Early investigations into improving bowel and bladder function in fetal ovine myelomeningocele repair

Amniotic fluid-derived stem cells: potential factories of natural and mimetic strategies for congenital malformations

Background

Mesenchymal stem cells (MSCs) from gestational tissues represent promising strategies for in utero treatment of congenital malformations, but plasticity and required high-risk surgical procedures limit their use. Here we propose natural exosomes (EXOs) isolated from amniotic fluid-MSCs (AF-MSCs), and their mimetic counterparts (MIMs), as valid, stable, and minimally invasive therapeutic alternatives.

Methods

MIMs were generated from AF-MSCs by combining sequential filtration steps through filter membranes with different porosity and size exclusion chromatography columns. Physiochemical and molecular characterization was performed to compare them to EXOs released from the same number of cells. The possibility to exploit both formulations as mRNA-therapeutics was explored by evaluating cell uptake (using two different cell types, fibroblasts, and macrophages) and mRNA functionality overtime in an in vitro experimental setting as well as in an ex vivo, whole embryo culture using pregnant C57BL6 dams.

Results

Molecular and physiochemical characterization showed no differences between EXOs and MIMs, with MIMs determining a 3-fold greater yield. MIMs delivered a more intense and prolonged expression of mRNA encoding for green fluorescent protein (GFP) in macrophages and fibroblasts. An ex-vivo whole embryo culture demonstrated that MIMs mainly accumulate at the level of the yolk sac, while EXOs reach the embryo.

Conclusions

The present data confirms the potential application of EXOs for the prenatal repair of neural tube defects and proposes MIMs as prospective vehicles to prevent congenital malformations caused by in utero exposure to drugs.

Allogenic umbilical cord-derived mesenchymal stromal cells improve motor function in prenatal surgical repair of myelomeningocele: An ovine model study

OBJECTIVE

To investigate the effects of an adjuvant allogenic umbilical cord mesenchymal stromal cell (UC-MSC) patch applied during fetal surgery on motor and sphincter function in the ovine MMC model.

DESIGN

MMC defects were surgically created at 75 days of gestation and repaired 14 days later.

POPULATION

Ovine MMC model: fetal lambs.

METHODS

We compared lambs that received a UC-MSC patch with a control group of lambs that received an acellular patch.

MAIN OUTCOME MEASURES

Clinical neurological assessment was performed at 2 and 24 hours of life and included determination of the Sheep Locomotor Rating scale (SLR), which has been validated in the ovine MMC model. Electrophysical examinations, spine scans and histological analyses were also performed.

RESULTS

Of the 13 operated lambs, nine were born alive: five had of these had received a UC-MSC patch and four an acellular patch. At 24 hours of life, lambs in the UC-MSC group had a significantly higher score (14 versus 5, P = 0.04). Amyotrophy was significantly more common in the control group (75% versus 0%, P = 0.02). All the lambs in the control group and none of those in the UC-MSC group were incontinent. No significant differences were observed between the UC-MSC and control groups in terms of the presence of spontaneous EMG activity, nerve conduction or spinal evoked potentials. In the microscopic examination, lambs in the UC-MSC group had less fibrosis between the spinal cord and the dermis (mean thickness, 453 versus 3921 μm, P = 0.03) and around the spinal cord (mean thickness, 47 versus 158 μm, P < 0.001). Examination of the spinal cord in the area of the MMC defect showed a higher large neuron density in the UC-MSC group (14.5 versus 5.6 neurons/mm2, P < 0.001). No tumours were observed.

CONCLUSIONS

Fetal repair of MMC using UC-MSC patches improves motor and sphincter function as well as spinal preservation and reduction of fibrosis.

Identifying predictive factors for bowel control in patients with spina bifida and spinal cord injuries

PURPOSE

This study aimed to assess our bowel management program (BMP) and identify predictive factors for bowel control in patients with Spina Bifida (SB) and Spinal Cord Injuries (SCI). Additionally, in patients with SB, we examined the impact of fetal repair (FRG) on bowel control.

METHODS

We included all patients with SB and SCI seen in the Multidisciplinary Spinal Defects Clinic at Children's Hospital Colorado from 2020 to 2023.

RESULTS

336 patients included. Fecal incontinence was present in 70% and bowel control in 30%. All patients with urinary control also had bowel control. Fecal incontinence prevalence was higher in patients with ventriculoperitoneal (VP) shunt (84%), urinary incontinence (82%), and wheelchair users (79%) compared to those who did not need a VP shunt (56%), had urinary continence (0%) and non-wheelchair users (52%), respectively (p =  < 0.001 in all three scenarios). After completing BMP, 90% remained clean for stool. There was no statistical significance when comparing bowel control in FRG with non-fetal repair group.

CONCLUSIONS

Urinary continence predicts bowel control in patients with SB and SCI. Risk factors for fecal incontinence were the need for a VP shunt, urinary incontinence, and wheelchair usage. We did not find any positive impact of fetal repair on bowel and urinary control.

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.