Vascularization and cellular isolation potential of a novel electrospun cell delivery vehicle

Electrospun Nanofibers for Improved Angiogenesis: Promises for Tissue Engineering Applications

Angiogenesis (or the development of new blood vessels) is a key event in tissue engineering and regenerative medicine; thus, a number of biomaterials have been developed and combined with stem cells and/or bioactive molecules to produce three-dimensional (3D) pro-angiogenic constructs. Among the various biomaterials, electrospun nanofibrous scaffolds offer great opportunities for pro-angiogenic approaches in tissue repair and regeneration. Nanofibers made of natural and synthetic polymers are often used to incorporate bioactive components (e.g., bioactive glasses (BGs)) and load biomolecules (e.g., vascular endothelial growth factor (VEGF)) that exert pro-angiogenic activity. Furthermore, seeding of specific types of stem cells (e.g., endothelial progenitor cells) onto nanofibrous scaffolds is considered as a valuable alternative for inducing angiogenesis. The effectiveness of these strategies has been extensively examined both in vitro and in vivo and the outcomes have shown promise in the reconstruction of hard and soft tissues (mainly bone and skin, respectively). However, the translational of electrospun scaffolds with pro-angiogenic molecules or cells is only at its beginning, requiring more research to prove their usefulness in the repair and regeneration of other highly-vascularized vital tissues and organs. This review will cover the latest progress in designing and developing pro-angiogenic electrospun nanofibers and evaluate their usefulness in a tissue engineering and regenerative medicine setting.

Prevascularized silicon membranes for the enhancement of transport to implanted medical devices

Recent advances in drug delivery and sensing devices for in situ applications are limited by the diffusion-limiting foreign body response of fibrous encapsulation. In this study, we fabricated prevascularized synthetic device ports to help mitigate this limitation. Membranes with rectilinear arrays of square pores with widths ranging from 40 to 200 μm were created using materials (50 μm thick double-sided polished silicon) and processes (photolithography and directed reactive ion etching) common in the manufacturing of microfabricated sensors. Vascular endothelial cells responded to membrane geometry by either forming vascular tubes that extended through the pore or completely filling membrane pores after 4 days in culture. Although tube formation began to predominate overgrowth around 75 μm and continued to increase at even larger pore sizes, tubes formed at these large pore sizes were not completely round and had relatively thin walls. Thus, the optimum range of pore size for prevascularization of these membranes was estimated to be 75-100 μm. This study lays the foundation for creating a prevascularized port that can be used to reduce fibrous encapsulation and thus enhance diffusion to implanted medical devices and sensors. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1602-1609, 2016.

Mesoporous bioactive glass surface modified poly(lactic-co-glycolic acid) electrospun fibrous scaffold for bone regeneration

A mesoporous bioactive glass (MBG) surface modified with poly(lactic-co-glycolic acid) (PLGA) electrospun fibrous scaffold for bone regeneration was prepared by dip-coating a PLGA electrospun fibrous scaffold into MBG precursor solution. Different surface structures and properties were acquired by different coating times. Surface morphology, chemical composition, microstructure, pore size distribution, and hydrophilicity of the PLGA-MBG scaffold were characterized. Results of scanning electron microscopy indicated that MBG surface coating made the scaffold rougher with the increase of MBG content. Scaffolds after MBG modification possessed mesoporous architecture on the surface. The measurements of the water contact angles suggested that the incorporation of MBG into the PLGA scaffold improved the surface hydrophilicity. An energy dispersive spectrometer evidenced that calcium-deficient carbonated hydroxyapatite formed on the PLGA-MBG scaffolds after a 7-day immersion in simulated body fluid. In vitro studies showed that the incorporation of MBG favored cell proliferation and osteogenic differentiation of human mesenchymal stem cells on the PLGA scaffolds. Moreover, the MBG surface-modified PLGA (PLGA-MBG) scaffolds were shown to be capable of providing the improved adsorption/release behaviors of bone morphogenetic protein-2 (BMP-2). It is very significant that PLGA-MBG scaffolds could be effective for BMP-2 delivery and bone regeneration.

Adipose stem cell-based regenerative medicine for reversal of diabetic hyperglycemia

Diabetes mellitus (diabetes) is a devastating disease that affects millions of people globally and causes a myriad of complications that lead to both patient morbidity and mortality. Currently available therapies, including insulin injection and beta cell replacement through either pancreas or pancreatic islet transplantation, are limited by the availability of organs. Stem cells provide an alternative treatment option for beta cell replacement through selective differentiation of stem cells into cells that recognize glucose and produce and secrete insulin. Embryonic stem cells, albeit pluripotent, face a number of challenges, including ethical and political concerns and potential teratoma formation. Adipose tissue represents an alternative source of multipotent mesenchymal stem cells, which can be obtained using a relatively simple, non-invasive, and inexpensive method. Similarly to other adult mesenchymal stem cells, adipose-derived stem cells (ADSCs) are capable of differentiating into insulin-producing cells. They are also capable of vasculogenesis and angiogenesis, which facilitate engraftment of donor pancreatic islets when co-transplanted. Additionally, anti-inflammatory and immunomodulatory effects of ADSCs can protect donor islets during the early phase of transplantation and subsequently improve engraftment of donor islets into the recipient organ. Although ADSC-therapy is still in its infancy, the potential benefits of ADSCs are far reaching.