Effect of platelet-rich plasma and platelet-rich fibrin matrix on healing of vertical meniscal tears in a rabbit model

Structurally sophisticated 3D-printed PCL-fibrin hydrogel meniscal scaffold promotes in situ regeneration in the rabbit knee meniscus

A meniscus injury is a common cartilage disease of the knee joint. Despite the availability of various methods for the treatment of meniscal injuries, the poor regenerative capacity of the meniscus often necessitates resection, leading to the accelerated progression of osteoarthritis. Advances in tissue engineering have introduced meniscal tissue engineering as a potential treatment option. In this study, we established the size of a standardized meniscal scaffold using knee Magnetic Resonance Imaging (MRI) data and created a precise Polycaprolactone (PCL) scaffold utilizing 3-Dimensional (3D) printing technology, which was then combined with Fibrin (Fib) hydrogel to form a PCL-Fib scaffold. The PCL scaffold offers superior biomechanical properties, while the Fib hydrogel creates a conducive microenvironment for cell growth, supporting chondrocyte proliferation and extracellular matrix (ECM) production. Physical and chemical characterization, biocompatibility testing, and in vivo animal experiments revealed the excellent biomechanical properties and biocompatibility of the scaffold, which enhanced in situ meniscal regeneration and reduced osteoarthritis progression. In conclusion, the integration of 3D printing technology and the Fib hydrogel provided a supportive microenvironment for chondrocyte proliferation and ECM secretion, facilitating the in situ regeneration and repair of the meniscal defect. This innovative approach presents a promising avenue for meniscal injury treatment and advances the clinical utilization of artificial meniscal grafts.

Current advances in animal model of meniscal injury: From meniscal injury to osteoarthritis

Meniscal injury is a prevalent orthopedic practice that causes articular cartilage wear and degeneration due to tissue damage or loss, and may eventually result in the occurrence of knee osteoarthritis (KOA). Hence, investigating the structural regeneration and mechanical function restoration of the meniscus after injury is pivotal research topic for preventing KOA. Animal models are essential for investigating therapeutic strategies for meniscal injuries and their clinical translation, yet no current model can fully recapitulate the complexity of human meniscal injuries. This review aims to categorize the prevalent animal models of meniscal injury by their establishment methods, elucidate their principles and procedures, and discuss the suitability and limitations of each model. We delineate the pros and cons of different models in simulating the pathology and biomechanics of human meniscal injury. We also analyze different animal species regarding their meniscal structure, function, and repair potential, and their implications for model selection. We conclude that selecting an appropriate animal model requires a comprehensive consideration of various factors, such as research aims, anticipated outcomes, and feasibility. Furthermore, to translate novel therapeutic approaches to clinical applications more safely and effectively, future model development should emphasize aspects such as choosing animals of suitable age. The Translational Potential of this Article: This review aims to categorize and discuss current animal models of meniscal injury by establishment methods and provides a comprehensive overview of the routinely employed experimental animals in each model to facilitate the clinical translation of OA-related research.

Advances in meniscus tissue engineering: Towards bridging the gaps from bench to bedside

Meniscus is vital for maintaining the anatomical and functional integrity of knee. Injuries to meniscus, commonly caused by trauma or degenerative processes, can result in knee joint dysfunction and secondary osteoarthritis, while current conservative and surgical interventions for meniscus injuries bear suboptimal outcomes. In the past decade, there has been a significant focus on advancing meniscus tissue engineering, encompassing isolated scaffold strategies, biological augmentation, physical stimulus, and meniscus organoids, to improve the prognosis of meniscus injuries. Despite noteworthy promising preclinical results, translational gaps and inconsistencies in the therapeutic efficiency between preclinical and clinical studies exist. This review comprehensively outlines the developments in meniscus tissue engineering over the past decade (Scheme 1). Reasons for the discordant results between preclinical and clinical trials, as well as potential strategies to expedite the translation of bench-to-bedside approaches are analyzed and discussed.

Biologic Augmentation of Isolated Meniscal Repair

PURPOSE OF REVIEW

The limited blood supply and intrinsic healing capacity of the meniscus contributes to suboptimal tissue regeneration following injury and surgical repair. Biologic augmentation techniques have been utilized in combination with isolated meniscal repair to improve tissue regeneration. Several innovative strategies such as Platelet-Rich Plasma (PRP), fibrin clots, mesenchymal stem cells (MSCs), bone marrow stimulation, meniscal scaffolds, and meniscal wrapping, are being explored to enhance repair outcomes. This article provides a comprehensive review of recent findings and conclusions regarding biologic augmentation techniques.

RECENT FINDINGS

Studies on PRP reveal mixed outcomes, with some suggesting benefits in reducing failure rates of isolated meniscal repair, while others question its efficacy. Fibrin clots and PRF (Platelet-rich fibrin), although promising, show inconsistent results and lack sufficient evidence for definitive conclusions. MSCs demonstrate potential in preclinical studies, but clinical trials have been limited and inconclusive. Bone marrow stimulation appears effective in certain contexts, but its broader applicability remains uncertain. Meniscal scaffolds, including CMI (Collagen Meniscal Implants) and Actifit (polyurethane scaffolds), show encouraging short- and mid-term outcomes but have not consistently surpassed traditional methods in the long term. Meniscal wrapping is infrequently studied but demonstrates positive short-term results with certain applications. The review reveals a diverse range of outcomes for biologic augmentation in meniscal repair. While certain techniques show promise, particularly in specific scenarios, the overall efficacy of these methods has yet to reach a consensus. The review underscores the necessity for standardized, high-quality research to establish the definitive effectiveness of these biologic augmentation methods.

The use of platelet rich plasma in the treatment of degenerative joint disease in cats: an exploratory case series

Objective

To evaluate the effectiveness of intra-articular autologous Platelet Rich Plasma (PRP) in managing Degenerative Joint Disease (DJD) in cats.

Design

Prospective pilot clinical trial.

Methods

Six domestic cats with clinically and radiographically diagnosed DJD received intra-articular injections of autologous PRP. Clinical assessments pre and post intra-articular injections were conducted using the Feline Musculoskeletal Pain Index (FMPI, owner assessed) and Visual Analog Scale (VAS, clinician assessed) at baseline, Day 14, Day 28, and Day 42-45.

Results

Significant improvements were noted in both FMPI and VAS scores at the end of the study period, indicating enhanced joint function and reduced pain.

Conclusion and clinical relevance

The study suggests the potential of PRP therapy as a safe and effective treatment for feline DJD, warranting further research with larger cohorts and longer follow-up to establish comprehensive treatment guidelines.

Surgical and Biological Treatment with a Platelet-Rich Fibrin Matrix for Patellar Tendinopathy: Clinical Outcomes and Return to Sport at 2-Year Follow-Up

BACKGROUND

Patellar tendinopathy (PT) involves anterior knee pain and functional. Platelet-rich fibrin matrix (PRFM) is a promising biological therapy for tendinopathies. We examined a cohort of PT patients treated with tendon debridement and autologous PRFM at the 24-month follow-up to assess whether the combined treatment facilitated return to sports and yielded satisfactory clinical and functional scores.

METHODS

Baseline and 24-month visual analogue scale (VAS), Victorian Institute of Sport Assessment Scale for Patellar Tendinopathy (VISA-P), Tegner Activity Scale (TAS), and Blazina scores were compared to evaluate treatment effectiveness. The Friedman test was used to compare repeated observations of VAS, VISA-P, TAS, and Blazina Score values. Return to sport rate, Tampa Scale of Kinesiophobia (TKS) score and patient satisfaction were collected at 24 months.

RESULTS

The postoperative clinical scores demonstrated significant improvement compared with their preoperative values (all p < 0.001). Specifically, the VISA-P score was 80.32 (±20.58), 92.10% of patients had resumed sports activities and patient satisfaction was 9.21 (±1.21) at 24 months.

CONCLUSIONS

Surgical debridement and autologous PRFM application in patients with chronic PT resulted in a higher rate of return to sports when compared to solely surgical treatment, significantly improved clinical outcomes and excellent patient satisfaction at 24 months.

[Study of centrifuge conditions for preparing rabbit leukocyte-poor platelet-rich plasma by single centrifugation]

Objective

To explore the best centrifuge condition for preparing rabbit leukocyte-poor platelet-rich plasma (LP-PRP) by using single centrifugation method.

Methods

Sixteen healthy New Zealand rabbits, aged 3-4 months, were utilized in the investigation. A total of 15 mL anticoagulated blood was extracted from the central ear artery of each rabbit, with a repeat of the blood collection procedure after 1 and 2 months. The obtained blood specimens were individually subjected to centrifugation at a radius of 16.7 cm and speeds of 1 200, 1 300, 1 400, and 1 500 r/min (equivalent to centrifugal forces of 269× g, 315× g, 365× g, and 420× g) for durations of 2, 3, 4, and 5 minutes, resulting in a total of 16 groups. Following centrifugation, collect plasma from each group to a distance of 1.5 mL from the separation plane. The volumes, platelet enrichment coefficient, and platelet recovery rates of LP-PRP in each group, under varying centrifugation conditions, were methodically computed and subsequently compared.

Results

The volume of LP-PRP obtained under all centrifugation conditions ranged from 1.8 to 7.6 mL. At a consistent centrifugal speed, an extension of centrifugation time leaded to a significant increase in the volume of LP-PRP, accompanied by a declining trend in the platelet enrichment coefficient of LP-PRP. When centrifuged for 2 minutes, the volume of LP-PRP at speeds of 1 200 and 1 300 r/min was less than 2.0 mL, while the volume of LP-PRP obtained under other conditions was more than 2.0 mL. When centrifuged for 4 and 5 minutes, the volume of LP-PRP obtained at each speed was more than 4 mL. LP-PRP with a platelet enrichment coefficient more than 2.0 could be prepared by centrifuging at 1 200 r/min for each time group and 1 300 r/min for 2 and 3 minutes, and the highest LP-PRP platelet enrichment coefficient could be obtained by centrifugation for 2 minutes at a speed of 1 200 r/min. The platelet recovery rates of LP-PRP obtained by centrifugation at 1 200 r/min for 4 and 5 minutes, as well as centrifugation at 1 400 r/min for 5 minutes, were both greater than 60%. There was no significant difference between the groups when centrifuged at 1 200 r/min for 4 and 5 minutes ( P>0.05).

Conclusion

In the process of preparing rabbit LP-PRP using a single centrifugation method, collecting 15 mL of blood and centrifuging at a radius of 16.7 cm and speed of 1 200 r/min for 4 minutes can prepare LP-PRP with a volume exceeding 2.0 mL, platelet enrichment coefficient exceeding 2.0, and platelet recovery rate exceeding 60%. This centrifugal condition can achieve the optimal LP-PRP action parameters in the shortest possible time.

Advances in Hydrogels for Meniscus Tissue Engineering: A Focus on Biomaterials, Crosslinking, Therapeutic Additives

Meniscus tissue engineering (MTE) has emerged as a promising strategy for meniscus repair and regeneration. As versatile platforms, hydrogels have gained significant attention in this field, as they possess tunable properties that allow them to mimic native extracellular matrices and provide a suitable microenvironment. Additionally, hydrogels can be minimally invasively injected and can be adjusted to match the shape of the implant site. They can conveniently and effectively deliver bioactive additives and demonstrate good compatibility with other functional materials. These inherent qualities have made hydrogel a promising candidate for therapeutic approaches in meniscus repair and regeneration. This article provides a comprehensive review of the advancements made in the research on hydrogel application for meniscus tissue engineering. Firstly, the biomaterials and crosslinking strategies used in the formation of hydrogels are summarized and analyzed. Subsequently, the role of therapeutic additives, including cells, growth factors, and other active products, in facilitating meniscus repair and regeneration is thoroughly discussed. Furthermore, we summarize the key issues for designing hydrogels used in MTE. Finally, we conclude with the current challenges encountered by hydrogel applications and suggest potential solutions for addressing these challenges in the field of MTE. We hope this review provides a resource for researchers and practitioners interested in this field, thereby facilitating the exploration of new design possibilities.

Evolution and Clinical Advances of Platelet-Rich Fibrin in Musculoskeletal Regeneration

Over the past few decades, various forms of platelet concentrates have evolved with significant clinical utility. The newer generation products, including leukocyte-platelet-rich fibrin (L-PRF) and advanced platelet-rich fibrin (A-PRF), have shown superior biological properties in musculoskeletal regeneration than the first-generation concentrates, such as platelet-rich plasma (PRP) and plasma rich in growth factors. These newer platelet concentrates have a complete matrix of physiological fibrin that acts as a scaffold with a three-dimensional (3D) architecture. Further, it facilitates intercellular signaling and migration, thereby promoting angiogenic, chondrogenic, and osteogenic activities. A-PRF with higher leukocyte inclusion possesses antimicrobial activity than the first generations. Due to the presence of enormous amounts of growth factors and anti-inflammatory cytokines that are released, A-PRF has the potential to replicate the various physiological and immunological factors of wound healing. In addition, there are more neutrophils, monocytes, and macrophages, all of which secrete essential chemotactic molecules. As a result, both L-PRF and A-PRF are used in the management of musculoskeletal conditions, such as chondral injuries, tendinopathies, tissue regeneration, and other sports-related injuries. In addition to this, its applications have been expanded to include the fields of reconstructive cosmetic surgery, wound healing in diabetic patients, and maxillofacial surgeries.

Applications and prospects of different functional hydrogels in meniscus repair

The meniscus is a kind of fibrous cartilage structure that serves as a cushion in the knee joint to alleviate the mechanical load. It is commonly injured, but it cannot heal spontaneously. Traditional meniscectomy is not currently recommended as this treatment tends to cause osteoarthritis. Due to their good biocompatibility and versatile regulation, hydrogels are emerging biomaterials in tissue engineering. Hydrogels are excellent candidates in meniscus rehabilitation and regeneration because they are fine-tunable, easily modified, and capable of delivering exogenous drugs, cells, proteins, and cytokines. Various hydrogels have been reported to work well in meniscus-damaged animals, but few hydrogels are effective in the clinic, indicating that hydrogels possess many overlooked problems. In this review, we summarize the applications and problems of hydrogels in extrinsic substance delivery, meniscus rehabilitation, and meniscus regeneration. This study will provide theoretical guidance for new therapeutic strategies for meniscus repair.

Platelet-rich plasma use in meniscus repair treatment: a systematic review and meta-analysis of clinical studies

Background

There is conflicting clinical evidence whether platelet-rich plasma (PRP) therapies could translate to an increased meniscus healing rate and improved functional outcomes. The objective of this systematic review and meta-analysis was to compare the failure rate and patient-reported functional outcomes in meniscus repair augmented with and without PRP.

Methods

We comprehensively searched the PubMed, Web of Science, Medline, Embase, and Cochrane Library databases to identify studies that compared the clinical efficacy of meniscus repair performed with PRP versus without PRP. The primary outcome was the meniscus repair failure rate, while the secondary outcomes were knee-specific patient-reported outcomes, including the International Knee Documentation Committee (IKDC) score, Lysholm knee scale, visual analog scale, Tegner activity level score, Western Ontario and McMaster Universities Osteoarthritis Index score, Single Assessment Numeric Evaluation score, and Knee injury and Osteoarthritis Outcome Score. Furthermore, subgroup analyses were performed by stratifying the studies according to the PRP preparation technique to investigate the potential sources of heterogeneity among studies.

Results

Our meta-analysis included nine studies (two RCTs and seven non-RCTs) with 1164 participants. The failure rate in the PRP group was significantly lower than that in the non-PRP group [odds ratio: 0.64, 95% confidence interval (CI) (0.42, 0.96), P = 0.03]. Furthermore, the PRP group was associated with a statistically significant improvement in the visual analog scale for pain [Mean difference (MD): − 0.76, 95% CI (− 1.32, − 0.21), P = 0.007] and Knee injury and Osteoarthritis Outcome Score-symptom [MD: 8.02, 95% CI (2.99, 13.05), P = 0.002] compared with the non-PRP group. However, neither the IKDC score nor the Lysholm knee scale showed any differences between the two groups. In addition, the results of subgroup analyses favored PRP over platelet-rich fibrin matrix (PRFM) regarding the IKDC score.

Conclusions

Although meniscus repairs augmented with PRP led to significantly lower failure rates and better postoperative pain control compared with those of the non-PRP group, there is insufficient RCT evidence to support PRP augmentation of meniscus repair improving functional outcomes. Moreover, PRP could be recommended in meniscus repair augmentation compared with PRFM. PRFM was shown to have no benefit in improving functional outcomes.

Post-Traumatic Osteoarthritis Assessment in Emerging and Advanced Pre-Clinical Meniscus Repair Strategies: A Review

Surgical repair of meniscus injury is intended to help alleviate pain, prevent further exacerbation of the injury, restore normal knee function, and inhibit the accelerated development of post-traumatic osteoarthritis (PTOA). Meniscus injuries that are treated poorly or left untreated are reported to significantly increase the risk of PTOA in patients. Current surgical approaches for the treatment of meniscus injuries do not eliminate the risk of accelerated PTOA development. Through recent efforts by scientists to develop innovative and more effective meniscus repair strategies, the use of biologics, allografts, and scaffolds have come into the forefront in pre-clinical investigations. However, gauging the extent to which these (and other) approaches inhibit the development of PTOA in the knee joint is often overlooked, yet an important consideration for determining the overall efficacy of potential treatments. In this review, we catalog recent advancements in pre-clinical therapies for meniscus injuries and discuss the assessment methodologies that are used for gauging the success of these treatments based on their effect on PTOA severity. Methodologies include histopathological evaluation of cartilage, radiographic evaluation of the knee, analysis of knee function, and quantification of OA predictive biomarkers. Lastly, we analyze the prevalence of these methodologies using a systemic PubMed® search for original scientific journal articles published in the last 3-years. We indexed 37 meniscus repair/replacement studies conducted in live animal models. Overall, our findings show that approximately 75% of these studies have performed at least one assessment for PTOA following meniscus injury repair. Out of this, 84% studies have reported an improvement in PTOA resulting from treatment.

Six-Month Outcomes of Clinically Relevant Meniscal Injury in a Large-Animal Model

BACKGROUND

The corrective procedures for meniscal injury are dependent on tear type, severity, and location. Vertical longitudinal tears are common in young and active individuals, but their natural progression and impact on osteoarthritis (OA) development are not known. Root tears are challenging and they often indicate poor outcomes, although the timing and mechanisms of initiation of joint dysfunction are poorly understood, particularly in large-animal and human models.

PURPOSE/HYPOTHESIS

In this study, vertical longitudinal and root tears were made in a large-animal model to determine the progression of joint-wide dysfunction. We hypothesized that OA onset and progression would depend on the extent of injury-based load disruption in the tissue, such that root tears would cause earlier and more severe changes to the joint.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sham surgeries and procedures to create either vertical longitudinal or root tears were performed in juvenile Yucatan mini pigs through randomized and bilateral arthroscopic procedures. Animals were sacrificed at 1, 3, or 6 months after injury and assessed at the joint and tissue level for evidence of OA. Functional measures of joint load transfer, cartilage indentation mechanics, and meniscal tensile properties were performed, as well as histological evaluation of the cartilage, meniscus, and synovium.

RESULTS

Outcomes suggested a progressive and sustained degeneration of the knee joint and meniscus after root tear, as evidenced by histological analysis of the cartilage and meniscus. This occurred in spite of spontaneous reattachment of the root, suggesting that this reattachment did not fully restore the function of the native attachment. In contrast, the vertical longitudinal tear did not cause significant changes to the joint, with only mild differences compared with sham surgery at the 6-month time point.

CONCLUSION

Given that the root tear, which severs circumferential connectivity and load transfer, caused more intense OA compared with the circumferentially stable vertical longitudinal tear, our findings suggest that without timely and mechanically competent fixation, root tears may cause irreversible joint damage.

CLINICAL RELEVANCE

More generally, this new model can serve as a test bed for experimental surgical, scaffold-based, and small molecule-driven interventions after injury to prevent OA progression.