Effects of aging on the histology and biochemistry of rat tendon healing

Introduction Tendon diseases and injuries are a serious problem for the aged population, often leading to pain, disability and a significant decline in quality of life. The purpose of this study was to determine the influence of aging on biochemistry and histology during tendon healing and to provide a new strategy for improving tendon healing. Method A total of 24 Sprague-Dawley rats were equally divided into a young and an aged group. A rat patellar tendon defect model was used in this study. Tendon samples were collected at weeks 2 and 4, and hematoxylin-eosin, alcian blue and immunofluorescence staining were performed for histological analysis. Meanwhile, reverse transcription-polymerase chain reaction (RT-PCR) and western blot were performed to evaluate the biochemical changes. Results The histological scores in aged rats were significantly lower than those in young rats. At the protein level, collagen synthesis-related markers Col-3, Matrix metalloproteinase-1 and Metallopeptidase Inhibitor 1(TIMP-1) were decreased at week 4 in aged rats compared with those of young rats. Though there was a decrease in the expression of the chondrogenic marker aggrecan at the protein level in aged tendon, the Micro-CT results from weeks 4 samples showed no significant difference(p>0.05) on the ectopic ossification between groups. Moreover, we found more adipocytes accumulated in the aged tendon defect with the Oil Red O staining and at the gene and protein levels the markers related to adipogenic differentiation. Conclusions Our findings indicate that tendon healing is impaired in aged rats and is characterized by a significantly lower histological score, decreased collagen synthesis and more adipocyte accumulation in patellar tendon after repair.

Decellularized Human Umbilical Cord Wharton Jelly Scaffold Improves Tendon Regeneration in a Rabbit Rotator Cuff Tendon Defect Model

Background: Owing to limited self-healing capacity, failure of rotator cuff tendon healing is a common complication after surgery. Biological scaffolds have garnered attention owing to their potential to enhance healing outcomes. Purpose: To verify the effect of the decellularized umbilical cord Wharton jelly (DUCWJ) scaffold as a bridging scaffold in a rabbit model of acute rotator cuff tendon defect. Study Design: Controlled laboratory study. Methods: We fabricated a DUCWJ scaffold using a physicochemical decellularized method, evaluating changes in the umbilical cord Wharton jelly before and after decellularization. Scanning electron microscopy and biomechanical testing were performed to determine the microstructure and mechanical properties. We assessed cytocompatibility and cell regulatory behavior of the scaffold toward tendon stem/progenitor cells (TSPCs). A supraspinatus tendon defect was created in 54 New Zealand White rabbits, allocated to the DUCWJ scaffold repair group and the negative control group (without scaffold). Histology, reverse transcription polymerase chain reaction, and biomechanical tensile strength were assessed at 4, 8, and 12 weeks postoperatively. Results: Decellularization completely removed cells from the umbilical cord Wharton jelly, retained a considerable amount of glycosaminoglycan and collagen, and preserved the microstructure and tensile strength. The DUCWJ scaffold facilitated migration and proliferation of TSPCs in vitro. Tendon-related gene expression revealed that the DUCWJ scaffold could maintain the tenocyte phenotype of TSPCs. In the in vivo study, the DUCWJ scaffold improved tendon healing and enhanced the biomechanical strength of repaired tendons. Histological evaluation scores of the DUCWJ group were significantly higher than those of the negative control at 4, 8, and 12 weeks after surgery ( P < .05). In repaired tendon tissues, reverse transcription polymerase chain reaction findings revealed that the DUCWJ scaffold stimulated tendon development and maturation. Furthermore, an overall increase in ultimate load and tensile modulus was noted over time; the DUCWJ group presented better results than the negative control group ( P < .05). Conclusion: The DUCWJ scaffold has an excellent 3-dimensional porous structure, good biocompatibility, and fundamental biomechanical characteristics, and it promotes migration, attachment, and proliferation of TSPCs. The in vivo animal study demonstrated that the DUCWJ scaffold has potential for tendon regeneration in an acute rotator cuff tendon defect model Clinical Relevance: DUCWJ scaffolds have potential as a regenerative material to augment rotator cuff healing in the clinical setting.

Improved Healing of Rabbit Patellar Tendon Defects After an Atelocollagen Injection

Background: Patellar tendinopathy is a common cause of limitations in daily life activities in young and/or active people. The patellar tendon consists of a complex of collagen fibers; therefore, collagen could be used as a scaffold in the treatment of patellar tendinopathy. Purpose: To evaluate the healing capacity of injected atelocollagen as a treatment scaffold for patellar tendon defect and, hence, its potential for the treatment of patellar tendinopathy. Study Design: Controlled laboratory study. Methods: After receiving a full-thickness patellar tendon defect, 24 New Zealand White rabbits were divided into a control group (without treatment) and an experimental group that received an atelocollagen injection into the defect. Six rabbits from each group were subsequently used for either histologic scoring or biomechanical testing. The Mann-Whitney U test was used to compare histologic evaluation scores and load to failure between the 2 groups. Statistical significance was set at P < .05. Results: The experimental group showed excellent repair of the damaged patellar tendon and good remodeling of the defective area. In contrast, the control group showed defective healing with loose, irregular matrix fibers and adipose tissue formation. A statistically significant difference was found between the 2 groups in both histologic scores and biomechanical tests at postoperative week 12. Conclusion: Injection of atelocollagen significantly improved the regeneration of damaged patellar tendons. Clinical Relevance: Atelocollagen gel injections could be used to treat patellar tendinopathy in outpatient clinic settings.

Cytokine and Growth Factor Delivery from Implanted Platelet-Rich Fibrin Enhances Rabbit Achilles Tendon Healing

Tendons are hypocellular and hypovascular tissues, and thus, their natural healing capacity is low. In this study, we sought to evaluate the efficacy of platelet-rich fibrin (PRF) to serve as a bioactive scaffold in promoting the healing of rabbit Achilles tendon injury. For in vitro study, the essence portion of PRF was determined through bioluminescent assay. Furthermore, we analyzed the time-sequential cytokines-release kinetics of PRF and evaluated their effects on tenocytes proliferation and tenogenic gene expressions. In animal study, the rabbit Achilles tendon defect was left untreated or implanted with normal/heat-denatured PRF scaffolds. Six weeks postoperatively, the specimens were evaluated through sonographic imaging and histological analysis. The results revealed significantly more activated platelets on bottom half of the PRF scaffold. Cytokine concentrations released from PRF could be detected from the first hour to six days. For the in vitro study, PRF enhanced cell viability and collagen I, collagen III, tenomodulin, and tenascin gene expression compared to the standard culture medium. For in vivo study, sonographic images revealed significantly better tendon healing in the PRF group in terms of tissue echogenicity and homogeneity. The histological analysis showed that the healing tissues in the PRF group had more organized collagen fiber, less vascularity, and minimal cartilage formation. In conclusion, bioactive PRF promotes in vitro tenocytes viability and tenogenic phenotypic differentiation. Administration of a PRF scaffold at the tendon defect promotes tissue healing as evidenced by imaging and histological outcomes.

Modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger

Purpose: To evaluate the effect of the modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger.Methods: 12 patients with the extensor tendon defect in zone Ⅱ were investigated retrospectively. They were all treated surgically by the modified retrograde tendon flap technique, featuring the creation of a new terminal slip to bridge the extensor tendon defect using extensor tendon inner lateral bands. At the final follow-up, the range of motion at each joint of the injured finger was recorded.Results: Average follow-up was 18 months (ranging from 11 to 26 mos). Eight patients achieved full active DIPJ extension, whereas one patient had an extensor lag of 10° and three had a lag of 5°. All patients achieved normal active flexion ranges and full passive motion ranges of DIPJ compared with their uninjured side. All the involved finger joints were clinically stable, with no tenderness, pain, nail deformity, or limitation using their hands for daily life.Conclusions: The modified retrograde tendon flap technique, which is easy to operate and popularize, may be the procedure of choice in patients with a gap deficiency in Zone Ⅱ of the extensor tendon of a finger.

Prenatal Diagnosis and Management of a Rare Central Tendon Defect Type of Congenital Diaphragmatic Hernia with a Massive Pericardial Effusion

The central tendon defect type of congenital diaphragmatic hernia (CDH) is extremely rare and usually associated with a significant pericardial effusion. Prenatal diagnostic ultrasound features of this quite rare entity remain often overlooked or misdiagnosed. There is a dearth of literature about the role of prenatal intervention, often through an elective pericardiocentesis, for the prevention of lung hypoplasia and to decrease the overall neonatal morbidity and mortality. To the best of our knowledge, till date, there is only one case that was subjected to a prenatal intervention. Here, we present a second case of a central tendon defect type of CDH with a large pericardial effusion that was subjected to a prenatal transthoracic pericardiocentesis. Although smooth intubation and ventilation were performed immediately after birth, the infant suffered for several months from respiratory instability. Laparoscopic central tendon hernia repair was performed, and neonate was discharged home at seven months of age. Although prenatal pericardiocentesis may facilitate smoother postnatal intubation and ventilation, its broader effect on respiratory function is uncertain and still remains elusive.