The Effect of Phospholipids (Surfactant) on Adhesion and Biomechanical Properties of Tendon: A Rat Achilles Tendon Repair Model

Challenges and opportunities of medicines for treating tendon inflammation and fibrosis: A comprehensive and mechanistic review

BACKGROUND

Tendinopathy refers to conditions characterized by collagen degeneration within tendon tissue, accompanied by the proliferation of capillaries and arteries, resulting in reduced mechanical function, pain, and swelling. While inflammation in tendinopathy can play a role in preventing infection, uncontrolled inflammation can hinder tissue regeneration and lead to fibrosis and impaired movement.

OBJECTIVES

The inability to regulate inflammation poses a significant limitation in tendinopathy treatment. Therefore, an ideal treatment strategy should involve modulation of the inflammatory process while promoting tissue regeneration.

METHODS

The current review article was prepared by searching PubMed, Scopus, Web of Science, and Google Scholar databases. Several treatment approaches based on biomaterials have been developed.

RESULTS

This review examines various treatment methods utilizing small molecules, biological compounds, herbal medicine-inspired approaches, immunotherapy, gene therapy, cell-based therapy, tissue engineering, nanotechnology, and phototherapy.

CONCLUSION

These treatments work through mechanisms of action involving signaling pathways such as transforming growth factor-beta (TGF-β), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), all of which contribute to the repair of injured tendons.

Phosphatidylethanolamines Are Associated with Nonalcoholic Fatty Liver Disease (NAFLD) in Obese Adults and Induce Liver Cell Metabolic Perturbations and Hepatic Stellate Cell Activation

Pathogenesis roles of phospholipids (PLs) in nonalcoholic fatty liver disease (NAFLD) remain incompletely understood. This study investigated the role of PLs in the progression of NAFLD among obese individuals via studying the alterations in serum PL composition throughout the spectrum of disease progression and evaluating the effects of specific phosphatidylethanolamines (PEs) on FLD development in vitro. A total of 203 obese subjects, who were undergoing bariatric surgery, were included in this study. They were histologically classified into 80 controls (C) with normal liver histology, 93 patients with simple hepatic steatosis (SS), 16 with borderline nonalcoholic steatohepatitis (B-NASH) and 14 with progressive NASH (NASH). Serum PLs were profiled by automated electrospray ionization tandem mass spectrometry (ESI-MS/MS). HepG2 (hepatoma cells) and LX2 (immortalized hepatic stellate cells or HSCs) were used to explore the roles of PL in NAFLD/NASH development. Several PLs and their relative ratios were significantly associated with NAFLD progression, especially those involving PE. Incubation of HepG2 cells with two phosphatidylethanolamines (PEs), PE (34:1) and PE (36:2), resulted in significant inhibition of cell proliferation, reduction of mitochondrial mass and membrane potential, induction of lipid accumulation and mitochondrial ROS production. Meanwhile, treatment of LX2 cells with both PEs markedly increased cell activation and migration. These effects were associated with a significant change in the expression levels of genes involved in lipogenesis, lipid oxidation, autophagy, apoptosis, inflammation, and fibrosis. Thus, our study demonstrated that elevated level of PEs increases susceptibility to the disease progression of obesity associated NAFLD, likely through a causal cascade of impacts on the function of different liver cells.

A Simplified Murine Model to Imitate Flexor Tendon Adhesion Formation without Suture

Peritendinous adhesion (PA) around tendons are daunting challenges for hand surgeons. Tenotomy with various sutures are considered classical tendon repair models (TRM) of tendon adhesion as well as tendon healing. However, potential biomimetic therapies such as anti-adhesion barriers and artificial tendon sheaths to avoid recurrence of PA are sometimes tested in these models without considering tendon healing. Thus, our aim is to create a simplified model without sutures in this study by using three 6 mm longitudinal and parallel incisions called the longitudinal incision model (LCM) in the murine flexor tendon. We found that the adhesion score of LCM has no significant difference to that in TRM. The range of motion (ROM) reveals similar adhesion formation in both TRM and LCM groups. Moreover, mRNA expression levels of collagen I and III in LCM shows no significant difference to that in TRM. The breaking force and stiffness of LCM were significantly higher than that of TRM. Therefore, LCM can imitate flexor tendon adhesion formation without sutures compared to TRM, without significant side effects on biomechanics with an easy operation.

Effects of low-density pulsed ultrasound treatment on transforming growth factor-beta, collagen level, histology, biomechanics, and function in repaired rat tendons

Objectives

The aim of this study is to compare the effects of low-density pulsed ultrasound (LIPUS) treatment on growth factors/collagen production, histological, biomechanical, and function of rats with Achilles tendon injury.

Materials and methods

A total of 44 Wistar Albino rats were used in the study between April 2017 and June 2018. The rats were randomized to two treatment groups. Group 1 (n=6) received LIPUS treatment (0.3 Watt/cm2; 1 MHz, 1:5 pulse mode) and Group 2 (n=6)received sham ultrasound (US) treatment following Achilles tendon surgery. Transforming growth factor-beta 1 (TGF-β1) and collagen gene expression levels were evaluated using polymerase chain reaction. The histological evaluation was performed with the Bonar scoring system. The tensile strength was measured by biomechanical testing and the function was evaluated with the Achilles Functional Index (AFI).

Results

Although TGF-β1 expression and tensile strength evaluation showed a tendency to improve in favor of the LIPUS group, no statistically significant difference was found (p=0.065 and p=0.053, respectively). The COL3 gene expression in the LIPUS group and the COL1 expression in the sham US group were significantly higher. Bonar scores and AFI scores showed a statistically significant improvement in the LIPUS group, compared to the sham US group.

Conclusion

Our study results show that LIPUS yields positive effects on tendon histology and functional status in repaired Achilles tendon in rats.

Facile fabrication of phospholipid-functionalized nanofiber-based barriers with enhanced anti-adhesion efficiency

Electrospun nanofibrous membranes (NFMs) have attracted considerable attention as a potential physical barrier for reducing postoperative adhesion. However, no anti-adhesion barrier can completely prevent adhesion formation. In this study, phospholipid-functionalized NFMs were readily fabricated by one-step electrospinning to obtain nanofiber-based barriers with enhanced wettability and anti-adhesion efficiency. The optimized phospholipid NFMs were shown to have a fiber diameter of 831 nm ± 135 nm that is drastically decreasing, high porosity of 87.6 % ± 1.1 %, and superior hydrophilicity. Moreover, the phospholipid NFMs with excellent cytocompatibility exhibited fibroblasts being significantly reduced (≈ 51 %) after incubation of 3 days compared to that of the NFMs (≈ 96 %), confirming long-lasting anti-adhesion capability against fibroblasts. Meanwhile, less cell adhesion and proliferation of Raw 264.7 macrophages on NFM-10Lec indicated its superior anti-inflammatory effects. Thus, the facile phospholipid-functionalized nanofibers provided a promising strategy for anti-adhesion applications.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

Evaluation of a new collagen-based medical device (ElastiCo®) for the treatment of acute Achilles tendon injury and prevention of peritendinous adhesions: An in vitro biocompatibility and in vivo investigation

Tendon healing still represents a challenge for clinicians because it is slow and incomplete. The most injured is the Achilles tendon, and surgery is the therapeutic strategy often adopted because it provides a quicker functional recovery. Peritendinous adhesions are the main complication of surgery with hyperplasia and chemotaxis of fibroblasts. A biomaterial that blocks fibroblast migration, without interfering with the passage of cytokines and growth factors, might be useful. The present study evaluated the biocompatibility of a new Type I collagen-based scaffold (ElastiCo®) and its ability to promote Achilles tendon healing, inhibiting adhesion formation. After verifying in vitro biocompatibility, physical, and mechanical properties of the scaffold, an in vivo study was performed in 28 rats, operated to induce an acute lesion in both Achilles tendons. One tendon was treated with the suture only and the contralateral one with suture wrapped with ElastiCo® film. After 8 and 16 weeks, it was observed that ElastiCo® reduced internal and external peritendinous adhesions and Collagen III content and increased Collagen I. Elastic modulus increased with both treatments over time. Current results highlighted the clinical translationality of ElastiCo® that could improve the quality of life in patients affected by Achilles tendon lesions surgically treated.

Do adipofascial flaps affect the mechanical properties of a repaired tendon? A biomechanical rat model study

The aim of this study was to evaluate the effect of vascularized and non-vascularized fascial flaps on tendon healing, specifically the maximum strain, maximum stress, elasticity and resistance of the repaired tendon. Rats were randomly divided into 3 groups: Group 1 - primary repair; Group 2 - vascularized pedicled fascial graft; Group 3 - non-vascularized free fascial graft. The rats were euthanized after 2 weeks and 40mm-long samples were taken from the Achilles tendon and gastrocnemius muscle. To evaluate the mechanical properties of the tendons, maximum load, maximum deformation, energy stored until yield point and stiffness on the load-deformation curve were measured. Based on this mechanical testing, the best group in terms of tissue strength and quality was the primary repair group. When the samples were examined individually, the two samples with the highest breaking force after the control group were in the pedicled graft group. The worst results overall were in the free graft group. We believe that if the blood flow is preserved for the fascial flap in the pedicled graft group, the tendon's breaking force would be higher.

Thermal pretreatment promotes the protective effect of HSP70 against tendon adhesion in tendon healing by increasing HSP70 expression

Tendon adhesion is a substantial challenge for tendon repair. Thermal pretreatment (TP) may decrease inflammation by upregulating heat shock proteins (HSPs). The present study intends to identify the function that TP serves when combined with HSP70 overexpression in tendon healing and adhesion in rats. Sprague‑Dawley male rats were used to establish a surgically ablative tendon postoperative suture model, and the positive expression of the HSP70 protein was measured using immunohistochemistry. Changes to the blood vessels and collagenous fiber, in addition to the maximum tensile strength and the tendon sliding distance, were detected under a microscope. Finally, HSP70, tumor growth factor β (TGF‑β), and insulin‑like growth factor 1 (IGF‑1) mRNA and protein levels were all determined by employing reverse transcription‑quantitative polymerase chain reaction and western blot analysis methods. The positive expression of the HSP70 protein increased following TP. Furthermore, TP reduced the infiltration of inflammatory cells and improved the collagenous arrangement, accompanied by an increased maximum tensile force and tendon gliding distance following surgery. In addition, TP increased the mRNA and protein expression levels of HSP70, TGF‑β and IGF‑1. Altogether, TP increases HSP70 expression, thereby reducing postoperative traumatic inflammation and establishing tendon adhesion and promoting tendon healing. Thus, TP may be a potential strategy for the treatment of tendon adhesion.

EFFECTS OF HIGH-DOSE VITAMIN C AND HYALURONIC ACID ON TENDON HEALING

OBJECTIVE

To assess the histopathologic and biomechanical effects of hyaluronic acid (HA) and high-dose vitamin C (VC) on rat Achilles tendon healing.

METHODS

Forty-eight Sprague-Dawley rats were randomized to HA and VC and control groups with equal numbers. Each group was further divided into two subgroups to be sacrificed on Day 15 (n=8) and Day 30 (n=8). The Achilles tendons were cut and repaired. While the control rats remained untreated, HA and VC were administered after repair. The repaired tendons were removed for biomechanical and histopathologic analyses. In the biomechanical tests, the tendons were stretched to failure and maximum forces were measured. For histopathologic examination, the specimens were interpreted semiquantitatively using Movin's grading scale and Bonar scores.

RESULTS

The highest mean forces were obtained in the HA group on Day 15 and in the VC group on Day 30, with a significant difference between HA and VC on Day 15 between control and VC on Day 30 (p<0.05). Histological examination showed both Movin and Bonar scores decreased in all groups on Day 30, with significant improvements in the HA and VC groups (p<0.05).

CONCLUSION

Our results demonstrated that both VC and HA had therapeutic effects on tendon healing, especially in the late phase. Level of Evidence I; High quality randomized trial with statistically significant difference.

A review on animal models and treatments for the reconstruction of Achilles and flexor tendons

Tendon is a connective tissue mainly composed of collagen fibers with peculiar mechanical properties essential to functional movements. The increasing incidence of tendon traumatic injuries and ruptures-associated or not with the loss of tissue-falls on the growing interest in the field of tissue engineering and regenerative medicine. The use of animal models is mandatory to deepen the knowledge of the tendon healing response to severe damages or acute transections. Thus, the selection of preclinical models is crucial to ensure a successful translation of effective and safe innovative treatments to the clinical practice. The current review is focused on animal models of tendon ruptures and lacerations or defective injuries with large tissue loss that require surgical approaches or grafting procedures. Data published between 2000 and 2016 were examined. The analyzed articles were compiled from Pub Med-NCBI using search terms, including animal model(s) AND tendon augmentation OR tendon substitute(s) OR tendon substitution OR tendon replacement OR tendon graft(s) OR tendon defect(s) OR tendon rupture(s). This article presents the existing preclinical models - considering their advantages and disadvantages-in which translational progresses have been made by using bioactive sutures or tissue engineering that combines biomaterials with cells and growth factors to efficiently treat transections or large defects of Achilles and flexor tendons.

Surgical Strategy for the Chronic Achilles Tendon Rupture

Background. Chronic Achilles tendon rupture is usually misdiagnosed and treated improperly. This study aims to better understand the treatment of chronic Achilles tendon rupture. Methods. Patients who were not able to perform a single-limb heel rise were chosen. Pre- and postoperative magnetic resonance imaging (MRI) were conducted. By evaluating the presence or absence of Achilles tendon stumps and the gap length of rupture, V-Y advancement, gastrocnemius fascial turndown flap, or flexor halluces longus tendon transfer were selected for tendon repair. The function of ankle and foot was assessed by American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scores and Achilles Tendon Total Rupture Score (ATRS). Results. Twenty-nine patients were followed up. One patient had superficial incision infection, which was healed after debridement and oral antibiotics. Three months postoperatively, MRI showed some signs of inflammation, which disappeared at one or two years postoperatively. All patients were able to perform a single-limb heel rise. Mean AOFAS scores and ATRS scores were increased at the latest follow-up. Conclusion. Surgical options can be determined by evaluating the presence of the Achilles tendon stumps and the gap length, which can avoid using the nearby tendon and yield satisfactory functional results.