Fetal Abdominal Wall Repair with a Collagen Biomatrix in an Experimental Sheep Model for Gastroschisis

Experimental Induction of Complex Gastroschisis in the Fetal Lamb: Systematic Review

We systematically reviewed experiments in the fetal lamb model of gastroschisis using PubMed, Embase, Web of Science, and Scopus, seeking for standardized surgical techniques to obtain complex gastroschisis. Eligible were studies where an abdominal wall defect was surgically induced and gross anatomical findings at birth were available. The primary outcome was complex gastroschisis, defined by the presence of bowel stenosis, atresia, volvulus, perforation, and/or necrosis. Secondary outcomes were fetal death and additional readouts reported. Of ten eligible studies, six included lambs that had no additional prenatal manipulations and were assessed at term (35 lambs). Gastroschisis was induced at day 70-80 (term = 140-145), typically (n = 4/6 studies) in the left lower abdomen with defect size ranging from 0.5 to 4.0 cm. Only one study, in which a 1.5 cm diameter silicone ring was utilized, resulted in complex gastroschisis in 100% of term survivors. Fetal loss was more frequent in studies where a silicone ring and/or a right-sided defect were used. No changes unique to complex gastroschisis were identified in additional readouts, including bowel histology. When gastroschisis becomes "complex" following induction is uncertain. This knowledge is essential in studying potential prenatal interventions that may change the natural course.

Fetal Surgery for Gastroschisis—A Review with Emphasis on Minimally Invasive Procedures

(1) Background: The morbidity of gastroschisis is defined by exposure of unprotected intestines to the amniotic fluid leading to inflammatory damage and consecutive intestinal dysmotility, the viscero-abdominal disproportion which results in an abdomen too small to incorporate the herniated and often swollen intestine, and by associated pathologies, such as in complex gastroschisis. To prevent intestinal damage and to provide for growth of the abdominal cavity, fetal interventions such as amnio exchange, gastroschisis repair or covering have been evaluated in several animal models and human trials. This review aims to evaluate the reported techniques for the fetal treatment of gastroschisis by focusing on minimally invasive procedures. (2) Methods: We conducted a systematic database search, quality assessment and analyzed relevant articles which evaluate or describe surgical techniques for the prenatal surgical management of gastroschisis in animal models or human application. (3) Results: Of 96 identified reports, 42 eligible studies were included. Fetal interventions for gastroschisis in humans are only reported for EXIT procedures and amnio exchange. In animal models, particularly in the fetal sheep model, several techniques of open or minimally invasive repair of gastroschisis or covering the intestine have been described, with fetoscopic covering being the most encouraging. (4) Discussion: Although some promising minimally invasive techniques have been demonstrated in human application and animal models, most of them are still associated with relevant fetal morbidity and mortality and barely appear to be currently applicable in humans. Further research on specific procedures, instruments and materials is needed before any human application.

Complex gastroschisis: a new indication for fetal surgery?

Gastroschisis (GS) is a congenital abdominal wall defect, in which the bowel eviscerates from the abdominal cavity. It is a non-lethal isolated anomaly and its pathogenesis is hypothesized to occur as a result of two hits: primary rupture of the 'physiological' umbilical hernia (congenital anomaly) followed by progressive damage of the eviscerated bowel (secondary injury). The second hit is thought to be caused by a combination of mesenteric ischemia from constriction in the abdominal wall defect and prolonged amniotic fluid exposure with resultant inflammatory damage, which eventually leads to bowel dysfunction and complications. GS can be classified as either simple or complex, with the latter being complicated by a combination of intestinal atresia, stenosis, perforation, volvulus and/or necrosis. Complex GS requires multiple neonatal surgeries and is associated with significantly greater postnatal morbidity and mortality than is simple GS. The intrauterine reduction of the eviscerated bowel before irreversible damage occurs and subsequent defect closure may diminish or potentially prevent the bowel damage and other fetal and neonatal complications associated with this condition. Serial prenatal amnioexchange has been studied in cases with GS as a potential intervention but never adopted because of its unproven benefit in terms of survival and bowel and lung function. We believe that recent advances in prenatal diagnosis and fetoscopic surgery justify reconsideration of the antenatal management of complex GS under the rubric of the criteria for fetal surgery established by the International Fetal Medicine and Surgery Society (IFMSS). Herein, we discuss how conditions for fetoscopic repair of complex GS might be favorable according to the IFMSS criteria, including an established natural history, an accurate prenatal diagnosis, absence of fully effective perinatal treatment due to prolonged need for neonatal intensive care, experimental evidence for fetoscopic repair and maternal and fetal safety of fetoscopy in expert fetal centers. Finally, we propose a research agenda that will help overcome barriers to progress and provide a pathway toward clinical implementation. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Interventional resealing of preterm premature rupture of the membranes: a systematic review and meta-analysis

OBJECTIVE

To compare the effectiveness and outcomes of interventional resealing of membranes, "amniopatch" for spontaneous vs. iatrogenic preterm premature rupture of the membranes (sPPROM and iPPROM).

METHODS

We performed a systematic review of literature involving an electronic search of the following databases: Ovid MEDLINE(R) and Epub Ahead of Print, In-Process and Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, Ovid EMBASE, Ovid Cochrane Central Register of Controlled Trials, and Scopus. An indirect meta-analysis was then performed to compare the obstetric, maternal, fetal, and neonatal outcomes of amniopatch between the sPPROM and iPPROM groups.

RESULTS

The mean gestational age (GA) at the time rupture was 17.8 ± 1.8 and 25.2 ± 3.8 weeks for iPPROM and sPPROM, respectively, p = .005. Mean GA at the time of amniopatch procedure was 19.2 ± 2.07 weeks for iPPROM and 23 ± 3.1 weeks of gestation for sPPROM, p = .023. The rates of fluid re-accumulation (sPPROM 26% and iPPROM 53%, p = .09) were comparable between the sPPROM and iPPROM groups. Neonatal outcomes except for the rate of IUFD were also comparable between the groups. The incidence of IUFD was significantly higher in the iPPROM group (ES: 24%; 95% CI: 8.00-44.0%; p < .001), compared to sPPROM (ES: 0%; 95% CI: 0.00-4.00%). Obstetric and maternal outcomes were comparable between the two groups.

CONCLUSIONS

Amniopatch appears to be a feasible and safe procedure for PPROM treatment. Further research is warranted to investigate the effectiveness of this procedure and establish a standardized criterion for the appropriate selection of patients that could benefit from this intervention.

Stereological Lung Parameters After Fetoscopic Abdominal Decompression of Congenital Diaphragmatic Hernia in an Ovine Model: A Pilot Study

Background: Fetoscopic endoluminal tracheal occlusion (FETO) improves lung maturation in severe cases of congenital diaphragmatic hernia (CDH) but it does not ameliorate lung compression by herniated abdominal organs. Surgically opening the fetal abdomen (abdominal decompression [AD]) reduces the intrathoracic pressure by diverting the abdominal organs into the amniotic cavity-a probable causal therapy for lung hypoplasia and pulmonary hypertension in CDH. Open surgical abdominal decompression has been reported: we describe a minimally invasive approach in an ovine model of CDH as a probable fetoscopic intervention. Materials and Methods: Eight fetuses were included, 2 were kept as HEALTHY controls. A CDH (left side, liver down) was created by open fetal surgery at midgestation in 6 fetuses, 2 were taken as CDH controls. Fetoscopic abdominal decompression (fAD) was performed 21 days later in 4 animals. The fetuses were retrieved at the end of gestation and evaluated by lung stereology. Results: fAD led to a near total evacuation of the thoracic cavity in 2 of the 4 animals. Fetuses with CDH had a lower total volume and fraction of alveolar air space, a lower volume fraction of the parenchyma, and an increase of the volume fraction of the alveolar septa and atelectasis, as well as an increased mean thickness of alveolar septa compared with HEALTHY fetuses. Fetuses treated with abdominal decompression showed an improvement of stereological parameters. Conclusions: In spite of relevant limitations (pilot study, small groups, spontaneous closure of the abdominal incision) we were able to demonstrate that abdominal decompression for CDH can be performed by fetoscopy. Our results support the hypothesis of causally improving lung development by abdominal decompression, thus implying increased survival in extreme cases of CDH. A refinement of the fetoscopic techniques and direct comparison to FETO appears warranted.

Is there a role for fetal interventions in gastroschisis management? - An updated comprehensive review

We conducted a comprehensive evidence-based review on the epidemiology and current standard of care of gastroschisis management as well as the pathophysiology, rationale and feasibility of fetal therapy as a viable alternative. Gastroschisis is a periumbilical abdominal wall defect characterized by abdominal viscera herniation in utero. It affects 4 in 10 000 live births, but the prevalence has steadily increased in recent years. Gastroschisis is typically diagnosed on routine second-trimester ultrasound. The overall prognosis is favorable, but complex gastroschisis, which accounts for about 10% to 15% of cases, is associated with a higher mortality, significant disease burden and higher healthcare costs due to long- and short-term complications. The current standard of care has yet to be established but generally involves continued fetal surveillance and multidisciplinary perinatal care. Postnatal surgical repair is achieved with primary closure, staged silo closure or sutureless repair. Experimental animal studies have demonstrated the feasibility of in utero closure, antiinflammatory therapy and prenatal regenerative therapy. However, reports of early preterm delivery and amnioinfusion trials have failed to show any benefit in humans. Further experimental studies and human trials are necessary to demonstrate the potential benefit of fetal therapy in gastroschisis.

Fetoscopic techniques for prenatal covering of gastroschisis in an ovine model are technically demanding and do not lead to permanent anchoring on the fetus until the end of gestation

INTRODUCTION

This is the cumulative technical report on the operative procedures and limitations of fetoscopic bag insertion, intestinal bag placement, and bag fixation to the fetus in a series of pilot studies in an ovine model for prenatal treatment of gastroschisis.

MATERIAL AND METHODS

In 24 German blackhead sheep, a surgically created gastroschisis was managed by fetoscopic placement of the extruded intestines into a bag. The bag was then fastened onto the fetal abdominal wall. Different materials (sterile gloves, latex condoms, laparosopic retrieval bags) and different fixation techniques (laparoscopic staplers, interrupted and continuous sutures) have been examined. The fetuses were retrieved and evaluated at the end of gestation.

RESULTS

Uterine bag insertion was successful in 15 of 24 (62.5%) and intestinal bag placement in 10 of 15 available fetuses (66.6%). The main factor limiting fetoscopic procedures was chorioamniotic separation (CAS). Sterilized condoms provided the most appropriate type of bags and the V-Loc™ running suture, the most expedient type of fixation, which was achieved in 9 of the 10 fetuses (complete = 2, partially = 7) by using a three port access (5 mm and 2 × 3 mm). All bags were encountered completely or partially dislocated from the fetus at the end of gestation.

CONCLUSIONS

Fetoscopic intestinal bag placement and fixation in gastroschisis technically demanding. None of the evaluated techniques led to permanent anchorage of the bag to the fetus. The development of specially designed instruments, bags and fixation methods is required to optimize this approach.

The effect of a cyclic uniaxial strain on urinary bladder cells

Purpose

Pre-conditioning of a cell seeded construct may improve the functional outcome of a tissue engineered construct for augmentation cystoplasty. The precise effects of mechanical stimulation on urinary bladder cells in vitro are not clear. In this study we investigate the effect of a cyclic uniaxial strain culture on urinary bladder cells which were seeded on a type I collagen scaffold.

Methods

Isolated porcine smooth muscle cells or urothelial cells were seeded on a type I collagen scaffolds and cultured under static and dynamic conditions. A uniform cyclic uniaxial strain was applied to the seeded scaffold using a Bose Electroforce Bio-Dynamic bioreactor. Cell proliferation rate and phenotype were investigated, including SEM analysis, RT-PCR and immunohistochemistry for α-Smooth muscle actin, calponin-1, desmin and RCK103 expression to determine the effects of mechanical stimulation on both cell types.

Results

Dynamic stimulation of smooth muscle cell seeded constructs resulted in cell alignment and enhanced proliferation rate. Additionally, expression of α-Smooth muscle actin and calponin-1 was increased suggesting differentiation of smooth muscle cells to a more mature phenotype.

Conclusions

Mechanical stimuli did not enhance the proliferation and differentiation of urothelial cells. Mechanical stimulation, i.e., preconditioning may improve the functional in vivo outcome of smooth muscle cell seeded constructs for flexible organs such as the bladder.

Electronic supplementary material

The online version of this article (doi:10.1007/s00345-017-2013-9) contains supplementary material, which is available to authorized users.

Prenatal coverage of experimental gastroschisis with a collagen scaffold to protect the bowel

BACKGROUND/PURPOSE

In fetuses with gastroschisis, toxic products in the amniotic fluid and constriction at the defect of the abdominal wall are considered causative of damage to the eviscerated bowel. The aim of this study was to cover the eviscerated bowel in gastroschisis with a collagen scaffold to protect the bowel and induce cell growth into the scaffold, which could lead to skin or abdominal wall formation replacing the scaffold.

METHODS

In 12 fetal lambs gastroschisis was surgically created at 79 days gestation. A dual-layer type I collagen scaffold was sutured into the skin of the abdominal wall around the defect covering the eviscerated bowel. Lambs were examined after caesarean section at 140 days' gestation.

RESULTS

Survival was 67%. In 7 of 8 surviving lambs the bowel was found to be covered after birth. One scaffold had ruptured. The bowel was found repositioned in the abdominal cavity in 5 lambs. In 2 lambs it was still partially outside. Only minor adherence of bowel loops and no fibrous peel formation were seen. Connective tissue and skin tissue replaced the scaffold.

CONCLUSIONS

Prenatal coverage of the bowel in experimental gastroschisis with a collagen scaffold is feasible in fetal lambs, significantly diminished damage to the bowel wall, and skin and connective tissue replaced the scaffold. This technique may be promising in the care of fetuses with this congenital anomaly.

The making of fetal surgery

Fetal diagnosis prompts the question for fetal therapy in highly selected cases. Some conditions are suitable for in utero surgical intervention. This paper reviews historically important steps in the development of fetal surgery. The first invasive fetal intervention in 1963 was an intra-uterine blood transfusion. It took another 20 years to understand the pathophysiology of other candidate fetal conditions and to develop safe anaesthetic and surgical techniques before the team at the University of California at San Francisco performed its first urinary diversion through hysterotomy. This procedure would be abandoned as renal and pulmonary function could be just as effectively salvaged by ultrasound-guided insertion of a bladder shunt. Fetoscopy is another method for direct access to the feto-placental unit. It was historically used for fetal visualisation to guide biopsies or for vascular access but was also abandoned following the introduction of high-resolution ultrasound. Miniaturisation revived fetoscopy in the 1990 s, since when it has been successfully used to operate on the placenta and umbilical cord. Today, it is also used in fetuses with congenital diaphragmatic hernia (CDH), in whom lung growth is triggered by percutaneous tracheal occlusion. It can also be used to diagnose and treat urinary obstruction. Many fetal interventions remain investigational but for a number of conditions randomised trials have established the role of in utero surgery, making fetal surgery a clinical reality in a number of fetal therapy programmes. The safety of fetal surgery is such that even non-lethal conditions, such as myelomeningocoele repair, are at this moment considered a potential indication. This, as well as fetal intervention for CDH, is currently being investigated in randomised trials.