Cells from a GDF5 origin produce zonal tendon‐to‐bone attachments following anterior cruciate ligament reconstruction

Abstract

Following anterior cruciate ligament (ACL) reconstruction surgery, a staged repair response occurs where cells from outside the tendon graft participate in tunnel integration. The mechanisms that regulate this process, including the specific cellular origin, are poorly understood. Embryonic cells expressing growth and differentiation factor 5 (GDF5) give rise to several mesenchymal tissues in the joint and epiphyses. We hypothesized that cells from a GDF5 origin, even in the adult tissue, would give rise to cells that contribute to the stages of repair. ACLs were reconstructed in Gdf5-Cre;R26R-tdTomato lineage tracing mice to monitor the contribution of Gdf5-Cre;tdTom + cells to the tunnel integration process. Anterior−posterior drawer tests demonstrated 58% restoration in anterior−posterior stability. Gdf5-Cre;tdTom + cells within the epiphyseal bone marrow adjacent to tunnels expanded in response to the injury by 135-fold compared with intact controls to initiate tendon-to-bone attachments. They continued to mature the attachments yielding zonal insertion sites at 4 weeks with collagen fibers spanning across unmineralized and mineralized fibrocartilage and anchored to the adjacent bone. The zonal attachments possessed tidemarks with concentrated alkaline phosphatase activity similar to native entheses. This study established that mesenchymal cells from a GDF5 origin can contribute to zonal tendon-to-bone attachments within bone tunnels following ACL reconstruction.

Functional biomaterials for tendon/ligament repair and regeneration

“…Adipose stem cells (ASCs) induced by growth differentiation factor 5 (GDF-5) promote tissue regeneration and differentiation [ 181 ]. Chen et al .…”

Development and maintenance of tendons and ligaments

“…Although cells intrinsic to the adult enthesis have poor capacity for repair, recent studies in mice suggest that extrinsic cells from the adjacent bone and tendon are a source of ESPCs during enthesis healing. Following enthesis reconstruction surgery, in which tendon grafts are inserted into bone tunnels, Gdf5-lineage cells from the underlying bone proliferate, infiltrate the tendon graft, and give rise to a zonal tendon-bone attachment (Hagiwara et al, 2020) (Fig. 5).…”

Distinct Inflammatory Macrophage Populations Sequentially Infiltrate Bone‐to‐Tendon Interface Tissue After Anterior Cruciate Ligament (ACL) Reconstruction Surgery in Mice

“…( 31 , 32 , 33 ) A key aspect of healing is bone formation that occurs within or extends from underlying bone into the fibrovascular interface tissue. ( 31 , 34 , 35 , 36 , 37 ) The interface tissue matures over the subsequent 3 weeks to become a more dense and organized fibrous tissue, with diminished cellularity and vascularity, and continuity of collagen fibers between bone and tendon. Close apposition of bone and tendon (ie, less intervening interface tissue) provides increased attachment strength and more secure healing.…”