Eccentric Training for Tendon Healing After Acute Lesion: A Rat Model

The effects of orthobiologics in the treatment of tendon pathologies: a systematic review of preclinical evidence

Purpose

The aim of this systematic review is to explore the current available knowledge about tendon disorders and orthobiologics derived by preclinical experiments to evaluate their role and efficacy in the different stages and conditions related to the tendon healing processes.

Methods

The systematic review was performed according to the PRISMA guidelines. Different electronic databases (MEDLINE, Web of Science, EMBASE) were searched for studies investigating orthobiologics (PRP and cell-based products from adipose tissue or bone marrow) in animal models or veterinary clinical trials for tendon pathologies (complete/partial tendon ruptures, rotator cuff tears, tendinopathy, enthesis-related injuries). Data regarding the specific product used, the treatment site/pathology, the host and the model were collected. The results were classified into the following categories: histological, biomechanical, molecular and imaging.

Results

A large pool of preclinical studies on tendon disorders have been found on platelet-rich plasma (PRP), while data about stromal vascular fraction (SVF) and bone marrow concentrate (BMAC) are still limited and frequently focused on expanded cells, rather than orthobiologics prepared at the point of care.

The effect of PRP is related to an acceleration of the healing process, without improvements in the final structure and properties of repaired tendon. Cell-based products have been reported to produce more durable results, but the level of evidence is currently insufficient to draw clear indications.

Conclusions

The preclinical results about orthobiologics applications to tendon pathologies would support the rationale of their clinical use and encourage the performance of clinical trials aimed to confirm these data in human subjects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-022-00468-w.

A novel murine muscle loading model to investigate Achilles musculotendinous adaptation

Achilles tendinopathy is a debilitating condition affecting the entire spectrum of society and a condition that increases the risk of tendon rupture. Effective therapies remain elusive, as anti-inflammatory drugs and surgical interventions show poor long-term outcomes. Eccentric loading of the Achilles muscle-tendon unit is an effective physical therapy for treatment of symptomatic human tendinopathy. Here, we introduce a novel mouse model of hindlimb muscle loading designed to achieve a tissue-targeted therapeutic exercise. This model includes the application of tissue (muscle and tendon)-loading "doses," coupled with ankle dorsiflexion and plantarflexion, inspired by human clinical protocols. Under computer control, the foot was rotated through the entire ankle joint range of motion while the plantar flexors simultaneously contracted to simulate body mass loading, consistent with human therapeutic exercises. This approach achieved two key components of the heel drop and raise movement: ankle range of motion coupled with body mass loading. Model development entailed the tuning of parameters such as footplate speed, number of repetitions, number of sets of repetitions, treatment frequency, treatment duration, and treatment timing. Initial model development was carried out on uninjured mice to define a protocol that was well tolerated and nondeleterious to tendon biomechanical function. When applied to a murine Achilles tendinopathy model, muscle loading led to a significant improvement in biomechanical outcome measures, with a decrease in cross-sectional area and an increase in material properties, compared with untreated animals. Our model facilitates the future investigation of mechanisms whereby rehabilitative muscle loading promotes healing of Achilles tendon injuries.NEW & NOTEWORTHY We introduce a novel mouse model of hindlimb muscle loading designed to achieve a tissue-targeted therapeutic exercise. This innovative model allows for application of muscle loading "doses," coupled with ankle dorsiflexion and plantarflexion, inspired by human loading clinical treatment. Our model facilitates future investigation of mechanisms whereby rehabilitative muscle loading promotes healing of Achilles tendon injuries.

Paternal Resistance Training Modulates Calcaneal Tendon Proteome in the Offspring Exposed to High-Fat Diet

The increase in high-energy dietary intakes is a well-known risk factor for many diseases, and can also negatively impact the tendon. Ancestral lifestyle can mitigate the metabolic harmful effects of offspring exposed to high-fat diet (HF). However, the influence of paternal exercise on molecular pathways associated to offspring tendon remodeling remains to be determined. We investigated the effects of 8 weeks of paternal resistance training (RT) on offspring tendon proteome exposed to standard diet or HF diet. Wistar rats were randomly divided into two groups: sedentary fathers and trained fathers (8 weeks, three times per week, with 8–12 dynamic movements per climb in a stair climbing apparatus). The offspring were obtained by mating with sedentary females. Upon weaning, male offspring were divided into four groups (five animals per group): offspring from sedentary fathers were exposed either to control diet (SFO-C), or to high-fat diet (SFO-HF); offspring from trained fathers were exposed to control diet (TFO-C) or to a high-fat diet (TFO-HF). The Nano-LC-MS/MS analysis revealed 383 regulated proteins among offspring groups. HF diet induced a decrease of abundance in tendon proteins related to extracellular matrix organization, transport, immune response and translation. On the other hand, the changes in the offspring tendon proteome in response to paternal RT were more pronounced when the offspring were exposed to HF diet, resulting in positive regulation of proteins essential for the maintenance of tendon integrity. Most of the modulated proteins are associated to biological pathways related to tendon protection and damage recovery, such as extracellular matrix organization and transport. The present study demonstrated that the father’s lifestyle could be crucial for tendon homeostasis in the first generation. Our results provide important insights into the molecular mechanisms involved in paternal intergenerational effects and potential protective outcomes of paternal RT.

Two Unique Cases of Ciprofloxacin-Associated Avulsion of Ligament and Tendon

Ciprofloxacin is recognized to have a deleterious relationship with tendons, particularly Achilles tendinopathy, which makes up most case reports. Tendinopathy seems to occur because of induction of collagen-degrading enzymes causing damage and ischemia of the poorly vascularized regions preventing repair. The focus on the relationship of ciprofloxacin and the Achilles tendon leaves patients on fluoroquinolones with non-Achilles tendinopathy symptoms at risk of misdiagnosis. There have not been any documented instances of ligament damage with ciprofloxacin administration in the literature, although ligament and tendon compositions are similar and should have similar susceptibility. This report includes two cases, one presenting with right lateral thumb pain and a medical history of gastroenteritis treated with ciprofloxacin. Physical examination showed swelling of the right metacarpophalangeal joint and ultrasound confirmed disruption of the radial collateral ligament at insertion on first metacarpal; the second case is of a woman presenting with right hip pain in setting of chronic recurrent diverticulitis treated with ciprofloxacin. She received work-up for lumbar disc disease and spondylosis. After standard therapy with pharmacotherapy and physical therapy for radiculopathy failed, magnetic resonance imaging was performed showing near complete avulsion of the right hamstring tendons from the ischial tuberosity.