Infoscience

Thesis

Tissue engineering for prenatal applications

Fetal therapies have become available for a restricted number of life-threatening clinical conditions. Harnessing tissue engineering for prenatal applications has not been widely pursued even though isolating cells from fetal and extraembryonic tissues has been routinely done for years. The objectives of this thesis were twofold: i) the development of materials based and tissue engineering based strategies to prevent iatrogenic preterm prelabour rupture of fetal membranes (iPPROM) after diagnostic or therapeutic interventions into the amniotic cavity and ii) the generation of tissue substitutes from patient derived fetal cells, which can be employed for prenatal or perinanal transplantation to restore or replace defective tissues. For the prevention of iPPROM, mussel-mimetic tissue adhesive (mussel glue) a biomaterial which was recently described to not compromise cell viability and to have good tissue sealing capability was compared to fibrin glue. In this in vivo study we assessed whether in a mid-gestational rabbit model punctured fetal membranes could be efficiently sealed with mussel glue. Mussel glue showed comparable in vivo performance to fibrin glue in sealing fetal membranes though no apparent healing of the membranes could be observed in any of the samples. The limited ability of naturally derived scaffolds to promote fetal membrane healing inspired the engineering of synthetic plugging material with specifically tailored biological and mechanical properties which could activate the cells in the amnion and induce a healing response. In this thesis the modularly designed biomimetic poly(ethylene glycol) (PEG)-based hydrogel platform (called TG-PEG from here on) was used together with fetal cells to demonstrate that upon presentation of appropriate biological cues in 3D tissue mimicking environment, mesenchymal progenitor cells from amnion can be mobilized, induced to proliferate and supported in maintaining their native extracellular matrix production, thus creating a suitable environment for healing to take place. These data provide the basis for future engineering of materials with defined mechanical and biochemical properties and the ability to present migration and proliferation inducing factors, namely PDGF, bFGF, or EGF which could be key in resolving the clinical problem of iPPROM and allowing the field of fetal surgery to move forward. Cleft palate, where the bones of the palatal halves fail to fuse properly, is one of the most common birth defects. Tissue engineering has been envisioned as a treatment option but current approaches have been limited by the lack of i) appropriate autologous cell sources and ii) structural organization and vascularization. Tissue engineering of cleft palates using of autologous amniocentesis-derived and thus ethically unproblematic fetal amniotic fluid cells (AFCs) could be done parallel to the ongoing pregnancy with living reconstruction material being ready when the child is born. We describe using TG-PEG hydrogels to first evaluate 3D osteogenic differentiation of AFCs and creation of vascular structures from AFC derived endothelial cells (enAFC) and undifferentiated AFC either in random or organized channel cocultures in vitro and in vivo. Next, these approaches were combined in an osteogenic matrix with a channel perfused with enAFC and finally the integration and functional properties of these fetal bone constructs was tested in ectopic mouse model.

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