Application of Stem Cell Therapy for ACL Graft Regeneration

Figure 1

Schematic model for graft regeneration after ACL reconstruction. (a) Early stage characterized by necrosis, fiber disintegration, and cytokine release; neutrophils, macrophagocytes, and mesenchymal stem cells (MSC) can be observed in the interface in order, and then macrophagocytes and MSC migrate into the inner tendon. The collagen fibers displayed a bimodal distribution, with large ones constituting the majority; (b) remodeling stage marked with Sharpey fibers (arrow), cell migration, vascularization, ECM remodeling, various growth factor activities, and disordered organization of collagen fibers (bimodal distribution with small ones constituting the majority); (c) ligamentization stage marked with vascularization gradually disappearing, fibrocartilage formation, and ordered collagen with almost unimodal small fibers; (d) normal ACL, 4-layer direct insertion including ligament, fibrocartilage, mineralized fibrocartilage, and bone in order. The collagen fibers showed unclear bimodal distribution.