Tissue-engineered augmentation of a rotator cuff tendon using a reconstituted collagen scaffold: a histological evaluation in sheep

Abstract

To determine if an absorbable collagen scaffold of high porosity would allow rapid tissue in-growth and permit the functional maturation and alignment of tendon-like tissue, scaffolds were sutured to the superficial surface of the infraspinatus tendons of adult sheep. Histology demonstrated complete ingrowth with fibrovascular tissue by 6 weeks and by 12 weeks the scaffold had induced the formation of a layer of dense, regularly-oriented collagenous tissue which significantly increased the thickness of the native tendon. This new tissue was well-integrated into the host tissues at both the bone interface and along the length of the tendon. At 26 weeks the scaffold was completely absorbed leaving a stable layer of mature tendon-like tissue over the surface of the host tendon which was still present at 52 weeks. The use of a reconstituted collagen scaffold consistently increased the thickness of a rotator cuff tendon by inducing the formation of a well-integrated and mature tendon-like tissue.

Keywords: collagen scaffold; histology; rotator cuff; sheep; tendon.

Figure 1.

(A) Scanning electron micrograph of the cross-section of a cryofractured reconstituted collagen scaffold. Bar=500 microns, original magnification=50×. (B) Histological section of the collagen scaffold prior to implantation. H&E, original magnification=50×. (C) Photograph of the collagen scaffold prior to implantation.

Figure 2.

Operative view of the reconstituted collagen scaffold sutured to the superior surface of the infraspinatus tendon. Scaffold size=15×30 mm.

Figure 3.

At 6 weeks after implantation the porosity of the collagen scaffold (CS) was fully ingrown with new fibrovascular tissue (fibroblasts, blood vessels, and matrix). NT=New Tissue. No inflammatory or foreign body reaction. H&E, original magnification=100×.

Figure 4.

New tissue induced by the collagen scaffold at 12 weeks after implantation. (A) Gross photograph of the new tissue (NT) on top of the tendon (T). The squares indicate areas that are shown histologically in Panels B, C, and D. (B) Regularly-oriented collagen fibers in the area of the square on the left in Panel A. No inflammatory or foreign body reaction. H&E, original magnification=100×. (C) Interface between the new tissue (NT) and the tendon (T) in the area of the square on the right in Panel A showing continuity of collagen fibers between the new tissue and the underlying tendon. No inflammatory or foreign body reaction. H&E, original magnification=100×. (D) Polarized light image of Panel C.

Figure 5.

Interface of the new tissue with bone at 12 weeks after implantation. (A) Integration of the new tissue (NT) into the native bone (NB). No inflammatory or foreign body reaction. H&E, original magnification=100×. (B) Polarized light image of Panel A. Arrows indicate Sharpey’s fibers at the interface of the new tissue with the native bone.

Figure 6.

At 26 weeks after implantation the new tissue consisted of well-organized connective tissue. The collagen scaffold was completely absorbed by 26 weeks. No inflammatory or foreign body reaction. H&E, original magnification=50×.

Figure 7.

(A) At 26 weeks after implantation the new tissue (NT) was well-integrated with the native bone (NB) with a layer of fibrocartilage (FC) at the bone interface. No inflammatory or foreign body reaction. H&E, original magnification=50×. (B) Polarized light image of Panel A.

Figure 8.

At 52 weeks after implantation the new tissue consisted of well-organized connective tissue that was well-integrated with the underlying tendon. No inflammatory or foreign body reaction. H&E, original magnification=100×.