Limited Added Effect of Proline‐Rich P6 Peptide to Cross‐Linked Hyaluronic Acid After Partial Lateral Meniscectomy in Sheep

This study evaluates whether a proline‐rich P6 peptide provides added benefit to a cross‐linked hyaluronic acid (HA) hydrogel after partial lateral meniscectomy‐associated osteoarthritis‐like change in sheep. The corrected four‐group framework includes Intact no‐surgery/no‐injection reference knees ( n = 7) and 16 surgically injured knees from eight sheep assigned to Mnx (meniscectomy only, n = 4), Mnx + HA ( n = 6), or Mnx + HA + P6 ( n = 6). Mnx + HA and Mnx + HA + P6 knees received intra‐articular injections at Weeks 0, 1, 2, and 4. Osteochondral tissues were evaluated at Week 12 by microCT, H&E scoring, and histochemical/immunohistochemical image analysis. Endpoint‐specific animal‐ or knee‐level models were used, with sheep identity included as a random effect when estimable. HA‐based treatment was associated with favorable trabecular microCT patterns after meniscectomy. However, the primary Mnx + HA + P6 versus Mnx + HA contrast was not significant for percent trabecular bone volume/BV/TV (+1.52 percentage points; 95% CI −2.22 to 5.26; p = 0.427). Histology and IHC/histochemical findings showed selected exploratory tissue‐pattern signals, including collagen‐associated matrix staining, but did not establish consistent peptide‐specific superiority. These findings support cross‐linked HA as an intra‐articular biomaterial platform while defining requirements for confirmatory HA‐peptide hydrogel studies.