, bladder and bowel incontinence, and sexual dysfunction. These children might develop varying degrees of neuropsychomotor delay, partly due to the severity of the injuries that affect the nervous system before birth, partly due to the related cerebral malformations (notably hydrocephalus-which may also lead to an increase in intracranial pressure-and Chiari II deformity). Traditionally, MMC was repaired surgically just after birth; however, intrauterine correction of MMC has been shown to have several potential benefits, including better sensorimotor outcomes (since exposure to amniotic fluid and its consequent deleterious effects is shortened) and reduced rates of hydrocephalus, among others. Fetal surgery for myelomeningocele, nevertheless, would not have been made possible without the development of experimental models of this pathological condition. Hence, the aim of the current article is to provide an overview of the animal models of MMC that were used over the years and describe how this knowledge has been translated into the fetal treatment of MMC in humans.

Fetal heart rate monitoring during fetoscopic repair of open spinal neural tube defects: a single-centre observational cohort study

BACKGROUND

During fetal surgery, the haemodynamic stability of the fetus depends on the haemodynamic stability of the mother. The primary objective of this study was to assess changes in fetal heart rate (FHR) throughout the different stages of surgery. The secondary objective was to assess potential changes in maternal physiological parameters and their association with FHR.

METHODS

This was a single-center observational cohort study conducted between 2015 and 2019 in 26 women undergoing intra-uterine fetoscopic repair of open spina bifida. The primary outcome was FHR. Maternal physiologic parameters were measured at the beginning, during and after surgery. The linear mixed-effects model fitted by maximum likelihood was used to assess changes in each variable at specific times throughout the surgery, and the repeated measures correlation coefficient was used to study the association between FHR and maternal physiological parameters.

RESULTS

One (3.8%) case of fetal bradycardia (FHR <110 beats per minute) required the administration of intramuscular atropine. No other significant FHR changes were observed during surgery. Maternal oesophageal temperature (P <0.001), lactate levels (P=0.002), and mean arterial pressure (P=0.016) changed significantly during surgery, although none of these changes was clinically relevant. The FHR showed a significant association with maternal carbon dioxide tension (r=0.285, 95% CI 0.001 to 0.526) and maternal heart rate (r=0.302, 95% CI 0.025 to 0.535).

CONCLUSION

The FHR remained stable during intra-uterine fetoscopic repair of open spina bifida. Maternal carbon dioxide tension and heart rate may have a mild influence on FHR.

Prenatal Neural Tube Anomalies: A Decade of Intrauterine Stem Cell Transplantation Using Advanced Tissue Engineering Methods

Neural tube defects (NTDs) are among the most common congenital defects during neurulation. Spina bifida is a type of NTD that can occur in different forms. Since myelomeningocele (MMC) is the most severe form of spina bifida, finding a satisfactory treatment for MMC is a gold standard for the treatment of spina bifida. The Management of Myelomeningocele Study (MOMS) demonstrated that intrauterine treatment of spina bifida could ameliorate the complications associated with spina bifida and would also reduce the placement of ventriculoperitoneal (VP) shunt by 50%. Recently developed tissue engineering (TE) approaches using scaffolds, stem cells, and growth factors allow treatment of the fetus with minimally invasive methods and promising outcomes. The application of novel patches with appropriate stem cells and growth factors leads to better coverage of the defect with fewer complications. These approaches with less invasive surgical procedures, even in animal models with similar characteristics as the human MMC defect, paves the way for the modern application of less invasive surgical methods. Significantly, the early detection of these problems and applying these approaches can increase the potential efficacy of MMC treatment with fewer complications. However, further studies should be conducted to find the most suitable scaffolds and stem cells, and their application should be evaluated in animal models. This review intends to discuss advanced TE methods for treating MMC and recent successes in increasing the efficacy of the treatment.

Imaging of open spinal dysraphisms in the era of prenatal surgery

Over the last decade fetal surgery to repair open spinal dysraphisms has become an acceptable and in some cases desirable alternative to the traditional method of postnatal closure. Fetal MRI is an essential part of the workup in these patients, not only to select the appropriate candidates for fetal surgery but also to guide prenatal counseling and perinatal management. In this article we review current surgical techniques for prenatal repair, relevant imaging findings in the era of fetal surgery, and expected imaging findings of the brain and spine in the fetal and postnatal periods.

A low-cost, novel endoscopic repeated-access port for small animal research

Repeated endoscopic access to the abdominal cavity of animal models is useful for a variety of research applications. However, repeated surgical access may affect the welfare of the animal and compromise results. We present the design and benchtop manufacturing process for a self-sealing endoscopic port requiring surgical incision only at implantation. It can be used for repeated body cavity access over a long time period. This device reduces costs, animals required for a given study, and potential suffering for each animal. This novel endoscopic port is designed for low-cost benchtop manufacturing without expensive equipment such as injection molding facilities. Devices manufactured using the method described in this work have been implanted successfully in hen models for investigation of ovarian cancer for over two years. All work followed Texas A&M University institutional guidelines and was covered under Animal Use Protocol 2017-0172, approved by TAMU Animal Care and Use Committee (IACUC). This method can be translated to produce similar devices for use in other small animal models besides the galline model used in this work. This method can be used to produce devices for slightly different purposes than repeated endoscopic access, such as production of an entry port for surgical tools.

Hydrogel and neural progenitor cell delivery supports organotypic fetal spinal cord development in an ex vivo model of prenatal spina bifida repair

Studying how the fetal spinal cord regenerates in an ex vivo model of spina bifida repair may provide insights into the development of new tissue engineering treatment strategies to better optimize neurologic function in affected patients. Here, we developed hydrogel surgical patches designed for prenatal repair of myelomeningocele defects and demonstrated viability of both human and rat neural progenitor donor cells within this three-dimensional scaffold microenvironment. We then established an organotypic slice culture model using transverse lumbar spinal cord slices harvested from retinoic acid–exposed fetal rats to study the effect of fibrin hydrogel patches ex vivo. Based on histology, immunohistochemistry, gene expression, and enzyme-linked immunoabsorbent assays, these experiments demonstrate the biocompatibility of fibrin hydrogel patches on the fetal spinal cord and suggest this organotypic slice culture system as a useful platform for evaluating mechanisms of damage and repair in children with neural tube defects.

Heritable spina bifida in sheep: A potential model for fetal repair of myelomeningocele

BACKGROUND/PURPOSE

In 2004, a heritable occurrence of spina bifida was reported in sheep on a farm in the United States. We maintained and characterized the spina bifida phenotype in this flock to assess its potential as an alternative surgical model.

METHODS

A breeding strategy was developed in which the sheep were crossed to maintain or increase the occurrence of spina bifida. Measurements and observations were recorded regarding lesion size, birthweight, ambulatory capacity, or urological function, and necropsies were performed on spina bifida afflicted lambs in conjunction with magnetic resonance imaging to determine the character of the spina bifida defects and assess the presence of Chiari-like malformations or hydrocephalus.

RESULTS

The defects were observed to be more prevalent in ram lambs, and the rate of spina bifida per litter could be increased through backcrossing or by selection of a productive ewe breed. The lambs displayed a range of ambulatory and urological deficits which could be used to evaluate new fetal repair methodologies. Finally, affected lambs were shown to demonstrate severe Chiari malformations and hydrocephalus.

CONCLUSIONS

We have determined that use of these sheep as a natural source for spina bifida fetuses is feasible and could supplement the deficits of current sheep models for myelomeningocele repair.

LEVEL OF EVIDENCE

Level IV.

Biomaterials in fetal surgery

Fetal surgery and fetal therapy involve surgical interventions on the fetus in utero to correct or ameliorate congenital abnormalities and give a developing fetus the best chance at a healthy life. Historical use of biomaterials in fetal surgery has been limited, and most biomaterials used in fetal surgeries today were originally developed for adult or pediatric patients. However, as the field of fetal surgery moves from open surgeries to minimally invasive procedures, many opportunities exist for innovative biomaterials engineers to create materials designed specifically for the unique challenges and opportunities of maternal-fetal surgery. Here, we review biomaterials currently used in clinical fetal surgery as well as promising biomaterials in development for eventual clinical translation. We also highlight unmet challenges in fetal surgery that could particularly benefit from novel biomaterials, including fetal membrane sealing and minimally invasive myelomeningocele defect repair. Finally, we conclude with a discussion of the underdeveloped fetal immune system and opportunities for exploitation with novel immunomodulating biomaterials.

Fetal Surgery

Fetal surgery is an established but still rapidly evolving specialty, born from the rationale that destructive embryologic processes, recognized early in gestation, can be curtailed by prenatal correction. As more and more centers begin offering fetal interventions, quality of care must be verified through transparency about clinical capabilities and resources. Level designations should be assigned based on capability, as in trauma and neonatal ICU centers for excellence, and volume requirements must be set for fetal surgery certification. Regionalization of this specialty care may be required to optimize outcomes.

Fetoscopic spina bifida repair

INTRODUCTION

Spina bifida is the most common non-lethal congenital birth defect of the central nervous system that causes chronic disability due to the combined effects of local nerve damage and the sequelae of non-communicating hydrocephalus. This abnormality can be identified early in gestation and the damage can be progressive over the course of pregnancy. Advances in fetal treatment have made minimally invasive prenatal surgery a realistic consideration for spina bifida in order to improve the outcome for children affected this condition.

EVIDENCE ACQUISITION

Prenatal surgery for spina bifida via open fetal surgery with hysterotomy decreases the rate of ventriculoperitoneal shunt placement and improves motor function compared to standard postnatal surgery. Maternal risks of open fetal surgery are primarily related to complications of the hysterotomy including thinning or rupture that begins in the index pregnancy but persists for every future pregnancy. Minimizing maternal risks is the largest impetus to explore and optimize a minimally invasive fetoscopic alternative. Techniques vary from using a complete percutaneous approach to open fetoscopy, which requires laparotomy but is minimally invasive to the uterus. This allows vaginal delivery at term and no scar complications are reported thus far. Fetal short-term neurosurgical outcomes compare favorably with improvement in hindbrain herniation >70% and decreased need for treatment for hydrocephalus between 40-45% after prenatal surgery performed either fetoscopically or through open fetal surgery.

EVIDENCE SYNTHESIS

Maternal obstetric outcomes are superior for fetoscopic spina bifida repair compared to open fetal surgery and avoids the ongoing risk in future pregnancy. Neonatal and infant benefits appear equivalent. The open fetoscopic approach minimizes the risk of ruptured membranes and subsequent preterm delivery as opposed to a completely percutaneous procedure. International collaboration is ongoing to share experience and assess long term treatment effects.

CONCLUSIONS

Continued refinement of a minimally invasive strategy for prenatal treatment of spina bifida is necessary to maximize benefits to the child and further minimize maternal risks and preterm birth.

Ethical Issues in Intrauterine Myelomeningocele Surgery

Intrauterine surgery shows that the prognosis of neonates with myelomeningocele (MMC) has improved, both in survival and in quality of life. In order to study the current efficacy of intrauterine surgery for MMC and to make an ethical analysis of its proportionality, we conducted a PubMed search using the keywords "myelomeningocele", "intrauterine surgery", "MOMS", and "trial". Thirty-eight articles were found. The literature investigated the risks and benefits of intrauterine surgery based on the physiological parameters of MMC. Intrauterine surgery produces clear benefits. However, it also has disadvantages, such as premature birth, fetal or neonatal death, and uterine complications. The option of surgery is positive. However, since the intervention is risky, the final decision must be prudential, and thus should involve an ethical analysis of therapeutic proportionality. This requires a specific clinical evaluation of the fetus ensuring fetal survival in all cases and minimizing the risks arising from extremely premature birth.

Using poly(l-lactic acid) and poly(ɛ-caprolactone) blends to fabricate self-expanding, watertight and biodegradable surgical patches for potential fetoscopic myelomeningocele repair

Our study focuses on the development and characterization of a self-expanding, watertight and biodegradable patch for fetoscopic myelomeningocele (MMC) prenatal repair. We fabricated poly(l-lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL) blend films by solution casting. Formulation c with average glass transition temperature of 37.6 ± 1.2°C was chosen for temporospatial recovery. Favorable results from surface studies reflected homogeneous dispersion of polymers in the blend. The cytotoxicity was studied in human foreskin fibroblasts. The blend film was cytocompatible, evidenced by matching percentage of live cells in exposed and control solutions. Subsequently, liquid water permeability experiments confirmed watertight nature of films. Finally, in vitro degradation was investigated in phosphate buffered saline (PBS) and amniotic fluid (AF) separately for 16 weeks. Similar weight loss (n = 6, p = 0.912) and significantly different (n = 3, p = 0.025) surface roughness was observed in PBS and AF, respectively, at 16 weeks. Functional group analysis displayed increasing carbonyl and hydroxyl bonds in PBS and AF, respectively, over time, indicating progression of hydrolytic degradation. Favorable characterization results provide strong evidence to employ PLA-PCL blend films as surgical patches in fetoscopic MMC repair. Designed patch serves as standalone system to successfully tackle impending hurdles of MMC repair and proves to be a superior alternative compared to existing patches. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 295-305, 2019.

Safety and efficacy of fetal surgery techniques to close a spina bifida defect in the fetal lamb model: A systematic review

OBJECTIVE

To determine the safety and efficacy of different neurosurgical techniques for closure of spina bifida (SB) in the fetal lamb model.

METHOD

Systematic review of studies reporting on fetal lambs undergoing induction and closure of SB compared with non-operated normal lambs (negative controls) and/or lambs not undergoing closure of the defect (positive controls). Primary outcomes were (1) survival at birth (safety) and/or (2) presence of Somatosensory Evoked Potentials on hind limbs and/or improvement in quantitative histological spinal cord findings and/or reversal of hindbrain herniation (efficacy).

RESULTS

Out of 1311, 36 full-text articles were eligible. Nineteen were included for quality assessment. Due to high bias, only 2 adequately powered studies were included in the final analysis. An open approach using a 2-layer closure (muscle flap or acellular-dermal-matrix patch plus skin) was the only safe (patch + skin) and effective (both techniques) technique for prenatal closure in this animal model. No comparable level of evidence was identified for other techniques.

CONCLUSION

The experimental literature on prenatal SB closure underscores the lack of standardization. At present, there is animal experimental evidence that a 2-layer closure by hysterotomy is safe and effective. This technique is currently clinically used in a subset of patients. As new clinical techniques are introduced, it would seem logic to preclinically validate them against this experimental standard.

Two-Port Fetoscopic Repair of Myelomeningocele in Fetal Lambs

OBJECTIVE

The aim of this study was to assess the feasibility and the effectiveness of a fetoscopic myelomeningocele (MMC) repair with a running single suture using a 2-port access in the sheep model.

METHODS

Eighteen fetuses underwent surgical creation of a MMC defect at day 75. Fetuses were then randomized into 3 groups. Four fetuses remained untreated (control group). In the other 14 fetuses, a prenatal repair was performed at day 90: 7 fetuses had an open repair (oMMC), and 7 fetuses had a fetoscopic repair (fMMC) using a single-layer running suture through a 2-port access. Lambs were sacrificed at term, and histological examinations were performed.

RESULTS

Hindbrain herniation was observed in all live lambs in the control group. A complete closure of the defect was achieved in all the lambs of the fMMC group. A complete healing of the defect and no hindbrain herniation were observed in all live lambs of the oMMC and fMMC groups. The durations of surgeries were not statistically different between the oMMC and the fMMC groups (60 vs. 53 min, p = 0.40), as was the risk of fetal loss (fMMC: 1/7, oMMC: 3/7, p = 0.56).

DISCUSSION

Fetoscopic repair of MMC can be performed using a single-layer running suture through a 2-port access and may be promising to reduce the risk of premature rupture of membranes.

Low-Fidelity Simulator for the Standardized Training of Fetoscopic Meningomyelocele Repair

BACKGROUND

Fetoscopic meningomyelocele repair in a gas-filled uterus is a new technique performed in very few centers. There are few opportunities as well as ethical prohibitions on the initial development and subsequent refinement of innovative fetal surgery techniques in humans, and using an animal model is both very expensive and logistically difficult.

METHOD

We developed a low-fidelity endoscopic fetal surgery simulation using a plastic doll and pieces of chicken breast to simulate a fetal meningomyelocele, and a polyurethane ball to simulate a gas-filled uterus, along with a standard endoscopy system and instruments.

EXPERIENCE

A unique two-port technique with significant differences from the standard laparoscopic surgery procedure was developed and refined through an iterative phase into a standardized methodology, and the simulator was then used to train three other teams to perform standardized fetoscopic meningomyelocele repair.

CONCLUSION

A low-fidelity fetoscopic surgery simulator is a useful tool for developing new fetoscopic operations and for training multidisciplinary fetal surgery teams without the need for extensive use of an animal model. This simulator may be used to further explore the human uterus as a new surgical space for additional fetal surgeries.

Fetoscopic patch coverage of experimental myelomenigocele using a two-port access in fetal sheep

PURPOSE

This study aims to assess the feasibility and the effectiveness of a fetoscopic myelomeningocele (MMC) coverage using a sealed inert patch through a two-port access, in the sheep model.

METHODS

Forty-four fetuses underwent surgical creation of a MMC defect at day 75 and were divided into four groups according to the MMC repair technique, performed at day 90. Group 1 remained untreated. Group 2 had an open surgery using suture of the defect. Groups 3 and 4 underwent defect coverage using a Gore®-polytetrafluoroethylene patch secured with surgical adhesive (Bioglue®), with an open approach (group 3) and a fetoscopic one (group 4). Lambs were killed at term, and histological examinations were performed.

RESULTS

Fetoscopic patch coverage was achieved in all the lambs of group 4. All the fetuses of group 2 had a complete closure of the defect whereas only 38% in group 3 and 14% in group 4. Fetal loss rate seems to be lower in group 4 than in groups 2 and 3.

CONCLUSION

Fetoscopic coverage of MMC defect can be performed using a sealed patch through a two-port access, but the patch and glue correction may not be the ideal technique to repair fetal MMC.

Cryopreserved human umbilical cord versus biocellulose film for prenatal spina bifida repair in a physiologic rat model

BACKGROUND

Prenatal spina bifida (SB) repair with a regenerative patch may improve neurological outcomes by decreasing inflammatory scarring.

OBJECTIVE

This study aims to compare cryopreserved human umbilical cord (HUC) and biocellulose film (BCF) patches sutured over SB lesions for regeneration of native cells and inflammatory response.

STUDY DESIGN

Sprague-Dawley rats were gavaged with retinoic acid (RA) on embryonic day 10 to induce SB. Hysterotomy was performed on embryonic day 20 and on HUC or BCF patches sutured over the defect. Pups were harvested 30 to 34 h later, and hematoxylin and eosin staining and Trichrome staining assessed basic cellular migration. Immunohistochemistry demonstrated the exact nature of the cellular migration. Patches and surrounding exudates were evaluated with microscopy and cells quantified.

RESULTS

Histology showed cellular migration with all HUC patches compared with none with BCF patches. Epithelial cells were noted migrating over the dorsal HUC surface, astrocytes were noted along the HUC surface adjacent to the lesion, and endothelial cells were noted within the HUC. HUC patches showed minimal inflammatory cells. Exudates surrounding the HUC patches had fewer inflammatory cells than exudates around BCF patches.

CONCLUSION

HUC promotes cellular migration of native cells with minimal inflammatory response compared with BCF. HUC may be the superior patch material for prenatal SB repair. © 2017 John Wiley & Sons, Ltd.

Prenatal ultrasound evaluation of segmental level of neurological lesion in fetuses with myelomeningocele: development of a new technique

OBJECTIVES

To report our preliminary experience in the use of prenatal ultrasound examination to assess lower-limb movements in fetuses with myelomeningocele. We aimed to determine the accuracy of this method to establish the segmental level of neurological lesion, as this is the best known predictor of the future ability to walk.

METHODS

This was a preliminary, observational study including fetuses with myelomeningocele operated on prenatally. The patterns of movements present and absent in the affected fetuses' lower limbs were evaluated systematically by ultrasound examination. According to the known nerve function associated with each muscle group, the segmental level of neurological lesion was established before birth. The agreement for the segmental levels assigned, between the prenatal ultrasound technique and the classical neurological clinical examination after birth (gold standard), was tested using the weighed kappa (wκ) index.

RESULTS

Seventy-one fetuses with myelomeningocele were evaluated at the Hospital Universitari Vall d'Hebron. After counseling, the parents opted for prenatal surgery (26 cases), termination of pregnancy (43 cases) or postnatal repair (two cases). Five patients did not fulfil the inclusion criteria for prenatal surgery and three were excluded after birth. In the 18 fetuses that underwent surgery and were analyzed, the agreement between prenatal and postnatal segmental levels assigned was 91.7% for the right limb (wκ = 0.80) and 88.9% for the left limb (wκ = 0.73).

CONCLUSIONS

The agreement found between prenatal and postnatal assignment of level of lesion in this preliminary study suggests that neurological sonographic evaluation is feasible before birth. This may provide accurate individualized information about the motor function and future ambulation prognosis of fetuses with myelomeningocele.

Fetoscopy for meningomyelocele repair: past, present and future

Meningomyelocele is a malformation with high prevalence, and one of its main comorbidities is Arnold-Chiari malformation type II. The intrauterine repair of this defect has been studied to reduce the progressive spinal cord damage during gestation. The purpose of the present review was to describe the evolution of fetal surgery for meningomyelocele repair. Searches on PubMed database were conducted including articles published in the last 10 years. Twenty-seven articles were selected, 16 experimental studies and 11 studies in humans. A recent study demonstrated that the fetal correction results in better prognosis of neurological and psychomotor development, but open surgery, which has being used widely, has considerable maternal risks. Studies in animal and human models show that the endoscopic approach is feasible and leads to lower maternal morbidity rates. Two endoscopic techniques are currently under assessment - one in Germany and another in Brazil, and we believe that the endoscopic approach will be the future technique for prenatal repair of this defect.

Repairing Fetal Membranes with a Self-adhesive Ultrathin Polymeric Film: Evaluation in Mid-gestational Rabbit Model

Preterm premature rupture of membranes causes 40% of all preterm births, affecting 150000 women each year in the United States. Prenatal diagnostic procedures and surgical interventions increase incidence of adverse events, leading to iatrogenic membrane rupture after a fetoscopic procedure in 45% of cases. We propose an ultrathin, self-adherent, poly-L-lactic acid patch ("nanofilm") as a reparative wound closure after endoscopic/fetoscopic procedures. These nanofilms are compatible with application in wet conditions and with minimally invasive instrumentation. Ex vivo studies to evaluate the nanofilm were conducted using human chorion-amnion (CA) membranes. A custom-built inflation device was used for mechanical characterization of CA membranes and for assessment of nanofilm adhesion and sealing of membrane defects up to 3 mm in size. These ex vivo tests demonstrated the ability of the nanofilm to seal human CA defects ranging in size from 1 to 3 mm in diameter. In vivo survival studies were conducted in 25 mid-gestational rabbits, defects were created by perforating the uterus and the CA membranes and subsequently using the nanofilm to seal these wounds. These in vivo studies confirmed the successful sealing of defects smaller than 3 mm observed ex vivo. Histological analysis of whole harvested uteri 7 days after surgery showed intact uterine walls in 59% of the nanofilm repaired fetuses, along with increased uterine size and intrauterine development in 63% of the cases. In summary, we have developed an ultrathin, self-adhesive nanofilm for repair of uterine membrane defects.

Limits of the surgically induced model of myelomeningocele in the fetal sheep

PURPOSE

The prevention of Chiari type II malformation (CM) is commonly used as a primary outcome for the evaluation of techniques of fetal myelomeningocele (MMC) surgery in the fetal lamb. The aim of our study was to investigate the frequency of the associated CM in the MMC fetal sheep model and to investigate the contribution of prenatal ultrasound evaluation of CM at the time of prenatal repair.

METHODS

A MMC-like lesion was surgically created at 75 days of gestation in 21 fetuses performing a L1-L5 laminectomy followed by an excision of the exposed dura and a midline myelotomy. At a 90-day gestation, among the 19 alived fetuses, a conventional repair of the MMC-like lesion was performed in seven, four of whom underwent cerebral ultrasound (US) examination before the repair. Twelve fetuses remained untreated (control group). All fetuses underwent post-mortem examination (PM) at 138 days.

RESULTS

At a 90-day gestation, CM was demonstrated by US examination in all four evaluated fetuses. At birth, CM was found in 3/6 control whether CM was absent in all alived fetuses in the prenatal repair group (n = 4).

CONCLUSIONS

Creation of a MMC-like lesion with an additional myelotomy does not always lead to hindbrain herniation. Our study suggests that CM should be assessed by ultrasound examination at the time of the prenatal repair to demonstrate the effectiveness of new techniques for the prenatal repair of MMC.

Tissue Engineering Strategies for Fetal Myelomeningocele Repair in Animal Models

Myelomeningocele (MMC), the most severe form of spina bifida, is a common and devastating malformation. Over two decades of experimental work in animal models have led to the development and clinical application of open fetal surgery for the repair of the MMC defect. This approach offers improved neurofunctional outcomes and is now a clinical option for the management of prenatally diagnosed MMC in selected patients. However, there are still opportunities for further improvement in the prenatal treatment of MMC. A less invasive approach would allow for an application earlier in gestation, with a reduction in maternal and fetal risks and the potential for reduced neurological injury. Tissue engineering offers a realistic and appealing alternative approach for the prenatal treatment of MMC. This review discusses the rationale for tissue engineering in MMC, addresses recent experimental progress and describes potential future directions.