Repair of damaged skeletal muscle tissue is limited by the regenerative capacity of native tissue. Current clinical approaches are not optimal for treatment of large volumetric skeletal muscle loss. As an alternative, tissue engineering represents a promising approach for the functional restoration of damaged muscle tissue. A typical tissue engineering process involves the design and fabrication of a scaffold that closely mimics the native skeletal muscle extracellular matrix allowing for organization of cells into a physiologically relevant, 3D architecture. In particular, anisotropic materials, which mimic the morphology of the native skeletal muscle ECM, can be fabricated using various biocompatible materialsto guide cell alignment, elongation, proliferation and differentiation into myotubes. In this article, we first provide an overview of fundamental concepts associated with muscle tissue engineering and the current status of the muscle tissue engineering approaches. We then review recent advances in development of anisotropic scaffolds with micro- or nano-scale features and examine how scaffold topographical, mechanical, and biochemical cues correlate to observed cellular function and phenotype development. Finally, we highlight some recent developments in both the design and utility of anisotropic materials in skeletal muscle tissue engineering along with their potential impact on future research and clinical application.

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Cancer therapeutics are developed through extensive screening; however, many therapeutics evaluated with 2D in vitro cultures during pre-clinical trials suffer from lower efficacy in patients. Replicating the in vivo tumor microenvironment in vitro with three-dimensional (3D) porous scaffolds offers the possibility of generating more predictive pre-clinical models to enhance cancer treatment efficacy. We developed a chitosan and hyaluronic acid (HA) polyelectrolyte complex 3D porous scaffold and evaluated its physical properties. Chitosan-HA (C-HA) scaffolds had a highly porous network. C-HA scaffolds were compared to 2D surfaces for in vitro culture of U-118 MG human glioblastoma (GBM) cells. C-HA scaffold cultures promoted tumor spheroid formation and increased stem-like properties of GBM cells as evidenced by the upregulation of CD44, Nestin, Musashi-1, GFAP, and HIF-1α as compared with 2D cultures. Additionally, the invasiveness of GBM cells cultured in C-HA scaffolds was significantly enhanced compared to those grown in 2D cultures. C-HA scaffold cultures were also more resistant to chemotherapy drugs, which corresponded to the increased expression of ABCG2 drug efflux transporter. These findings suggest that C-HA scaffolds offer promise as an in vitro GBM platform for study and screening of novel cancer therapeutics.

Ribonucleic acid interference (RNAi) is a powerful molecular tool that has potential to revolutionize the treatment of cancer. One major challenge of applying this technology for clinical application is the lack of site-specific carriers that can effectively deliver short interfering RNA (siRNA) to cancer cells. Here we report the development and assessment of a cancer-cell specific magnetic nanovector construct for efficient siRNA delivery and non-invasive monitoring through magnetic resonance imaging (MRI). The base of the nanovector construct is comprised of a superparamagnetic iron oxide nanoparticle core coated with polyethylene glycol (PEG)-grafted chitosan, and polyethylenimine (PEI). The construct was then further functionalized with siRNA and a tumor-targeting peptide, chlorotoxin (CTX), to improve tumor specificity and potency. Flow cytometry, quantitative RT-PCR, and fluorescence microscopy analyses confirmed receptor-mediated cellular internalization of nanovectors and enhanced gene knockdown through targeted siRNA delivery. The ability of this nanovector construct to generate specific contrast enhancement of brain tumor cells was demonstrated through MR imaging. These findings suggest that this CTX enabled nanoparticle carrier may be well suited for delivery of RNAi therapeutics to cancer cells.

Tissue-engineered nanofibrous matrices can potentially serve as an implantable scaffold for the reconstruction of damaged or lost tissue by regulating cell proliferation, organization, and function. In this study, we developed a polyblend chitosan-polycaprolactone (PCL) nanofibrous scaffold with unidirectional fiber orientation by electrospinning for skeletal muscle tissue reconstruction and investigated the effect of the fiber alignment on cell organization and differentiation in comparison with randomly oriented nanofibers and 2D films of the same material. The chitosan-PCL material was shown to support skeletal muscle cell attachment and proliferation, and the fiber alignment promoted skeletal muscle cell morphogenesis and aligned myotube formation in the nanofiber orientation. Reverse-transcription PCR analyses revealed an up-regulation of differentiation-specific genes, troponin T and myosin heavy chain, in muscle cells on the aligned nanofiber scaffolds, confirming the ability of aligned chitosan-PCL nanofibers to enhance muscle cell differentiation. These results suggest that chitosan-PCL nanofibrous scaffolds with unidirectional fiber orientation can significantly enhanced muscle cell development making it a potential scaffold for enhanced skeletal myogenesis.