Comparative Effects on Fetal Hematopoiesis and Placental Inflammation From Mesenchymal and Hematopoietic Stem Cells as Agents of Transamniotic Stem Cell Therapy (TRASCET) in a Syngeneic Model of Intrauterine Growth Restriction

PURPOSE

We compared transamniotic stem cell therapy (TRASCET) using either mesenchymal (MSCs) or hematopoietic (HSCs) stem cells on fetal hematopoiesis in a syngeneic model of intrauterine growth restriction (IUGR).

METHODS

Lewis dams exposed to cycling hypoxia (10.5% O2) in late gestation had their fetuses (n = 83) either receiving no intervention (untreated; n = 9), or intra-amniotic injections of either HSCs (HSC; n = 34), MSCs primed to an enhanced anti-inflammatory phenotype (primed-MSC; n = 28), or saline (sham; n = 12). Normal controls (n = 18) were also studied. Complete peripheral blood counts and placental ELISA for inflammation and angiogenesis markers were performed at term.

RESULTS

Overall survival from hypoxia was 41% (34/83). Red blood count (RBC), hematocrit (Hct) and hemoglobin levels (Hb) were all significantly decreased from normal in all hypoxia groups. TRASCET with primed-MSC had significantly higher RBC, Hct, and Hb levels than sham (p = 0.01-0.03, pairwise), though not than untreated (which had no surgical blood loss). The HSC group had only significantly higher Hb levels than sham (p = 0.005). TRASCET with primed-MSC had significantly lower levels of placental TNF-α than sham (p = 0.04), but not untreated.

CONCLUSIONS

MCSs seem more effective than HSCs in enhancing hematopoiesis when used as donor cells for TRASCET in a syngeneic model of IUGR.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

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).

Fetal Secretory IgA Delivery via Transamniotic Fetal Immunotherapy (TRAFIT) in a Rodent Model

PURPOSE

We sought to determine the feasibility and routing kinetics of transamniotic fetal delivery of secretory immunoglobulin-A (SIgA), in a rodent model.

METHODS

Fetuses (n = 94) from seven time-dated pregnant dams received intra-amniotic injections on gestational day 17 (E17, term = E21-22) of either saline (n = 15) or a solution of 1 mg/mL of ≥95% homogeneous human SIgA (n = 79). Animals were euthanized daily at E18-E21 for quantification of the IgA component by ELISA at gestational membranes, placenta, and select fetal anatomical sites against saline controls procured at term. Statistical analysis was by Mann-Whitney U-test.

RESULTS

None of the saline-injected animals had detectable human IgA. SIgA-injected fetuses showed human IgA in the stomach aspirate, intestinal wall, lungs, liver, and serum at all time points. IgA levels were significantly higher in the gastric aspirate and in the intestine than in all other sites (p < 0.001 for both), with intestinal levels remaining stable through E18-E21 (p = 0.09-0.62 pairwise). Serum and placental levels were consistently low throughout, reaching near zero levels by E21.

CONCLUSIONS

The chronology of exogenous secretory-IgA kinetics after intra-amniotic injection is suggestive of fetal uptake by ingestion, leading to consistent levels in the gastrointestinal tract. Transamniotic fetal immunotherapy (TRAFIT) with secretory-IgA may become a novel strategy for enhancing early mucosal immunity.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

TYPE OF STUDY

Animal and laboratory study.

Morphometric, Developmental, and Anti-Inflammatory Effects of Transamniotic Stem Cell Therapy (TRASCET) on the Fetal Heart and Lungs in a Model of Intrauterine Growth Restriction

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) can attenuate placental inflammation and minimize intrauterine growth restriction (IUGR). We sought to determine whether MSC-based TRASCET could mitigate fetal cardiopulmonary effects of IUGR. Pregnant Sprague-Dawley dams were exposed to alternating 12-h hypoxia (10.5% O2) cycles in the last fourth of gestation. Their fetuses (n = 155) were divided into 4 groups. One group remained untreated (n = 42), while three groups received volume-matched intra-amniotic injections of either saline (sham; n = 34), or of syngeneic amniotic fluid-derived MSCs, either in their native state (TRASCET; n = 36) or "primed" by exposure to interferon-gamma and interleukin-1beta before administration in vivo (TRASCET-primed; n = 43). Normal fetuses served as additional controls (n = 30). Multiple morphometric and biochemical analyses were performed at term for select markers of cardiopulmonary development and inflammation previously shown to be affected by IUGR. Among survivors (75%; 117/155), fetal heart-to-body weight ratio was increased in both the sham and untreated groups (P < 0.001 for both) but normalized in the TRASCET and TRASCET-primed groups (P = 0.275, 0.069, respectively). Cardiac b-type natriuretic peptide levels were increased in all hypoxia groups compared with normal (P < 0.001), but significantly decreased from sham and untreated in both TRASCET groups (P < 0.0001-0.005). Heart tumor necrosis factor-alpha levels were significantly elevated in sham and TRASCET groups (P = 0.009, 0.002), but normalized in the untreated and TRASCET-primed groups (P = 0.256, 0.456). Lung transforming growth factor-beta levels were significantly increased in both sham and untreated groups (P < 0.001, 0.003), but normalized in both TRASCET groups (P = 0.567, 0.303). Similarly, lung endothelin-1 levels were elevated in sham and untreated groups (P < 0.001 for both), but normalized in both TRASCET groups (P = 0.367, 0.928). We conclude that TRASCET with MSCs decreases markers of fetal cardiac strain, insufficiency, and inflammation, as well as of pulmonary fibrosis and hypertension in the rodent model of IUGR.

Fetal Alloimmune Hemolytic Anemia (AHA) as a Potential Target for Transamniotic Fetal Immunotherapy (TRAFIT)

PURPOSE

Fetal alloimmune hemolytic anemia (AHA) resulting from maternal antibodies against fetal erythrocytes may require fetal administration of immunoglobulin-G (IgG) via invasive methods. IgG can reach the fetal circulation after transamniotic fetal immunotherapy (TRAFIT). We sought to both develop a model of AHA and to test TRAFIT as a potential treatment.

METHODS

Sprague-Dawley fetuses (n = 113) received intra-amniotic injections on gestational-day 18 (E18, term = E21) of either saline (control; n = 40), anti-rat-erythrocyte antibodies (AHA; n = 37), or anti-rat-erythrocyte antibodies plus IgG (AHA + IgG; n = 36). At term, blood was procured for red blood count (RBC), hematocrit, or ELISA for inflammatory markers.

RESULTS

There was no difference in survival [95% (107/113)] across groups (p = 0.87). Both hematocrit and RBC were significantly lower in the AHA group than controls (p < 0.001). Although still significantly lower than controls (p < 0.001), both hematocrit and RBC significantly increased in AHA + IgG group compared to AHA alone (p < 0.001). Pro-inflammatory TNF-α and IL1-β were significantly elevated from controls in the AHA group, but not in AHA + IgG (p < 0.001-0.159).

CONCLUSIONS

Intra-amniotic injection of anti-rat-erythrocyte antibodies can reproduce manifestations of fetal AHA, constituting a practical model of this disease. Transamniotic fetal immunotherapy with IgG reduces anemia in this model and may emerge as a new minimally invasive means of treatment.

TYPE OF STUDY

Animal and laboratory study.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Hematogenous Routing of Exogenous mRNA Delivered Into the Amniotic Fluid

INTRODUCTION

Therapies based on exogenous messenger RNA (mRNA) administration have emerged as a powerful novel strategy for the actual or potential treatment of an assortment of diseases, including congenital surgical pathologies. We sought to determine whether the minimally invasive transamniotic route could be an alternative for prenatal mRNA delivery.

METHODS

Pregnant Sprague-Dawley dams underwent laparotomy followed by volume-matched intra-amniotic injections in all their fetuses (n = 120) of either a suspension of a custom firefly luciferase mRNA encapsulated by a lipid- and synthetic cationic polymer-based composite, or of a suspension of the same encapsulation components without mRNA, on gestational day 17 (E17; term = E21-22). On E18, E19, E20, and E21, samples from 14 fetal anatomical sites and maternal serum were procured for the screening of mRNA incorporation by host cells by measurement of luciferase activity via microplate luminometry. Statistical analysis was by Mann-Whitney U-test, including Bonferroni-adjustment.

RESULTS

Overall survival was 87.5% (105/120). Controlled by the encapsulating composite without mRNA, luciferase activity was detected in the animals that received encapsulated mRNA in the following fetal annexes: amniotic fluid, amnion, chorion, umbilical cord, and placenta (P = 0.033 to <0.001), as well as in the following fetal sites: liver, stomach, intestines, and lungs (P = 0.043-0.002).

CONCLUSIONS

Packaged exogenous mRNA can be incorporated by the fetus at least at select anatomical sites after simple intra-amniotic administration in a rodent model. The pattern and chronology of mRNA incorporation are compatible with transplacental hematogenous routing, as well as with fetal swallowing/aspiration. Further study of transamniotic mRNA administration is warranted.

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.

Transamniotic Fetal Administration of Genetically Modified Hematopoietic Stem Cells Carrying a Human Transgene in a Syngeneic Rat Model

Hematopoietic stem cell (HSC)-based gene therapy has already reached clinical reality in a few applications. Fetal administration of genetically modified HSCs has only been feasible to date through invasive and morbid methods. It has been recently shown that native donor HSCs can reach the fetal circulation and bone marrow after simple delivery into the amniotic fluid, at least in a syngeneic healthy model. We sought to determine whether the transamniotic route could also be a practical alternative for the fetal administration of genetically modified HSCs in a comparable model. Pregnant Lewis rat dams underwent volume-matched intra-amniotic injections in all their fetuses (n = 47) on gestational day 17 (E17; term = E21-22) of donor HSCs genetically modified using a custom lentiviral vector designed to constitutively express both a firefly luciferase reporter gene and a human adenosine deaminase (ADA) transgene. Donor HSCs consisted of syngeneic cells isolated from the amniotic fluid and phenotyped by flow cytometry. Fetuses were euthanized at term, when seven select sites relevant to HSC-based therapies were screened for either luciferase activity by luminometry or for the presence of human ADA mRNA by digital droplet polymerase chain reaction (ddPCR). Among survivors (30/47; 64%), positive luminescence and positive human ADA expression were detected in the bone marrow (respectively, 33% and 76%), liver (respectively, 11% and 81%), spleen (respectively, 11% and 67%), thymus (respectively, 33% and 67%), lungs (respectively, 44% and 86%), and brain (respectively, 22% and 90%). Nucleated peripheral blood cells were analyzed only by ddPCR, showing positive human ADA expression at 54%. We conclude that genetically modified HSCs can reach the fetal circulation and fetal bone marrow after simple intra-amniotic administration in a syngeneic rat model. Gene therapy by transamniotic HSC delivery may become a practicable, minimally invasive strategy for the prenatal treatment of select hemoglobinopathies, immunodeficiencies, and inherited metabolic disorders.

Transamniotic stem cell therapy (TRASCET) for intrauterine growth restriction (IUGR): A comparison between placental and amniotic fluid donor mesenchymal stem cells

PURPOSE

Transamniotic stem cell therapy (TRASCET) with donor mesenchymal stem cells (MSCs) has been shown experimentally to reverse central effects of intrauterine growth restriction (IUGR). We sought to compare amniotic-fluid and placenta-derived MSCs (afMSCs and pMSCs, respectively) as TRASCET donor cells in a murine IUGR model.

METHODS

Pregnant Sprague-Dawley dams (n=8) were exposed to alternating 12-hour hypoxia (10.5% O₂) cycles, starting on gestational day 15 (E15; term=E21-22). On E17, fetuses (n=100) were divided into four groups. An untreated group had no further manipulations (n=24). Three groups received volume-matched intra-amniotic injections of either saline (sham; n=27), or suspensions of afMSCs (n=24), or pMSCs (n=25). Normal fetuses served as controls (n=21). All infused MSCs consisted of syngeneic Lewis rat cells phenotyped by flow cytometry and GFP-labeled. At term, fetal and placental morphometrics were calculated, and placental TNF-α levels were determined by ELISA. Statistical comparisons were by Fischer's T-test or Wilcoxon rank sum test (p≤0.05).

RESULTS

Overall survival of the hypoxic groups was 83% (83/100). Compared to normal, maternal-adjusted fetal weights were significantly decreased in all hypoxia groups (pairwise p<0.001), however only the afMSC group showed higher adjusted-fetal weights than sham (p<0.001). Placental efficiency was decreased in untreated, sham, and pMSC groups (p<0.001-0.056) but normalized in the afMSC group (p=0.205). Maternal-adjusted placental weights were lower than normal in all hypoxia groups (p<0.001-0.045), except for the pMSC group (p=0.387).

CONCLUSIONS

Amniotic fluid-derived mesenchymal stem cells are superior to their placenta-derived counterparts in transamniotic stem cell therapy for intrauterine growth restriction in a rat model.

LEVEL OF EVIDENCE

Basic/Translational science.

Early functional analysis on the pulmonary hemodynamic effects of Transamniotic Stem Cell Therapy (TRASCET) in the nitrofen model of congenital diaphragmatic hernia

PURPOSE

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) has been shown to impact pulmonary vascular development and remodeling in experimental congenital diaphragmatic hernia (CDH), with secondary structural cardiac effects. We sought to determine whether TRASCET has any functional impact on term fetal pulmonary hemodynamics in the nitrofen model.

METHODS

Time-dated pregnant rat dams (n = 13) received nitrofen on gestational day 9 (E9) to induce fetal CDH. Fetuses (n = 155) were divided into three groups: untreated (n = 45), and two groups receiving volume-matched intra-amniotic injections on E17 of either saline (sham; n = 46), or a suspension of amniotic fluid-derived MSCs (afMSCs) (TRASCET; n = 64). Donor afMSCs were syngeneic, phenotyped by flow cytometry, and "primed" by exposure to interferon-gamma and interleukin-1beta prior to administration in vivo. At term (E21), fetuses underwent Doppler flow assessment at the mid-pulmonary artery and 4-chamber echocardiogram. Pulmonary vascular resistance was estimated by pulmonary artery acceleration time (PAAT), max velocity (MaxV) and velocity time integral (VTI). Cardiac function was assessed by global longitudinal strain (GLS) and ejection fraction (EF) using speckle analyses. Healthy fetuses (n = 11) served as additional controls. Statistical analysis was by the Mann-Whitney U test RESULTS: High resolution ultrasound data could be obtained from 8 to 13 fetuses per group. The PAAT and the PAAT normalized to cardiac cycle time were significantly improved by TRASCET compared to both untreated and sham-treated CDH (p = 0.004 to <0.001 in all pairwise comparisons). The flow profile sharpness (MaxV:VTI) was increased in untreated (p = 0.06) and sham (p = 0.01) groups but normalized by TRASCET (p<0.01). There was no difference in GLS between TRASCET and either the untreated or sham groups (p = 0.25 to p = 0.93).

CONCLUSION

Transamniotic stem cell therapy improves pulmonary vascular resistance in early term fetuses in the Nitrofen model of congenital diaphragmatic hernia. Further focus on the functional pulmonary hemodynamic impact of this therapy is justified.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

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.

Routing kinetics of human immunoglobulin-G after transamniotic fetal immunotherapy (TRAFIT) in a rodent model

PURPOSE

The transamniotic route was recently discovered as a minimally invasive means of fetal immunoglobulin administration, however by unclear mechanisms. We sought to examine IgG routing after intra-amniotic delivery.

METHODS

Sprague-Dawley fetuses (n = 78) received intra-amniotic injections of 15 mg/mL of human IgG on gestational-day 18 (E18; term=21 and 22 days). Amniotic fluid, amnion, chorion, placenta, fetal serum, liver, and stomach-aspirate samples were procured on E19, E20, and E21 for IgG quantification by ELISA. Statistical analysis was by median regression with Bonferroni-adjusted significance at p < 0.017.

RESULTS

Human IgG was detected at all sampled sites across all time points, though at significantly higher levels in the gestational membranes and fetal serum than in the stomach aspirate and liver (p < 0.001 for both). Gestational membranes showed a daily decrease after injection, stabilizing by E20 and E21 (p = 0.792 to < 0.001). Placental levels were significantly lower at E21 than E19 (p = 0.010). Fetal serum showed the highest human IgG levels at term.

CONCLUSIONS

The chronology of exogenous IgG kinetics after intra-amniotic injection is suggestive of direct placental transport leading to consistently high fetal serum levels, possibly combined with some fetal ingestion. Transamniotic fetal immunotherapy (TRAFIT) may become a practicable strategy for the prenatal treatment of select alloimmune disorders and infections.

LEVEL OF EVIDENCE

N/A (Animal and Laboratory study).

TYPE OF STUDY

Animal and Laboratory Study.

Intrauterine Growth Restriction (IUGR) as a potential target for transamniotic stem cell therapy

BACKGROUND

We sought to determine whether intrauterine growth restriction (IUGR) could be a target for mesenchymal stem cell (MSC)-based transamniotic stem cell therapy (TRASCET).

METHODS

Pregnant dams subjected to hypoxia (10.5% O₂) cycles had their fetuses divided into four groups: untreated (n = 24) and three groups receiving volume-matched intra-amniotic injections of either saline (sham; n = 16), or suspensions of luciferase-labeled, syngeneic amniotic fluid-derived MSCs that were either native (TRASCET-unprimed; n = 29), or primed by exposure to IFNγ and IL-1β (TRASCET-primed; n = 31). Normal fetuses served as additional controls (n = 22). Multiple analyses were performed at term.

RESULTS

Compared to normal, fetal weights were significantly decreased in all hypoxia groups (p = 0.002 to <0.001), except for TRASCET-primed. Placental efficiency (fetal/placental weight) was significantly decreased in all hypoxia groups (p = 0.002 to <0.001), but normalized in both TRASCET groups. A significant increase in metrial expression of IFNγ in both the untreated and sham groups (p = 0.04 to 0.02) was reversed only in the TRASCET-primed group. Luciferase DNA was present in both TRASCET groups' placentas.

CONCLUSIONS

Transamniotic stem cell therapy with primed mesenchymal stem cells reverses some of the effects of intrauterine growth restriction in a rat model. Further study into this novel approach for the treatment of this disease is warranted.

LEVEL OF EVIDENCE

N/A (Animal and Laboratory Study).

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.

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.

Enhancement of transamniotic stem cell therapy for spina bifida by genetic engineering of donor mesenchymal stem cells with an Fgf2 transgene

BACKGROUND/PURPOSE

We examined whether engineered overexpression of fibroblast growth factor-2 (Fgf2) in donor mesenchymal stem cells (MSCs) could enhance spina bifida coverage induced by transamniotic stem cell therapy (TRASCET).

METHODS

Pregnant Sprague-Dawley dams (n = 24) exposed to retinoic acid for induction of fetal spina bifida were divided in three groups. An untreated group had no further manipulations. Two groups received volume-matched intra-amniotic injections into all fetuses (n = 157) of either amniotic fluid-derived MSCs (afMSC; n = 85) or afMSCs transduced with an Fgf2 transgene (Fgf2-afMSC; n = 72) on gestational day 17 (term=21-22 days). Defect coverage was categorized at term by histology and pan-cytokeratin immunohistochemistry. Statistical coverage comparisons were by logistic regression.

RESULTS

Among 84 survivors with isolated spina bifida, 71 had definitive histology. Defect coverage rates in both the afMSC (38.5%) and Fgf2-afMSC (73.3%) groups were statistically significantly higher than in the untreated group (10%; p<0.001 for both). There was a significantly higher coverage rate in the Fgf2-afMSC group compared with the afMSC group (p = 0.025).

CONCLUSIONS

Fgf2 overexpression in donor mesenchymal stem cells increases defect coverage rates in a rodent model of transamniotic stem cell therapy for spina bifida. Genetic engineering of donor cells is a promising strategy for the enhancement of this emerging therapy.

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.

A novel two-component, expandable bioadhesive for exposed defect coverage: Applicability to prenatal procedures

BACKGROUND/PURPOSE

We sought to test select properties of a novel, expandable bioadhesive composite that allows for enhanced adhesion control in liquid environments.

METHODS

Rabbit fetuses (n = 23) underwent surgical creation of spina bifida on gestational day 22-25 (term 32-33 days). Defects were immediately covered with a two-component tough adhesive consisting of a hydrogel made of a double network of ionically crosslinked alginate and covalently crosslinked polyacrylamide linked to a bridging chitosan polymer adhesive. Animals were euthanized prior to term for different analyses, including hydraulic pressure testing.

RESULTS

Hydrogels remained adherent in 70% (16/23) of the recovered fetuses and in all of the last 14 fetuses as the procedure was optimized. Adherent hydrogels showed a median two-fold (IQR: 1.7-2.4) increase in area at euthanasia, with defect coverage confirmed by ultrasound and histology. The median maximum pressure to repair failure was 15 mmHg (IQR: 7.8-55.3), exceeding reported neonatal cerebrospinal fluid pressures.

CONCLUSIONS

This novel bioadhesive composite allows for selective, stable attachment of an alginate-polyacrylamide hydrogel to specific areas of the spina bifida defect in a fetal rabbit model, while the hydrogel expands with the defect over time. It could become a valuable alternative for the prenatal repair of spina bifida and possibly other congenital anomalies.

TYPE OF STUDY

N/A (animal and laboratory study).

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Initial Mechanistic Screening of Transamniotic Stem Cell Therapy in the Rodent Model of Spina Bifida: Host Bone Marrow and Paracrine Activity

PURPOSE

Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) can induce spina bifida coverage with neoskin. We initiated a mechanistic analysis of this host response.

METHODS

Pregnant dams (n = 28) exposed to retinoic acid to induce fetal spina bifida were divided into an untreated group and 2 groups receiving intra-amniotic injections on gestational day 17 (E17; term = E21-22) of either amniotic fluid-derived MSCs (afMSCs; n = 105) or saline (n = 107). Gene expressions of multiple paracrine and cell clonality markers were quantified at term by RT-qPCR at the defect and fetal bone marrow. Defects were examined histologically for neoskin coverage. Comparisons were by Mann-Whitney U tests and logistic regression.

RESULTS

Defect coverage was associated with significant downregulation of both epidermal growth factor (Egf; p = 0.031) and fibroblast growth factor-2 (Fgf-2; p = 0.042) expressions at the defect and with significant downregulation of transforming growth factor-beta-1 (Tgfb-1; p = 0.021) and CD45 (p = 0.028) expressions at the fetal bone marrow.

CONCLUSIONS

Coverage of experimental spina bifida is associated with local and bone marrow negative feedback of select paracrine factors, as well as increased relative mesenchymal stem cell activity in the bone marrow. Further analyses informed by these findings may lead to strategies of nonsurgical induction of prenatal coverage of spina bifida.

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.

An experimental study on magnetic esophageal compression anastomosis in piglets

INTRODUCTION

Fashioning a patent, watertight anastomosis in patients with esophageal atresia is a challenging task in pediatric surgery, particularly when performed under tension. A reproducible suture-less alternative would decrease operative time. We evaluated magnetic esophageal compression anastomoses in a novel bypass-loop swine model.

METHODS

Eight-week-old piglets underwent thoracotomy to mobilize the esophagus at the carina to create a U-shaped loop. Custom-made 8 mm diameter Neodymium Magnets were inserted into the esophagus proximal and distal to the loop, then mated side-to-side at the future anastomosis site. Pigs were observed for 8 (n = 4), 10 (n = 6), and 12 (n = 2) days and then sacrificed. The magnetic compression anastomosis was evaluated macroscopically, by radiography, burst pressure testing, and histology.

RESULTS

All 12 pigs survived until the endpoint. Separation of the magnets occurred at a median of 9 days. Contrast esophagrams showed patency and no leak. All anastomoses withstood pressures well over 13 kPa without leak. Histopathology showed epithelialized circular scar tissue.

CONCLUSION

Magnetic compression anastomoses of the esophagus using our specially-designed magnets are formed between the 8th and 10th postoperative day, are patent and mechanically resistant to supraphysiologic intraluminal pressures. These data lay the basis for a potential clinical application in patients born with esophageal atresia.

LEVEL OF EVIDENCE

Not applicable (experimental animal study).

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).

A comparison between placental and amniotic mesenchymal stem cells in transamniotic stem cell therapy for experimental gastroschisis

PURPOSE

We compared placental and amniotic fluid-derived mesenchymal stem cells (pMSCs and afMSCs, respectively) in transamniotic stem cell therapy for experimental gastroschisis.

METHODS

Gastroschisis was surgically created in 126 rat fetuses at gestational day 18 (term = 22 days), immediately followed by volume-matched intraamniotic injections of suspensions of afMSCs (n = 32), pMSCs (n = 33), or normal saline (NS) (n = 33). Untreated fetuses served as controls (n = 28). Blinded observers performed computerized measurements of total and segmental (serosa, muscularis, and mucosa) intestinal wall thickness on the herniated bowel at term. Statistical analysis included ANOVA, the Wald test, and Levene's test (p < 0.05).

RESULTS

Among survivors, there were statistically significant decreases in segmental and total bowel wall thicknesses in both the afMSC and pMSC groups vs. the untreated (p < 0.001 to 0.003) and saline (p < 0.001 to 0.011) groups. There were significant differences between the afMSC and pMSC groups favoring the former in both therapeutic impact and its variability (p < 0.001 to 0.031). Labeled cells were comparably identified within the intestinal wall in the afMSC and pMSC groups.

CONCLUSIONS

Both placental and amniotic mesenchymal stem cells can mitigate bowel damage in experimental gastroschisis as agents of transamniotic stem cell therapy. However, amniotic cells lead to improved and more consistent outcomes.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Regenerative medicine and spina bifida: Recent developments in induced fetal regeneration

Regenerative medicine as it applies to spina bifida is a multi-pronged endeavor involving spinal cord repair, tissue engineering and fetal regeneration, all of which can mutually overlap to variable extents. The efforts involving spinal cord repair, whether they be cell-based or not, are virtually indistinguishable from the enormous body of work related to spinal cord recovery after traumatic injury. Tissue engineering, on the other hand, can involve a variety of structures besides constructs used for covering the spina bifida defect, for example the urinary bladder, bone, muscle and skin. This brief review will not delve into any of these two main areas, which actually can also involve fetal interventions within their respective realms, but rather be devoted to a very recent development making use of the uniquely enhanced ability of the fetus to repair, or regenerate areas of tissue damage, coined transamniotic stem cell therapy, or TRASCET. TRASCET is a still experimental therapeutic paradigm for the treatment of not only spina bifida, but also other birth defects, based on the principle of harnessing/enhancing the normal biological role of a select population of stem cells that naturally occur in the amniotic fluid, specifically amniotic fluid-derived mesenchymal stem cells (afMSCs), for therapeutic benefit.

Fetal bone marrow homing of donor mesenchymal stem cells after transamniotic stem cell therapy (TRASCET)

PURPOSE

Donor cell engraftment patterns following transamniotic stem cell therapy (TRASCET) with amniotic fluid mesenchymal stem cells (afMSCs) are incompatible with solely direct amniotic seeding. We sought to determine whether fetal bone marrow is a component of such engraftment and to examine the chronology of afMSC placental trafficking.

METHODS

Two groups of Sprague-Dawley rat fetuses received volume-matched intraamniotic injections on gestational day 17 (E17; term E22): either afMSCs labeled with a luciferase reporter gene or luciferase protein alone. Placental samples were procured at daily time points thereafter until term. Fetal bone marrow was obtained at term only owing to size constraints. Specimens were screened for luminescence via microplate luminometry.

RESULTS

Donor afMSCs were identified in the bone marrow and placenta of fetuses receiving labeled afMSCs, but not in those receiving luciferase alone (P<0.001). Luminescence was significantly higher in placentas at E18 compared to E19 (P<0.001), E20 (P=0.007), and E21 (P=0.004), with no difference with E22/term (P=0.97).

CONCLUSIONS

Donor mesenchymal stem cells home to the fetal bone marrow after intraamniotic injection. The chronology of placental trafficking is suggestive of controlled cell routing rather than plain cell clearance. Fetal bone marrow engraftment of donor cells significantly expands potential applications of transamniotic stem cell therapy.

Donor mesenchymal stem cells home to maternal wounds after transamniotic stem cell therapy (TRASCET) in a rodent model

PURPOSE

Transamniotic stem cell therapy (TRASCET) with amniotic fluid-derived MSCs (afMSCs) has emerged experimentally as a practical treatment strategy for congenital anomalies. In this study, we sought to determine whether afMSCs migrate to the mother following TRASCET.

METHODS

Pregnant rat dams were divided into three groups. Two groups received volume-matched injections into all amniotic cavities of either a suspension of afMSCs labeled with a luciferase reporter gene or the luciferase protein alone. In a third group, a suspension of labeled cells was aliquoted onto the serosal surface of the uterus. Maternal samples from the laparotomy scar (fascia and skin separately), bone marrow, and peripheral blood were procured, along with placenta and umbilical cord. Specimens were screened for luminescence via microplate luminometry.

RESULTS

Luminescence was detected in 60% (9/15) of the fascial scars from the group receiving intraamniotic injection of afMSCs, but in none of the other groups (P<0.001). There was a direct correlation between the presence of donor cells in the placenta and their presence in maternal fascia (Wald test=10.2; P=0.001).

CONCLUSIONS

Amniotic mesenchymal stem cells migrate to maternal sites of injury after intraamniotic injection. Maternal homing of donor cells must be considered in the setting of transamniotic stem cell therapy.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Comparisons of human amniotic mesenchymal stem cell viability in FDA-approved collagen-based scaffolds: Implications for engineered diaphragmatic replacement

BACKGROUND/PURPOSE

We sought to examine amniotic fluid mesenchymal stem cell (afMSC) viability within two FDA-approved collagen-based scaffolds, as a prerequisite to clinical translation of afMSC-based engineered diaphragmatic repair.

METHODS

Human afMSCs were seeded in a human-derived collagen hydrogel and in a bovine-derived collagen sheet at 3 matching densities. Cell viability was analyzed at 1, 3, and 5days using an ATP-based 3D bioluminescence assay. Statistical comparisons were by ANOVA (P<0.05).

RESULTS

There was a highly significant 3-way interaction between scaffold type, seeding density, and time in 3D culture as determinants of cell viability, clearly favoring the human hydrogel (P<0.001). In both scaffolds, cell viability was highest at the highest seeding density of 150,000 cells/mL. Time in 3D culture impacted cell viability at the optimal seeding density in the human hydrogel, with the highest levels on days 1 (P<0.001) and 5 (P=0.05) with no significant effect in the bovine sheet (P=0.39-0.96).

CONCLUSIONS

Among clinically-approved cell delivery vehicles, mesenchymal stem cell viability is significantly enhanced in a collagen hydrogel when compared with a collagen sheet. Cell viability can be further optimized by seeding density and time in 3D culture. These data further support the regulatory viability of clinical trials of engineered diaphragmatic repair.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

A comparison between placental and amniotic mesenchymal stem cells for transamniotic stem cell therapy (TRASCET) in experimental spina bifida

PURPOSE

We compared placental-derived and amniotic fluid-derived mesenchymal stem cells (pMSCs and afMSCs, respectively) in transamniotic stem cell therapy (TRASCET) for experimental spina bifida.

METHODS

Pregnant dams (n=29) exposed to retinoic acid for the induction of fetal spina bifida were divided into four groups. Three groups received volume-matched intraamniotic injections of either saline (n=38 fetuses) or a suspension of 2×10(6) cells/mL of syngeneic, labeled afMSCs (n=73) or pMSCs (n=115) on gestational day 17 (term=21-22days). Untreated fetuses served as controls. Animals were killed before term. Statistical comparisons were by Fisher's exact test (p<0.05).

RESULTS

Survival was similar across treatment groups (p=0.08). In fetuses with isolated spina bifida (n=100), there were higher percentages of defect coverage (either partial or complete) in both afMSC and pMSC groups compared with saline and untreated groups (p<0.001-0.03 in pairwise comparisons). There were no differences in coverage rates between afMSC and pMSC groups (p=0.94) or between saline and untreated groups (p=0.98).

CONCLUSIONS

Both pMSC and afMSC can induce comparable rates of coverage of experimental spina bifida after concentrated intraamniotic injection in the rodent model. This broadens the options for timing and cell source for TRASCET as a potential alternative in the prenatal management of spina bifida.

Trans-amniotic stem cell therapy (TRASCET) minimizes Chiari-II malformation in experimental spina bifida

PURPOSE

We sought to study the impact of trans-amniotic stem cell therapy (TRASCET) in the Chiari-II malformation in experimental spina bifida.

METHODS

Sprague-Dawley fetuses (n=62) exposed to retinoic acid were divided into three groups at term (21-22 days gestation): untreated isolated spina bifida (n=21), isolated spina bifida treated with intra-amniotic injection of concentrated, syngeneic, labeled amniotic fluid mesenchymal stem cells (afMSCs) on gestational day 17 (n=28), and normal controls (n=13). Analyses included measurements of brainstem and cerebellar placement on high resolution MRI and histology. Statistical comparisons included ANOVA.

RESULTS

In parallel to the expected induced coverage of the spina bifida in the afMSC-treated group (P<0.001), there were statistically significant differences in brainstem displacement across the groups (P<0.001), with the highest caudal displacement in the untreated group. Significant differences in cerebellar displacement were also noted, albeit less pronounced. Pairwise comparisons were statistically significant, with P=0.014 between treated and normal controls in caudal brainstem displacement and P<0.001 for all other comparisons. Labeled afMSCs were identified in 71% of treated fetuses.

CONCLUSIONS

Induced coverage of spina bifida by TRASCET minimizes the Chiari-II malformation in the retinoic acid rodent model, further suggesting it as a practical alternative for the prenatal management of spina bifida.

Limb reconstruction with decellularized, non-demineralized bone in a young leporine model

Limb salvage from a variety of pathological processes in children is often limited by the unavailability of optimal allograft bone, or an appropriate structural bone substitute. In this study, we sought to examine a practical alternative for pediatric limb repair, based on decellularized, non-demineralized bone grafts, and to determine whether controlled recellularization prior to implantation has any impact on outcome. Growing New Zealand rabbits (n = 12) with a complete, critical-size defect on the left tibiofibula were equally divided into two groups. One group received a decellularized, non-demineralized leporine tibiofibula graft. The other group received an equivalent graft seeded with mesenchymal stem cells labeled with green fluorescent protein (GFP), at a fixed density. Animals were euthanized at comparable time points 3-8 weeks post-implantation. Statistical analysis was by the Student t-test and Fisher's exact test (P < 0.05). There was no significant difference in the rate of non-union between the two groups, including on 3D micro-CT. Incorporated grafts achieved adequate axial bending rigidity, torsional rigidity, union yield and flexural strength, with no significant differences or unequal variances between the groups. Correspondingly, there were no significant differences in extracellular calcium levels, or alkaline phosphatase activity. Histology confirmed the presence of neobone in both groups, with GFP-positive cells in the recellularized grafts. It was shown that osseous grafts derived from decellularized, non-demineralized bone undergo adequate remodeling in vivo after the repair of critical-size limb defects in a growing leporine model, irrespective of subsequent recellularization. This methodology may become a practical alternative for pediatric limb reconstruction.

Operative indications in recurrent ileocolic intussusception

BACKGROUND

Air-contrast enema (ACE) is standard treatment for primary ileocolic intussusception. Management of recurrences is less clear. This study aimed to delineate appropriate therapy by quantifying the relationship between recurrence and need for bowel resection, pathologic lead points (PLP), and complication rates.

METHODS

After IRB approval, a single institution review of patients with ileocolic intussusception from 1997 to 2013 was performed, noting recurrences, outcomes, and complications. Fisher's exact and t-tests were used.

RESULTS

Of 716 intussusceptions, 666 were ileocecal. Forty-four underwent bowel resection, with 29 PLPs and 9 ischemia/perforation. Recurrence after ACE occurred in 96 (14%). Recurrence did not predict PLP (P=0.25). Recurrence (≥3) was associated with higher resection rate (P=0.03), but not ischemia/perforation (P=0.75). ACE-related complications occurred in 4 (0.5%) patients. Successful initial ACE had 98% negative predictive value for resection and PLP (e.g., after successful ACE, 2% had resections, 2% PLP). After failed initial ACE, 36% received resection, and 23% had PLP (P<0.001).

CONCLUSIONS

Recurrence is associated with a greater risk of resection but not PLP or ACE-complication. Failed ACE is associated with increased risk for harboring PLP and receiving resection. ACE should be the standard treatment in recurrent intussusception, regardless of number of recurrences.

Extraluminal helicoidal stretch (Helixtretch): a novel method of intestinal lengthening

PURPOSE

We sought to test a novel, extraluminal method of intestinal lengthening that precludes violation of the intestinal wall.

METHODS

Sprague-Dawley rats (n=45) with size-matched bowel segments isolated by Roux-en-Y reconstruction were divided into three groups. Group 1 (n=14) had no further manipulations. In Groups 2 (n=12) and 3 (n=19), the isolated segment was wrapped around a length-matched device in a helicoidal fashion. In Group 2, the device consisted of plain polyurethane tubing. In Group 3, it consisted of a gradually expanding hygroscopic hydrogel (12.5mm final diameter). Euthanasia was performed at 8-21 days. Statistical analysis was by two-way ANOVA (P<0.05).

RESULTS

Overall survival was 87% (39/45). There was a statistically significant increase in bowel length in Group 3 compared to the other two groups (P<0.001). This increase correlated with the number of helicoidal coils (P=0.018), but not with post-operative time (P>0.50). There were no significant differences in total DNA/protein ratio across the groups (P=0.65). Histologically, there was an apparent increase in the goblet cell density in Group 3.

CONCLUSIONS

Measured extraluminal helicoidal stretch (Helixtretch) is tolerated by the intestine. Helixtretch induces bowel lengthening in a rodent model. Further analysis of this novel, minimally invasive alternative for intestinal augmentation is warranted.

The impact of gestational age on targeted amniotic cell profiling in experimental neural tube defects

PURPOSE

The proportions of select stem cells in term amniotic fluid have been shown to correlate with the type and size of experimental neural tube defects (NTDs). We sought to determine the impact of gestational age upon this form of targeted amniotic cell profiling.

METHODS

Sprague-Dawley fetuses with retinoic acid-induced NTDs (n = 110) underwent amniotic fluid procurement at four time points in gestation. Samples were analyzed by flow cytometry for the presence of cells concomitantly expressing Nestin and Sox-2 (neural stem cells, aNSCs) and cells concomitantly expressing CD29 and CD44 (mesenchymal stem cells, aMSCs). Statistical analysis was by nonparametric Kruskal-Wallis ANOVA (p < 0.05).

RESULTS

There was a statistically significant impact of gestational age on the proportions of both aMSCs (p = 0.01) and aNSCs (p < 0.01) in fetuses with isolated spina bifida. No such impact was noted in normal fetuses (p > 0.10 for both cells), in isolated exencephaly (p > 0.10 for both cells), or in combination defects (p > 0.10 for both cells). Gestational age had no effect on aNSC/aMSC ratios.

CONCLUSIONS

Targeted quantitative amniotic cell profiling varies with gestational age in experimental isolated spina bifida. This finding should be considered prior to the eventual translation of this diagnostic adjunct into the prenatal evaluation of these anomalies. © 2014 S. Karger AG, Basel.

Tissue engineering in congenital diaphragmatic hernia

Engineered diaphragmatic repair is emblematic of perinatal regenerative medicine and of the fetal tissue engineering concept. The alternative of a cellularized graft for the repair of a congenital diaphragmatic defect in the neonatal period is both biologically justifiable by the mechanisms behind diaphragmatic hernia recurrence as well as an ideal match for fetal mesenchymal stem cell-based constructs. It has been among the most developed experimental pursuits in neonatal tissue engineering, of which clinical application should be forthcoming.

A comparative analysis of human mesenchymal stem cell response to hypoxia in vitro: Implications to translational strategies

PURPOSE

Mesenchymal stem cells (MSCs) are particularly valuable for structural tissue replacement. We compared the response to hypoxia among human MSCs derived from four different clinically relevant sources as an adjunct to translational developments.

METHODS

Immunophenotypically indistinguishable human MSC lineages derived from bone marrow (bmMSCs), adipose tissue (adMSCs), amniotic fluid (afMSCs), and umbilical cord blood (cbMSCs) were submitted to either room air or 1% O2, under otherwise standard culture conditions. Cell expansion and quantitative RT-PCR data were obtained at different time points. Statistical analysis was by two-way mixed model and the F-test (P<0.05).

RESULTS

The effect of hypoxia on expansion kinetics was dependent on cell source. Only prenatal sources of MSCs - afMSCs (P=0.002) and cbMSCs (P<0.001) - proliferated significantly faster under hypoxia than normoxia. Increased HIF1-alpha expression correlated consistently with increased cell expansion only among afMSCs. There were no significant variabilities in Survivin, Oct-4, and VEGF expressions.

CONCLUSIONS

Mesenchymal stem cell tolerance to hypoxia in vitro varies with cell source. Prenatal cells, particularly those derived from amniotic fluid, are more robust than their postnatal counterparts. HIF1-alpha may play a role in the amniotic fluid-derived cells' enhanced response. These findings should inform the choice of mesenchymal stem cells for prospective regenerative strategies.

Prenatal tracheal reconstruction with a hybrid amniotic mesenchymal stem cells-engineered construct derived from decellularized airway

PURPOSE

This study was aimed at examining an airway construct engineered from autologous amniotic mesenchymal stem cells (aMSCs) and a xenologous decellularized airway scaffold as a means for tracheal repair.

METHODS

Fetal lambs (N = 13) with a tracheal defect were divided into 2 groups. One group (acellular, n = 6) was repaired with a decellularized leporine tracheal segment. The other group (engineered, n = 7) received an identical graft seeded with expanded/labeled autologous aMSCs. Newborns were euthanized for multiple analyses.

RESULTS

Eleven lambs survived to term, 10 of which could breathe at birth. Engineered grafts showed a significant increase in diameter in vivo (P = .04) unlike acellular grafts (P = .62), although variable stenosis was present in all implants. Engineered constructs exhibited full epithelialization, compared with none of the acellular grafts (P = .002). Engineered grafts had a significantly greater degree of increase in elastin levels after implantation than acellular implants (P = .04). No such differences were noted in collagen and glycosaminoglycan contents. Donor cells were detected in engineered grafts, which displayed a pseudostratified columnar epithelium.

CONCLUSIONS

Constructs engineered from aMSCs and decellularized airway undergo enhanced remodeling and epithelialization in vivo when compared with equivalent acellular implants. Amniotic mesenchymal stem cell-engineered airways may become an alternative for perinatal airway repair.

Craniofacial repair with fetal bone grafts engineered from amniotic mesenchymal stem cells

BACKGROUND

Ethically acceptable applications of fetal tissue engineering as a perinatal therapy can be expanded beyond life-threatening anomalies by amniotic fluid cell-based methods, in which cell procurement poses no additional risk to the mother. We sought to start to determine whether osseous grafts engineered from amniotic mesenchymal stem cells (aMSCs) could be an adjunct to craniofacial repair.

METHODS

New Zealand rabbits (n = 12) underwent creation of a full-thickness diploic nasal bone defect. We then equally divided animals into two groups based on how the defect was repaired: namely, size-matched implants of electrospun biodegradable nanofibers with or without nuclear labeled, allogeneic aMSCs maintained in osteogenic medium. We killed animals 8 wk post-implantation for multiple analyses. Statistical analysis included analysis of variance, post-hoc Bonferroni adjusted comparisons, and Levene's F-test, as appropriate (P < 0.05), with significance set at P < 0.05.

RESULTS

Micro-computed tomography scanning (two- and three-dimensional) showed no significant differences in defect radiodensity between groups. However, extracellular calcium levels were significantly higher in engineered grafts than in acellular implants (P = 0.003). There was significantly greater variability in mineralization in acellular implants than in engineered grafts by both direct calcium (P = 0.008) and micro-computed tomography measurements (P = 0.032). There were no significant differences in alkaline phosphatase activity or variance between groups. We documented labeled cells in the engineered grafts.

CONCLUSIONS

Craniofacial repair with osseous grafts engineered from aMSCs lead to enhanced and more consistent mineralization compared with an equivalent acellular prosthetic repair. Amniotic fluid-derived engineered bone may become a practical adjunct to perinatal craniofacial reconstruction.

Amniotic and placental mesenchymal stem cell isolation and culture

The amniotic fluid and placenta are sources of diverse progenitor cell populations, including -mesenchymal, hematopoietic, trophoblastic, and possibly more primitive stem cells. Given that much of the amniotic cavity and placenta share a common origin, namely the inner cell mass of the morula, perhaps it is not surprising that most types of progenitor cells that can be isolated from these two sources also share many characteristics. This chapter focuses solely on the most abundant and easy to isolate progenitor cell population found therein, the mesenchymal stem cells (MSCs). Unlike some of the other stem cell types, MSCs are present throughout gestation. Methods of isolation, expansion, freezing, and thawing of these cells will be presented with preference given to the simplest methods available for any given procedure.

Preclinical regulatory validation of an engineered diaphragmatic tendon made with amniotic mesenchymal stem cells

PURPOSE

Under a Food and Drug Administration directive, we examined definite long-term safety and efficacy aspects of an engineered diaphragmatic tendon graft as a regulatory prerequisite for clinical trials.

METHODS

Newborn lambs (N = 27) underwent partial diaphragmatic replacement with a Teflon patch, a composite acellular bioprosthesis, or the same bioprosthesis seeded with autologous amniotic mesenchymal stem cells processed under Good Manufacturing Practice guidelines. Multiple safety and efficacy analyses were performed at different time points up to 14 months of age (ovine adulthood).

RESULTS

There was no mortality. None of the blood tests or full body autopsy specimens showed any abnormality. There was a significantly higher failure rate in animals that received an acellular bioprosthetic graft vs an engineered graft, with no significant differences between Teflon and acellular bioprosthetic implants. Tensile strength and total collagen levels were significantly higher in engineered grafts than in acellular bioprosthetic grafts. On histology, lysozyme and myeloperoxidase stainings were unremarkable in all grafts.

CONCLUSIONS

Diaphragmatic repair with a clinically viable autologous tendon engineered with amniotic mesenchymal stem cells leads to improved outcomes when compared with an equivalent acellular bioprosthesis, with no local or systemic adverse effects. Clinical trials of engineered diaphragmatic repair appear practicable within regulatory guidelines.

Serial amnioinfusions prevent fetal pulmonary hypoplasia in a large animal model of oligohydramnios

BACKGROUND/PURPOSE

Severe neonatal pulmonary hypoplasia incurs mortality rates approaching 71% to 95%. We sought to determine the utility of serial amnioinfusions through a subcutaneously implanted intraamniotic catheter to prevent pulmonary hypoplasia in fetal obstructive uropathy.

METHODS

Fetal lambs (n = 32) were divided into 3 groups. Group I (n = 12) underwent a sham operation, group II (n = 15) underwent a complete urinary tract obstruction via ligation of the urachus and urethra with a subcutaneous tunneled intraamniotic port-a-cath without amnioinfusions, and group III (n = 5) underwent a creation of a complete urinary tract obstruction with a port-a-cath as described in group II with serial amnioinfusions. Lung tissue was analyzed by lung volume to body weight ratios and stereology. Statistical analysis was performed by analysis of variance and Bonferroni comparisons (P < .05).

RESULTS

Obstructed fetuses grossly had smaller lungs than treated and control animals. Lung volume to body weight ratios were statistically significant between groups. Airspace fractions were comparable between groups I and III (average = 0.53 and 0.55, respectively), although both were significantly greater than group II (average = 0.48) (P = .049).

CONCLUSIONS

Serial amnioinfusions through an intraamniotic port-a-cath prevented pulmonary hypoplasia in an ovine model of complete obstructive uropathy. The use of an easily accessible device for amnioinfusions may be a viable option to treat oligohydramnios.

Amniotic mesenchymal stem cells enhance normal fetal wound healing

Fetal wound healing involves minimal inflammation and limited scarring. Its mechanisms, which remain to be fully elucidated, hold valuable clues for wound healing modulation and the development of regenerative strategies. We sought to determine whether fetal wound healing includes a hitherto unrecognized cellular component. Two sets of fetal lambs underwent consecutive experiments at midgestation. First, fetuses received an intra-amniotic infusion of labeled autologous amniotic mesenchymal stem cells (aMSCs), in parallel to different surgical manipulations. Subsequently, fetuses underwent creation of 2 symmetrical, size-matched skin wounds, both encased by a titanium chamber. One of the chambers was left open and the other covered with a semipermeable membrane that allowed for passage of water and all molecules, but not any cells. Survivors from both experiments had their wounds analyzed at different time points before term. Labeled aMSCs were documented in all concurrent surgical wounds. Covered wounds showed a significantly slower healing rate than open wounds. Paired comparisons indicated significantly lower elastin levels in covered wounds at the mid time points, with no significant differences in collagen levels. No significant changes in hyaluronic acid levels were detected between the wound types. Immunohistochemistry for substance P was positive in both open and covered wounds. We conclude that fetal wound healing encompasses an autologous yet exogenous cellular component in naturally occurring aMSCs. Although seemingly not absolutely essential to the healing process, amniotic cells expedite wound closure and enhance its extracellular matrix profile. Further scrutiny into translational implications of this finding is warranted.

Chest wall repair with engineered fetal bone grafts: an efficacy analysis in an autologous leporine model

PURPOSE

We sought to compare the efficacy of engineered fetal bone grafts with acellular constructs in an autologous model of chest wall repair.

METHODS

Rabbits (n = 10) with a full-thickness sternal defect were equally divided in 2 groups based on how the defect was repaired, namely, either with an autologous bone construct engineered with amniotic mesenchymal stem cells on a nanofibrous scaffold or a size-matched identical scaffold with no cells. Animals were killed at comparable time-points 18 to 20 weeks postimplantation for multiple analyses.

RESULTS

Gross evidence of nonunion confirmed by micro-computed tomography scanning was present in 3 (60%) of 5 of the acellular implants but in no engineered grafts. Histology confirmed the presence of bone in both types of repair, albeit seemingly less robust in the acellular grafts. Mineral density in vivo was significantly higher in engineered grafts than in acellular ones, with more variability among the latter. There was no difference in alkaline phosphatase activity between the groups.

CONCLUSIONS

Chest wall repair with an autologous osseous graft engineered with amniotic mesenchymal stem cells leads to improved and more consistent outcomes in the midterm when compared with an equivalent acellular prosthetic repair in a leporine model. Amniotic fluid-derived engineered bone may become a practical alternative for perinatal chest wall reconstruction.

A large animal model of the fetal tracheal stenosis/atresia spectrum

BACKGROUND

Treatment of congenital tracheal stenosis/atresia remains essentially unresolved. Previous models of this disease entity have been restricted to rodents and the chick. We sought to establish the principles of a large, surgical animal model of this spectrum of fetal anomalies.

METHODS

Fetal lambs (n = 8) underwent open surgery at 90-112 days gestation. Their cervical tracheas were encircled by a biocompatible polytetrafluoroethylene wrap, so as to extrinsically restrict their external diameter by 25%. Survivors (n = 7) were killed at different time points post-operatively before term. The manipulated tracheal segments were compared with their respective proximal portions (controls). Analyses included morphometry, histology and quantitative extracellular matrix measurements.

RESULTS

At necropsy, the typical gross appearance of tracheal stenosis/atresia was present in all manipulated tracheal segments. Histological findings included the virtual disappearance of the membranous portion of the trachea, along with infolding, fragmentation, and/or posterior fusion of cartilaginous rings, often with disappearance of the airway mucosa. There were significant decreases in diameter (P < 0.001) and total collagen levels (P = 0.005) on the manipulated trachea compared with the control portions. No significant differences were observed in overall elastin or glycosaminoglycan contents. A significant time-dependent increase in elastin was noted on the control, but not the experimental side.

CONCLUSIONS

In a surgical ovine model, controlled extrinsic compression of the fetal trachea leads to morphological and biochemical findings compatible with the congenital tracheal stenosis/atresia spectrum. This simple and easily reproducible prenatal model can be instrumental in the development of emerging therapies for these congenital anomalies.

Prenatal urinary matrix metalloproteinase profiling as a potential diagnostic tool in fetal obstructive uropathy

BACKGROUND/PURPOSE

The diagnostic evaluation, patient stratification, and prenatal counseling for congenital obstructive uropathy remain sub-optimal. Matrix metalloproteinase (MMP) expression profiles are emerging as a valuable diagnostic tool in assorted disease processes. We sought to determine whether congenital obstructive uropathy impacts MMP expression in fetal urine.

METHODS

Fetal lambs (n = 25) were divided in two groups: group I (n = 12) underwent a sham operation and group II (n = 13) underwent creation of a complete urinary tract obstruction. Gelatin zymography panels for 4 MMP species were performed on fetal urine in both groups at comparable times post-operatively. Statistical analysis was by the Fisher's exact test (P < .05).

RESULTS

Overall fetal survival was 80% (20/25). A variety of significant differences in MMP expression between the two groups were identified. The following profiles were present only in obstructed animals: any MMP other than MMP-2 (P = .029), including any MMP other than 63 kDa and 65 kDa (P = .009); 2 or more MMPs excluding MMP-2s (0.029); and 3 or more MMPs (P = .029).

CONCLUSIONS

Limited matrix metalloproteinase expression is present in the urine of normal ovine fetuses. Fetal obstructive uropathy impacts urinary MMP expression in various distinguishable patterns. Prenatal urinary MMP profiling may become a practical and valuable diagnostic tool in the evaluation of congenital obstructive uropathy.

Optical properties of human amniotic fluid: implications for videofetoscopic surgery

OBJECTIVE

Videofetoscopy typically demands the substitution of oft-turbid amniotic fluid with clear crystalloid. This maneuver can be cumbersome and may lead to complications. We sought to determine the optical properties of the amniotic fluid, as a pre-requisite for optimizing video image processing during videofetoscopy and eventually avoid amniotic fluid replacement.

METHODS

Human amniotic fluid samples (n = 21) were procured at 19-36 weeks of gestation. Optical refraction and reflection indices were recorded as percentages of light transmission through the fluid using an integrated spectrometer covering wavelengths of 400-950 nm, with 1.0 nm resolution. Statistical analysis was by one-way ANOVA (p < 0.05).

RESULTS

Peak optical refraction fell within a relatively limited window of the near-infrared spectrum, at 848.1 +/- 52.3 nm, regardless of gestational age or overall light absorbance. Within the visible spectrum, transmission was highest at the highest wavelengths. A statistically significant inverse relationship existed between gestational age and overall light transmission. Light reflection was negligible in all samples.

CONCLUSIONS

Light transmission through amniotic fluid is optimal in the near-infrared spectrum and at the highest visible wavelengths, regardless of gestational age. Overall light transmission through amniotic fluid decreases throughout gestation. The light source and camera of videofetoscopy systems should be designed accordingly, possibly obviating the need for routine intraoperative amniotic fluid exchange.