Systematic Review of Biological Modulation of Healing in Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Whether biological modulation is effective to promote healing in anterior cruciate ligament (ACL) reconstruction remains unclear. PURPOSE: To perform a systematic review of both clinical and experimental evidence of preclinical animal studies on biological modulation to promote healing in ACL reconstruction. STUDY DESIGN: Systematic review; Level of evidence, 2. METHODS: A systematic search was performed using the PubMed, Ovid, and Scopus search engines. Inclusion criteria were clinical and animal studies involving subjects with ACL injury with the use of biological modulation to promote healing outcomes. Methodological quality of clinical studies was evaluated using the Critical Appraisal Skill Programme (CASP) appraisal tool, and animal studies were evaluated by a scoring system based on a published checklist of good animal studies. RESULTS: Ten clinical studies and 50 animal studies were included. Twenty-five included studies were regarded as good quality, with a methodological score ≥5. These studies suggested that transforming growth factor-beta (TGF-ß), mesenchymal stem cells, osteogenic factors, and modalities that reduce local inflammation may be beneficial to promote graft healing in ACL reconstruction. CONCLUSION: This systematic review suggests that biological modulation is able to promote healing on top of surgical treatment for ACL injuries. This treatment strategy chiefly works through promotion of healing at the tunnel-graft interface, but the integrity of the intra-articular midsubstance of the graft would be another target for biological modulation.

Expression of Wnt pathway mediators in metaplasic tissue in animal model and clinical samples of tendinopathy.

OBJECTIVE: Tissue metaplasia is observed in both ossified failed healing animal model and clinical samples of tendinopathy. The Wnt signalling pathway plays a vital role in pathological calcification. We hypothesized that the Wnt signalling pathway might contribute to tissue metaplasia and failed healing in tendinopathy. This study aimed to examine the spatial-temporal expression of Wnt pathway mediators in an ossified failed tendon healing animal model and clinical samples of tendinopathy. The effect of Wnt3a on the osteogenic differentiation of tendon-derived stem cells (TDSCs) was also examined. METHODS: Ossified failed tendon healing was induced by the injection of collagenase into the patellar tendon of rats. At various times the tendons were harvested for immunohistochemical staining of Wnt3a, ß-catenin, Lrp5 and Tcf1. Patellar tendon samples were obtained from 13 patients with patellar tendinopathy (11 unossified and 2 ossified) and 10 controls. Immunohistochemical staining of Wnt3a, ß-catenin, Lrp5 and Tcf1 was similarly performed. Rat patellar TDSCs were treated with Wnt3a. The osteogenic differentiation of TDSCs was examined by ALP activity, alizarin red S staining and mRNA expression of osteogenic markers. RESULTS: There was increased expression of Wnt3a, ß-catenin, Lrp5 and Tcf1 in the healing fibroblast-like cells, chondrocyte-like cells and ossified deposits in the animal model and in some clinical samples of tendinopathy. Wnt3a increased ALP activity, calcium nodule formation and expression of osteogenic markers in TDSCs. CONCLUSION: Activation of the Wnt signalling pathway and its effect on TDSCs might contribute to tissue metaplasia and failed healing in some cases of tendinopathy.

Expression of chondro-osteogenic BMPs in clinical samples of patellar tendinopathy.

PURPOSE: The pathogenesis of patellar tendinopathy remains unclear. Expression of BMP-2/-4/-7 was reported in an ossified failed tendon healing animal model of patellar tendinopathy. This study aimed to investigate the expression of these chondro-osteogenic BMPs in clinical samples of patellar tendinopathy. METHODS: Patellar tendon samples were collected from 16 consecutive patients with patellar tendinopathy and 16 consecutive controls undergoing anterior cruciate ligament reconstruction with bone-patellar tendon-bone autograft in the authors' hospital after getting their consent. The expression of BMP-2/-4/-7 was examined in all samples using immunohistochemistry. Ossification observed in two tendinopathy samples was characterized by histology, alizarin red S staining, alcian blue staining, TRAP staining and immunohistochemical staining of Sox9, osteopontin (OPN) and osteocalcin (OCN). RESULTS: Regions of hypo- and hyper-cellularity and vascularity, with loss of crimp structure of collagen matrix, were observed in patellar tendinopathy samples. Round cells and in some cases, cells with typical chondrocyte phenotype were observed. For the ossified tendinopathy samples with positive alizarin red S staining, OPN-positive and Sox9-positive chondrocyte-like cells in alcian blue-stained extracellular matrix, OCN-positive osteoblast-like cells and TRAP-positive multi-nucleated cells were observed around the ossified deposits. No expression of BMP-2/-4/-7 was observed in healthy patellar tendons. However, the expression of BMP-2/-4/-7 was observed in all patellar tendinopathy samples with or without ossification. CONCLUSIONS: Clinical samples of patellar tendinopathy showed ectopic expression of BMP-2/-4/-7. This was not evident in control samples from healthy patellar tendons. LEVEL OF EVIDENCE: Prognostic studies, Level III.

Increased deposition of sulfated glycosaminoglycans in human patellar tendinopathy.

OBJECTIVE: To investigate if the increased proteoglycans in patellar tendinopathy involves a qualitative change in the types of proteoglycans. DESIGN: This is an observational study based on the biochemical analysis of proteoglycans. SETTING: : University Teaching Hospital. PATIENTS: Patellar tendon samples from 12 patients with patellar tendinopathy and 12 healthy controls were collected and proteoglycans were extracted for biochemical analyses. All patients fulfilled the diagnostic criteria of having patellar tendinopathy with well-defined clinical features, more than 6 months of insufficient nonoperative treatment including physiotherapeutic modalities, and verification by ultrasound or magnetic resonance imaging. Twelve control subjects, 10 men and 2 women with an average age of 31 years (range 16 to 38 years), represented patients with anterior cruciate ligament deficiency who were operated on using the healthy patellar tendon as an autograft. The control subjects had no previous history or clinical signs of patellar tendon injury. INTERVENTIONS: The independent variable is the presence of pathological conditions of patellar tendinopathy. MAIN OUTCOME MEASUREMENTS: The dependent variables include the electromobility of proteoglycans, staining intensity of proteoglycan core proteins, and the tissue content of glycosaminoglycan disaccharides. RESULTS: The results indicated that the increased proteoglycans in pathological tissues also exhibited qualitative changes as compared to those in healthy patellar tendons. Dermatan monosulfates were significantly increased in the proteoglycans extracted from the pathological tissues of patellar tendinopathy. CONCLUSIONS: Our results indicate that proteoglycans deposited in the pathological tissues of patellar tendinopathy were oversulfated as compared to healthy tendons, which may represent a new pathological attribute for the understanding of chronic pain in patellar tendinopathy.

Increased expression of transforming growth factor-beta1 in patellar tendinosis.

Patellar tendinosis is characterized by longstanding localized and activity-related pain, swelling and tenderness on palpation, and characteristic features on magnetic resonance imaging and ultrasonography and during surgical excision. Histologic examination of tendinosis tissues shows disrupted collagen matrix, increased cellularity, and increased proteoglycan stainability, but lack of inflammatory cell infiltration despite the clinical signs resembling inflammation. Disturbances in inflammatory response may be associated with the development of tendinosis. Expression of cyclooxygenase-2 and transforming growth factor-beta1 were detected in tendinosis, and the in vitro production of prostaglandin E2 by tendinosis and healthy tendon fibroblast cultures also was observed. Eleven patients with patellar tendinosis and 12 control subjects with healthy patellar tendons, but deficient anterior cruciate ligaments, were included in the current study. The percentages of immunopositive cells in tendinosis samples for cyclooxygenase-2 and transforming growth factor-beta1 were 66.75 and 56.40, respectively, which were significantly higher than those of the control subjects (25.15 and 23.06 respectively). Tendinosis fibroblast culture also produced more prostaglandin E2 and active transforming growth factor-beta1. These findings indicate the involvement of prostaglandins and cytokines that may explain the clinical symptoms and nonhealing features of tendinosis.