Three-dimensionally printed recombinant human parathyroid hormone-soaked nanofiber sheet accelerates tendon-to-bone healing in a rabbit model of chronic rotator cuff tear.

BACKGROUND

Recombinant human parathyroid hormone (rhPTH) promotes tendon-to-bone healing in humans and animals with rotator cuff tear (RCT). However, problems regarding repeated systemic rhPTH injections in humans exist. This study was conducted to evaluate the effect of topical rhPTH administration using 3-dimensionally (3D) printed nanofiber sheets on tendon-to-bone healing in a rabbit RCT model compared to that of direct topical rhPTH administration.

METHODS

Eighty rabbits were randomly assigned to 5 groups (n = 16 each). To create the chronic RCT model, we induced complete supraspinatus tendon tears in both shoulders and left them untreated for 6 weeks. All transected tendons were repaired in a transosseous manner with saline injection in group A, hyaluronic acid (HA) injection in group B, 3D-printed nanofiber sheet fixation in group C, rhPTH and HA injection in group D, and 3D-printed rhPTH- and HA-soaked nanofiber sheet fixation in group E. Genetic (messenger RNA expression evaluation) and histologic evaluations (hematoxylin and eosin and Masson trichrome staining) were performed in half of the rabbits at 4 weeks postrepair. Genetic, histologic, and biomechanical evaluations (mode of tear and load to failure) were performed in the remaining rabbits at 12 weeks.

RESULTS

For genetic evaluation, group E showed a higher collagen type I alpha 1 expression level than did the other groups (P = .008) at 4 weeks. However, its expression level was downregulated, and there was no difference at 12 weeks. For histologic evaluation, group E showed greater collagen fiber continuity, denser collagen fibers, and more mature tendon-to-bone junction than did the other groups (P = .001, P = .001, and P = .003, respectively) at 12 weeks. For biomechanical evaluation, group E showed a higher load-to-failure rate than did the other groups (P < .001) at 12 weeks.

CONCLUSION

Three-dimensionally printed rhPTH-soaked nanofiber sheet fixation can promote tendon-to-bone healing of chronic RCT.