Manufacture and preparation of human placenta-derived mesenchymal stromal cells for local tissue delivery

Proliferative Effects of Mesenchymal Stromal Cells on Neuroblastoma Cell Lines: Are They Tumor Promoting or Tumor Inhibiting?

BACKGROUND

Neuroblastoma is a common pediatric malignancy with poor survival for high-risk disease. Mesenchymal stromal cells (MSCs) have innate tumor-homing properties, enabling them to serve as a cellular delivery vehicle, but MSCs have demonstrated variable effects on tumor growth. We compared how placental MSCs (PMSCs) and bone marrow-derived MSCs (BM-MSCs) affect proliferation of neuroblastoma (NB) cells in vitro.

METHODS

Indirect co-culture assessed proliferative effects of 18 MSCs (early-gestation PMSCs (n = 9), term PMSCs (n = 5), BM-MSCs (n = 4) on three high-risk NB cell lines (NB1643, SH-SY5Y, and CHLA90). Controls were NB cells cultured in media alone. Proliferation was assessed using MTS assay and measured by fold change (fc) over controls. PMSCs were sub-grouped by neuroprotective effect: strong (n = 7), intermediate (n = 3), and weak (n = 4). The relationship between MSC type, PMSC neuroprotection, and PMSC gestational age on NB cell proliferation was assessed.

RESULTS

NB cell proliferation varied between MSC groups. BM-MSCs demonstrated lower proliferative effects than PMSCs (fc 1.18 vs 1.44, p < 0.001). Neither gestational age nor neuroprotection significantly predicted degree of proliferation. Proliferative effects of MSCs varied among NB cell lines. BM-MSCs had less effect on CHLA90 (fc 1.01) compared to NB1643 (fc 1.33) and SH-SY5Y (fc 1.20). Only NB1643 showed a difference between early and term PMSCs (p = 0.04).

CONCLUSION

Effects of MSCs on NB cell proliferation vary by MSC source and NB cell line. BM-MSCs demonstrated lower proliferative effects than most PMSCs. MSC neuroprotection was not correlated with proliferation. Improved understanding of MSC proliferation-promoting mechanisms may provide valuable insight into selection of cells best suited as drug delivery vehicles.

LEVEL OF EVIDENCE

N/A.

TYPE OF STUDY

Original Research.

Development and Characterization of Bioinspired Lipid Raft Nanovesicles for Therapeutic Applications

Lipid rafts are highly ordered regions of the plasma membrane enriched in signaling proteins and lipids. Their biological potential is realized in exosomes, a subclass of extracellular vesicles (EVs) that originate from the lipid raft domains. Previous studies have shown that EVs derived from human placental mesenchymal stromal cells (PMSCs) possess strong neuroprotective and angiogenic properties. However, clinical translation of EVs is challenged by very low, impure, and heterogeneous yields. Therefore, in this study, lipid rafts are validated as a functional biomaterial that can recapitulate the exosomal membrane and then be synthesized into biomimetic nanovesicles. Lipidomic and proteomic analyses show that lipid raft isolates retain functional lipids and proteins comparable to PMSC-EV membranes. PMSC-derived lipid raft nanovesicles (LRNVs) are then synthesized at high yields using a facile, extrusion-based methodology. Evaluation of biological properties reveals that LRNVs can promote neurogenesis and angiogenesis through modulation of lipid raft-dependent signaling pathways. A proof-of-concept methodology further shows that LRNVs could be loaded with proteins or other bioactive cargo for greater disease-specific functionalities, thus presenting a novel type of biomimetic nanovesicles that can be leveraged as targeted therapeutics for regenerative medicine.

TLR4 Modulates Senescence and Paracrine Action in Placental Mesenchymal Stem Cells via Inhibiting Hedgehog Signaling Pathway in Preeclampsia

Preeclampsia (PE) is a heterogeneous disease closely associated with the accelerated senescence of the placentas. Placental mesenchymal stem cells (PMSCs) modulate placental development, which is abnormally senescent in PE together with abnormal paracrine. Both pivotal in the placenta development, Toll-like receptor 4 (TLR4) and Hedgehog (HH) pathway are also tightly involved in regulating cellular senescence. This study was aimed at demonstrating that TLR4/HH pathway modulated senescence of placentas and PMSCs in vitro and in vivo. Preeclamptic and normal PMSCs were isolated. Smoothed agonist (SAG) and cyclopamine were used to activate and inhibit HH pathway, respectively. Lipopolysaccharide (LPS) was used to activate TLR4 in vitro and establish the classic PE-like rat model. qRT-PCR, Western blotting, and immunofluorescence were used to detect the expression of TLR4 and HH components (SHH, SMO, and Gli1). Cellular biological function such as proliferation, apoptosis, and migration was compared. Cell cycle analysis, β-galactosidase staining, and the protein expressions of p16 and p53 were detected to analyze the cellular senescence. The secretion levels of human matrix metalloproteinase 9 (MMP-9) and soluble fms-like tyrosine kinase-1 (sFlt-1) were measured in the conditioned medium. Cell migration, invasion, and tube formation were analyzed in HTR8/SVneo cells or human umbilical vein endothelial cells (HUVECs). Our study demonstrated that activation of TLR4 accelerated senescence of PMSCs via suppressing HH pathway both in vitro and in vivo, accompanied by the detrimental paracrine to impair the uterine spiral artery remodeling and placental angiogenesis. Meanwhile, induction of HH pathway could alleviate PE-like manifestations, improve pregnancy outcomes, and ameliorate multiorgan injuries, suggesting that strengthening the HH pathway may serve as a potential therapy in PE.

Significance of Placental Mesenchymal Stem Cell in Placenta Development and Implications for Preeclampsia

The well-developed placentation is fundamental for the reproductive pregnancy while the defective placental development is the pathogenetic basis of preeclampsia (PE), a dangerous complication of pregnancy comprising the leading causes of maternal and perinatal morbidity and mortality. Placenta-derived mesenchymal stem cells (PMSCs) are a group of multipotent stem cells that own a potent capacity of differentiating into constitutive cells of vessel walls. Additionally, with the paracrine secretion of various factors, PMSCs inextricably link and interact with other component cells in the placenta, collectively improving the placental vasculature, uterine spiral artery remolding, and uteroplacental interface immunoregulation. Recent studies have further indicated that preeclamptic PMSCs, closely implicated in the abnormal crosstalk between other ambient cells, disturb the homeostasis and development in the placenta. Nevertheless, PMSCs transplantation or PMSCs exosome therapies tend to improve the placental vascular network and trophoblastic functions in the PE model, suggesting PMSCs may be a novel and putative therapeutic strategy for PE. Herein, we provide an overview of the multifaceted contributions of PMSCs in early placental development. Thereinto, the intensive interactions between PMSCs and other component cells in the placenta were particularly highlighted and further extended to the implications in the pathogenesis and therapeutic strategies of PE.

Impact of Gestational Age on Neuroprotective Function of Placenta-Derived Mesenchymal Stromal Cells

INTRODUCTION

The Management of Myelomeningocele Study demonstrated that in utero repair of myelomeningocele improved motor outcomes compared with postnatal repair. However, even after in utero repair, many children were still unable to walk. We have previously demonstrated that augmentation of in utero repair with early-gestation placental mesenchymal stromal cells (PMSCs) improves motor outcomes in lambs compared with standard in utero repair. The neuroprotective potential of PMSCs of all gestational ages has not been evaluated previously.

METHODS

PMSCs were isolated from discarded first trimester (n = 3), second trimester (n = 3), and term (n = 3) placentas by explant culture. Cytokine array analysis was performed. Secretion of two neurotrophic factors, brain-derived neurotrophic factor and hepatocyte growth factor, was evaluated by enzyme-linked immunosorbent assay. An in vitro neuroprotective assay demonstrated to be associated with in vivo function was performed.

RESULTS

All cell lines secreted immunomodulatory and neuroprotective cytokines and secreted the neurotrophic factors evaluated. Increased neuroprotective capabilities relative to no PMSCs were demonstrated in two of the three first trimester cell lines (5.61, 4.96-6.85, P < 0.0001 and 2.67, 1.67-4.12, P = 0.0046), two of the three second trimester cell lines (2.82, 2.45-3.43, P = 0.0004 and 3.25, 2.62-3.93, P < 0.0001), and two of the three term cell lines (2.72, 2.32-2.92, P = 0.0033 and 2.57, 1.41-4.42, P = 0.0055).

CONCLUSIONS

We demonstrated variation in neuroprotective function between cell lines and found that some cell lines from each trimester had neuroprotective properties. This potentially expands the donor pool of PMSCs for clinical use. Further in-depth studies are needed to understand potential subtle differences in cell function at different gestational ages.

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

INTRODUCTION

Fetal myelomeningocele (MMC) repair improves lower extremity motor function. We have previously demonstrated that augmentation of fetal MMC repair with placental mesenchymal stromal cells (PMSCs) seeded on extracellular matrix (PMSC-ECM) further improves motor function in the ovine model. However, little progress has been made in improving bowel and bladder function, with many patients suffering from neurogenic bowel and bladder. We hypothesized that fetal MMC repair with PMSC-ECM would also improve bowel and bladder function.

METHODS

MMC defects were surgically created in twelve ovine fetuses at median gestational age (GA) 73 days, followed by defect repair at GA101 with PMSC-ECM. Fetuses were delivered at GA141. Primary bladder function outcomes were voiding posture and void volumes. Primary bowel function outcome was anorectal manometry findings including resting anal pressure and presence of rectoanal inhibitory reflex (RAIR). Secondary outcomes were anorectal and bladder detrusor muscle thickness. PMSC-ECM lambs were compared to normal lambs (n = 3).

RESULTS

Eighty percent of PMSC-ECM lambs displayed normal voiding posture compared to 100% of normal lambs (p = 1). Void volumes were similar (PMSC-ECM 6.1 ml/kg vs. normal 8.8 ml/kg, p = 0.4). Resting mean anal pressures were similar between cohorts (27.0 mmHg PMSC-ECM vs. normal 23.5 mmHg, p = 0.57). RAIR was present in 3/5 PMSC-ECM lambs that underwent anorectal manometry and all normal lambs (p = 0.46). Thicknesses of anal sphincter complex, rectal wall muscles, and bladder detrusor muscles were similar between cohorts.

CONCLUSION

Ovine fetal MMC repair augmented with PMSC-ECM results in near-normal bowel and bladder function. Further work is needed to evaluate these outcomes in human patients.

In Vitro Model of Human Trophoblast in Early Placentation

The complex process of placental implantation and development affects trophoblast progenitors and uterine cells through the regulation of transcription factors, cytokines, adhesion receptors and their ligands. Differentiation of trophoblast precursors in the trophectoderm of early ontogenesis, caused by the transcription factors, such as CDX2, TEAD4, Eomes and GATA3, leads to the formation of cytotrophoblast and syncytiotrophoblast populations. The molecular mechanisms involved in placental formation inside the human body along with the specification and differentiation of trophoblast cell lines are, mostly due to the lack of suitable cell models, not sufficiently elucidated. This review is an evaluation of current technologies, which are used to study the behavior of human trophoblasts and other placental cells, as well as their ability to represent physiological conditions both in vivo and in vitro. An in vitro 3D model with a characteristic phenotype is of great benefit for the study of placental physiology. At the same time, it provides great support for future modeling of placental disease.

Bioactive extracellular matrix scaffolds engineered with proangiogenic proteoglycan mimetics and loaded with endothelial progenitor cells promote neovascularization and diabetic wound healing

Diabetic ischemic wound treatment remains a critical clinical challenge. Neovascularization plays a significant role in wound healing during all stages of the tissue repair process. Strategies that enhance angiogenesis and neovascularization and improve ischemic pathology may promote the healing of poor wounds, particularly diabetic wounds in highly ischemic conditions. We previously identified a cyclic peptide LXW7 that specifically binds to integrin αvβ3 on endothelial progenitor cells (EPCs) and endothelial cells (ECs), activates vascular endothelial growth factor (VEGF) receptors, and promotes EC growth and maturation. In this study, we designed and synthesized a multi-functional pro-angiogenic molecule by grafting LXW7 and collagen-binding peptides (SILY) to a dermatan sulfate (DS) glycosaminoglycan backbone, named LXW7-DS-SILY, and further employed this multi-functional molecule to functionalize collagen-based extracellular matrix (ECM) scaffolds. We confirmed that LXW7-DS-SILY modification significantly promoted EPC attachment and growth on the ECM scaffolds in vitro and supported EPC survival in vivo in the ischemic environment. When applied in an established Zucker Diabetic Fatty (ZDF) rat ischemic skin flap model, LXW7-DS-SILY-functionalized ECM scaffolds loaded with EPCs significantly improved wound healing, enhanced neovascularization and modulated collagen fibrillogenesis in the ischemic environment. Altogether, this study provides a promising novel treatment to accelerate diabetic ischemic wound healing, thereby reducing limb amputation and mortality of diabetic patients.

Long-term safety evaluation of placental mesenchymal stromal cells for in utero repair of myelomeningocele in a novel ovine model

PURPOSE

Augmentation of in utero myelomeningocele repair with human placental mesenchymal stromal cells seeded onto extracellular matrix (PMSC-ECM) improves motor outcomes in an ovine myelomeningocele model. This study evaluated the safety of PMSC-ECM application directly onto the fetal spinal cord in preparation for a clinical trial.

METHODS

Laminectomy of L5-L6 with PMSC-ECM placement directly onto the spinal cord was performed in five fetal lambs at gestational age (GA) 100-106 days. Lambs and ewes were monitored for three months following delivery. Lambs underwent magnetic resonance imaging (MRI) of the brain and spine at birth and at three months. All organs from lambs and uteri from ewes underwent histologic evaluation. Lamb spinal cords and brains and ewe placentas were evaluated for persistence of PMSCs by polymerase chain reaction for presence of human DNA.

RESULTS

MRIs demonstrated no evidence of abnormal tissue growth or spinal cord tethering. Histological analysis demonstrated no evidence of abnormal tissue growth or treatment related adverse effects. No human DNA was identified in evaluated tissues.

CONCLUSION

There was no evidence of abnormal tissue growth or PMSC persistence at three months following in utero application of PMSC-ECM to the spinal cord. This supports proceeding with clinical trials of PMSC-ECM for in utero myelomeningocele repair.

LEVEL OF EVIDENCE

N/A TYPE OF STUDY: Basic science.

Placental Mesenchymal Stromal Cells: Preclinical Safety Evaluation for Fetal Myelomeningocele Repair

BACKGROUND

Myelomeningocele (MMC) is the congenital failure of neural tube closure in utero, for which the standard of care is prenatal surgical repair. We developed clinical-grade placental mesenchymal stromal cells seeded on a dural extracellular matrix (PMSC-ECM), which have been shown to improve motor outcomes in preclinical ovine models. To evaluate the long-term safety of this product prior to use in a clinical trial, we conducted safety testing in a murine model.

METHODS

Clinical grade PMSCs obtained from donor human placentas were seeded onto a 6 mm diameter ECM at a density of 3 × 105 cells/cm2. Immunodeficient mice were randomized to receive either an ECM only or PMSC-ECM administered into a subcutaneous pocket. Mice were monitored for tumor formation until two study endpoints: 4 wk and 6 mo. Pathology and histology on all tissues was performed to evaluate for tumors. Quantitative polymerase chain reaction (qPCR) was performed to evaluate for the presence of human DNA, which would indicate persistence of PMSCs.

RESULTS

Fifty-four mice were included; 13 received ECM only and 14 received PMSC-ECM in both the 4-wk and 6-mo groups. No mice had gross or microscopic evidence of tumor development. A nodular focus of mature fibrous connective tissue was identified at the subcutaneous implantation pocket in the majority of mice with no significant difference between ECM only and PMSC-ECM groups (P = 0.32 at 4 wk, P > 0.99 at 6 mo). Additionally, no human DNA was detected by qPCR in any mice at either time point.

CONCLUSIONS

Subcutaneous implantation of the PMSC-ECM product did not result in tumor formation and we found no evidence that PMSCs persisted. These results support the safety of the PMSC-ECM product for use in a Phase 1/2a human clinical trial evaluating fetal MMC repair augmented with PMSC-ECM.

The Unique Properties of Placental Mesenchymal Stromal Cells: A Novel Source of Therapy for Congenital and Acquired Spinal Cord Injury

Spinal cord injury (SCI) is a devasting condition with no reliable treatment. Spina bifida is the most common cause of congenital SCI. Cell-based therapies using mesenchymal stem/stromal cells (MSCS) have been largely utilized in SCI. Several clinical trials for acquired SCI use adult tissue-derived MSC sources, including bone-marrow, adipose, and umbilical cord tissues. The first stem/stromal cell clinical trial for spina bifida is currently underway (NCT04652908). The trial uses early gestational placental-derived mesenchymal stem/stromal cells (PMSCs) during the fetal repair of myelomeningocele. PMSCs have been shown to exhibit unique neuroprotective, angiogenic, and antioxidant properties, all which are promising applications for SCI. This review will summarize the unique properties and current applications of PMSCs and discuss their therapeutic role for acquired SCI.

Fetal myelomeningocele repair: a narrative review of the history, current controversies and future directions

Fetal surgery is a relatively new field of medicine. The purpose of this narrative review is to present the history of how fetal surgery became the standard of care for myelomeningocele (MMC), the current controversies of this treatment, and active areas of research that may change how MMC is treated. Fetal surgery for MMC emerged out of the University of California, San Francisco in the 1980s in the laboratory of Dr. Michael Harrison. Initial research focused on testing the hypothesis that the in utero repair of MMC could improve outcomes in the ovine model. Evidence from this model suggested that in utero repair decreases the secondary damage to the exposed neural tissue and improves post-natal neurologic outcomes, opening the door for human intervention. This was followed by the Management of Myelomeningocele Study (MOMS), which was a multicenter randomized controlled trial comparing the prenatal versus postnatal MMC repair. The MOMS trial was stopped early due to the improved outcomes of the prenatal repair, establishing the open fetal MMC repair as the standard of care. Since the MOMS trial, two primary areas of controversy have arisen: the operative approach and criteria for the repair. The three operative approaches include open, endoscopic and a hybrid approach combining open and endoscopic. Several of the inclusion and exclusion criteria from the MOMS trial have been challenged, to include body mass index, gestational diabetes, other fetal abnormalities, maternal infections and Rh alloimmunization. New areas of research have also emerged, exploring cell based therapies to improve fetal outcomes, alternatives to fetal surgery and alternatives to primary skin closure of the fetus.

Neural crest-like stem cells for tissue regeneration

Neural crest stem cells (NCSCs) are a transient population of cells that arise during early vertebrate development and harbor stem cell properties, such as self‐renewal and multipotency. These cells form at the interface of non‐neuronal ectoderm and neural tube and undergo extensive migration whereupon they contribute to a diverse array of cell and tissue derivatives, ranging from craniofacial tissues to cells of the peripheral nervous system. Neural crest‐like stem cells (NCLSCs) can be derived from pluripotent stem cells, placental tissues, adult tissues, and somatic cell reprogramming. NCLSCs have a differentiation capability similar to NCSCs, and possess great potential for regenerative medicine applications. In this review, we present recent developments on the various approaches to derive NCLSCs and the therapeutic application of these cells for tissue regeneration.

Perinatal Derivatives: Where Do We Stand? A Roadmap of the Human Placenta and Consensus for Tissue and Cell Nomenclature

Progress in the understanding of the biology of perinatal tissues has contributed to the breakthrough revelation of the therapeutic effects of perinatal derivatives (PnD), namely birth-associated tissues, cells, and secreted factors. The significant knowledge acquired in the past two decades, along with the increasing interest in perinatal derivatives, fuels an urgent need for the precise identification of PnD and the establishment of updated consensus criteria policies for their characterization. The aim of this review is not to go into detail on preclinical or clinical trials, but rather we address specific issues that are relevant for the definition/characterization of perinatal cells, starting from an understanding of the development of the human placenta, its structure, and the different cell populations that can be isolated from the different perinatal tissues. We describe where the cells are located within the placenta and their cell morphology and phenotype. We also propose nomenclature for the cell populations and derivatives discussed herein. This review is a joint effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the processing and in vitro characterization and clinical application of PnD.

Surviving Lambs with Myelomeningocele Repaired in utero with Placental Mesenchymal Stromal Cells for 6 Months: A Pilot Study

BACKGROUND

Fetal repair of myelomeningocele (MMC) with placental mesenchymal stromal cells (PMSCs) rescues ambulation in the ovine model up to 48 h postnatally. Outcomes past 48 h are unknown as MMC lambs have not been survived past this timepoint.

OBJECTIVE

We aimed to survive lambs for 6 months following the fetal repair of MMC with PMSCs.

METHODS

Fetal MMC lambs were repaired with PMSCs. Lambs received either no additional treatment or postnatal bracing and physical therapy (B/PT). Motor function was assessed with the sheep locomotor rating (SLR). Lambs with an SLR of 15 at birth were survived for 6 months or until a decline in SLR less than 15, whichever came first. All lambs underwent a perimortem MRI.

RESULTS

The lambs with no postnatal treatment (n = 2) had SLR declines to 7 and 13 at 29 and 65 days, respectively, and were euthanized. These lambs had a spinal angulation of 57° and 47°, respectively. The B/PT lamb (n = 1) survived for 6 months with a sustained SLR of 15 and a lumbar angulation of 42°.

CONCLUSION

Postnatal physical therapy and bracing counteracted the inherent morbidity of the absent paraspinal muscles in the ovine MMC model allowing for survival and maintenance of rescued motor function of the prenatally treated lamb up to 6 months.

In utero treatment of myelomeningocele with placental mesenchymal stromal cells - Selection of an optimal cell line in preparation for clinical trials

BACKGROUND

We determined whether in vitro potency assays inform which placental mesenchymal stromal cell (PMSC) lines produce high rates of ambulation following in utero treatment of myelomeningocele in an ovine model.

METHODS

PMSC lines were created following explant culture of three early-gestation human placentas. In vitro neuroprotection was assessed with a neuronal apoptosis model. In vivo, myelomeningocele defects were created in 28 fetuses and repaired with PMSCs at 3 × 10⁵ cells/cm² of scaffold from Line A (n = 6), Line B (n = 7) and Line C (n = 5) and compared to no PMSCs (n = 10). Ambulation was scored as ≥13 on the Sheep Locomotor Rating Scale.

RESULTS

In vitro, Line A and B had higher neuroprotective capability than no PMSCs (1.7 and 1.8 respectively vs 1, p = 0.02, ANOVA). In vivo, Line A and B had higher large neuron densities than no PMSCs (25.2 and 27.9 respectively vs 4.8, p = 0.03, ANOVA). Line C did not have higher neuroprotection or larger neuron density than no PMSCs. In vivo, Line A and B had ambulation rates of 83% and 71%, respectively, compared to 60% with Line C and 20% with no PMSCs.

CONCLUSION

The in vitro neuroprotection assay will facilitate selection of optimal PMSC lines for clinical use.

LEVEL OF EVIDENCE

n/a.

TYPE OF STUDY

Basic science.

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

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

Extracellular Matrix Mimicking Nanofibrous Scaffolds Modified With Mesenchymal Stem Cell-Derived Extracellular Vesicles for Improved Vascularization

The network structure and biological components of natural extracellular matrix (ECM) are indispensable for promoting tissue regeneration. Electrospun nanofibrous scaffolds have been widely used in regenerative medicine to provide structural support for cell growth and tissue regeneration due to their natural ECM mimicking architecture, however, they lack biological functions. Extracellular vesicles (EVs) are potent vehicles of intercellular communication due to their ability to transfer RNAs, proteins, and lipids, thereby mediating significant biological functions in different biological systems. Matrix-bound nanovesicles (MBVs) are identified as an integral and functional component of ECM bioscaffolds mediating significant regenerative functions. Therefore, to engineer EVs modified electrospun scaffolds, mimicking the structure of the natural EV-ECM complex and the physiological interactions between the ECM and EVs, will be attractive and promising in tissue regeneration. Previously, using one-bead one-compound (OBOC) combinatorial technology, we identified LLP2A, an integrin α4β1 ligand, which had a strong binding to human placenta-derived mesenchymal stem cells (PMSCs). In this study, we isolated PMSCs derived EVs (PMSC-EVs) and demonstrated they expressed integrin α4β1 and could improve endothelial cell (EC) migration and vascular sprouting in an ex vivo rat aortic ring assay. LLP2A treated culture surface significantly improved PMSC-EV attachment, and the PMSC-EV treated culture surface significantly enhanced the expression of angiogenic genes and suppressed apoptotic activity. We then developed an approach to enable "Click chemistry" to immobilize LLP2A onto the surface of electrospun scaffolds as a linker to immobilize PMSC-EVs onto the scaffold. The PMSC-EV modified electrospun scaffolds significantly promoted EC survival and angiogenic gene expression, such as KDR and TIE2, and suppressed the expression of apoptotic markers, such as caspase 9 and caspase 3. Thus, PMSC-EVs hold promising potential to functionalize biomaterial constructs and improve the vascularization and regenerative potential. The EVs modified biomaterial scaffolds can be widely used for different tissue engineering applications.

Clonal isolation of endothelial colony-forming cells from early gestation chorionic villi of human placenta for fetal tissue regeneration

BACKGROUND

Endothelial colony-forming cells (ECFCs) have been implicated in the process of vascularization, which includes vasculogenesis and angiogenesis. Vasculogenesis is a de novo formation of blood vessels, and is an essential physiological process that occurs during embryonic development and tissue regeneration. Angiogenesis is the growth of new capillaries from pre-existing blood vessels, which is observed both prenatally and postnatally. The placenta is an organ composed of a variety of fetal-derived cells, including ECFCs, and therefore has significant potential as a source of fetal ECFCs for tissue engineering.

AIM

To investigate the possibility of isolating clonal ECFCs from human early gestation chorionic villi (CV-ECFCs) of the placenta, and assess their potential for tissue engineering.

METHODS

The early gestation chorionic villus tissue was dissociated by enzyme digestion. Cells expressing CD31 were selected using magnetic-activated cell sorting, and plated in endothelial-specific growth medium. After 2-3 wks in culture, colonies displaying cobblestone-like morphology were manually picked using cloning cylinders. We characterized CV-ECFCs by flow cytometry, immunophenotyping, tube formation assay, and Dil-Ac-LDL uptake assay. Viral transduction of CV-ECFCs was performed using a Luciferase/tdTomato-containing lentiviral vector, and transduction efficiency was tested by fluorescent microscopy and flow cytometry. Compatibility of CV-ECFCs with a delivery vehicle was determined using an FDA approved, small intestinal submucosa extracellular matrix scaffold.

RESULTS

After four passages in 6-8 wks of culture, we obtained a total number of 1.8 × 10⁷ CV-ECFCs using 100 mg of early gestational chorionic villus tissue. Immunophenotypic analyses by flow cytometry demonstrated that CV-ECFCs highly expressed the endothelial markers CD31, CD144, CD146, CD105, CD309, only partially expressed CD34, and did not express CD45 and CD90. CV-ECFCs were capable of acetylated low-density lipoprotein uptake and tube formation, similar to cord blood-derived ECFCs (CB-ECFCs). CV-ECFCs can be transduced with a Luciferase/tdTomato-containing lentiviral vector at a transduction efficiency of 85.1%. Seeding CV-ECFCs on a small intestinal submucosa extracellular matrix scaffold confirmed that CV-ECFCs were compatible with the biomaterial scaffold.

CONCLUSION

In summary, we established a magnetic sorting-assisted clonal isolation approach to derive CV-ECFCs. A substantial number of CV-ECFCs can be obtained within a short time frame, representing a promising novel source of ECFCs for fetal treatments.

Placental Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Myelin Regeneration in an Animal Model of Multiple Sclerosis

Mesenchymal stem/stromal cells (MSCs) display potent immunomodulatory and regenerative capabilities through the secretion of bioactive factors, such as proteins, cytokines, chemokines as well as the release of extracellular vesicles (EVs). These functional properties of MSCs make them ideal candidates for the treatment of degenerative and inflammatory diseases, including multiple sclerosis (MS). MS is a heterogenous disease that is typically characterized by inflammation, demyelination, gliosis and axonal loss. In the current study, an induced experimental autoimmune encephalomyelitis (EAE) murine model of MS was utilized. At peak disease onset, animals were treated with saline, placenta-derived MSCs (PMSCs), as well as low and high doses of PMSC-EVs. Animals treated with PMSCs and high-dose PMSC-EVs displayed improved motor function outcomes as compared to animals treated with saline. Symptom improvement by PMSCs and PMSC-EVs led to reduced DNA damage in oligodendroglia populations and increased myelination within the spinal cord of treated mice. In vitro data demonstrate that PMSC-EVs promote myelin regeneration by inducing endogenous oligodendrocyte precursor cells to differentiate into mature myelinating oligodendrocytes. These findings support that PMSCs’ mechanism of action is mediated by the secretion of EVs. Therefore, PMSC-derived EVs are a feasible alternative to cellular based therapies for MS, as demonstrated in an animal model of the disease.

Hypoxic Preconditioning Enhances Survival and Proangiogenic Capacity of Human First Trimester Chorionic Villus-Derived Mesenchymal Stem Cells for Fetal Tissue Engineering

Prenatal stem cell-based regenerative therapies have progressed substantially and have been demonstrated as effective treatment options for fetal diseases that were previously deemed untreatable. Due to immunoregulatory properties, self-renewal capacity, and multilineage potential, autologous human placental chorionic villus-derived mesenchymal stromal cells (CV-MSCs) are an attractive cell source for fetal regenerative therapies. However, as a general issue for MSC transplantation, the poor survival and engraftment is a major challenge of the application of MSCs. Particularly for the fetal transplantation of CV-MSCs in the naturally hypoxic fetal environment, improving the survival and engraftment of CV-MSCs is critically important. Hypoxic preconditioning (HP) is an effective priming approach to protect stem cells from ischemic damage. In this study, we developed an optimal HP protocol to enhance the survival and proangiogenic capacity of CV-MSCs for improving clinical outcomes in fetal applications. Total cell number, DNA quantification, nuclear area test, and cell viability test showed HP significantly protected CV-MSCs from ischemic damage. Flow cytometry analysis confirmed HP did not alter the immunophenotype of CV-MSCs. Caspase-3, MTS, and Western blot analysis showed HP significantly reduced the apoptosis of CV-MSCs under ischemic stimulus via the activation of the AKT signaling pathway that was related to cell survival. ELISA results showed HP significantly enhanced the secretion of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) by CV-MSCs under an ischemic stimulus. We also found that the environmental nutrition level was critical for the release of brain-derived neurotrophic factor (BDNF). The angiogenesis assay results showed HP-primed CV-MSCs could significantly enhance endothelial cell (EC) proliferation, migration, and tube formation. Consequently, HP is a promising strategy to increase the tolerance of CV-MSCs to ischemia and improve their therapeutic efficacy in fetal clinical applications.

Spinal Angulation: A Limitation of the Fetal Lamb Model of Myelomeningocele

INTRODUCTION

The surgically induced fetal lamb model is the most commonly used large animal model of myelomeningocele (MMC) but is subject to variation due to surgical technique during defect creation.

MATERIAL AND METHODS

Thirty-one fetal lambs underwent creation of the MMC defect, followed by defect repair with either an extracellular matrix (ECM) patch (n = 10) or ECM seeded with placental mesenchymal stromal cells (n = 21). Postnatal hindlimb function was assessed using the Sheep Locomotor Rating (SLR) scale. Postmortem magnetic resonance imaging of the lumbar spine was used to measure the level and degree of spinal angulation, as well as cross-sectional area of remaining vertebral bone.

RESULTS

Median level of angulation was between the 2nd and 3rd lumbar vertebrae, with a median angle of 24.3 degrees (interquartile range 16.2-35.3). There was a negative correlation between angulation degree and SLR (r = -0.44, p = 0.013). Degree of angulation also negatively correlated with the normalized cross-sectional area of remaining vertebral bone (r = -0.75, p < 0.0001).

DISCUSSION

Surgical creation of fetal MMC leads to varying severity of spinal angulation in the ovine model, which affects postnatal functional outcomes. Postnatal assessment of spinal angulation aids in standardization of the surgical model of fetal MMC repair.

Neuroprotective effect of placenta-derived mesenchymal stromal cells: role of exosomes

We have established early-gestation chorionic villus-derived placenta mesenchymal stromal cells (PMSCs) as a potential treatment for spina bifida (SB), a neural tube defect. Our preclinical studies demonstrated that PMSCs have the potential to cure hind limb paralysis in the fetal lamb model of SB via a paracrine mechanism. PMSCs exhibit neuroprotective function by increasing cell number and neurites, as shown by indirect coculture and direct addition of PMSC-conditioned medium to the staurosporine-induced apoptotic human neuroblastoma cell line, SH-SY5Y. PMSC-conditioned medium suppressed caspase activity in apoptotic SH-SY5Y cells, suggesting that PMSC secretome contributes to neuronal survival after injury. As a part of PMSC secretome, PMSC exosomes were isolated and extensively characterized; their addition to apoptotic SH-SY5Y cells mediated an increase in neurites, suggesting that they exhibit neuroprotective function. Proteomic and RNA sequencing analysis revealed that PMSC exosomes contain several proteins and RNAs involved in neuronal survival and development. Galectin 1 was highly expressed on the surface of PMSCs and PMSC exosomes. Preincubation of exosomes with anti-galectin 1 antibody decreased their neuroprotective effect, suggesting that PMSC exosomes likely impart their effect via binding of galectin 1 to cells. Future studies will include in-depth analyses of the role of PMSC exosomes on neuroprotection and their clinical applications.-Kumar, P., Becker, J. C., Gao, K., Carney, R. P., Lankford, L., Keller, B. A., Herout, K., Lam, K. S., Farmer, D. L., Wang, A. Neuroprotective effect of placenta-derived mesenchymal stromal cells: role of exosomes.

Fischernolides A–D, four novel diterpene-based meroterpenoid scaffolds with antitumor activities from Euphorbia fischeriana

Fischernolides A–D (1–4), representing the rare 28-carbon meroterpenoid skeleton of abietane and an acylphloroglucinol conjugate, bearing an α-furanone or α-pyrone ring, were isolated and identified from the roots of Euphorbia fischeriana.

High density placental mesenchymal stromal cells provide neuronal preservation and improve motor function following in utero treatment of ovine myelomeningocele

PURPOSE

The purpose of this study was to determine whether seeding density of placental mesenchymal stromal cells (PMSCs) on extracellular matrix (ECM) during in utero repair of myelomeningocele (MMC) affects motor function and neuronal preservation in the ovine model.

METHODS

MMC defects were surgically created in 33 fetuses and repaired following randomization into four treatment groups: ECM only (n = 10), PMSC-ECM (42 K cells/cm²) (n = 8), PMSC-ECM (167 K cells/cm²) (n = 7), or PMSC-ECM (250-300 K cells/cm²) (n = 8). Motor function was evaluated using the Sheep Locomotor Rating Scale (SLR). Serial sections of the lumbar spinal cord were analyzed by measuring their cross-sectional areas which were then normalized to normal lambs. Large neurons (LN, diameter 30-70 μm) were counted manually and density calculated per mm² gray matter.

RESULTS

Lambs treated with PMSCs at any density had a higher median SLR score (15 [IQR 13.5-15]) than ECM alone (6.5 [IQR 4-12.75], p = 0.036). Cross-sectional areas of spinal cord and gray matter were highest in the PMSC-ECM (167 K/cm²) group (p = 0.002 and 0.006, respectively). LN density was highest in the greatest density PMSC-ECM (250-300 K/cm²) group (p = 0.045) which positively correlated with SLR score (r = 0.807, p < 0.0001).

CONCLUSIONS

Fetal repair of myelomeningocele with high density PMSC-ECM resulted in increased large neuron density, which strongly correlated with improved motor function.

TYPE OF STUDY

Basic science.

LEVEL OF EVIDENCE

N/A.

Single-cell RNA-seq reveals the diversity of trophoblast subtypes and patterns of differentiation in the human placenta

The placenta is crucial for a successful pregnancy and the health of both the fetus and the pregnant woman. However, how the human trophoblast lineage is regulated, including the categorization of the placental cell subtypes is poorly understood. Here we performed single-cell RNA sequencing (RNA-seq) on sorted placental cells from first- and second-trimester human placentas. New subtypes of cells of the known cytotrophoblast cells (CTBs), extravillous trophoblast cells (EVTs), Hofbauer cells, and mesenchymal stromal cells were identified and cell-type-specific gene signatures were defined. Functionally, this study revealed many previously unknown functions of the human placenta. Notably, 102 polypeptide hormone genes were found to be expressed by various subtypes of placental cells, which suggests a complex and significant role of these hormones in regulating fetal growth and adaptations of maternal physiology to pregnancy. These results document human placental trophoblast differentiation at single-cell resolution and thus advance our understanding of human placentation during the early stage of pregnancy.

Isolation of myogenic progenitor cell population from human placenta: A pilot study

PURPOSE

The purpose of this study was to demonstrate a method of isolating myogenic progenitor cells from human placenta chorionic villi and to confirm the myogenic characteristics of the isolated cells.

METHODS

Cells were isolated from chorionic villi of a second trimester male placenta via a combined enzymatic digestion and explant culture. A morphologically distinct subpopulation of elongated and multinucleated cells was identified. This subpopulation was manually passaged from the explant culture, expanded, and analyzed by fluorescence in situ hybridization (FISH) assay, immunocytochemistry, and flow cytometry. Myogenic characteristics including alignment and fusion were tested by growing these cells on aligned polylactic acid microfibrous scaffold in a fusion media composed of 2% horse serum in Dulbecco's modified Eagle medium/high glucose.

RESULTS

The expanded subpopulation was uniformly positive for integrin α-7. Presence of Y-chromosome by FISH analysis confirmed chorionic villus origin rather than maternal cell contamination. Isolated cells grew, aligned, and fused on the microfibrous scaffold, and they expressed myogenin, desmin, and MHC confirming their myogenic identity.

CONCLUSION

Myogenic progenitor cells can be isolated from human chorionic villi. This opens the possibility for translational and clinical applications using autologous myogenic cells for possible engraftment in treatment of chest and abdominal wall defects.

Fetal surgical repair with placenta-derived mesenchymal stromal cell engineered patch in a rodent model of myelomeningocele

PURPOSE

The purpose of this study is to determine the feasibility of fetal surgical repair of myelomeningocele (MMC) in a rodent model using human placental mesenchymal stromal cells (PMSCs) seeded onto extracellular matrix (ECM) and to characterize the resulting changes in spinal cord tissue.

METHODS

Fetal rodents with retinoic acid (RA) induced MMC underwent surgical repair of the MMC defect using an ECM patch on embryonic age (EA) 19 and were collected via caesarean section on EA 21. Various seeding densities of PMSC-ECM and ECM only controls were evaluated. Cross-sectional compression (width/height) and apoptotic cell density of the lumbosacral spinal cord were analyzed.

RESULTS

67 dams treated with 40mg/kg of RA resulted in 352 pups with MMC defects. 121 pups underwent MMC repair, and 105 (86.8%) survived to term. Unrepaired MMC pups had significantly greater cord compression and apoptotic cell density compared to normal non-MMC pups. Pups treated with PMSC-ECM had significantly less cord compression and demonstrated a trend towards decreased apoptotic cell density compared to pups treated with ECM only.

CONCLUSION

Surgical repair of MMC with a PMSC-seeded ECM disc is feasible with a postoperative survival rate of 86.8%. Fetal rodents repaired with PMSC-ECM have significantly less cord deformity and decreased histological evidence of apoptosis compared to ECM only controls.

Placental mesenchymal stromal cells seeded on clinical grade extracellular matrix improve ambulation in ovine myelomeningocele

PURPOSE

The purpose of this study was to investigate the effects of placental mesenchymal stromal cells (PMSCs) seeded on a clinical grade porcine small intestinal submucosa (SIS)-derived extracellular matrix (ECM) on hindlimb motor function in an ovine fetal repair model of myelomeningocele (MMC).

METHODS

MMC defects were surgically created in 21 fetuses at median gestational age 78 (range 76-83) days. Fetuses were randomly assigned to repair 25days later with ECM only or PMSC-ECM. Surviving fetuses were delivered at term. Motor function was evaluated using the Sheep Locomotor Rating (SLR) scale (0-15). Histologic analysis of the spinal cord (SC) was completed.

RESULTS

Fetal viability was 71%. 5 of 8 (63%) lambs repaired with PMSC-ECM ambulated independently versus only 1 of 6 (17%) repaired with ECM only (p=0.04, χ2 test). SLR scores and large neuron densities were higher in the PMSC-ECM group. The cross-sectional areas of the SC and the gray matter were equally preserved.

CONCLUSIONS

Fetal repair of MMC with PMSCs seeded on SIS-ECM improves hindlimb motor function in lambs. Using ECM helps to preserve the architecture of the SC, but adding PMSCs improves the lamb's ability to walk and increases large neuron density. Clinical studies are needed to show benefits in humans.

LEVELS OF EVIDENCE/TYPE OF STUDY

Basic Science.

Effect of 2-octylcyanoacrylate on placenta derived mesenchymal stromal cells on extracellular matrix

PURPOSE

Determine the effect of 2-octylcyanoacrylate on placenta derived mesenchymal stromal cells (PMSCs) seeded onto extracellular matrix (ECM) in order to assess its biocompatibility as a potential adhesive for in-vivo fetal cell delivery.

METHODS

PMSCs isolated from chorionic villus tissue were seeded onto ECM. A MTS proliferation assay assessed cellular metabolic activity at various time points in PMSC-ECM with direct, indirect, and no glue contact. Conditioned media collected prior to and 24 hours after glue exposure was analyzed for secretion of human brain-derived neurotrophic factor, hepatocyte growth factor, and vascular endothelial growth factor.

RESULTS

Direct and indirect contact with 2-octylcyanoacrylate results in progressively decreased cellular metabolic activity over 24 hours compared to no glue controls. Cells with direct contact are less metabolically active than cells with indirect contact. 24 hours of glue exposure resulted in suppression of growth factor secretion that is near complete with direct contact.

DISCUSSION

Exposure to 2-octylcyanoacrylate results in decreased metabolic activity and decreased measurable secretion of growth factors by PMSCs seeded onto ECM. Thus, the application of 2-octylcyanoacrylate glue should be limited when working with cell-engineered scaffolds as its inhibitory effects on cell growth and secretory function can limit the therapeutic potential of cell-based interventions.