Substance P Inhibitor Promotes Tendon Healing in a Collagenase-Induced Rat Model of Tendinopathy

Tendon extracellular-matrix-derived tissue engineering micro-tissue for Achilles tendon injury regeneration in rats

BACKGROUND

Achilles tendon is vital in maintaining the stability and function of ankle joint. It is quite difficult to achieve the structural and functional repair of Achilles tendon in tissue engineering.

METHODS

A tissue-engineered tendon micro-tissue was prepared using rat tail tendon extracellular matrix (TECM) combined with rat adipose stem cells (ADSCs) to repair Achilles tendon injuries. The TECM was prepared by repeated freezing and thawing. The in vitro characteristics of TECM and its effect on ADSCs proliferation were detected. This tissue-engineered tendon micro-tissue for Achilles tendon repair in vivo was evaluated based on general characteristics, gait analysis, ultrasound findings, histological analysis, and biomechanical testing.

RESULTS

The results showed that the TECM scaffold had good biocompatibility for ADSCs. At 2 weeks post-surgery, collagen types I and III and tenomodulin expression were higher, and vascular endothelial growth factor expression was lower in the micro-tissue group than other groups. At 4 and 8 weeks post-surgery, the results of histological analysis and ultrasound findings showed that the repaired tendon tissue was smooth and lustrous, and was arranged regularly and evenly in the micro-tissue group. Gait analysis confirmed that better motor function recovery was noted in micro-tissue group than other groups. In addition, the mechanical properties of the repaired tendon tissue in micro-tissue group were better than other groups.

CONCLUSION

Tissue-engineered tendon micro-tissue fabricated by TECM and ADSCs has good biocompatibility and can promote structural and functional repair of tendon in vivo. This composite biomaterial has broad application prospects in tissue engineering.

The effect of Sildenafil, a phosphodiesterase-5 inhibitor, on tendon healing: an experimental study in rat model of achilles tendon injury

INTRODUCTION

Sildenafil Citrate has various effects on the body, including widening blood vessels, inhibiting platelet aggregation, promoting the growth of blood vessels, stimulating apoptosis and adhesion of fibroblasts, and reducing inflammation. This research aims to explore how Sildenafil Citrate affects surgically treated Achilles tendons, both in terms of tissue structure and mechanical properties.

MATERIALS AND METHODS

Forty-eight Wistar-albino rats weighing 350-400 g were randomly divided into groups, 6 in each group, as the study group was given Sildenafil Citrate and the control group given saline, respectively. The Achilles tendon rupture model was created under ketamine and xylazine anesthesia. During the entire experiment, rats were housed in eight separate cages, six of them each. The study group and control group of the first group were sacrificed at the end of 1 week, and Achilles tendon samples were taken. After that, Achilles tendon samples were taken after sacrificing the second group at 14 days, the third group at 21 days, and the fourth group at 28 days, respectively. Neovascularization, inflammation, fibrosis and fibroblastic activities of the harvested Achilles tendons were evaluated histopathologically. Biomechanically, stretching was applied to the Achilles tendons and continued until the tendon ruptured. the maximum force values at the moment of rupture were calculated.

RESULTS

The mean maximum strength value of group T21, which was given sildenafil citrate for 21 days, was 31.1 ± 4.36 N, and the mean maximum strength value of group C21, which was the control group, was 20.56 ± 6.92 N. A significant difference was observed between the groups (p: 0.008). Group T28 (45.17 ± 5.54 N) also demonstrated greater strength than group C28 (34.62 ± 3.21 N) in the comparison (p: 0.004). The study also noted significant differences between the groups in neovascularization, in the first week, 1 mild, 3 moderate and 2 prominent neovascularization was observed in group T7, in group T28, moderate neovascularization was observed in 4 specimens and prominent neovascularization was observed in 2 specimens (p: 0.001). Furthermore, the groups showed significant differences in their levels of fibrosis, inflammation and fibroblastic proliferation (p: 0.017, p: 0.036, (p: 0.035) respectively).

CONCLUSIONS

Study has demonstrated that sildenafil citrate can enhance the biomechanical and histopathological aspects of tendon healing, resulting in a stronger tendon.

Inhibition of IKKβ via a DNA-Based In Situ Delivery System Improves Achilles Tendinopathy Healing in a Rat Model

BACKGROUND

The inhibition of IKKβ by the inhibitor 2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-(4-piperidinyl)-3-pyridine carbonitrile (ACHP) is a promising strategy for the treatment of Achilles tendinopathy. However, the poor water solubility of ACHP severely hinders its in vivo application. Moreover, the effective local delivery of ACHP to the tendon and its therapeutic effects have not been reported.

PURPOSE

To investigate the therapeutic effects of IKKβ inhibition via injection of ACHP incorporated into a DNA supramolecular hydrogel in a collagenase-induced tendinopathy rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Dendritic DNA, a Y-shaped monomer, and a crosslinking monomer were mixed with ACHP and self-assembled into an ACHP-DNA supramolecular hydrogel (ACHP-Gel). The effects of ACHP-Gel in tendon stem/progenitor cells were investigated via RNA sequencing and validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR). A total of 120 collagenase-induced rats were randomly assigned to 5 groups: blank, phosphate-buffered saline (PBS), DNA-Gel, ACHP, and ACHP-Gel. Healing outcomes were evaluated using biomechanic and histologic evaluations at 4 and 8 weeks.

RESULTS

ACHP-Gel enhanced the solubility of ACHP and sustained its release for ≥21 days in vivo, which significantly increased the retention time of ACHP and markedly reduced the frequency of administration. RNA sequencing and qRT-PCR showed that ACHP effectively downregulated genes related to inflammation and extracellular matrix remodeling and upregulated genes related to tenogenic differentiation. The cross-sectional area (P = .024), load to failure (P = .002), stiffness (P = .039), and elastic modulus (P = .048) significantly differed between the ACHP-Gel and PBS groups at 8 weeks. The ACHP-Gel group had better histologic scores than the ACHP group at 4 (P = .042) and 8 weeks (P = .009). Type I collagen expression (COL-I; P = .034) and the COL-I/collagen type III ratio (P = .015) increased while interleukin 6 expression decreased (P < .001) in the ACHP-Gel group compared with the ACHP group at 8 weeks.

CONCLUSION

DNA supramolecular hydrogel significantly enhanced the aqueous solubility of ACHP and increased its release-retention time. Injection frequency was markedly reduced. ACHP-Gel suppressed inflammation in Achilles tendinopathy and promoted tendon healing in a rat model.

CLINICAL RELEVANCE

ACHP-Gel injection is a promising strategy for the treatment of Achilles tendinopathy in clinical practice.

Irreversible Electroporation Improves Tendon Healing in a Rat Model of Collagenase-Induced Achilles Tendinopathy

BACKGROUND

Treatment of painful chronic tendinopathy is challenging, and there is an urgent need to develop new regenerative methods. Irreversible electroporation (IRE) can lead to localized cell ablation by electrical pulses and induce new cell and tissue growth. Previously, the authors' group reported that electroporation-ablated tendons fully regenerated.

PURPOSE

To assess the efficiency of IRE in improving tendon healing using a collagenase-induced Achilles tendinopathy rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

After screening for the IRE ablation parameters, a collagenase-induced Achilles tendinopathy rat model was used to assess the efficacy of IRE in improving tendon healing via biomechanical, behavioral, histological, and immunofluorescence assessments.

RESULTS

The experiments showed that the parameter of 875 V/cm 180 pulses could ablate most tenocytes, and apoptosis was the main type of death in vitro. In vivo, IRE promoted the healing process of chronic tendinopathy in the Achilles tendon of rats, based on biomechanical, behavioral, and histological assessments. Finally, immunofluorescence results revealed that IRE improved blood supply in the early stages of tendon repair and could potentially reduce neuropathic pain.

CONCLUSION

IRE enhanced tendon tissue healing in a rat model of collagenase-induced Achilles tendinopathy.

CLINICAL RELEVANCE

IRE may as a potential alternative treatment for tendinopathy in clinical usage.