Characterization of the structure of rabbit anterior cruciate ligament and its stem/progenitor cells

Background It is known that anterior cruciate ligament (ACL) of the knee joint is prone to injuries with poor healing potential. The healing capacity of a tissue‐like ACL is dependent on its structural components and the properties of the stem cells (SCs). Therefore, this study aimed to characterize the structure of ACL tissue and the properties of the SCs derived from the tissue components. Methods The tissue structure of rabbit ACL was determined using a scanning electron microscope, hematoxylin and eosin, and immunohistochemical staining. The biological properties of SCs derived from the structural components of ACL were studied by colony formation, cell proliferation assay, SC marker expression and collagen exhibition, and multidifferentiation potential. Results The two distinct components of ACL are classified as sheath and core, which possess differential properties in terms of collagen type, organization, and presence of blood vessels. The sheath tissue contains vascular SCs and the core tissue contains ligamentous SCs, respectively. The two types of SCs differ in clonogenicity, proliferation, and multidifferentiation potential. Conclusion This study shows that ACL consists of sheath and core tissues, which contain sheath and core SCs with distinctive biological properties. These findings highlight the need for use of both sheath and core SCs to promote the repair of the complex structure of injured ACL. Rabbit anterior cruciate ligament sheath and core tissues possess differential properties in terms of collagen type, organization, and presence of blood vessels. The sheath tissue contains vascular stem cells (SCs) and the core tissue contains ligamentous SCs, respectively. The two types of SCs differ in clonogenicity, proliferation, and multidifferentiation potential.