Elsevier

Regulatory Peptides

Volume 184, 10 June 2013, Pages 1-5
Regulatory Peptides

Thymosin β4 enhances the healing of medial collateral ligament injury in rat

https://doi.org/10.1016/j.regpep.2013.03.026Get rights and content

Highlights

  • We investigated the effects of Tβ4 on ligament repair following injury.

  • Administration of Tβ4 promotes the healing process of MCL histologically in a rat model.

  • Administration of Tβ4 promotes the healing process of MCL mechanically.

  • We provide a basis for potential clinical use of Tβ4 in repairing ligaments.

Abstract

The role played by thymosin β4 (Tβ4) in the process of wound healing was reported in several organs. However, there have been no reports that investigated the role of Tβ4 in the repair process after ligament injury. The purpose of this study was to determine whether administration of Tβ4 would improve ligament repair following injury. The medial collateral ligament (MCL) was sharply transected on the day of surgery. Then, the treatment group received 100 μL of fibrin sealant containing 1 μg of Tβ4 placed in the ligament gap. Healing tissues were evaluated by hematoxylin and eosin stain, transmission electron microscopy, and biomechanical test at 4 weeks after surgery. Histologically, healing tissues in Tβ4-treated group exhibited uniform and evenly spaced fiber bundles. However, the collagen fibers were not evenly spaced in control rats. Moreover, diameters of collagen fibrils within granulation tissue from the Tβ4-treated rats were significantly increased. In Tβ4-treated MCLs, the mechanical properties of these healing tissues were significantly higher at 4 weeks after surgery.

In terms of the mechanical properties of the healing femur–medial collateral ligament-tibia complexes, the Tβ4-treated group had significantly better biomechanical properties than the control group at 4 weeks after surgery. Local administration of Tβ4 promotes the healing process of MCL, both histologically and mechanically, in a rat model. These findings provide a basis for potential clinical use of Tβ4 in repairing ligaments.

Introduction

Injury to the medial collateral ligament (MCL) is the most common knee ligament injury and frequently occurs in various types of athletic accidents [1]. MCL has been the most-used model for ligament and tendon healing studies because of its accessibility, frequency of injury, and healing properties [2]. Ligament is composed of a few cells and parallel arrays of collagen fibers. Although MCL can heal without surgical intervention, its regeneration is very difficult and requires a very long period. Moreover, the return at the initial state of the histological, biochemical and biomechanical properties in the healing tissue is never reached [3]. The restoration of mechanical strength is one of the goals of ligament healing. A method to accelerate the healing of this ligament could lead to reductions in recovery time, and increased patient compliance with a shorter rehabilitation requirement. Although recent in vivo studies have reported that growth factors, biological scaffold, and stem cell therapies enhance healing in the injured MCL [4], [5], [6], but the best protocol to improve ligament healing has not yet been established.

Recently, thymosin β4 (Tβ4) showed premise in being an efficacious treatment for tissue injuries in dermis and heart by its physiological functions, such as wound healing, angiogenesis, and cell migration [7], [8], [9]. Tβ4 is a highly conserved water-soluble peptide. It has multiple biological activities that contribute to reduce tissue damage and to promote tissue repair [10]. Tβ4 treatment could result in stem cell activation, mediate oligodendrocyte differentiation during the process of brain injury, and thus promote functional recovery [11], [12]. It could also regulate angiogenesis by mobilizing and recruiting progenitor cells during the repair damaged myocardium [13]. A recent paper reported that the expression level of Tβ4 was high in muscle injury site, where it serves as a chemoattractant for myoblasts. This result indicated that Tβ4 has an ability to facilitate skeletal muscle regeneration [14]. The administration of Tβ4 into rat skin excision wounds improved the organization of collagen fibers in the absence of myofibroblast, and incisional wounds in the Tβ4-treated group healed with minimal scaring and without loss in wound breaking strength [10], [15]. Moreover, Tβ4 elevates granulation tissue deposition, induces angiogenesis, and enhances collagen deposition in wound repair [7], [16]. However, the use of Tβ4 in improving the healing of MCL injury has not been reported previously.

Based on these facts, we hypothesized that the addition of Tβ4 would induce collagen fiber bundles to be better organized in healing ligament, which would form a basis for increased mechanical property. The fibrin sealant was considered to act as a useful vehicle releasing Tβ4 in the in vivo conditions. The purpose of this experimental study was to evaluate the in vivo effect of the local application of Tβ4 in fibrin sealant on the healing MCL in rat knee joint using histological studies and mechanical testing.

Section snippets

Surgical procedure

60 adult, male, Sprague-Dawley rats weighing between 180 and 200 g were used in this study. Animal experiments were carried out under the Rules and Regulations of the Animal Care and Use Committee at Harbin Medical University. On the day of surgery, the rats were anesthetized with xylazine and ketamine. With a sterile technique, a 1.5-cm skin incision was made over the medial aspect of the right knee, and the MCL was exposed. The ligament was then sharply transected together with the fascia

Results

No adverse effect of Tβ4 on the rats' overall well-being was apparent in either group. There were no significant differences among 3 groups with regard to the average weight of the animals during the experimental period. One day after surgery, all rats resumed normal cage activity.

Discussion

MCL injuries account for a significant percentage of knee ligament injury and enormous associated costs. The number of MCL injuries will continue to increase as our population continues to age and remain active. Methods of treating ligament injuries have seen substantial improvements. However, formation of the fibrotic scar tissue and decreased function are still common problems. Therefore, a new strategy needs to be developed to optimize the remodeling of MCL injury.

Previous studies found that

Acknowledgments

This work was supported by grants from the National Natural Sciences Foundation of China (no.30901516, 81272049, 81150024), Reserve Talents of Universities Overseas Research Program of Heilongjiang, and Natural Science Foundation of Heilongjiang (QC2011C049).

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