Use of ultra-high molecular weight polycaprolactone scaffolds for ACL reconstruction

Abstract

Previously, we reported on the implantation of electrospun polycaprolactone (PCL) grafts for use in ACL tissue engineering in a small animal model. In the present study, we hypothesized that grafts fabricated from ultra-high molecular weight polycaprolactone (UHMWPCL) would have similarly favorable biologic properties but superior mechanical properties as compared to grafts fabricated from PCL. Two forms of polycaprolactone were obtained (UHMWPCL, MW ¼ 500 kD, and PCL, MW ¼ 80 kD) and electrospun into scaffolds that were used to perform ACL reconstruction in 7-8 week old male Lewis rats. The following groups were examined: UHMWPCL, PCL, flexor digitorum longus (FDL) allograft, native ACL, as well as sham surgery in which the ACL was transsected. At 16 weeks post-operatively, biomechanical testing, histology, and immunohistochemistry (IHC) were performed. Analysis of cellularity indicated that there was no significant difference among the UHMWPCL, PCL, and FDL allograft groups. Quantification of birefringence from picrosirius red staining demonstrated significantly more aligned collagen fibers in the allograft than the PCL group, but no difference between the UHMWPCL and allograft groups. The peak load to failure of the UHMWPCL grafts was significantly higher than PCL, and not significantly different from FDL allograft. This in vivo study establishes the superiority of the higher molecular weight version of polycaprolactone over PCL as a scaffold material for ACL reconstruction. By 16 weeks after implantation, the UHMWPCL grafts were not significantly different from the FDL allografts in terms of cellularity, peak load to failure, stiffness, and collagen fiber alignment. ß

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

“…Similarly, Bosworth et al reported that tightly wound PCL yarn could be utilized as a substrate for tendon fibroblast adhesion and proliferation 37 . Modifications to traditional PCL have also been investigated as materials for ligament scaffolds, particularly ultra-high molecular weight PCL (UHMWPCL) and PCL with the addition of L-lactic acid (PCLC) with promising results 38,39 . In the current study, a scaffold composed of multiple nanofiber bundles was created to better mimic the hierarchal structure of the collagen in the native ACL on macro, micro, and nano size scales, and provide space for matrix deposition between and around the nanofiber bundles.…”

Mechanical Considerations for Electrospun Nanofibers in Tendon and Ligament Repair

“…There are many factors that influence the degradation properties of polymers such as crystalline structure [222] and molecular weight [223] , which have both been reported to slow degradation of electrospun meshes when these properties are higher. Consideration of such factors are important for electrospun nanofiber scaffold design especially because the crystalline structure of electrospun nanofibers is sensitive to many different processing conditions such as solvent, fiber diameter [80] , and collector type/configuration [224] .…”

Current Status of Tissue-engineered Scaffolds for Rotator Cuff Repair

“…26, 27 Poly (ε-caprolactone) (PCL) generally has a lower elastic modulus than PGA, PLA or PLGA blends, 28 but strain at failure is greater, and degradation kinetics are slower than PGA, PLA or PLGA blends. Recently ultra-high molecular weight PCL has been reported to be comparable to anterior cruciate ligament allografts in the rat, 29 and this polymer may prove to be useful for rotator cuff tendon tissue engineering. While 6-hydroxylcaproic acid is produced as an intermediate of hydrolysis during degradation of PCL, no osteolysis has been identified in long term implantation studies in animal models, and PCL is currently one of the most widely used polymers in the field of tissue engineering.…”