Platelet-Rich Plasma Injection Can Be a Viable Alternative to Corticosteroid Injection for Conservative Treatment of Rotator Cuff Disease: A Meta-analysis of Randomized Controlled Trials

Leptin Enhances M1 Macrophage Polarization and Impairs Tendon-Bone Healing in Rotator Cuff Repair: A Rat Model

BACKGROUND

Rotator cuff tears are common, affecting more than 60% of individuals older than 80 years, and they have been implicated in 70% of patients with shoulder pain. M1 polarization-related inflammation has been reported to be associated with poor healing outcomes of rotator cuff injury, and leptin, an adipokine, has been reported to be a potential activator of inflammation. However, whether leptin affects rotator cuff repair remains unknown.

QUESTIONS/PURPOSES

Using in vitro cell experiments and an in vivo rat rotator cuff tear model, we therefore asked: (1) Does leptin promote the M1 polarization of macrophages in vitro and in vivo? (2) Does leptin impair biomechanical strength, the histologic structure of the tendon-bone interface, bone mineral density (BMD), or gait in the rotator cuff tear scenario? (3) Does leptin promote M1 polarization by upregulating the tumor necrosis factor (TNF) pathway?

METHODS

The impact of leptin on M1 macrophage polarization in vitro was determined by reverse transcription-polymerase chain reaction (RT-PCR), the Western blot test, and immunofluorescence staining. The effect of leptin on tendon-bone healing was assessed in an in vivo rat rotator cuff tear model by comparing a leptin group with a suture group in terms of gait, biomechanical tensile strength, the histologic structure of the tendon-bone interface, and BMD. In the in vivo experiments, 8-week-old male Sprague Dawley rats were used, adapting a previously developed rat rotator cuff tear model. The supraspinatus tendon was resected from the greater tuberosity bilaterally, and then the tendon was secured to its anatomical footprint using the transosseous single-row technique. In total, 30 rats were randomized into two groups (suture, leptin) by drawing lots (15 rats in each group). They were assessed at 2, 4, and 8 weeks after the surgery. In the suture group, 100 µL of normal saline was injected into the subacromial space after the deltoid muscle was restitched to the original position. In the leptin group, 100 µL of leptin solution (200 ng/mL) was injected into the subacromial space after the deltoid muscle was restitched to the original position. Biomechanical properties including maximal failure load, stiffness, and tensile failure stress were determined to assess the biomechanical strength at 4 and 8 weeks after the surgery. Histologic staining was conducted to compare the structure of the tendon-bone interface between treatment groups. Micro-MRI and micro-CT assessments were conducted to compare the overall healing outcome and BMD between treatment groups. Gait analysis was conducted to compare the stride length and strength between treatment groups. M1 macrophage polarization in vivo at the tendon-bone interface was assessed by immunofluorescence staining. Finally, to explore the underlying mechanism of the effects of leptin, Necrostatin-1 (Nec-1) was used to block the TNF signaling pathway in the in vitro macrophage study, and RT-PCR and Western blot were used to explore the underlying mechanism.

RESULTS

Leptin enhanced LPS-induced M1 polarization of macrophages in vitro, showing increased gene expression of CD86, Nos2, and TNF-α as well as increased protein expression of CD86, TNF-α, interleukin-6 (IL-6), and inducible NO synthase (iNOS). The in vivo polarization showed that the M1 polarization of macrophages at the tendon-bone interface was promoted. At 2 weeks postoperatively, there were more M1 cells in the leptin group (53 ± 5 versus 77 ± 8, mean difference 24 [95% confidence interval (CI) 11 to 37]; p = 0.002), although the proportion of M1 cells (ratio of the number of M1 cells to the total number of macrophages) was not higher (18.6% ± 2.9% versus 21.5% ± 1.7%, mean difference 2.9% [95% CI -2.8% to 8.7%]; p = 0.36). At 4 weeks postoperatively, the leptin group exhibited more M1 cells (31 ± 4 versus 50 ± 6, mean difference 19 [95% CI 6 to 32]; p = 0.008) and at a higher proportion (16.4% ± 2.6% versus 23.0% ± 3.0%, mean difference 6.6% [95% CI 0.8% to 12.4%]; p = 0.03). The in vivo experiments showed that leptin impaired tendon-bone healing. At 4 weeks postoperatively, the biomechanical properties of both groups were not different in terms of maximal failure load (12.7 ± 1.6 N versus 12.4 ± 1.8 N, mean difference -0.3 N [95% CI -2.6 to 1.8]; p = 0.91), stiffness (5.1 ± 0.7 N/mm versus 4.6 ± 0.8 N/mm, mean difference -0.5 N/mm [95% CI -1.3 to 0.5]; p = 0.44), and tensile failure stress (2.0 ± 0.3 N/mm2 versus 2.0 ± 0.3 N/mm2, mean difference 0.0 N/mm2 [95% CI -0.4 to 0.4]; p = 0.99). At 8 weeks postoperatively, the leptin group showed worse maximal failure load (17.6 ± 1.4 N versus 14.1 ± 1.4 N, mean difference -3.5 N [95% CI -5.7 to -1.3]; p = 0.002), stiffness (7.0 ± 0.6 N/mm versus 5.2 ± 0.6 N/mm, mean difference -1.8 N/mm [95% CI -2.7 to -0.9]; p < 0.001), and tensile failure stress (3.4 ± 0.3 N/mm2 versus 2.8 ± 0.4 N/mm2, mean difference -0.6 N/mm2 [95% CI -1.0 to -0.2]; p = 0.007). Results of histologic staining, image assessments, and gait analysis also demonstrated that leptin impaired the healing process. In vitro experiments showed that leptin upregulated the gene expression of molecules in the TNF pathway, including CCL2 and receptor-interacting protein kinase 1 (RIPK1), and M1 markers, such as TNF-α, CD86, and Nos2; the addition of Nec-1 neutralized the effect of leptin on macrophage polarization, reducing the expression of M1 markers, including TNF-α, CD86, and Nos2, and blocking the TNF signaling pathway, including CCL2 and RIPK. The protein expression exhibited similar trends.

CONCLUSION

Based on the results of this study, leptin appears to impair tendon-bone healing in a rat model of rotator cuff tear, promote M1 macrophage polarization at the tendon-bone interface, and upregulate the TNF signaling pathway in macrophages to promote M1 polarization.

CLINICAL RELEVANCE

Obesity and fatty infiltration of the rotator cuff muscle are associated with poor healing of rotator cuff tears. In this study, the effect of leptin, an adipose factor, on tendon-bone healing and the underlying mechanism were explored. Future studies might focus on developing novel approaches to improve the tendon-bone healing in patients with obesity by targeting leptin or the TNF signaling pathway with the aid of biomaterials.

Growth Hormone-Releasing Peptide 2 May Be Associated With Decreased M1 Macrophage Production and Increased Histologic and Biomechanical Tendon-Bone Healing Properties in a Rat Rotator Cuff Tear Model

PURPOSE

To explore the potential of growth hormone-releasing peptide 2 (GHRP-2) for tendon-bone healing in a rat rotator cuff tear (RCT) model.

METHODS

The impact of GHRP-2 on M1 macrophage polarization in vitro was determined using real-time polymerase chain reaction, Western blot, and immunofluorescence staining. GHRP-2 was then applied in a rat RCT model, and the healing of the tendon-bone interface was systemically evaluated by histologic staining, radiologic assessments, gait analysis, and biomechanical tests. M1 macrophage polarization at the tendon-bone interface was assessed by immunofluorescence staining.

RESULTS

GHRP-2 was found to reduce the expression of Cd86, Nos2, and tnfa (all P < .01), suggesting inhibited M1 macrophage polarization in vitro. The in vivo experiments showed that the proportion of M1 macrophages was reduced both 2 and 4 weeks after surgery (P < .01), and the number of M1 was reduced 4 weeks after surgery (P < .01) at the tendon-bone interface. The in vivo experiments also showed that histologic scores and bone mineral density were increased by GHRP-2 at 8 weeks postsurgery (P < .01), suggesting improved healing of the tendon-bone interface. Furthermore, the GHRP-2 group showed a better biomechanical property at both 4 and 8 weeks postsurgery, including maximal failure load, stiffness, and tension (all P < .01), and better gait parameters at 8 weeks postsurgery, including mean area of the left front foot and mean intensity of the right front foot (all P < .05).

CONCLUSIONS

GHRP-2 may be associated with decreased M1 macrophage production and increased histologic and biomechanical tendon-bone healing properties in a rat RCT model.

CLINICAL RELEVANCE

The present study might be a transitional study to show the efficacy of GHRP-2 in enhancing bone-tendon healing and reduce retear rate after rotator cuff repair.

Clinical Effects of Additional Platelet-Rich Plasma Application to Exercise Therapy in Patients with Subacromial Impingement Syndrome: A Double-Blind Randomized Controlled Trial

Background

Exercise therapy (ET) is the main and initial treatment modality for treating subacromial impingement syndrome (SIS). The isolated or combined use of platelet-rich plasma (PRP) applications in treating SIS is increasing and promising. A comparison was made on the effectiveness of ET alone and in combination with PRP on pain, functionality, and quality of life (QoL) in patients with SIS.

Purposes/Hypothesis

The purposes of this study were to (1) investigate the possible positive effects of PRP injections combined with ET in treating SIS on pain, functionality, and QoL and (2) propose an alternative treatment protocol. It was hypothesized that the group receiving PRP applications in addition to ET would have a better QoL due to less pain and higher functionality 6 months after treatment.

Study Design

Randomized controlled trial; Level of evidence, 2.

Methods

Volunteer patients diagnosed with SIS were included based on history and physical examination findings. All participants underwent magnetic resonance imaging to confirm the diagnosis and exclude possible accompanying pathologies. The patients were randomly divided into 2 groups. The first group underwent ET at home for 8 weeks (ET group), and the second group received the same ET program and an additional 2 PRP injections, at the beginning of the study and the end of the fourth week (PRP group). Patients were evaluated initially and 6 months after the treatment using the visual analog scale (VAS) for pain score, Constant-Murley Score (CMS), and the 36-Item Short Form Health Survey (SF-36). The Kolmogorov-Smirnov test determined the conformity of the data to a normal distribution, chi-square analysis was used to compare categorical variables between groups, and the Mann-Whitney U test was used to compare continuous and intergroup variables. Intragroup changes before and after treatment were evaluated with the Wilcoxon signed-rank test. P < .05 was considered statistically significant.

Results

A total of 67 patients were initially enrolled; 5 were excluded and 6 were lost to follow-up (1 because of a COVID diagnosis). Thus, 56 patients (56 shoulders) were included for analysis. There were 28 patients in the ET group and 28 patients in the PRP group. There were no statistical differences between groups regarding participant characteristics and clinical evaluations before treatment. A statistically significant improvement was observed in pain (VAS subgroups), functionality (CMS subgroups), and QoL (SF-36 subgroups) evaluations of patients in both the ET and the PRP groups compared with before the treatment and 6 months after treatment (P < .05). At the 6-month posttreatment evaluation, the PRP group was statistically significantly superior to isolated ET in terms of VAS rest (P = .001) and night (P = .004) scores. This superiority was also in favor of the PRP group in flexion strength (P = .001), abduction strength (P = .046), and abduction degree (P = .041) measurements. There was no significant difference between ET and PRP groups regarding VAS activity, CMS, and SF-36 scores (P > .05) at 6 months.

Conclusion

Our study showed that both isolated ET and additional PRP application to ET are effective methods in SIS treatment regarding pain, function, and QoL. Combining ET with PRP was superior in reducing pain and improving abduction degree and strength.

Editorial Commentary: Waiting at Least 1 Month After an Intra-articular Corticosteroid Injection for Performing a Knee, Shoulder, and Hip Arthroscopy Could Minimize the Risk for Postoperative Infection: Platelet-Rich Plasma Is an Alternative

An intra-articular corticosteroid is associated with a higher risk of joint infection. Identifying the necessary time interval from the injection to the arthroscopic procedure that does not impose an additional risk of infection is critical for the safety of our patients. Increasing evidence suggests that there is a high risk of infection at the first 4 weeks after the injection, but it seems that this risk declines to normal levels after that period. Interestingly, this time interval of 4 weeks is comparable between knee, shoulder, and hip injection and subsequent arthroscopy. A delay of an arthroscopic intervention at any joint for at least 4 weeks is recommended. Finally, platelet-rich plasma (PRP) is equally effective as corticosteroids in terms of pain management and anti-inflammatory response, with the advantage of promoting healing. PRP may also be associated with a lower risk of postoperative infection in patients undergoing arthroscopy, representing a biologic alternative.

The Second Annual Musculoskeletal Biologics Special Issue Highlights Evidence-Based Therapies

Orthopaedic biologics continues to hold great promise. The editors of Arthroscopy; Arthroscopy Techniques; and Arthroscopy, Sports Medicine, and Rehabilitation once again Call for Papers and invite authors to submit clinical musculoskeletal biologics original scientific research and technical notes with video. Our top articles are awarded inclusion in the Annual Musculoskeletal Biologics Special Issue.

Orthopaedic Musculoskeletal Biologics Research Impacts Patient Care: The Second Annual Arthroscopy Orthobiologics Virtual Special Issue

The field of orthobiologics is rapidly evolving, offering clinicians a shift in treatment from symptom relief to the potential for disease modification and tissue repair. These agents, derived from autologous tissues, components of blood, and growth factors, are used as surgical adjuncts or as standalone treatments. Their clinical applications are expanding to encompass a variety of conditions, supported by a growing base of research efforts. Arthroscopy and its companion publications are committed to evidence-based research with a robust history of publications that enhance clinical decision-making and impact patient care. This curated collection of articles highlights the year's most compelling advancements in orthopaedic musculoskeletal biologics research.

Rotator cuff tears

Rotator cuff tears are the most common upper extremity condition seen by primary care and orthopaedic surgeons, with a spectrum ranging from tendinopathy to full-thickness tears with arthritic change. Some tears are traumatic, but most rotator cuff problems are degenerative. Not all tears are symptomatic and not all progress, and many patients in whom tears become more extensive do not experience symptom worsening. Hence, a standard algorithm for managing patients is challenging. The pathophysiology of rotator cuff tears is complex and encompasses an interplay between the tendon, bone and muscle. Rotator cuff tears begin as degenerative changes within the tendon, with matrix disorganization and inflammatory changes. Subsequently, tears progress to partial-thickness and then full-thickness tears. Muscle quality, as evidenced by the overall size of the muscle and intramuscular fatty infiltration, also influences symptoms, tear progression and the outcomes of surgery. Treatment depends primarily on symptoms, with non-operative management sufficient for most patients with rotator cuff problems. Modern arthroscopic repair techniques have improved recovery, but outcomes are still limited by a lack of understanding of how to improve tendon to bone healing in many patients.

An Update on Orthobiologics: Cautious Optimism

Orthobiologics are rapidly growing in use given their potential to augment healing for multiple musculoskeletal conditions. Orthobiologics consist of a variety of treatments including platelet-rich plasma and stem cells that provide conceptual appeal in providing local delivery of growth factors and inflammation modulation. The lack of standardization in nomenclature and applications within the literature has led to a paucity of high-quality evidence to support their frequent use. The purpose of this review was to describe the current landscape of orthobiologics and the most recent evidence regarding their use.

Editorial Commentary: Platelet-Rich Plasma May Be Superior to Corticosteroid Injection for Rotator Cuff Disease Because of Improved Chance of Healing, Longer-Lasting Pain Relief, and No Detriment if Surgery Is Needed

Both corticosteroid and platelet-rich plasma (PRP) injections have benefits for patients with rotator cuff tendinopathy. Currently, the published clinical differences are small, and statistical differences aren't as significant without a clinical difference, so the answer is personal. PRP is expensive, but rotator cuff healing is possible, resulting in the best chance to avoid surgery. And, if surgery is required, PRP results in no detriment, unlike corticosteroid. PRP may result in lasting pain relief. Based on the current literature, we prefer PRP despite the cost.