^{Hierarchically Structured Electrospun Scaffolds with Chemically Conjugated Growth Factor for Ligament Tissue Engineering}

Abstract

The anterior cruciate ligament (ACL) of the knee is vital for proper joint function and is commonly ruptured during sports injuries or car accidents. Due to a lack of intrinsic healing capacity and drawbacks with allografts and autografts, there is a need for a tissue engineered ACL replacement. Our group has previously used aligned sheets of electrospun polycaprolactone nanofibers to develop solid cylindrical bundles of longitudinally aligned nanofibers. We have shown that these nanofiber bundles support cell proliferation and elongation and the hierarchical structure and material properties are similar to the native human ACL. It is possible to combine multiple nanofiber bundles to create a scaffold that attempts to mimic the macro-scale structure of the ACL. The goal of this work was to develop a hierarchical bioactive scaffold for ligament tissue engineering using connective tissue growth factor (CTGF) conjugated nanofiber bundles and evaluate the behavior of mesenchymal stem cells (MSCs) on these scaffolds in vitro and in vivo. CTGF was immobilized onto the surface of individual nanofiber bundles or scaffolds consisting of multiple nanofiber bundles. The conjugation efficiency and the release of conjugated CTGF was assessed using X-ray photoelectron spectroscopy, assays, and immunofluorescence staining. Scaffolds were seeded with MSCs and maintained in vitro for 7 days (individual nanofiber bundles), in vitro for 21 days (scaled-up scaffolds of 20 nanofiber bundles) or in vivo for 6 weeks (small scaffolds of 4 nanofiber bundles) and ligament specific tissue formation was assessed in comparison to non-CTGF conjugated control scaffolds. Results showed that CTGF conjugation encouraged cell proliferation and ligament specific tissue formation in vitro and in vivo. The results suggest that hierarchical electrospun nanofiber bundles conjugated with CTGF are a scalable and bioactive scaffold for ACL tissue engineering.

Modulating microfibrillar alignment and growth factor stimulation to regulate mesenchymal stem cell differentiation

“…Furthermore, electrospinning permits the fabrication of aligned fibers that serve as a template for the deposition of a unidirectional organized extracellular matrix (ECM) by resident cells, thereby generating anisotropy for tissues where direction dependence is essential for function. This makes them an ideal biomaterial for ligament tissue engineering [19][20][21][22]. However, directing stem cell differentiation within such scaffolds towards the different tissue types that make up the bone-ligament interface remains a challenge.…”

“…Appropriate presentation of growth factors is key to regulating the differentiation of MSCs [29,30]. Numerous studies have reported fibroblastic differentiation of MSCs using CTGF [22,29], while TGFβ superfamily members are key mediators of chondrogenesis [31,32].…”

Mechanical properties of a hierarchical electrospun scaffold for ovine anterior cruciate ligament replacement

“…We have previously shown that the sub‐structural components of the scaffold mimic the hierarchical structure and material properties of the native ACL . Additionally, we have shown that ovine bone marrow‐derived stem cells seeded on the scaffold deposit collagen in vitro, and implantation into the ovine stifle joint is clinically feasible . Taken together, these advances suggest that the novel scaffold could perform well as a tissue engineered ACL replacement.…”

Electrospun Fibrous Architectures for Drug Delivery, Tissue Engineering and Cancer Therapy

“…Their study revealed that fiber meshes with thinner fiber diameter could be more effectively functionalized by pNE, and thus had higher muscle cell proliferation and adhesion and treatment efficacy for repairing impaired musculus rectus abdominis in a rat muscle injury model. In the study of Pauly et al, connective tissue growth factor (CTGF) was conjugated onto longitudinally aligned PCL fiber bundles to mimic the hierarchical structures of native human anterior cruciate ligament (ACL) for ACL regeneration. CTGF was sustainably released over 2 weeks, evidenced by an ELISA assay.…”