Abstract
Summary Statement
A novel biomimetic polydioxanone tendon patch with woven and electrospun components is biocompatible, recapitulates native tendon architecture and creates a tissue-healing microenvironment directed by a subpopulation of regenerative macrophages. The woven component provides tensile strength while the tendon heals.
Introduction
There is great interest in the use of biomimetic devices to augment tendon repairs. Ideally, implants improve healing without causing adverse local or systemic reactions. Biocompatibility remains a critical issue prior to implantation into humans, as some implants elicit a foreign body response (FBR) involving inflammation, poor wound healing and even fistulae formation. Additionally, the effect on articular cartilage locally or systemically with placement of a juxta-articular implant has not been examined. The purpose of this study is to test the in vivo biocompatibility of a novel hybrid woven and electrospun polydioxanone patch in a rat tendon transection model.
Patients and Methods
Sixty Lewis rats were divided into 4 groups in which the infraspinatus was surgically transected 3 mm from its insertion. Tendons were repaired with a woven and electrospun polydioxanone patch (PDOe) and 5-0 Prolene sutures. Vicryl and Silk patches or a simple Prolene suture repair served as comparators. Animals were sacrificed at 1, 2, 4, 6 and 12 weeks to examine the biocompatibility of the implants. Immunohistochemistry was used to examine macrophage subpopulations and hematoxylin and eosin staining was used to assess foreign-body giant cells and both analyzed with a one-way ANOVA with significance set at p<.05. Articular cartilage was scrutinised with semi-quantitative analysis. Hind paw inflammatory indices were used to determine the systemic effects and biomechanical testing the tensile strength of the materials over time.
Results
The PDOe patch remained grossly quiescent at all time-points. There was a severe inflammatory reaction to Vicryl at one and 2-week time-points with gross exudate. Silk patches were associated with larger fibrous capsules at each time point. There were no adverse systemic effects and articular cartilage remained normal with no differences between materials to controls. Immunohistochemistry showed a significantly higher ratio of regenerative to inflammatory macrophages for the PDOe patch compared to other constructs at each time-point and similar to controls. Silk and Vicryl patches had a greater than 10-fold increase in foreign-body giant cells compared to the PDOe patch and controls (p<.05) suggesting incorporation rather than rejection and walling off of the biomaterial. Tensile strength of the PDOe patch increased in the first 2 weeks to greater than 90 N and gradually declined to a mean of 22 N at 12 weeks.
Discussion/Conclusion
The novel PDOe patch appears to be biocompatible and illicit very little FBR in this rat tendon injury model. Importantly, there was no joint reaction to the biomaterial which has not been addressed previously. We believe the electrospun component of the patch recapitulates native tendon architecture creating a tissue healing microenvironment directed by a regenerative macrophage subpopulation. These results corroborate earlier in vitro work that showed incorporation of tenocytes within the electrospun scaffold. The woven component of the scaffold provides tensile strength as the tendon heals and begins to degrade after healing is underway making it less likely to elicit a FBR. Based on these and earlier in vitro data we believe this implant shows excellent biocompatibility and is ready to proceed to human trials.
