Donor mesenchymal stem cell linetics after transamniotic stem cell therapy (TRASCET) for experimental spina bifida

Bidirectional Feto-Maternal Traffic of Donor Mesenchymal Stem Cells Following Transamniotic Stem Cell Therapy (TRASCET)

PURPOSE

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) has emerged experimentally as a potential treatment for different congenital diseases and maternal diseases of pregnancy. The broad applicability of TRASCET is predicated on hematogenous routing of donor MSCs via the placenta. We investigated whether donor MSC kinetics includes bidirectional traffic between the fetus and mother.

METHODS

Eight time-dated dams had their fetuses (n = 96) divided in 4 groups on gestational day 17 (E17, term = E21). Groups populating one uterine horn received intra-amniotic injections (50 μL) of either donor amniotic fluid-derived MSCs (2×106 cells/mL) labelled with a firefly luciferase reporter gene (MSC-injected, n = 32), or of acellular luciferase (luciferase-injected, n = 26). Contra-lateral (CL) horn fetuses received no injection (MSC-CL, n = 20 and luciferase-CL, n = 18). At term, samples from 11 fetal anatomical sites from CL fetuses, along with placentas from all fetuses and maternal blood were screened for luciferase activity via microplate luminometry.

RESULTS

Overall survival was 95 % (91/96). When controlled by the acellular injection, positive luciferase activity was observed in the placentas of all MSC-injected fetuses, confirming viability of the donor cells at term. When controlled by the acellular injection group, MSC-CL fetuses showed positive luciferase activity in the bone marrow, peripheral blood, brain and skin (p = <0.001-0.048). No luciferase activity was detected in any maternal blood sample.

CONCLUSION

Amniotic fluid-derived MSCs can traffic between the fetus and mother in both directions after simple intra-amniotic injection, in a healthy rat model. This phenomenon must be considered in TRASCET performed in twin/multiple pregnancies.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Transamniotic stem cell therapy (TRASCET): An emerging minimally invasive strategy for intrauterine stem cell delivery

Transamniotic stem cell therapy (TRASCET) is an emerging strategy for prenatal stem cell therapy involving the least invasive method described to date of delivering select stem cells to virtually any anatomical site in the fetus, including the blood and bone marrow, as well as to fetal annexes, including the placenta. Such broad therapeutic potential derives, to a large extent, from unique routing patterns following stem cell delivery into the amniotic fluid, which have commonalities with naturally occurring fetal cell kinetics. First reported experimentally only less than a decade ago, TRASCET has yet to be attempted clinically, though a first clinical trial appears imminent. Despite significant experimental advances, much promise and perhaps excessive publicity, most cell-based therapies have yet to deliver meaningful large-scale impact to patient care. The few exceptions typically consist of therapies based on the amplification of the normal biological role played by the given cells in their natural environment. Therein lays much of the appeal of TRASCET, in that it, too, is in essence a magnification of naturally occurring processes in the distinctive environment of the maternal-fetal unit. As much as fetal stem cells possess unique characteristics compared with other stem cells, so does the fetus when compared with any other age group, converging into a scenario that enables therapeutic paradigms exclusive to prenatal life. This review summarizes the diversity of applications and biological responses associated with the TRASCET principle.

Brain protection by transamniotic stem cell therapy (TRASCET) in a model of intrauterine growth restriction (IUGR)

PURPOSE

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) has been shown experimentally to reverse some of the effects of intrauterine growth restriction (IUGR), apparently by attenuating placental inflammation. Neurodevelopmental deficits driven by neuroinflammation are major complications of IUGR. We sought to determine whether MSC-based TRASCET also mitigates inflammation in the fetal brain.

METHODS

Pregnant Sprague-Dawley dams (n = 8) were exposed to alternating 12-hour hypoxia (10.5% O₂) cycles from gestational day 15 (E15) until term (E21). One group remained untreated (n = 28 fetuses). Three groups received volume-matched intra-amniotic injections into all fetuses (n = 72) of either saline (sham; n = 19), or a suspension of amniotic fluid-derived MSCs, either in native state (TRASCET; n = 20), or primed by exposure to interferon-gamma (IFN-γ) and interleukin-1beta (IL-1β) for 24 h prior to administration in vivo (TRASCET-Primed; n = 29). Donor MSCs were syngeneic Lewis rat cells phenotyped by flow cytometry. Normal fetuses served as controls (n = 20). Multiple analyses were performed at term, including ELISA in fetal brains for the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and IL-1β. Statistical comparisons were by Wilcox-rank sum test, including Bonferroni-adjusted significance.

RESULTS

Overall survival was 75% (88/116). Gross brain weights were significantly decreased from normal in both the untreated and sham groups (both p<0.001) and significantly increased in both TRASCET groups when compared to untreated and sham (p = 0.003 to <0.001). TRASCET-Primed led to significantly lower levels of TNF-α and IL-1β compared to untreated (both p<0.001) and sham (p = 0.017 and p = 0.011, respectively). Non-primed TRASCET led to significantly lower levels of TNF-α and IL-1β compared to untreated (p = 0.009 to <0.001), but not sham (p = 0.133 and p = 0.973, respectively).

CONCLUSIONS

Transamniotic stem cell therapy with primed mesenchymal stem cells reverses some of the central nervous system effects of intrauterine growth restriction in a rat model, possibly by modulating neuroinflammation.

TYPE OF STUDY

Animal and laboratory study.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Biodistribution of allogenic umbilical cord-derived mesenchymal stromal cells after fetal repair of myelomeningocele in an ovine model

Background

Myelomeningocele (MMC) is a spinal cord congenital defect that leads to paraplegia, sphincter disorders and potential neurocognitive disabilities. Prenatal surgery of MMC provides a significant benefit compared to surgery at birth. Mesenchymal stromal cell (MSC) therapy as an adjuvant treatment for prenatal surgery showed promising results in animal experiments which could be considered for clinical use in human fetuses. Despite numerous reassuring studies on the safety of MSCs administration in humans, no study focused on MSCs biodistribution after a local MSCs graft on the fetal spinal cord.

Aim

The purpose of our study was to assess the biodistribution of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) at birth in lambs who had a prenatal myelomeningocele repair using a fibrin patch seeded with allogenic UC-MSCs.

Methods

After isolation, UC-MSCs were tagged using a green fluorescent protein (GFP)-containing lentiviral vector. MMC defects were surgically created at 75 days of gestation and repaired 15 days later using UC-MSCs patch. Lambs were delivered at 142 days and sacrificed. DNA extraction was performed among biopsies of the different organs and q-PCR analysis was used to detect the expression of GFP (GFP DNA coding sequence).

Results

In our 6 surviving lambs grafted with UC-MSCs, GFP lentivirus genomic DNA was not detected in the organs.

Conclusion

These reassuring data will support translational application in humans, especially since the first human clinical trial using mesenchymal stromal cells for in-utero treatment of MMC started recently in U.S.A.

Routing pathway of syngeneic donor hematopoietic stem cells after simple intra-amniotic delivery

BACKGROUND

We sought to determine the pathway through which syngeneic hematopoietic stem cells (HSCs) delivered into the amniotic fluid can reach the fetal circulation.

METHODS

Lewis rat fetuses were divided in two groups based on the content of intra-amniotic injections performed on gestational day 17 (E17; term=E21-22): either a suspension of luciferase-labeled syngeneic HSCs (n = 137), or acellular luciferase (n = 44). Samples from placenta, chorion, amnion, amniotic fluid, umbilical cord, and 8 fetal sites were procured at 5 daily time points thereafter until term for analysis.

RESULTS

When controlled by acellular luciferase, donor HSCs were identified in the amnion, chorion, placenta, and amniotic fluid of fetuses receiving cells at all time points (p = 0.033 to <0.001), peaking first at the amnion and subsequently at the chorion and placenta. Cells could be detected in the fetal liver as early as day 1, progressively expanding to all the other fetal sites over time, in parallel to their increased presence in the chorion and placenta.

CONCLUSIONS

The chronology of syngeneic donor hematopoietic stem cell trafficking after intra-amniotic injection is suggestive of controlled routing through the gestational membranes and placenta. Hematogenous donor cell routing is a constituent of transamniotic hematopoietic stem cell therapy, significantly expanding its potential applications.

Amniotic fluid-derived stem cell potential for therapeutic and surgical use: A review of the literature

OBJECTIVE

Spina bifida is a debilitating neutral tube defect affecting many infants. The impact and severity of spina bifida depends on whether the patient exhibits a closed defect, spina bifida occulta, or an open defect, spina bifida aperta. Patients with spina bifida have physical and mental disabilities which merit further research into less invasive, more successful treatments. In addition to serving as protection for the growing fetus and facilitating nutrient exchange, amniotic fluid (AF) is a rich source of a mixed population of stem cells. As such, in vitro culture of AF-derived stem cells has shown promise among therapeutic and surgical applications. We present a critical evaluation of the current preclinical efforts, amniotic fluid-derived stem cell (AFSC) culture process, and the subsequent therapeutic application, with a focus on improvements for spina bifida outcomes in the pediatric patient population.

METHOD

An evidence - based literature review to investigate the current literature surrounding AFSC culture and use, with an emphasis on the benefits for spina bifida treatment.

RESULTS

47 literature sources from PubMed and three studies from ClinicalTrials.gov.

CONCLUSION

This review synthesizes the current literature, which shows promising data on AFSC pluripotency, as well as successful in utero coverage from AFSC - supported environments in a multitude of animal models.

Passive perinatal immunotherapy via transamniotic antibody delivery

PURPOSE

We sought to determine whether the amniotic cavity/fluid could be an attainable route of administration of therapeutic antibodies to the fetus/neonate.

METHODS

Time-dated pregnant dams (n = 9) received volume-matched intra-amniotic injections of either saline (n = 29), or different concentrations of a human IgG that lacked homology with rodents: 5 mg/mL (n = 28); 10 mg/mL (n = 28); or 15 mg/mL (n = 24). At term, the presence of the IgG was quantified by ELISA in the serum, bone marrow, spleen, thymus, and brain of all neonates, and in the maternal serum. Statistical analysis was by median regression with significance set at Bonferroni-adjusted p<0.008.

RESULTS

Overall fetal survival was 83% (90/109), with no difference between the groups. Human IgG was detected in the serum, bone marrow, spleen, thymus, and brain of all fetuses for all three injected concentrations, but not in the saline injected controls (p<0.001). A dose dependent relationship between injection concentration and final IgG load was noted in the bone marrow, spleen, and thymus (p = 0.004 to <0.001). Human IgG was also detected in maternal serum.

CONCLUSIONS

IgG antibodies can reach high levels in the fetal/neonatal circulation after simple intra-amniotic administration in a healthy rodent model. Transamniotic fetal immunotherapy (TRAFIT) may become a practicable strategy for the perinatal management of select diseases.

LEVEL OF EVIDENCE

N/A (animal and laboratory study) TYPE OF STUDY: Animal and laboratory study.

OUP accepted manuscript

Spinal bifida aperta (SBA) is a congenital malformation with a high incidence. Bone marrow mesenchymal stem cell (BMSC) transplantation has the potential to repair the structure of damaged tissues and restore their functions. This is an optional treatment that can be used as a supplement to surgery in the treatment of SBA. However, the application of BMSCs is limited, as the neuronal differentiation rate of BMSCs is not satisfactory when used in treating severe SBA. Thus, we aimed to assess the effect of neural stem cell (NSC)-derived exosomes on BMSC neuronal differentiation and observe the therapeutic effect in an ex vivo rat SBA embryo model. We found that NSC-derived exosomes increased the neuronal differentiation rate of BMSCs in vitro and in the SBA embryo model ex vivo. Proteomic analysis showed that NSC-derived exosomes were enriched in Netrin1, which positively regulated neuronal differentiation. Netrin1 increased the neuronal differentiation rate of BMSCs and NSCs and upregulated the expression of the neuronal markers, microtubule-associated protein (Map2), neurofilament, and β3-tubulin. Bioinformatic analysis revealed that Netrin1 treatment increased the expression of the transcription factors Hand2 and Phox2b, related to neuronal differentiation. Furthermore, the Netrin1-induced NSC neuronal differentiation was significantly blocked by Phox2b knockdown. We suggest that NSC-derived exosomal Netrin1 induces neuronal differentiation via the Hand2/Phox2b axis by upregulating the expression of Hand2 and Phox2b. Therefore, NSC-derived exosomes are a critical inducer of BMSC neuronal differentiation and represent a potential treatment agent that can benefit BMSC treatment in SBA.

In utero treatment of myelomeningocele with allogenic umbilical cord-derived mesenchymal stromal cells in an ovine model

PURPOSE OF THE STUDY

The purpose of our study was to investigate the effects of ovine umbilical cord-derived mesenchymal stromal cells (UC-MSCs) seeded in a fibrin patch as an adjuvant therapy for fetal myelomeningocele repair in the ovine model.

MATERIALS AND METHODS

MMC defects were surgically created at 75 days of gestation and repaired 15 days later with UC-MSCs patch or an acellular patch. At birth, motor function, tail movements, and voiding abilities were recorded. Histological and immunohistochemical analysis included study of MMC defect's healing, spinal cord, UC-MSCs survival, and screening for tumors.

RESULTS

Six lambs were born alive in each group. There was no difference between the two groups on the median sheep locomotor rating score but all lambs in the control group had a score between lower than 3 compared to 50% in UC-MSCs group. There were more lambs with tail movements and voiding ability in UC-MSCs group (83% vs 0% and 50% vs 0%, respectively). gray matter area and large neurons density were higher in UC-MSCs group (2.5 vs 0.8 mm² and 19.3 vs 1.6 neurons/mm² of gray matter, respectively). Fibrosis thickness at the myelomeningocele scar level was reduced in UC-MSCs group (1269 µm vs 2624 µm). No tumors were observed.

CONCLUSION

Fetal repair of myelomeningocele using allogenic UC-MSCs patch provides a moderate improvement in neurological functions, gray matter and neuronal preservation and prevented from fibrosis development at the myelomeningocele scar level.

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 surgery and stem cell therapy for meningomyelocele

PURPOSE OF REVIEW

To review the advance of maternal--fetal surgery, the research of stem cell transplantation and tissue engineering in prenatal management of fetal meningomyelocele (fMMC).

RECENT FINDINGS

Advance in the imaging study provides more accurate assessment of fMMC in utero. Prenatal maternal--fetal surgery in fMMC demonstrates favourable postnatal outcome. Minimally invasive fetal surgery minimizes uterine wall disruption. Endoscopic fetal surgery is performed via laparotomy-assisted or entirely percutaneous approach. The postnatal outcome for open and endoscopic fetal surgery shares no difference. Single layer closure during repair of fMMC is preferred to reduce postnatal surgical intervention. All maternal--fetal surgeries impose anesthetic and obstetric risk to pregnant woman. Ruptured of membrane and preterm delivery are common complications. Trans-amniotic stem cell therapy (TRASCET) showed potential tissue regeneration in animal models. Fetal tissue engineering with growth factors and dura substitutes with biosynthetic materials promote spinal cord regeneration. This will overcome the challenge of closure in large fMMC. Planning of the maternal--fetal surgery should adhere to ethical framework to minimize morbidity to both fetus and mother.

SUMMARY

Combination of endoscopic fetal surgery with TRASCET or tissue engineering will be a new vision to achieve to improve the outcome of prenatal intervention in fMMC.

Fetal hematogenous routing of a donor hematopoietic stem cell line in a healthy syngeneic model of transamniotic stem cell therapy

BACKGROUND/PURPOSE

In utero administration of hematopoietic stem cells (HSCs) has a variety of actual or potential clinical applications but is hindered by invasive, morbid administration techniques. We sought to determine whether donor HSCs could reach the fetal circulation after simple intra-amniotic delivery in a syngeneic rat model of transamniotic stem cell therapy (TRASCET).

METHODS

Pregnant Lewis rat dams underwent volume-matched intra-amniotic injections in all fetuses (n = 90) on gestational day 17 (E17; term=E21-22) of a suspension of commercially available syngeneic Lewis rat HSCs labeled with luciferase (n = 37 fetuses) or an acellular suspension of recombinant luciferase (n = 53). HSC phenotype was confirmed by flow cytometry. Fetuses were euthanized at term for screening of luciferase activity at select anatomical sites. Statistical comparisons were by Fisher's exact test.

RESULTS

Among survivors (47/90; 52.2%), donor HSCs were identified selectively in the placenta (p = 0.003), umbilical cord (p < 0.001), bone marrow (p < 0.001), thymus (p = 0.009), bowel (p = 0.003), kidney (p = 0.022), and skin (p < 0.001) when compared with acellular luciferase controls.

CONCLUSIONS

Donor hematopoietic stem cells undergo hematogenous routing and can reach the fetal bone marrow after simple intra-amniotic delivery in a syngeneic rat model. Transamniotic stem cell therapy may become a practicable, minimally invasive strategy for the prenatal administration of these cells.

Transamniotic Stem Cell Therapy for Experimental Congenital Diaphragmatic Hernia: Structural, Transcriptional, and Cell Kinetics Analyses in the Nitrofen Model

PURPOSE

We examined select pulmonary effects and donor cell kinetics after transamniotic stem cell therapy (TRASCET) in a model of congenital diaphragmatic hernia (CDH).

METHODS

Pregnant dams (n = 58) received nitrofen on gestational day 9.5 (E9) to induce fetal CDH. Fetuses (n = 681) were divided into 4 groups: untreated (n = 99) and 3 groups receiving volume-matched intra-amniotic injections on E17 of either saline (n = 142), luciferase-labeled amniotic fluid-derived mesenchymal stem cells (afMSCs; n = 299), or acellular recombinant luciferase (n = 141). Pulmonary morphometry, quantitative gene expression of pulmonary vascular tone mediators, or screening for labeled afMSCs were performed at term (E22). Statistical comparisons were by Mann-Whitney U-test, nested ANOVA, and Wald test.

RESULTS

TRASCET led to significant downregulation of endothelial nitric oxide synthase and endothelin receptor-A expressions compared to both untreated and saline groups (both p < 0.001). TRASCET also led to a significant decrease in arteriole wall thickness compared to the untreated group (p < 0.001) but not the saline group (p = 0.180). Donor afMSCs were identified in the bone marrow and umbilical cord (p = 0.035 and 0.015, respectively, vs. plain luciferase controls).

CONCLUSIONS

The effects of TRASCET in experimental CDH appear to be centered on the pulmonary vasculature and to derive from circulating donor cells.

Preclinical stem cell therapy in fetuses with myelomeningocele: A systematic review and meta-analysis

OBJECTIVE

We performed a systematic review to summarize the efficacy and safety of in utero stem cells application in preclinical models with myelomeningocele (MMC).

METHODS

The study was registered with PROSPERO (CRD42019160399). We searched MEDLINE, Embase, Web of Science, Scopus and CENTRAL for publications articles on stem cell therapy in animal fetuses with MMC until May 2020. Publication quality was assessed by the SYRCLE's tool. Meta-analyses were pooled if studies were done in the same animal model providing similar type of stem cell used and outcome measurements. Narrative synthesis was performed for studies that could not be pooled.

RESULTS

Nineteen and seven studies were included in narrative and quantitative syntheses, respectively. Most used mesenchymal stem cells (MSCs) and primarily involved ovine and rodent models. Both intra-amniotic injection of allogeneic amniotic fluid (AF)-MSCs in rat MMC model and the application of human placental (P)-MSCs to the spinal cord during fetal surgery in MMC ovine model did not compromise fetal survival rates at term (rat model, relative risk [RR] 1.03, 95% CI 0.92-1.16; ovine model, RR 0.94, 95% CI 0.78-1.13). A single intra-amniotic injection of allogeneic AF-MSCs into rat MMC model was associated with a higher rate of complete defect coverage compared to saline injection (RR 16.35, 95% CI 3.27-81.79). The incorporation of human P-MSCs as a therapeutic adjunct to fetal surgery in the ovine MMC model significantly improved sheep locomotor rating scale after birth (mean difference 5.18, 95% CI 3.36-6.99).

CONCLUSIONS

Stem cell application during prenatal period in preclinical animal models is safe and effective.

Transamniotic mesenchymal stem cell therapy for neural tube defects preserves neural function through lesion-specific engraftment and regeneration

Neural tube defects (NTDs) lead to prenatal mortality and lifelong morbidity. Currently, surgical closure of NTD lesions results in limited functional recovery. We previously suggested that nerve regeneration was critical for NTD therapy. Here, we report that transamniotic bone marrow-derived mesenchymal stem cell (BMSC) therapy for NTDs during early development may achieve beneficial functional recovery. In our ex vivo rat embryonic NTD model, BMSCs injected into the amniotic cavity spontaneously migrated into the defective neural tissue. Hepatocyte growth factor and its receptor c-MET were found to play critical roles in this NTD lesion-specific migration. Using the in vivo rat fetal NTD model, we further discovered that the engrafted BMSCs specifically differentiated into the cell types of the defective tissue, including skin and different types of neurons in situ. BMSC treatment triggered skin repair in fetuses, leading to a 29.9 ± 5.6% reduction in the skin lesion area. The electrophysiological functional recovery assay revealed a decreased latency and increased motor-evoked potential amplitude in the BMSC-treated fetuses. Based on these positive outcomes, ease of operation, and reduced trauma to the mother and fetus, we propose that transamniotic BMSC administration could be a new effective therapy for NTDs.

Postnatal fate of donor mesenchymal stem cells after transamniotic stem cell therapy in a healthy model

PURPOSE

We sought to examine donor mesenchymal stem cell (MSC) fate after birth following transamniotic stem cell therapy (TRASCET) in a healthy model.

METHODS

Lewis rat fetuses (n = 91) were divided into two groups based on the content of volume-matched intraamniotic injections performed on gestational day 17 (term = 21-22 days): either a suspension of amniotic fluid-derived MSCs (afMSCs) labeled with luciferase (n = 38) or acellular luciferase only (n = 53). Infused afMSCs consisted of syngeneic Lewis rat cells phenotyped by flow cytometry. Samples from 14 anatomical sites (heart, lung, brain, liver, spleen, pancreas, bowel, kidney, thyroid, skin, skeletal muscle, thymus, peripheral blood and bone marrow) from survivors were screened for luciferase activity 16 days after birth. Statistical analysis was by logistic regression and the Wald test (p < 0.05).

RESULTS

Overall survival was 32% (29/91). When controlled by the acellular luciferase injections, donor afMSCs were not identified at any anatomical site in any neonate as measured by relative light units (all p > 0.05). Donor afMSC viability was confirmed in term placentas.

CONCLUSIONS

Donor mesenchymal stem cells are not detectable in the neonate after intraamniotic injection in a normal syngeneic rodent model. This finding suggests that clinical trials of transamniotic stem cell therapy may be amenable to regulatory approval.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Hematogenous Donor Cell Routing Pathway After Transamniotic Stem Cell Therapy

Donor mesenchymal stem cells (MSCs) have been documented in fetal and maternal circulations after plain intra-amniotic injection, with diverse therapeutic effects. We sought to determine the pathway of this unique cell kinetic route. Rat fetuses (n = 226) were divided into two groups based on the content of intra-amniotic injections performed on gestational day 17 (E17): either a concentrated suspension of luciferase-labeled syngeneic amniotic fluid-derived MSCs (afMSCs; n = 111), or acellular luciferase (n = 115). Samples from placenta, chorion, amnion, amniotic fluid, stomach fluid, peripheral blood, and umbilical cord were procured at five daily time points thereafter until term (E18-22) for luminometry. In addition, 53 sets of fresh gestational membranes (chorion/amnion combined) from nonmanipulated term fetuses were secured to transwell inserts for in vitro analysis of MSC migration using luciferase-labeled afMSCs. Statistical analyses included the Mann-Whitney U-test, Wald test, nonlinear regression modeling, and Fisher's exact test. In vivo, luciferase activity was observed in the amnion, chorion, and placenta of fetuses receiving cells, but not in those receiving acellular luciferase (P < 0.001). There was a consistent nonlinear age-dependent relationship of luciferase activity between the amnion, chorion, and placenta following a parabolic bimodal pattern characterized by significantly higher early preterm (E18) and late-term (E22) activities (P < 0.001), with no differences between E21 and E22 (P = 0.12). In vitro, the presence of cells was documented by luminometry in 21/53 (39.6%) of the assays, in suspension and/or attached to the plastic substrate, and within all screened gestational membrane sets, irrespective of stimuli with collagen coating or fetal bovine serum. We conclude that, after intra-amniotic injection, donor MSCs undergo controlled cell routing, as opposed to passive clearance. Transgestational membrane transport appears to constitute the path for donor cells to reach the placenta, a known gateway to the fetal circulation, significantly expanding the potential applications of transamniotic stem cell therapy.

Fetal surgical intervention for myelomeningocele: lessons learned, outcomes, and future implications

Fetal myelomeningocele (fMMC) closure (spina bifida aperta) has become a care option for patients that meet inclusion criteria, but it is clear that fetal intervention, while improving outcomes, is not a cure. This review will: (1) focus on the rationale for fMMC surgery based on preclinical studies and observations that laid the foundation for human pilot studies and a randomized controlled trial; (2) summarize important clinical outcomes; (3) discuss the feasibility, efficacy, and safety of recent developments in fetal surgical techniques and approaches; and (4) highlight future research directions. Given the increased risk of maternal and fetal morbidity associated with prenatal intervention, accompanied by the increasing number of centres performing interventions worldwide, teams involved in the care of these patients need to proceed with caution to maintain technical expertise, competency, and patient safety. Ongoing assessment of durability of the benefits of fMMC surgery, as well as additional refinement of patient selection criteria and counselling, is needed to further improve outcomes and reduce the risks to the mother and fetus. WHAT THIS PAPER ADDS: High-quality prospective studies are needed to broaden the indication for fetal surgery in the general myelomeningocele population. Innovative minimally invasive approaches have had promising results, yet lack comprehensive and robust experimental or clinical evaluation. Important information to help families make informed decisions regarding fetal surgery for myelomeningocele is provided.

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.

Donor mesenchymal stem cell kinetics after transamniotic stem cell therapy (TRASCET) in a rodent model of gastroschisis

PURPOSE

We sought to comprehensively scrutinize donor mesenchymal stem cell kinetics following transamniotic stem cell therapy (TRASCET) in experimental gastroschisis.

METHODS

A gastroschisis was surgically created in 102 rat fetuses at gestation day 18 (term = 22 days), immediately followed by volume-matched amniotic injections of either amniotic fluid mesenchymal stem cells (afMSCs) labeled with a luciferase reporter gene (n = 58), or luciferase protein alone (n = 44). Samples from multiple anatomical sites from survivors were screened for luciferase activity via microplate luminometry at term. Statistical analysis included Mann-Whitney U-test, Wald test, and kappa coefficient (p < 0.05).

RESULTS

Overall survival was 42% (43/102), with no significant difference between the two groups (p = 0.82). When controlled by acellular luciferase, donor afMSCs were identified selectively in the placenta (p < 0.001) and bowel (p = 0.005), independently of the dams (respectively, p < 0.001 and p = 0.041). Bowel homing was documented exclusively in areas exposed to the amniotic cavity. There was no mutual correlation between placental and bowel homing (kappa = -0.02; p = 0.91).

CONCLUSIONS

Amniotic mesenchymal stem cells home to specific sites after TRASCET in the setting of gastroschisis. Placental homing and intestinal homing are central yet seemingly independent constituents of cell trafficking, suggesting that both direct amniotic seeding and hematogenous routing take place.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Congenital diaphragmatic hernia as a potential target for transamniotic stem cell therapy

PURPOSE

We sought to determine whether TRASCET could impact congenital diaphragmatic hernia (CDH).

METHODS

Twelve pregnant dams received Nitrofen on gestational day 9.5 (E9; term = 22 days) to induce fetal CDH. Fetuses were divided into three groups: untreated (n = 31) and two groups receiving volume-matched intraamniotic injections of either saline (n = 37) or a suspension of 2 × 10⁶ cells/mL of amniotic fluid-derived mesenchymal stem cells (afMSCs; n = 65) on E17. Animals were euthanized at term. Expression of fibroblast growth factor-10 (FGF-10), vascular endothelial growth factor-A (VEGF-A), and surfactant protein-C (SPC) was quantified by qRT-PCR. Statistical analysis was by the Mann-Whitney U test with Bonferroni adjusted criterion (p ≤ 0.01).

RESULTS

Among survivors with CDH (n = 27/133), the TRASCET group showed significant downregulation of FGF-10 and VEGF-A gene expressions compared to the untreated (p < 0.001 for both) and saline groups (p = 0.005 and p = 0.004, respectively). SPC expression was higher in the TRASCET group compared to the untreated group (p = 0.01), but not the saline group (p = 0.043). Lung laterality had minimal impact on these comparisons.

CONCLUSIONS

Transamniotic stem cell therapy affects select processes of lung development in experimental congenital diaphragmatic hernia. Further scrutiny into this novel therapy as a potential component of the prenatal management of this disease is warranted.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Transamniotic stem cell therapy (TRASCET) in a rabbit model of spina bifida

PURPOSE

Transamniotic stem cell therapy (TRASCET) with select mesenchymal stem cells (MSCs) has been shown to induce partial or complete skin coverage of spina bifida in rodents. Clinical translation of this emerging therapy hinges on its efficacy in larger animal models. We sought to study TRASCET in a model requiring intra-amniotic injections 60 times larger than those performed in the rat.

METHODS

Rabbit fetuses (n = 65) with surgically created spina bifida were divided into three groups. One group (untreated) had no further manipulations. Two groups received volume-matched intra-amniotic injections of either saline or a concentrated suspension of amniotic fluid MSCs (afMSCs) at the time of operation. Infused afMSCs consisted of banked heterologous rabbit afMSCs with mesenchymal identity confirmed by flow cytometry, labeled with green fluorescent protein. Defect coverage at term was blindly categorized only if the presence of a distinctive neoskin was confirmed histologically. Statistical comparisons were by logistic regression and the likelihood ratio test.

RESULTS

Among survivors with spina bifida (n = 19), there were statistically significant higher rates of defect coverage (all partial) in the afMSC group when compared with the saline and untreated groups (0-50%; p = 0.022-0.036), with no difference between the saline and untreated groups (p = 1.00). Donor afMSCs were identified locally, though sparsely and not in the neoskin.

CONCLUSIONS

Concentrated intra-amniotic injection of amniotic mesenchymal stem cells can induce partial coverage of experimental spina bifida in a leporine model. Transamniotic stem cell therapy may become a feasible strategy in the prenatal management of spina bifida.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Transamniotic Stem Cell Therapy

Transamniotic stem cell therapy (TRASCET) is a novel prenatal therapeutic alternative for the treatment of congenital anomalies. It is based upon the principle of augmenting the pre-existing biological role of select populations of fetal stem cells for targeted therapeutic benefit. For example, amniotic fluid-derived mesenchymal stem cells (afMSCs) play an integral role in fetal tissue repair, validating the use of afMSCs in regenerative strategies. The simple intra-amniotic delivery of these cells in expanded numbers via TRASCET has been shown to promote the repair of and/or significantly ameliorate the effects associated with major congenital anomalies such as neural tube and abdominal wall defects. For example, TRASCET can induce partial or complete coverage of experimental spina bifida through the formation of a host-derived rudimentary neoskin, thus protecting the spinal cord from further damage secondary to amniotic fluid exposure. Furthermore, TRASCET can significantly reduce the bowel inflammation associated with gastroschisis, a common major abdominal wall defect. After intra-amniotic injection, donor stem cells home to the placenta and the fetal bone marrow in the spina bifida model, suggesting a role for hematogenous cell routing rather than direct defect seeding. Therefore, the expansion of TRASCET to congenital diseases without amniotic fluid exposure, such as congenital diaphragmatic hernia, as well as to maternal diseases, is currently under investigation in this emerging and evolving field of fetal stem cell therapy.