Repair of Tendon Defect with Dermal Fibroblast Engineered Tendon in a Porcine Model

Abstract

Harvesting autologous tenocytes for tendon engineering may cause secondary tendon defect at the donor site. Dermal fibroblasts are an easily accessible cell source and do not cause major donor site defect. This study aims to explore the possibility of tendon engineering using dermal fibroblasts. A total of 45 hybrid pigs were randomly divided into three groups: experimental group (n = 15)--repair of tendon defect with a dermal fibroblast engineered tendon; control group 1 (n = 15)--repair of defect with a tenocyte engineered tendon; and control group 2 (n = 15)-repair of defect with a scaffold alone. Both autologous dermal fibroblasts and tenocytes were seeded on polyglycolic acid (PGA) unwoven fibers to form a cell-scaffold construct and cultured in vitro for 7 days before in vivo implantation to repair a defect of flexor digital superficial tendon. Specimens were harvested at weeks 6, 14, and 26 for gross, histological, and mechanical analyses. Microscopy revealed good attachment of both dermal fibroblasts and tenocytes on PGA fibers and matrix production. In vivo results showed that fibroblast and tenocyte engineered tendons were similar to each other in their gross view, histology, and tensile strength. At 6 weeks, parallel collagen alignment was observed at both ends, but not in the middle in histology, with more cellular components than natural tendons. At weeks 14 and 26, both engineered tendons exhibited histology similar to that of natural tendon. Collagens became parallel throughout the tendon structure, and PGA fibers were completely degraded. Interestingly, dermal fibroblast and tenocyte engineered tendons did not express type III collagen at 26 weeks, which remained observable in normal pig skin and control group 2 tissue using polarized microscopy, suggesting a possible phenotype change of implanted dermal fibroblasts. Furthermore, both fibroblast and tenocyte engineered tendons shared similar tensile strength, about 75% of natural tendon strength. At 6 weeks in control group 2, neo-tissue was formed only at the peripheral area by host cells. A cord-like tissue was formed at weeks 14 and 26. However, the formed tissue was histologically disorganized and mechanically weaker than both cell-engineered tendons (p < 0.05). These results suggest that dermal fibroblasts may have the potential as seed cells for tendon engineering.

Substrate topography: A valuable in vitro tool, but a clinical red herring for in vivo tenogenesis

“…Further, in a subcutaneous model, none of the substrates induced cellular orientation parallel to the direction of the substrate topography. It is tempting to hypothesise that two-dimensional imprinted substrates are overwhelmed with body fluids and protein adsorption upon implantation, prohibiting favourable cell / material interaction at the substrate-tissue nano-biointerface and that three-dimensional fibrous constructs are more effective for directional neural [77][78][79], tendon [29,35,80], bone [81][82][83] and skin [84][85][86] neotissue formation and promote relatively enhanced cell growth, motility, matrix deposition and neotissue growth through the provision of a true three-dimensional environment.…”

“…electro-spinning [26][27][28][29][30][31], fibre extrusion [32][33][34][35], isoelectric focusing [36,37] and imprinting [38][39][40]) have been at the forefront of scientific and technological research and innovation to recapitulate native tendon extracellular matrix (ECM) supramolecular assemblies. Although fibrous constructs (e.g.…”

The past, present and future in scaffold-based tendon treatments

“…Porcine dermal fibroblasts and TCs loaded on PLGA electro-spun fibres have been shown to promote tenogenic function in vitro and improved healing, as evidenced by improved gross morphology, histological analysis and biomechanical properties, in vivo [413][414][415][416]. In conjugation with BMSCs, electro-spun PLGA scaffolds have demonstrated suppression of lymphocytes in vitro and improved biomechanical properties and acceptable integration into the native tendon tissue [417].…”

Development of Novel Biodegradable Polymer Scaffolds for Vascular Tissue Engineering

“…Nonwoven PGA meshes have been used extensively by our group 15,16 and others to culture engineered vessels and other tissues such as cartilage, 18 skin, 19 tendon, and ligaments. 20,21 However, PGA-based tissues often contain polymer fragments at the end of culture. 15,16,22,23 To achieve a goal of creating biological connective tissues with minimal to no synthetic polymeric fragments in the final product, and hence maximal mechanical properties, there was an obvious need for a scaffold that degrades very rapidly, and yet supports cellular adhesion and collagenous matrix deposition.…”