Histological characteristics of ligament healing after bio-enhanced repair of the transected goat ACL

Abstract

BackgroundRecently, healing of a ruptured anterior cruciate ligament (ACL) is reconsidered. In a previous study, we have shown that the transected ACL can heal after treatment with the triple X locking suture alone or combined with small intestine submucosa (SIS). The first research question of this study was whether the healing ACLs in both groups show histological characteristics that are typical for ligament healing. Secondly, did the combined treatment with SIS lead to improved histological healing, in terms of the morphology of the fibrous synovial layer, the extracellular matrix (ECM), collagen fiber orientation, cellularity, ratio of myofibroblasts, and collagen type 3 staining. The hypothesis was that SIS enhances the healing by the scaffolding effect, endogenous growth factors, and chemoattractants.MethodsIn the Suture group, the left ACL was transected and sutured with the triple X locking suture repair technique. In the Suture-SIS group, the left ACL underwent the same procedure with the addition of SIS. The right ACL served as internal control. Standard histology and immunostaining of α-smooth muscle actin (SMA) and collagen type 3 were used.ResultsMicroscopy showed that the fibrous synovial layer around the ACL was reestablished in both groups. The collagen fibers in the Suture-SIS group stained denser, were more compactly arranged, and the ECM contained fewer voids and fat vacuoles. Neovasculature running between the collagen fibers was observed in both experimental groups. Collagen type 3 stained less in the Suture-SIS group. The cellularity in the Suture group, Suture-SIS group and Control was 1265 ± 1034 per mm2, 954 ± 378 per mm2, 254 ± 92, respectively; 49%, 26% and 20% of the cells stain positive for α-SMA, respectively.ConclusionThe healing ACL in both treated groups showed histological characteristics which are comparable to the spontaneously healing medial collateral ligament and showed that the ACL has a similar intrinsic healing response. Though, no definitive conclusions on the beneficial effects of the SIS scaffold on the healing process can be made.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model

“…Histologic features of the ACL healing response after experimental transection, followed or not by surgery, are only scarcely described in the literature. Collagen fibers mild disorganization, decreased presence of voids and fat vacuoles, spindle-shaped fibroblasts, and neovascularization (assessed in the present study, respectively, through cystic changes, chondroid metaplasia, and inflammation criteria) were previously identified as healing response features in transected ACLs, 12 weeks after suture alone or combined with augmentation using small intestine submucosa [56]. Interestingly, neovascularization is sometimes considered as a healing, or as a degenerative pattern of ACL.…”

“…Some authors allocated the absence of spontaneous ACL healing to the gap formed between the ACL ends and subsequent interposition of synovial fluid, which impair the possibility of a guided regeneration process [5]. Indeed, healing of ACL remnants has been previously observed on histology 12 weeks after surgery in a goat model of mid-substance transection followed by locking suture, alone or combined with small intestine submucosa [56]. Some authors suggested spontaneous healing capacities of the ruptured ACL when in contact with its surrounding tissues [57].…”

Current Progress in Tendon and Ligament Tissue Engineering

“…In tendon, the resident cells, which consist of tenoblasts and [192] with permission from Springer Nature and Ref. [193]) tenocytes accounted for 90-95% of the cellular components, the rest are chondrocytes, synovial cells and vascular cells [27]. In ligament, the resident cells are made up of ligamentocytes that represent only a small percentage of the total ligament volume [25].…”

Adaptation of Fibril-Reinforced Poroviscoelastic Properties in Rabbit Collateral Ligaments 8 Weeks After Anterior Cruciate Ligament Transection

“…4,6,10,13,25,27,31 Nevertheless, only few studies have reported the physiological and biomechanical alterations of the collateral ligaments within the knee joint following ACLT. 28,35,37,54 Experimental and numerical studies have investigated collateral ligament mechanics following ACLT. For instance, large stresses were measured on the collateral ligaments of human cadaveric knees under weight-bearing conditions after ACLT.…”