Category: Hindfoot Introduction/Purpose: Entheses have a special fibrocartilage transition zone where tendons and ligaments attach to bone. Enthesis injury is very common, and the reattachment of tendon to bone is a great challenge because healing takes place between a soft tissue (tendon) and a hard tissue (bone). We have now developed a kartogene (KGN)-containing polymer scaffold (KGN-P) that can precisely deliver KGN to damaged enthesis area. The effects of the KGN-containing polymer on the healing of wounded TBJ were investigated in vitro and in vivo. Methods: The proliferation and chondrogenesis of rat Achilles tendon stem cells (TSCs) grown in four conditions were measured: normal medium (Control); normal medium with 100 nM KGN (KGN); lysine diisocyanate (LDI)-glycerol scaffold with normal medium (LDI-P); LDI-glycerol-KGN scaffold with normal medium (KGN-P).A wound (1 mm) was created on each hind leg Achilles enthesis of all 8 rats (3 months old). The wounds were then treated either with 10 ul saline (Wound); or 10 ul of 10 uM KGN (KGN); or LDI polymer scaffold (LDI-P); or KGN-containing polymer scaffold (KGN-P). The rats were sacrificed on day 15 and 30 post-surgery, and their Achilles entheses were collected for gross inspection and histochemical analysis. Results: KGN-containing polymers have sponge-like structures (Fig. 1A-D), and release KGN in a time- and temperature-dependent manner (Fig. 1E). KGN-P scaffold induced chondrogenesis of TSCs (Fig. 2D, 2H) without changing cell proliferation (Fig. 2I), and enhanced fibrocartilage-like tissue formation (Fig. 3E). KGN (Fig. 3C) and LDI-P (Fig. 3D) treated groups exhibited unhealed wound areas as in saline group (Fig. 3B). Finally, KGN-P and KGN treated rat TSCs underwent chondrogenesis by upregulating collagen II, aggrecan, and SOX-9 expression (Fig. 3F). Conclusion: Our results showed that KGN-containing polymer scaffold enhanced wounded enthesis healing by inducing TSC chondrogenesis and promoting the formation of the fibrocartilage in the wound site. The KGN-P may be used for regeneration of wounded entheses in clinical settings. Future research will focus on optimizing KGN concentration and releasing rate in the polymer scaffold during enthesis healing.
Viscoelastic properties of the Achilles tendon in vivo