Vascularization and biocompatibility of poly(ε-caprolactone) fiber mats for rotator cuff tear repair

Rotator cuff tear is the most frequent tendon injury in the adult population. Despite current improvements in surgical techniques and the development of grafts, failure rates following tendon reconstruction remain high. New therapies, which aim to restore the topology and functionality of the interface between muscle, tendon and bone, are essentially required. One of the key factors for a successful incorporation of tissue engineered constructs is a rapid ingrowth of cells and tissues, which is dependent on a fast vascularization. The dorsal skinfold chamber model in female BALB/cJZtm mice allows the observation of microhemodynamic parameters in repeated measurements in vivo and therefore the description of the vascularization of different implant materials. In order to promote vascularization of implant material, we compared a porous polymer patch (a commercially available porous polyurethane based scaffold from Biomerix™) with electrospun polycaprolactone (PCL) fiber mats and chitosan-graft-PCL coated electrospun PCL (CS-g-PCL) fiber mats in vivo. Using intravital fluorescence microscopy microcirculatory parameters were analyzed repetitively over 14 days. Vascularization was significantly increased in CS-g-PCL fiber mats at day 14 compared to the porous polymer patch and uncoated PCL fiber mats. Furthermore CS-g-PCL fiber mats showed also a reduced activation of immune cells. Clinically, these are important findings as they indicate that the CS-g-PCL improves the formation of vascularized tissue and the ingrowth of cells into electrospun PCL scaffolds. Especially the combination of enhanced vascularization and the reduction in immune cell activation at the later time points of our study points to an improved clinical outcome after rotator cuff tear repair.