A Novel Bioresorbable Construct for Tendon Regeneration

A Novel Bioresorbable Construct for Tendon RegenerationLucy Bosworth 1,*, Sandra Downes 11 School of Materials, University of Manchester, Grosvenor Street, Manchester, M1 * lucy.bosworth@manchester.ac.ukIntroduction: Tendons are highly organised structures, which are principally composed of aligned collagen type I fibres (extracellular matrix (ECM)) that lie parallel to the tendon axis [1]. Their hierarchical configuration is established on the grouping of these fibres into bundles of increasing size to form the overall tendon structure. The main cell type is tenocytes; these are located amongst the collagen fibres in a columnar array and are responsible for ECM production and regulation [2]. Tendons are commonly affected by injury and degenerative diseases, leading to chronic pain and spontaneous rupture. The rate of these tendinopathies is increasing, mostly due to population aging and an increased participation in sporting and recreational activities [3]. A poor healing response, whereby scar tissue formation is organisationally, biochemically and biomechanically inferior, leaves tendons prone to further morbidity and risk of rupture. Current interventions often have a poor outcome, resulting in loss of function, further degeneration and rupture [4,5]. Surgery involving autografts and allografts can cause additional morbidity and tissue rejection respectively [6]. There is no commercially approved synthetic, biodegradable repair device available for clinical use. Using electrospinning, we have developed a technique that enables fabrication of bioresorbable nanofibres, which can be purposefully oriented and manipulated to create 3D scaffolds that mimic the tendon hierarchical structure. Materials and Methods: Electrospinning parameters: voltage - 20kV, flow rate - 0.05ml/min, distance to collector ??? 15cm. Solution properties: polymer ??? polycaprolactone (PCL) Mn 80,000, concentration 10%w/v (PCL/acetone). Fibres were collected on a fine edged rotating mandrel. Mandrel rotation speeds varied depending on the fibre orientation required; randomly oriented fibres 50RPM and aligned fibres 500RPM. 3D bundles were developed from manipulation of the collected aligned fibres. Cellular interactions with fibrous scaffolds were investigated over a two-week period to determine the effects of material contact guidance on cell morphology. This was assessed by scanning electron microscopy (SEM). The mechanical properties of the fibrous scaffolds were also investigated to determine the tensile strength of the scaffolds investigated. This was achieved by loading the samples to failure using an Instron with 1N load cell and 5mm/min crosshead speed.Results and Conclusions: The fibrous scaffolds conferred contact guidance to the seeded tenocytes, which could be visually assessed from SEM micrographs. Cells cultured on both the aligned fibres and 3D bundles demonstrated cell alignment parallel to the fibres??? orientation; whereas randomly oriented fibres resulted in cells??? spreading over the fibres in varying directions. These results demonstrate a need for appropriate scaffold biomimicry when aiming to recreate the cells??? natural environment. Mechanical loading of the scaffolds demonstrated 3D bundles (Modulus 9.05(??2.55)MPa; Tensile strength 3.32(??0.67)MPa) to have superior tensile properties compared to aligned (Modulus 4.84(??0.13)MPa; Tensile strength 1.30(??0.14)MPa) and random (Modulus 1.54(??0.26)MPa; Tensile strength 0.45(??0.09)MPa) fibrous scaffolds. The data highlights a clear difference in tensile properties depending on fibre orientation and whether the scaffold is a 2D fibrous mat or 3D fibrous bundle. We have developed a technique to electrospin aligned, degradable 3D nanofibrous scaffolds, which mimic the morphology of natural tendon and stimulate tendon cells to secrete new tissue of appropriate organisation and composition.References[1] Sharma P, et al. The Surgeon, 2005, 3(5)[2] Kidoaki S, et al. Biomaterials, 2005, 26:37-46 [3] Smith, RKW, et al. Comparative Biochemistry and Physiology Part A, 2002, 133:1039???1050[4] Miedema HS, et al. Rheumatology 1998, 37(5):555-561[5] Maffulli N, et al. J R Soc Med 2004, 97(10):472-476[6] Sahoo S, et al. Tissue Engineering 2006, 12(1):91-9.