Due to advances in stem cell biology, embryonic stem (ES) cells can be induced to differentiate into a particular mature cell lineage when cultured as embryoid bodies. Although transplantation of ES cells-derived neural progenitor cells has been demonstrated with some success for either spinal cord injury repair in small animal model, control of ES cell differentiation into complex, viable, higher ordered tissues is still challenging. Mouse ES cells have been induced to become neural progenitors by adding retinoic acid to embryoid body cultures for 4 days. In this study, we examine the use of electrospun biodegradable polymers as scaffolds not only for enhancing the differentiation of mouse ES cells into neural lineages but also for promoting and guiding the neurite outgrowth. A combination of electrospun fiber scaffolds and ES cells-derived neural progenitor cells could lead to the development of a better strategy for nerve injury repair.

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Biodegradable nanofibers produced by electrospinning represent a new class of promising scaffolds to support nerve regeneration. We begin with a brief discussion on the electrospinning of nanofibers and methods for controlling the structure, porosity, and alignment of the electrospun nanofibers. The methods include control of the nanoscale morphology and microscale alignment of the nanofibers, as well as the fabrication of macroscale, three-dimensional tubular structures. We then highlight recent studies that utilize electrospun nanofibers to manipulate biological processes relevant to nervous tissue regeneration, including stem cell differentiation, guidance of neurite extension, and peripheral nerve injury treatments. The main objective of this feature article is to provide valuable insights into methods for investigating the mechanisms of neurite growth on novel nanofibrous scaffolds and optimization of the nanofiber scaffolds and conduits for repairing peripheral nerve injuries.

This paper reports the fabrication of scaffolds consisting of radially aligned poly(ε-caprolactone) nanofibers by utilizing a collector comprised of a central point electrode and a peripheral ring electrode. This novel class of scaffolds was able to present nanoscale topographic cues to cultured cells, directing and enhancing their migration from the periphery to the center. We also established that such scaffolds could induce faster cellular migration and population than nonwoven mats consisting of random nanofibers. Dural fibroblast cells cultured on these two types of scaffolds were found to express type I collagen, the main extracellular matrix component in dural mater. The type I collagen exhibited a high degree of organization on the scaffolds of radially aligned fibers and a haphazard distribution on the scaffolds of random fibers. Taken together, the scaffolds based on radially aligned, electrospun nanofibers show great potential as artificial dural substitutes and may be particularly useful as biomedical patches or grafts to induce wound closure and/or tissue regeneration. Keywordselectrospinning; aligned nanofibers; dural substitutes; wound closure Dura mater is a membranous connective tissue located at the outermost of the three layers of the meninges surrounding the brain and spinal cord, which covers and supports the dural sinuses and carries blood from the brain towards the heart. 1 Dural substitutes are often needed after a neurosurgical procedure to expand or replace the resected dura mater. 2 Although a lot of efforts have been made, the challenge to develop a suitable dural substitute has been met with limited success. 3 Autografts (e.g., fascia lata, temporalis fascia, and pericranium) are preferred because they do not provoke severe inflammatory or immunologic reactions, but they are limited by potential drawbacks such as difficulty in achieving a watertight closure, formation of scar tissue, insufficiently accessible graft materials to close large dural defects, and additional incisions for harvesting the graft. 4,5 Allografts and xenografts are often associated with adverse effects such as graft dissolution, encapsulation, foreign body reaction, scarring, and adhesion formation. Lyophilized human * Address correspondence to: xia@biomed.wustl.edu. † These two authors contributed equally to this work. NIH Public AccessAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2011 September 28.Published in final edited form as: ACS Nano. 2010 September 28; 4(9): 5027-5036. doi:10.1021/nn101554u. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript dura mater as a dural substitute has also been clarified as a source of Creutzfeldt-Jakob disease. 6,7 In terms of materials, nonabsorbable synthetic polymers, such as silicone and expanded polytetrafluoroethylene (ePTFE), often cause serious complications. These may include induction of granulation tissue formation due to their chronic stimulation of the surrounding tissues and long-term foreign body reactions. [8]...

Electrospun nanofibers can be readily assembled into various types of scaffolds for applications in neural tissue engineering. The objective of this study is to examine and understand the unique patterns of neurite outgrowth from primary dorsal root ganglia (DRG) cultured on scaffolds of electrospun nanofibers having different orders, structures, and surface properties. We found that the neurites extended radially outward from the DRG main body without specific directionality when cultured on a nonwoven mat of randomly oriented nanofibers. In contrast, the neurites preferentially extended along the long axis of fiber when cultured on a parallel array of aligned nanofibers. When seeded at the border between regions of aligned and random nanofibers, the same DRG simultaneously expressed aligned and random neurite fields in response to the underlying nanofibers. When cultured on a double-layered scaffold where the nanofibers in each layer were aligned along a different direction, the neurites were found to be dependent on the fiber density in both layers. This bi-axial pattern clearly demonstrates that neurite outgrowth can be influenced by nanofibers in different layers of a scaffold, rather than the topmost layer only. Taken together, these results will provide valuable information pertaining to the design of nanofiber scaffolds for neuroregenerative applications, as well as the effects of topology on neurite outgrowth, growth cone guidance, and axonal regeneration.Keywords electrospun nanofibers; patterning; coating; neurite outgrowth; guidance Structural and biomolecular patterns play an important role in the embryonic development of the nervous system. In building the intricate neural networks, axons must be precisely guided to the synaptic targets and various cell populations have to be spatially distributed into a specific pattern. The effectiveness of these two processes critically depends on the presence of patterned cues to guide neurite outgrowth. The cues can typically be divided into two main categories: chemical cues based on neurite attractive/repulsive molecules (e.g., netrins, slits, semaphorins, and ephrins), 1 and physical cues that may include applied tension/stress, electrical polarization, magnetic field, and topography. [2][3][4][5] The effects of topographic cues on neurite extension have been extensively investigated through the use of substrates containing microgrooves or microchannels of different depths and widths, typically generated using microlithography. Neurites have been demonstrated to grow parallel to a channel when the channel was 20-40 μm wide, but perpendicular to a channel when the width increased to the range of 40-60 μm. 6 Also, neurites have been aligned perpendicular to shallow grooves of 1 μm in width and hundreds of nanometers in depth. 7 In addition, neonatal rat DRG neurons have been cultured on poly(dimethyl siloxane) (PDMS) substrates patterned with grooves and coated with poly-L -lysine (PLL) and laminin, and it was *Address correspondence to: xia@biomed.wu...