Biomaterials in fetal surgery

Enzymatic self-assembly of short peptides for cell spheroid formation

Cell spheroids, including organoids, serve as a valuable link between in vitro systems and in vivo animal models, offering powerful tools for studying cell biology in a three-dimensional environment. However, existing methods for generating cell spheroids are time consuming or difficult to scale up for large-scale production. Our recent study has revealed that transcytotic peptide assemblies, which transform from nanoparticles to nanofibers by enzymatic reactions, can create an intercellular fibril/gel, accelerating cell spheroid formation from a 2D cell culture or a cell suspension. While this finding presents an alternative approach for generating cell spheroids, the specific structural features required for efficient cell spheroid formation remain unclear. Based on our observation that a phosphotetrapeptide with a biphenyl cap at its N-terminus enables cell spheroid formation, we produced 10 variants of the original peptide. The variants explored modifications to the peptide backbone, length, electronic properties of the biphenyl capping group, and the type of phosphorylated amino acid residue. We then evaluated their ability for inducing cell spheroid formation. Our analysis revealed that, among the tested molecules, peptides with C-terminal phosphotyrosine, low critical micelle concentration, and dephosphorylation-guided nanoparticle to nanofiber morphological transition were the most effective in inducing the formation of cell spheroids. This work represents the first example to correlate the thermodynamic properties (e.g., self-assembling ability) and kinetic behavior (e.g., enzymatic dephosphorylation) of peptides with the efficacy of controlling intercellular interaction, thus offering valuable insights into using enzymatic self-assembly to generate peptide assemblies for biological applications.

Collagen-Heparin-FGF2-VEGF Scaffolds Induce a Regenerative Gene Expression Profile in a Fetal Sheep Wound Model

BACKGROUND

The developmental abnormality spina bifida is hallmarked by missing tissues (e.g. skin) and exposure of the spinal cord to the amniotic fluid, which can negatively impact neurological development. Surgical closure of the skin in utero limits neurological damage, but in large defects this results in scarring and contractures. Stimulating skin regeneration in utero would greatly benefit treatment outcome. Previously, we demonstrated that a porous type I collagen (COL) scaffold, functionalized with heparin (HEP), fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor (VEGF) (COL-HEP/GF) improved pre- and postnatal skin regeneration in a fetal sheep full thickness wound model. In this study we uncover the early events associated with enhanced skin regeneration.

METHODS

We investigated the gene expression profiles of healing fetal skin wounds two weeks after implantation of the COL(-HEP/GF) scaffolds. Using laser dissection and microarrays, differentially expressed genes (DEG) were identified in the epidermis and dermis between untreated wounds, COL-treated wounds and wounds treated with COL-HEP/GF. Biological processes were identified using gene enrichment analysis and DEG were clustered using protein-protein-interaction networks.

RESULTS

COL-HEP/GF influences various interesting biological processes involved in wound healing. Although the changes were modest, using protein-protein-interaction networks we identified a variety of clustered genes that indicate COL-HEP/GF induces a tight but subtle control over cell signaling and extracellular matrix organization.

CONCLUSION

These data offer a novel perspective on the key processes involved in (fetal) wound healing, where a targeted and early interference during wound healing can result in long-term enhanced effects on skin regeneration.

Recyclable surgical, consumer, and industrial adhesives of poly(α-lipoic acid)

Polymer adhesives play an important role in many medical, consumer, and industrial products. Polymers of α-lipoic acid (αLA) have the potential to fulfill the need for versatile and environmentally friendly adhesives, but their performance is plagued by spontaneous depolymerization. We report a family of stabilized αLA polymer adhesives that can be tailored for a variety of medical or nonmedical uses and sustainably sourced and recycled in a closed-loop manner. Minor changes in monomer composition afforded a pressure-sensitive adhesive that functions well in dry and wet conditions, as well as a structural adhesive with strength equivalent to that of conventional epoxies. αLA surgical superglue successfully sealed murine amniotic sac ruptures, increasing fetal survival from 0 to 100%.

Isolated Fetal Ventriculomegaly: Diagnosis and Treatment in the Prenatal Period

Fetal ventriculomegaly (VM) is a defect of the central nervous system, typically diagnosed during the second-trimester ultrasound in fetuses with an atrial diameter (AD) of >10 mm. Non-isolated ventriculomegaly (NIVM) is heterogeneous in nature, coexisting with additional intracranial and/or extracranial malformations and genetic syndromes, resulting in an unfavorable prognosis for the further development of the child. Both the pregnancy management and counseling are dependent on the findings of combined ultrasound/MRI, genetic testing, and gestational age at diagnosis. The purpose of this review is to propose a hypothesis that diagnostic advancements allow to define the process of identification of the isolated forms of VM (IVM). Based on the evidence presented in the literature, we consider whether prenatal decompression for severe isolated VM (ISVM) is supported by the experimental trials and whether it might be implemented in clinical practice. Also, we describe the evolution of the diagnostic methods and expert opinions about the previously used prenatal decompression techniques for ISVM. In conclusion, we introduce the idea that fetal surgery centers have either reached or nearly reached the necessary level of expertise to perform such procedures. Endoscopic cystoventriculostomy (ETV) appears to be the most promising, as it is associated with minimal perinatal complications and favorable neurological outcomes in the neonatal period. Randomized trials with long-term neurodevelopmental follow-up of children who underwent prenatal decompression due to ISVM are necessary.

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

Background

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

Methods

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

Results

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

Conclusions

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

Development of a double-layer electrospun patch as a potential prenatal treatment for myelomeningocele

Myelomeningocele (MMC) is a congenital defect of the spine characterised by meningeal and spinal cord protrusion through the open vertebral arches. This defect causes progressive prenatal damage of the spinal cord, leading to lifelong handicap. Although mid-trimester surgical repair may reduce part of the handicap, an earlier and less invasive approach would further improve the prognosis, possibly minimising maternal and foetal risks. Several studies have proposed an alternative approach to surgical repair by covering the defect with a patch and protecting the exposed neural tissue. Our study aims to elaborate on a waterproof and biodegradable bioactive patch for MMC prenatal foetal repair. We developed a double-layer patch that can provide a waterproof coverage for the spinal cord, with a bioactive side, conducive to cell proliferation, and an antiadhesive side to avoid its attachment to the medulla.

Cell spheroid creation by transcytotic intercellular gelation

Cell spheroids bridge the discontinuity between in vitro systems and in vivo animal models. However, inducing cell spheroids by nanomaterials remains an inefficient and poorly understood process. Here we use cryogenic electron microscopy to determine the atomic structure of helical nanofibres self-assembled from enzyme-responsive D-peptides and fluorescent imaging to show that the transcytosis of D-peptides induces intercellular nanofibres/gels that potentially interact with fibronectin to enable cell spheroid formation. Specifically, D-phosphopeptides, being protease resistant, undergo endocytosis and endosomal dephosphorylation to generate helical nanofibres. On secretion to the cell surface, these nanofibres form intercellular gels that act as artificial matrices and facilitate the fibrillogenesis of fibronectins to induce cell spheroids. No spheroid formation occurs without endo- or exocytosis, phosphate triggers or shape switching of the peptide assemblies. This study-coupling transcytosis and morphological transformation of peptide assemblies-demonstrates a potential approach for regenerative medicine and tissue engineering.

Tissue Glue-Based Sealing Patch for the in vivo Prevention of Iatrogenic Prelabor Preterm Rupture of Fetal Membranes

INTRODUCTION

One of the main concerns for all fetal surgeries is the risk of preterm delivery due to the preterm prelabor rupture of the fetal membranes (iPPROM). Clinical approaches to seal fetal membrane (FM) defects are missing due to the lack of appropriate strategies to apply sealing biomaterials at the defect site.

METHODS

Here, we test the performance of a previously developed strategy to seal FM defects with cyanoacrylate-based sealing patches in an ovine model up to 24 days after application.

RESULTS

Patches sealed tightly the fetoscopy-induced FM defects and remained firmly attached to the defect over 10 days. At 10 days after treatment, 100% (13/13) of the patches were attached to the FMs, and 24 days after treatment 25% (1/4) of the patches placed in CO2 insufflation, and 33% (1/3) in NaCl infusion remained. However, all successfully applied patches (20/24) led to a watertight sealing at 10 or 24 days after treatment. Histological analysis indicated that cyanoacrylates induced a moderate immune response and disrupted the FM epithelium.

CONCLUSION

Together, these data show the feasibility of minimally invasive sealing of FM defects by locally gathering tissue adhesive. Further development to combine this technology with refined tissue glues or healing-inducing materials holds great promise for future clinical translation.

In vivo Sealing of Fetoscopy-Induced Fetal Membrane Defects by Mussel Glue

INTRODUCTION

The benefits of fetal surgery are impaired by the high incidence of iatrogenic preterm prelabor rupture of the fetal membranes (iPPROM), for which chorioamniotic separation has been suggested as a potential initiator. Despite the urgent need to prevent iPPROM by sealing the fetoscopic puncture site after intervention, no approach has been clinically translated.

METHODS

A mussel-inspired biomimetic glue was tested in an ovine fetal membrane (FM) defect model. The gelation time of mussel glue (MG) was first optimized to make it technically compatible with fetal surgery. Then, the biomaterial was loaded in polytetrafluoroethylene-coated nitinol umbrella-shaped receptors and applied on ovine FM defects (N = 10) created with a 10 French trocar. Its sealing performance and tissue response were analyzed 10 days after implantation by amniotic fluid (AF) leakage and histological methods.

RESULTS

All ewes and fetuses recovered well after the surgery, and 100% ewe survival and 91% fetal survival were observed at explantation. All implants were tight at explantation, and no AF leakage was observed in any of them. Histological analysis revealed a mild tissue response to the implanted glue.

CONCLUSION

MG showed promising properties for the sealing of FM defects and thereby the prevention of preterm birth. Studies to analyze the long-term tissue response to the sealant should be performed.

VARIATIONS OF THE STRUCTURE, TOPOGRAPHY, BLOOD SUPPLY AND INNERVATION OF THE BRACHIORADIALIS IN HUMAN FETUS

OBJECTIVE

The aim of the research was to establish the features of age-related and individual anatomical variability of the brachioradialis, its blood supply, and innervation options.

PATIENTS AND METHODS

Materials and methods: The study of the variant anatomy of the brachioradialis and its vascular and nervous structures was carried out on 25 preparations of human fetuses of 4-7 months, 81.0-270.0 mm parietal-coccygeal length (PCL) using macromicroscopic preparation, injection vessels, and morphometry.

RESULTS

Results: Spindle-like (56%) and round (24%) shapes of the brachioradialis were found in most of the studied fetuses; its elongated flat (12%) and triangular (8%) forms occur less often. In a fetus of 185.0 mm TKD, the right brachioradialis consisted of two separate parts: upper and lower, which were connected at the level of the middle of the forearm into a common short muscle belly. In another human fetus of 220.0 mm TKD, the right brachioradialis also consisted of two separate parts - upper and lower, triangular in shape, but separated by a pronounced horizontal gap.

CONCLUSION

Conclusions: The features of the fetal anatomy of the brachioradialis are established: its variability and bilateral asymmetry of shape and size, variability of the places of origin and attachment, etc. In individual human fetuses, the brachioradialis consists of two separate parts that have special topographical relationships. The area of the greatest concentration of both extra- and intramuscular nerves and arteries is the upper and middle third of the brachioradialis. In the area of the forearm, the course of radial vascular-nerve formations is determined by the brachioradialis.

Biomaterials science and engineering to address unmet needs in women's health

Medical conditions that primarily or disproportionately affect women have historically been poorly studied. In contrast to the musculoskeletal and cardiovascular systems, there is no lengthy record of biomaterials research addressing women's health needs. In this article, the historical reasons for this discrepancy are examined. The anatomy of both the nonpregnant and pregnant reproductive tissues is reviewed, including the ovaries, uterus, and (fetal) placenta. Examples of biomaterials-related women's health research are described, including tissue engineering, organoids, and microphysiological systems. The future of the field is considered with dual focuses. First, there is a significant need for novel approaches to advance women's health through materials and biomaterials, particularly in complex biomimetic hydrogels. Second, there is an exciting opportunity to enlarge the community of biomaterials scientists and engineers working in women's health to encourage more contributions to its rapidly emerging product development pipeline.

Graphical abstract

Medical gloves modified by a one-minute spraying process with blood-repellent, antibacterial and wound-healing abilities

During clinical surgery, bleeding that occurs in the operative region is inevitable. Due to the blood adhesion on ordinary medical gloves, it reduces surgery quality to a certain extent and even prolongs operation time. Herein, we show that medical blood-repellent gloves (MBRG) can be obtained by spraying the blood-repellent mist spray (MS) on the surface of ordinary medical gloves, which are available for immediate use in around one minute. After the modification, MBRG not only have a significantly higher blood repellent rate than that of ordinary medical gloves, but also can effectively inhibit the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), and even promote the healing of infected wounds. MS is easy to prepare, low-toxic, and can be widely used on the surface of various medical gloves, such as rubber gloves, polyethylene film gloves, and nitrile gloves, which may have an impact on the development of future medical gloves.

Supramolecular Adhesive Hydrogels for Tissue Engineering Applications

Tissue engineering is a promising and revolutionary strategy to treat patients who suffer the loss or failure of an organ or tissue, with the aim to restore the dysfunctional tissues and enhance life expectancy. Supramolecular adhesive hydrogels are emerging as appealing materials for tissue engineering applications owing to their favorable attributes such as tailorable structure, inherent flexibility, excellent biocompatibility, near-physiological environment, dynamic mechanical strength, and particularly attractive self-adhesiveness. In this review, the key design principles and various supramolecular strategies to construct adhesive hydrogels are comprehensively summarized. Thereafter, the recent research progress regarding their tissue engineering applications, including primarily dermal tissue repair, muscle tissue repair, bone tissue repair, neural tissue repair, vascular tissue repair, oral tissue repair, corneal tissue repair, cardiac tissue repair, fetal membrane repair, hepatic tissue repair, and gastric tissue repair, is systematically highlighted. Finally, the scientific challenges and the remaining opportunities are underlined to show a full picture of the supramolecular adhesive hydrogels. This review is expected to offer comparative views and critical insights to inspire more advanced studies on supramolecular adhesive hydrogels and pave the way for different fields even beyond tissue engineering applications.

Biomaterial-based treatments for the prevention of preterm birth after iatrogenic rupture of the fetal membranes

Minimally invasive interventions to ameliorate or correct fetal abnormalities are becoming a clinical reality. However, the iatrogenic premature preterm rupture of the fetal membranes (FMs) (iPPROM), which may result in...

Minimally Invasive Precise Application of Bioadhesives to Prevent IPPROM on a Pregnant Sheep Model

INTRODUCTION

Iatrogenic preterm premature rupture of the membrane remains the Achille's heel of fetoscopy. The aim of this study was to show in vivo feasibility of fetal membrane (FM) defect sealing by the application of tissue glues with umbrella-shaped receptors.

METHODS

First, we adapted our previously described ex vivo strategy and evaluated the adhesion strength of different tissue glues, Histoacryl® and Glubran2®, by bonding polytetrafluoroethylene or silicone encapsulated nitinol glue receptor to human FM. Then, we exposed pregnant sheep uterus through a laparotomy and placed a 10-French trocar into the amniotic cavity through which the umbrella-shaped glue receptor (n = 9) was inserted and fixated onto the FM with the tissue glues (n = 8). The tightness of the sealed defects was assessed 4 h post-surgery.

RESULTS

Both tissue glues tested resulted in adhesion of the glue receptors to the FM ex vivo. In vivo, all glue receptors opened in the amniotic cavity (n = 9) and all successfully placed glue receptors sealed the FM defect (n = 8). Four hours post-surgery, 2 treatment sites showed minimal leakage whereas the negative control without glue (n = 1) showed substantial leakage.

DISCUSSION

This in vivo study confirms that fetoscopically induced FM defects can be sealed by the application of tissue adhesives.

Comprehensive quantitative characterization of the human term amnion proteome

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We report an unprecedented quantitative high coverage of the human amnion proteome.

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We identified novel proteins that hold great promise for understanding fetal membrane biology.

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Together, this comprehensive proteome provides a basis for the evaluation of pre-term or diseased fetal membranes.

The loss of fetal membrane (FM) integrity and function at an early time point during pregnancy can have devastating consequences for the fetus and the newborn. However, biomaterials for preventive sealing and healing of FMs are currently non-existing, which can be partly attributed to the current fragmentary knowledge of FM biology. Despite recent advances in proteomics analysis, a robust and comprehensive description of the amnion proteome is currently lacking. Here, by an optimized protein sample preparation and offline fractionation before liquid chromatography coupled to mass spectrometry (LC-MS) analysis, we present a characterization of the healthy human term amnion proteome, which covers more than 40% of the previously reported transcripts in similar RNA sequencing datasets and, with more than 5000 identifications, greatly outnumbers previous reports. Together, beyond providing a basis for the study of compromised and preterm ruptured FMs, this comprehensive human amnion proteome is a stepping-stone for the development of novel healing-inducing biomaterials. The proteomic dataset has been deposited in the ProteomeXchange Consortium with the identifier PXD019410.

Ionizable lipid nanoparticles for in utero mRNA delivery

Clinical advances enable the prenatal diagnosis of genetic diseases that are candidates for gene and enzyme therapies such as messenger RNA (mRNA)-mediated protein replacement. Prenatal mRNA therapies can treat disease before the onset of irreversible pathology with high therapeutic efficacy and safety due to the small fetal size, immature immune system, and abundance of progenitor cells. However, the development of nonviral platforms for prenatal delivery is nascent. We developed a library of ionizable lipid nanoparticles (LNPs) for in utero mRNA delivery to mouse fetuses. We screened LNPs for luciferase mRNA delivery and identified formulations that accumulate within fetal livers, lungs, and intestines with higher efficiency and safety compared to benchmark delivery systems, DLin-MC3-DMA and jetPEI. We demonstrate that LNPs can deliver mRNAs to induce hepatic production of therapeutic secreted proteins. These LNPs may provide a platform for in utero mRNA delivery for protein replacement and gene editing.

Supramolecular Cross-Links in Mussel-Inspired Tissue Adhesives

Here we introduce a tissue-adhesive patch with orthogonal cohesive and adhesive chemistries; supramolecular ureido-4-pyrimidinone (UPy) cross-links provide cohesive strength, and catechols provide mussel-inspired tissue adhesion. In the development of tissue-adhesive biomaterials, prior research has focused on forming strong adhesive interfaces in wet conditions, leaving the use of supramolecular cross-links for cohesive strength underexplored. In developing this adhesive patch, the influence of the comonomers' composition and amphiphilicity on adhesion was investigated by lap shear adhesion to wet tissue. We determined failed lap joints' failure mechanism using catechol-specific Arnow's stain and identified formulations with improved cohesive strength. The adhesive materials were cytocompatible in mammalian cell conditioned media viability studies. We found that using orthogonal motifs to independently control adhesives' cohesive and adhesive strengths resulted in stronger tissue adhesion. The design principles presented here advance the development of wet tissue adhesives and could allow for the future design of biomaterials with desirable stimuli-responsive properties.

Exploiting the placenta for nanoparticle-mediated drug delivery during pregnancy

A major challenge to treating diseases during pregnancy is that small molecule therapeutics are transported through the placenta and incur toxicities to the developing fetus. The placenta is responsible for providing nutrients, removing waste, and protecting the fetus from toxic substances. Thus, the placenta acts as a biological barrier between the mother and fetus that can be exploited for drug delivery. Nanoparticle technologies provide the opportunity for safe drug delivery during pregnancy by controlling how therapeutics interact with the placenta. In this Review, we present nanoparticle drug delivery technologies specifically designed to exploit the placenta as a biological barrier to treat maternal, placental, or fetal diseases exclusively, while minimizing off-target toxicities. Further, we discuss opportunities, challenges, and future directions for implementing drug delivery technologies during pregnancy.

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.

Bio-engineering of fetal cartilage for in utero spina bifida repair

PURPOSE

During in utero surgical spina bifida repair, a multi-layer closure is used to cover the defect. These soft tissues, however, might be not sufficient to protect the spinal cord during the future life. Our goal is to develop a more rigid protective tissue construct consisting of bioengineered cartilage and skin.

METHODS

Ovine fetal chondrocytes were tested for their in vitro chondrogenic potential in three-dimensional cultures. Scaffolds based on natural biopolymers (collagen I, fibrin glue) were loaded with varying amounts of fetal chondrocytes and assessed for their ability to support cartilage formation in vitro. The bioengineered constructs were analyzed using cartilage-specific histology stainings and compared to native fetal cartilage.

RESULTS

Fetal chondrocytes actively produced cartilage extracellular matrix in three-dimensional cultures, even at high passages. Among all bioengineered scaffolds, only the collagen I-based hydrogels loaded with high densities of fetal chondrocytes showed cartilage-like structure in vitro but also extensive shrinking.

CONCLUSION

Fetal chondrocytes represent a good cell source for cartilage bioengineering. Collagen I scaffolds support cartilage formation in vitro, but the construct shrinking constitutes a major limitation. Future steps include the identification of suitable bioprintable materials which maintain their shape and size, as well as the analysis of the interphase between bioengineered cartilage and skin.