Engineered blood and lymphatic capillaries in 3-D VEGF-fibrin-collagen matrices with interstitial flow

In vitro endothelial cell organization into capillaries is a long standing challenge of tissue engineering. We recently showed the utility of low level interstitial flow in guiding the organization of endothelial cells through a 3-D fibrin matrix-containing covalently bound vascular endothelial growth factor (VEGF). Here this synergistic phenomenon was extended to explore the effects of matrix composition on in vitro capillary morphogenesis of human blood versus lymphatic endothelial cells (BECs and LECs). Different mixtures of fibrin and collagen were used in conjunction with constant concentrations of matrix-bound VEGF and slow interstitial flow over 10 days. Interestingly, the BECs and LECs each showed a distinct preference in terms of organization for matrix composition: LECs organized the most extensively in a fibrin-only matrix, while BEC organization was optimized in the compliant collagen-containing matrices. Furthermore, the BECs and LECs produced architecturally different structures; while BECs organized in thick, branched networks containing wide lumen, the LECs were elongated into slender, overlapping networks with fine lumen. These data demonstrate the importance of the 3-D matrix composition in facilitating and coordinating BEC and LEC capillary morphogenesis, which is important for in vitro vascularization of engineered tissues

Conditional human VEGF‐mediated vascularization in chicken embryos using a novel temperature‐inducible gene regulation (TIGR) system

Advanced heterologous transcription control systems for adjusting desired transgene expression are essential for gene function assignments, drug discovery, manufacturing of difficult to produce protein pharmaceuticals and precise dosing of gene‐based therapeutic interventions. Conversion of the Streptomyces albus heat shock response regulator (RheA) into an artificial eukaryotic transcription factor resulted in a vertebrate thermosensor (CTA; cold‐inducible transactivator), which is able to adjust transcription initiation from chimeric target promoters (PCTA) in a low‐temperature‐ inducible manner. Evaluation of the temperature‐dependent CTA-PCTA interaction using a tailored ELISA‐like cell‐free assay correlated increased affinity of CTA for PCTA with temperature downshift. The temperature‐inducible gene regulation (TIGR) system enabled tight repression in the chicken bursal B‐cell line DT40 at 41°C as well as precise titration of model product proteins up to maximum expression at or below 37°C. Implantation of microencapsulated DT40 cells engineered for TIGR‐controlled expression of the human vascular endothelial growth factor A (hVEGF121) provided low‐temperature‐induced VEGF‐mediated vascularization in chicken embryo

Bioengineering of foetal membrane repair

ISSN:1424-7860ISSN:1424-399

Bioengineering of foetal membrane repair

Preterm premature rupture of the foetal membranes (fruber vorzeitiger Blasensprung) has remained a devastating complication of pregnancy with very high risk of pregnancy loss. Several methods of sealing spontaneously ruptured membranes to stop amniotic fluid leakage and prolong pregnancy have been tested, but no one of them has achieved a clinical breakthrough. Also, needle and foetoscopic puncture of membranes for diagnostic or surgical interventions in the amniotic cavity carry a significant risk of persistent membrane leakage and subsequent rupture - thus limiting the developing field of intrauterine foetal surgery. Efforts are concentrated on taking action before rupture rather than reacting after rupture: one avenue of research concerns prophylactic plugging of foetoscopic access sites in foetal membranes at the time of intervention, thus inhibiting leakage and rupture. Foetal membrane injuries, spontaneous or iatrogenic, constitute extreme challenges to repair: thinness of foetal membrane tissue, difficult localisation and accessibility of the rupture site, the need for injectable sealants, vet gluing conditions and poor wound healing in this tissue all complicate repair. The goal is to achieve immediate and at the same time long-lasting closure of the membrane leak. Here we review approaches to closure of foetal membrane defects with liquid sealants or solid biomaterial scaffolds, with the focus on prophylactic plugging of foetoscopic access sites