Currently, there are no effective clinical or experimental treatments to fully restore the function of the torn acetabular labrum. To fill the gap, here, we report the finding of progenitor cells in labral tissue, which can be recruited and stimulated to repair torn acetabular labral tissue. This study aimed to develop a biomolecule releasing bioadhesive which can speed up labral tissue healing by eliciting autologous labral progenitor cellular responses. A click chemistry‐based bioadhesive, capable of releasing biomolecules, was synthesized to exert ~3× adhesion strength compared with fibrin glue. Via the release of platelet‐derived growth factor (PDGF), the adhesive was shown to actively recruit and stimulate the proliferation of labral progenitor cells to the tear sites and within the adhesive. Finally, the ability of this biomolecules‐releasing adhesive designed to promote labral tissue regeneration was evaluated using discarded human acetabular labrum tissue compared with surgical suture ex vivo. Histological analysis shows that PDGF‐releasing bioadhesive yielded significantly more labrum cell responses and extracellular matrix protein (proteoglycan and collagen) production at the tear tissue site than surgical suture controls. The results confirm that the new PDGF‐releasing bioadhesive can activate the responses of autologous labral progenitor cells to significantly improve labral tissue regeneration. Clinical significance: These PDGF‐releasing bioadhesives may serve as a new and effective tool for repairing and regenerating acetabular labrum tears.

A fraction of the OA patient population is affected by post-traumatic osteoarthritis (PTOA) following acute joint injuries. Stopping or reversing the progression of PTOA following joint injury could improve long-term functional outcomes, reduced disability, and medical costs. To more effectively treat articular cartilage injury, we have developed a novel cell-based therapy that involves the pre-targeting of apoptotic chondrocytes and the delivery of healthy, metabolically active chondrocytes using click chemistry. Specifically, a pre-targeting agent was prepared via conjugating apoptotic binding peptide (ApoPep-1) and trans-cyclooctene (TCO) onto polyethylene glycol (PEG) polymer carrier. The pre-targeting agent would be introduced to injured areas of articular cartilage, leading to the accumulation of TCO groups on the injured areas from actively binding to apoptotic chondrocytes. Subsequently, methyltetrazine (Tz)-bearing chondrocytes would be immobilized on the surface of TCO-coated injured cartilage via Tz-TCO click chemistry reaction. Using an ex vivo human cartilage explant PTOA model, the effectiveness of this new approach was evaluated. Our studies show that this novel approach (Tz-TCO click chemistry) significantly enhanced the immobilization of healthy and metabolically active chondrocytes to the areas of apoptotic chondrocytes. Histological analyses demonstrated that this treatment regimen would significantly reduce the area of cartilage degeneration and enhance ECM regeneration. The results support that Tz-TCO click chemistry-mediated cell delivery approach has great potential in clinical applications for targeting and treatment of cartilage injury.

Background: The healing capacity of the human glenoid labrum varies by tear location. Current evidence suggests that the healing capacity of meniscal and cartilage injuries relates to cellular composition and vascularity. However, little is known about the histological characteristics of the glenoid labrum and how they may affect healing potential in specific anatomic regions. Hypothesis: Regenerative characteristics of the glenoid labrum differ based on the anatomic region. Study Design: Descriptive laboratory study. Methods: Human glenoid labra from fresh unpreserved cadavers were transversely sectioned in different anatomic regions. Masson trichrome stain was used to determine dense and loose extracellular matrix regions and vessel densities. Hematoxylin and eosin, Ki-67+, and CD90+/CD105+ stains were performed to determine total, proliferative, and progenitor cell densities, respectively. Regression models demonstrated relationships between vascular area, progenitor cell quantity, and probability of successful operation. Results: Among all labral aspects, the superior glenoid labrum had the highest percentage (56.8% ± 6.9%) of dense extracellular matrix or avascular tissue ( P < .1). The vascular region of the superior labrum had the fewest total cells (321 ± 135 cells/mm2; P < .01) and progenitor cells (20 ± 4 cells/mm2; P < .001). Vascular area was directly correlated with progenitor cell quantity ( P = .006002). An increase in probability of successful operation was associated with a linear increase in vascular area ( R2 = 0.765) and an exponential increase in progenitor cell quantity ( R2 = 0.795). Subsequently, quadratic models of vascularity and progenitor cell quantity around the labral clock were used to assess relative healing potential. Quadratic models for percentage vascular area ( P = 6.35e-07) and weighted progenitor cell density ( P = 3.03e-05) around the labral clock showed that percentage vascular area and progenitor cell quantity increased as labral tissue neared the inferior aspect and diminished near the superior aspect. Conclusion: Anatomic regions of the glenoid labrum differ in extracellular matrix composition, vascularity, and cell composition. The superior glenoid labrum is deficient in vascularity and progenitor cells, which may explain the high failure rates for repairs in this location. Clinical Relevance: Improved understanding of the composition of distinct glenoid labral positions may help to improve therapeutic strategies for labral pathology.

Glenoid labral tears occur with repetitive dislocation events and are common injuries observed in shoulder arthroscopic procedures. Although surgery can restore shoulder anatomy, repair is associated with poor clinical outcomes, which may be attributed to the poor regenerative capability of glenoid labral fibrocartilage. Thus, this study was designed to assess whether in situ tissue regeneration via biomolecule‐stimulated recruitment of progenitor cells is a viable approach for the regeneration of labral tears. We developed a click chemistry‐based bioadhesive to improve labral repair and reduce local inflammatory responses due to trauma. Additionally, we previously identified the presence of progenitor cells in the human labrum, which can be recruited by platelet‐derived growth factor (PDGF). Thus, we hypothesized that PDGF‐releasing adhesives could induce the regenerative responses of progenitor cells at the injury site to improve labral healing. In a rat glenoid labral tear model, we evaluated the effect of PDGF‐releasing adhesives on promoting progenitor cells to participate in labral tear healing. After 3 and 6 weeks, the labrum was histologically analyzed for inflammatory responses, progenitor cell recruitment, proliferation, and extracellular matrix (ECM) production (collagen and glycosaminoglycan). Our results showed that adhesives alone considerably reduced local inflammatory responses and labral tissue dissolution. PDGF‐releasing adhesives significantly increased progenitor cell recruitment, proliferation, and ECM production. These results demonstrate that by accelerating autologous progenitor cell responses, PDGF‐releasing adhesives represent a novel clinically relevant strategy to improve the healing of glenoid labral tears.