Effects of Platelet-Rich Plasma Composition on Anabolic and Catabolic Activities in Equine Cartilage and Meniscal Explants

Platelet-Rich Plasma for Knee Osteoarthritis: What Does the Evidence Say?

The utilization of platelet-rich-plasma as a therapeutic intervention for knee osteoarthritis has gained immense attention since 2008. The increase in the number of scientific publications dedicated to this area can be attributed to the majority of favorable results reported in clinical trials and basic science studies. However, despite the growing evidence, the use of platelet-rich plasma in clinical practice still poses controversial aspects. The potential mechanisms of action described for platelet-rich-plasma so far indicate that it could serve as a disease-modifying drug, acting to counteract important aspects of knee osteoarthritis pathophysiology (cartilage breakdown, inflammation, and bone remodeling). Nevertheless, its efficacy in slowing down the progression of knee osteoarthritis remains unproven. While inconsistencies have been noted, the majority of controlled clinical trials and meta-analyses advocate for the utilization of platelet-rich-plasma in treating knee osteoarthritis, as it has demonstrated greater efficacy than hyaluronic acid and placebo, with a follow-up of at least 1 year. Despite advancements made in certain areas, significant diversity persists regarding the formulations used, therapeutic regimen, extended follow-up periods, patient selection, and assessment of clinically relevant outcomes. Consequently, the leading clinical practice guidelines do not recommend its use. In light of the emerging evidence, this narrative review aims to provide an objective evaluation of the recent available scientific literature (last 5 years) focused on randomized clinical trials and meta-analyses to present a current overview of the topic.

Autologous Platelet and Extracellular Vesicle-Rich Plasma as Therapeutic Fluid: A Review

The preparation of autologous platelet and extracellular vesicle-rich plasma (PVRP) has been explored in many medical fields with the aim to benefit from its healing potential. In parallel, efforts are being invested to understand the function and dynamics of PVRP that is complex in its composition and interactions. Some clinical evidence reveals beneficial effects of PVRP, while some report that there were no effects. To optimize the preparation methods, functions and mechanisms of PVRP, its constituents should be better understood. With the intention to promote further studies of autologous therapeutic PVRP, we performed a review on some topics regarding PVRP composition, harvesting, assessment and preservation, and also on clinical experience following PVRP application in humans and animals. Besides the acknowledged actions of platelets, leukocytes and different molecules, we focus on extracellular vesicles that were found abundant in PVRP.

Use of allogeneic freeze-dried conditioned serum for the prevention of degradation in cartilage exposed to IL-1ß

Background

Autologous conditioned serum (ACS) has been extensively used in the field of veterinary orthopaedics and sports medicine. Due to the autologous and blood-derived nature of this product, issues such as individual variability, need for storage at low temperatures and non-availability for immediate are frequently encountered for ACS use in the field. To address those issues, we proposed the evaluation of an off-the-shelf allogeneic freeze-dried version of conditioned serum in an in vitro model of osteoarthritis. In this study, we evaluated if origin (autologous and allogeneic) and preparation (frozen and freeze-dried) of conditioned serum could influence in its effect in an in vitro model.

Results

IL-1β stimulation in cartilage led to a significant increase in media GAG and decreased levels of GAG in cartilage explants at the termination of the experiment. No significant differences were noted in outcomes measured in the cartilage explants with respect to the main effects of treatment (frozen versus freeze-dried serum), autologous versus allogeneic preparations or based on serum concentration.

Conclusions

The study did not observe any substantial differences in the response of cartilage to allogeneic freeze-dried CS when compared to other independent parameters (autologous and frozen preparations). Further investigation using in vivo systems appears warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03227-2.

Mesenchymal Stem Cells From Different Sources in Meniscus Repair and Regeneration

Meniscus damage is a common trauma that often arises from sports injuries or menisci tissue degeneration. Current treatment methods focus on the repair, replacement, and regeneration of the meniscus to restore its original function. The advance of tissue engineering provides a novel approach to restore the unique structure of the meniscus. Recently, mesenchymal stem cells found in tissues including bone marrow, peripheral blood, fat, and articular cavity synovium have shown specific advantages in meniscus repair. Although various studies explore the use of stem cells in repairing meniscal injuries from different sources and demonstrate their potential for chondrogenic differentiation, their meniscal cartilage-forming properties are yet to be systematically compared. Therefore, this review aims to summarize and compare different sources of mesenchymal stem cells for meniscal repair and regeneration.

Cellular components and TGF-β1 content of a closed Tube system for Platelet Rich Plasma acquisition in horse]

ABSTRACT Platelet-rich plasma (PRP) has been proposed as an agent to accelerate the healing process and stimulate the regenerative capacity of tissues due to its abundance of growth factors. A large variety of kits and protocols are available to obtain PRP by different cell-separation systems. However, the lack of standardization may lead to inconsistent results. The aim of this study was to characterize cellular composition, platelet parameters using the ADVIA 120 flow cytometer, and TGF-β1 concentration from the PRP product obtained through a closed system, using simple centrifugation. Six clinically healthy horses were used in this study. The protocol in the closed system resulted in approximately 1.6-fold higher platelet and approximately 2.0-fold lower white blood cell concentrations in comparison with whole blood values. The evaluated system was efficient in concentrating platelets and in retrieving a small number of leukocytes, using a protocol of single centrifugation at low speed.

Current Models for Development of Disease-Modifying Osteoarthritis Drugs

Osteoarthritis (OA) is a painful and disabling disease that affects millions of people worldwide. Symptom-alleviating treatments exist, although none with long-term efficacy. Furthermore, there are currently no disease-modifying OA drugs (DMOADs) with demonstrated efficacy in OA patients, which is, in part, attributed to a lack of full understanding of the pathogenesis of OA. The inability to translate findings from basic research to clinical applications also highlights the deficiencies in the available OA models at simulating the clinically relevant pathologies and responses to treatments in humans. In this review, the current status in the development of DMOADs will be first presented, with special attention to those in Phase II-IV clinical trials. Next, current in vitro, ex vivo, and in vivo OA models are summarized and the respective advantages and disadvantages of each are highlighted. Of note, the development and application of microphysiological or tissue-on-a-chip systems for modeling OA in humans are presented and the issues that need to be addressed in the future are discussed. Microphysiological systems should be given serious consideration for their inclusion in the DMOAD development pipeline, both for their ability to predict drug safety and efficacy in human clinical trials at present, as well as for their potential to serve as a test platform for personalized medicine. Impact statement At present, no disease-modifying osteoarthritis (OA) drugs (DMOADs) have been approved for widespread clinical use by regulatory bodies. The failure of developing effective DMOADs is likely owing to multiple factors, not the least of which are the intrinsic differences between the intact human knee joint and the preclinical models. This work summarizes the current OA models for the development of DMOADs, discusses the advantages/disadvantages of each, and then proposes future model development to aid in the discovery of effective and personalized DMOADs. The review also highlights the microphysiological systems, which are emerging as a new platform for drug development.

Regenerative Medicine for Equine Musculoskeletal Diseases

Simple Summary

Lameness due to musculoskeletal disease is the most common diagnosis in equine veterinary practice. Many of these orthopaedic disorders are chronic problems, for which no clinically satisfactory treatment exists. Thus, high hopes are pinned on regenerative medicine, which aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. Some regenerative medicine therapies have already made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising but diverse results. This review summarises the current knowledge of commonly used regenerative medicine treatments and critically discusses their use.

Abstract

Musculoskeletal injuries and chronic degenerative diseases commonly affect both athletic and sedentary horses and can entail the end of their athletic careers. The ensuing repair processes frequently do not yield fully functional regeneration of the injured tissues but biomechanically inferior scar or replacement tissue, causing high reinjury rates, degenerative disease progression and chronic morbidity. Regenerative medicine is an emerging, rapidly evolving branch of translational medicine that aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. It includes tissue engineering but also cell-based and cell-free stimulation of endogenous self-repair mechanisms. Some regenerative medicine therapies have made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising results. However, the qualitative and quantitative spatiotemporal requirements for specific bioactive factors to trigger tissue regeneration in the injury response are still unknown, and consequently, therapeutic approaches and treatment results are diverse. To exploit the full potential of this burgeoning field of medicine, further research will be required and is ongoing. This review summarises the current knowledge of commonly used regenerative medicine treatments in equine patients and critically discusses their use.

Optimal double-spin method for maximizing the concentration of platelets in equine platelet-rich plasma

This study optimized the double-spin conditions for preparing equine platelet-rich plasma (PRP): leukocyte-rich PRP (L-PRP) and leukocyte-poor PRP (P-PRP). Whole blood samples were centrifuged at various double-spin conditions. Both L-PRP and P-PRP were prepared at each stage, and complete blood counts and growth factor concentrations were compared. Samples centrifuged at 160 × 900 g, 160 × 2,000 g, and 400 × 2,000 g exhibited the highest platelet counts. P-PRP had significantly lower leukocyte and erythrocyte contents than L-PRP, especially at 400 × 2,000 g. No significant differences were observed in growth factor concentrations. Our data suggest that optimum L-PRP preparation should include centrifugation under the aforementioned conditions, whereas centrifugation at 400 × 2,000 g is optimal for P-PRP.

Large Animal Models in Regenerative Medicine and Tissue Engineering: To Do or Not to Do

Rapid developments in Regenerative Medicine and Tissue Engineering has witnessed an increasing drive toward clinical translation of breakthrough technologies. However, the progression of promising preclinical data to achieve successful clinical market authorisation remains a bottleneck. One hurdle for progress to the clinic is the transition from small animal research to advanced preclinical studies in large animals to test safety and efficacy of products. Notwithstanding this, to draw meaningful and reliable conclusions from animal experiments it is critical that the species and disease model of choice is relevant to answer the research question as well as the clinical problem. Selecting the most appropriate animal model requires in-depth knowledge of specific species and breeds to ascertain the adequacy of the model and outcome measures that closely mirror the clinical situation. Traditional reductionist approaches in animal experiments, which often do not sufficiently reflect the studied disease, are still the norm and can result in a disconnect in outcomes observed between animal studies and clinical trials. To address these concerns a reconsideration in approach will be required. This should include a stepwise approach using in vitro and ex vivo experiments as well as in silico modeling to minimize the need for in vivo studies for screening and early development studies, followed by large animal models which more closely resemble human disease. Naturally occurring, or spontaneous diseases in large animals remain a largely untapped resource, and given the similarities in pathophysiology to humans they not only allow for studying new treatment strategies but also disease etiology and prevention. Naturally occurring disease models, particularly for longer lived large animal species, allow for studying disorders at an age when the disease is most prevalent. As these diseases are usually also a concern in the chosen veterinary species they would be beneficiaries of newly developed therapies. Improved awareness of the progress in animal models is mutually beneficial for animals, researchers, human and veterinary patients. In this overview we describe advantages and disadvantages of various animal models including domesticated and companion animals used in regenerative medicine and tissue engineering to provide an informed choice of disease-relevant animal models.

Importance of Timing of Platelet Lysate-Supplementation in Expanding or Redifferentiating Human Chondrocytes for Chondrogenesis

Osteoarthritis (OA) in articular joints is a prevalent disease. With increasing life expectancy, the need for therapies other than knee replacement arises. The intrinsic repair capacity of cartilage is limited, therefore alternative strategies for cartilage regeneration are being explored. The purpose of this study is first to investigate the potential of platelet lysate (PL) as a xeno-free alternative in expansion of human OA chondrocytes for cell therapy, and second to assess the effects of PL on redifferentiation of expanded chondrocytes in 3D pellet cultures. Chondrocytes were isolated from human OA cartilage and subjected to PL in monolayer culture. Cell proliferation, morphology, and expression of chondrogenic genes were assessed. Next, PL-expanded chondrocytes were cultured in 3D cell pellets and cartilage matrix production was assessed after 28 days. In addition, the supplementation of PL to redifferentiation medium for the culture of expanded chondrocytes in 3D pellets was evaluated. Glycosaminoglycan (GAG) and collagen production were evaluated by quantitative biochemical analyses, as well as by (immuno)histochemistry. A dose-dependent effect of PL on chondrocyte proliferation was found, but expression of chondrogenic markers was decreased when compared to FBS-expanded cells. After 28 days of subsequent 3D pellet culture, GAG production was significantly higher in pellets consisting of chondrocytes expanded with PL compared to controls. However, when used to supplement redifferentiation medium for chondrocyte pellets, PL significantly decreased the production of GAGs and collagen. In conclusion, chondrocyte proliferation is stimulated by PL and cartilage production in subsequent 3D culture is maintained. Furthermore, the presences of PL during redifferentiation of 3D chondrocyte strongly inhibits GAG and collagen content. The data presented in the current study indicate that while the use of PL for expansion in cartilage cell therapies is possibly beneficial, intra-articular injection of the product in the treatment of OA might be questioned.

Effects of Autologous Conditioned Serum, Autologous Protein Solution, and Triamcinolone on Inflammatory and Catabolic Gene Expression in Equine Cartilage and Synovial Explants Treated With IL-1β in Co-culture

Autologous conditioned serum (ACS) and autologous protein solution (APS) are newer therapeutic options for osteoarthritis (OA). Co-culture of cartilage and synovium stimulated with IL-1β produces a similar physiologic response to tissues from naturally-ocurring OA. The study objective was to investigate the effects of ACS, APS, and triamcinolone (TA) on inflammatory and catabolic gene expression of inflamed joint tissues in co-culture. Blood was collected and processed for ACS and APS from six horses. Cartilage and synovial explants were harvested from the stifle, placed in co-culture, and treated as: (1) unstimulated control (2) stimulated control (3) ACS at 25% v/v (4) ACS at 50% v/v (5) APS at 25% v/v (6) APS at 50% v/v, (7) TA (10⁻⁶ M). Treatment groups 2–7 were stimulated with IL-1β (10 ng/ml). Cultures were maintained for 96 hours, and then both media and explants were harvested for measurement of gene expression and protein. IL-1β stimulation significantly increased IL-1β (p = 0.029), IL-8 (p = 0.011) and MMP-3 (p = 0.043) expression in synovium and IL-1β (p = 0.003) and TNF-α (p = 0.001) expression in cartilage. Treatment with 50% ACS and APS v/v downregulated IL-1β expression in cartilage more than TA treatment (p = 0.001 and p = 0.0004) and APS downregulated MMP-1 expression in synovial membrane (p = 0.025). Treatment with ACS and APS caused a trend in upregulation of IL-10 expression in synovium and type II collagen and aggrecan expression in cartilage. PGE₂ media concentrations were significantly reduced following treatment with APS (13.7-fold decrease, p = 0.0001) and ACS (4.13-fold decrease, p = 0.024); while TA did not reduce PGE₂ significantly (2.3-fold decreased p = 0.406). As disease-modifying therapies, ACS and APS modified the cellular response from synovial membrane and articular cartilage. ACS and APS may offer an improved strategy to improve clinical signs of horses with naturally occurring OA, compared to TA treatment.

Platelet-Rich Products and Their Application to Osteoarthritis

Autologous platelet-rich plasma (PRP) is a biological preparation made from the patient's own plasma that contains a platelet concentration above the whole blood baseline. Owing to the release of growth factors and other cytokines after degranulation, platelets have a central role in inflammation and in different stages of the healing process. For this reason, PRP-derived products have been used to enhance healing of musculoskeletal injuries and modulate progression of inflammatory processes, including osteoarthritis (OA). Osteoarthritis is one of the main causes of musculoskeletal disabilities in horses, and currently, there is no effective treatment for this disease. Treatments that focus on the modulation of inflammation and disease progression offer new hope for OA. Platelet-rich plasma provides a more practical and accessible option of therapy compared to other forms of biological treatment (i.e., stem cell therapies) and is believed to induce the production of functional matrix. However, several factors related to PRP production, including methods of preparation and application, and intraindividual variability, lead to an inconsistent product, precluding reliable conclusions about its efficacy for clinical use. The aim of this study was to review the benefits related to the clinical use of PRP in OA as well as factors that influence its use, the limitations of this treatment, and future directions of PRP research and therapy.

Evaluation of allogeneic freeze-dried platelet lysate in cartilage exposed to interleukin 1-β in vitro

Background

Platelet-rich plasma (PRP) as well as other platelet-derived products have been used as a potential disease-modifying treatment for musculoskeletal diseases, such as osteoarthritis (OA). The restorative properties of such products rely mainly on the high concentrations of growth factors, demonstrating encouraging results experimentally and clinically. Yet, the autologous blood-derived nature of the PRP product lead to limitations that precludes it’s widespread use. The main limitations for PRP use are; product variability, the need for minimum laboratory settings in most cases, and the need for storage at low temperatures to preserve its properties. Based on these limitations, the objective of this study was to investigate an allogeneic off-the-shelf platelet lysate (PL) in cartilage exposed to interleukin 1β (IL-1β). For this purpose, blood and cartilage were harvested from eight skeletally mature and healthy horses. Blood was processed into PL aliquots and divided into three groups (Frozen, Freeze-dried and Filtered freeze-dried), used in autologous and allogeneic conditions and in three different concentrations (1.5, 3 and 6-fold). Different PL preparations were then applied in cartilage culture with interleukin-1 beta and cultured for 10 days. Cartilage and media samples were collected and analyzed for total GAG and ³⁵SO₄-labeled GAG content.

Results

No significant differences between the controls and PL groups in cartilage and media were demonstrated. The effects of PL on cartilage matrix were concentration dependent and intermediate concentrations (3-fold) in PL showed increased ³⁵SO₄-labelled GAG in cartilage.

Conclusion

In conclusion, the allogeneic freeze-dried PL presented equivalent effects compared to frozen autologous PL. Intermediate platelet concentration on average demonstrated improved results, demonstrating less GAG loss compared to other concentrations.

Anti-Inflammatory Effects of Novel Standardized Platelet Rich Plasma Releasates on Knee Osteoarthritic Chondrocytes and Cartilage in vitro

Background:

Platelet Rich Plasma (PRP) has recently emerged as a potential treatment for osteoarthritis (OA), but composition heterogeneity hampers comparison among studies, with the result that definite conclusions on its efficacy have not been reached.

Objective:

1) To develop a novel methodology to prepare a series of standardized PRP releasates (PRP-Rs) with known absolute platelet concentrations, and 2) To evaluate the influence of this standardization parameter on the anti-inflammatory properties of these PRP-Rs in an in vitro and an ex vivo model of OA.

Methods:

A series of PRPs was prepared using the absolute platelet concentration as the standardization parameter. Doses of platelets ranged from 0% (platelet poor plasma, PPP) to 1.5·105 platelets/µl. PRPs were then activated with CaCl2 to obtain releasates (PRP-R). Chondrocytes were stimulated with 10% of each PRP-R in serum-free culture medium for 72 h to assess proliferation and viability. Cells were co-stimulated with interleukin (IL)-1β (5 ng/ml) and 10% of each PRP-R for 48 h to determine the effects on gene expression, secretion and intra-cellular content of common markers associated with inflammation, catabolism and oxidative stress in OA. OA cartilage explants were co-stimulated with IL-1β (5 ng/ml) and 10% of either PRP-R with 0.75·105 platelets/µl or PRP-R with 1.5·105 platelets/µl for 21 days to assess matrix inflammatory degradation.

Results:

Chondrocyte viability was not affected, and proliferation was dose-dependently increased. The gene expression of all pro-inflammatory mediators was significantly and dose-independently reduced, except for that of IL-1β and IL-8. Immunoblotting corroborated this effect for inducible NO synthase (NOS2). Secreted matrix metalloproteinase-13 (MMP-13) was reduced to almost basal levels by the PRP-R from PPP. Increasing platelet dosage led to progressive loss to this anti-catabolic ability. Safranin O and toluidine blue stains supported the beneficial effect of low platelet dosage on cartilage matrix preservation.

Conclusion:

We have developed a methodology to prepare PRP releasates using the absolute platelet concentration as the standardization parameter. Using this approach, the composition of the resulting PRP derived product is independent of the donor initial basal platelet count, thereby allowing the evaluation of its effects objectively and reproducibly. In our OA models, PRP-Rs showed antiinflammatory, anti-oxidant and anti-catabolic properties. Platelet enrichment could favor chondrocyte proliferation but is not necessary for the above effects and could even be counter-productive.

The Concentration of Plasma Provides Additional Bioactive Proteins in Platelet and Autologous Protein Solutions

BACKGROUND

Currently, platelet-poor plasma (PPP) is a discarded waste product of platelet-rich plasma (PRP) and may contain valuable proteins.

PURPOSE/HYPOTHESIS

The study's goal was to evaluate the concentration of plasma as a potential additive biotherapy for the treatment of osteoarthritis. We hypothesized that a novel polyacrylamide concentration device would efficiently concentrate insulin-like growth factor-1 (IGF-1) from PPP and be additive to PRP or autologous protein solution (APS).

STUDY DESIGN

Descriptive laboratory study.

METHODS

A laboratory study was conducted with human and equine whole blood from healthy volunteers/donors. Fresh samples of blood and plasma were processed and characterized for platelet, white blood cell, and growth factor/cytokine content and then quantified by enzyme-linked immunosorbent assays specific for IGF-1, transforming growth factor-β, interleukin-1β, and interleukin-1 receptor antagonist as representatives of cartilage anabolic and inflammatory mediators.

RESULTS

A potent cartilage anabolic protein, IGF-1, was significantly concentrated by the polyacrylamide concentration device in both human and equine PPP. The polyacrylamide device also substantially increased plasma proteins over whole blood, most dramatically key proteins relevant to the treatment of osteoarthritis, including transforming growth factor-β (29-fold over blood) and interleukin-1 receptor antagonist (70-fold over plasma).

CONCLUSION

Concentrated PPP is a unique source for biologically relevant concentrations of IGF-1. PRP and APS can produce greater concentrations of other anabolic and anti-inflammatory proteins not found in plasma.

CLINICAL RELEVANCE

The polyacrylamide device efficiently concentrated PPP to create a unique source of IGF-1 that may supplement orthopaedic biologic therapies.

Variables affecting the potential efficacy of PRP in providing chronic pain relief

Although chronic pain affects about 1% of the US population, it remains largely resistant to treatment. Despite great variability in pain outcomes, the application of autologous platelet-rich plasma (PRP) has become increasingly popular in attempts to reduce chronic pain. The variability in PRP efficacy raises the question of whether PRP actually has an analgesic capacity, and if so, can that capacity be made consistent and maximized. The best explanation for the variability in PRP analgesic efficacy is the failure during PRP preparation and application to take into account variables that can increase or eliminate its analgesic capabilities. This suggests that if the variables are reduced and controlled, a PRP preparation and application protocol can be developed leading to PRP inducing reliable, complete, and long-term pain relief. The goal of this study was to examine some of the variables that influence platelets and see how they might be controlled to increase the analgesic potential of PRP. Among the variables examined are the physiological status of the patient, methods used to prepare PRP, and methods of PRP application. The goal of modifying these variables is to minimize platelet serotonin content, maximize platelet content of factors that reduce inflammation and pain, while maintaining their bioactivity, maximize platelet capacity to aggregate at injury sites, induce rapid and simultaneous release of their contents, and optimize PRP application protocols. It is concluded that controlling some or many of these variables will lead to PRP that induces reliable, maximum, and long-term relief of chronic pain.

Chondrocyte-based intraoperative processing strategies for the biological augmentation of a polyurethane meniscus replacement

Purpose/aim of study: Menisectomies account for over 1.5 million surgical interventions in Europe annually, and there is a growing interest in regenerative strategies to improve outcomes in meniscal replacement. The overall objective of this study was to evaluate the role of intraoperatively applied fresh chondrocyte (FC) isolates compared to minced cartilage (MC) fragments, used without cell isolation, to improve bioactivity and tissue integration when combined with a polyurethane replacement.

MATERIALS AND METHODS

First, to optimize the intraoperative cell isolation protocol, caprine articular cartilage biopsies were digested with 750 U/ml or 3000 U/ml collagenase type II (ratio of 10 ml per g of tissue) for 30 min, 1 h or 12 h with constant agitation and compared to culture-expanded chondrocytes in terms of matrix deposition when cultured on polyurethane scaffolds. Finally, FCs and MC-augmented polyurethane scaffolds were evaluated in a caprine meniscal explant model to assess the potential enhancements on tissue integration strength.

RESULTS

Adequate numbers of FCs were harvested using a 30 min chondrocyte isolation protocol and were found to demonstrate improved matrix deposition compared to standard culture-expanded cells in vitro. Upon evaluation in a meniscus explant defect model, both FCs and MC showed improved matrix deposition at the tissue-scaffold interface and enhanced push-out strength, fourfold and 2.5-fold, respectively, compared with the acellular implant.

CONCLUSIONS

Herein, we have demonstrated a novel approach that could be applied intraoperatively, using FCs or MC for improved tissue integration with a polyurethane meniscal replacement.

Cell-Based Therapies for Joint Disease in Veterinary Medicine: What We Have Learned and What We Need to Know

Biological cell-based therapies for the treatment of joint disease in veterinary patients include autologous-conditioned serum, platelet-rich plasma, and expanded or non-expanded mesenchymal stem cell products. This narrative review outlines the processing and known mechanism of action of these therapies and reviews current preclinical and clinical efficacy in joint disease in the context of the processing type and study design. The significance of variation for biological activity and consequently regulatory approval is also discussed. There is significant variation in study outcomes for canine and equine cell-based products derived from whole blood or stem cell sources such as adipose and bone marrow. Variation can be attributed to altering bio-composition due to factors including preparation technique and source. In addition, study design factors like selection of cases with early vs. late stage osteoarthritis (OA), or with intra-articular soft tissue injury, influence outcome variation. In this under-regulated field, variation raises concerns for product safety, consistency, and efficacy. Cell-based therapies used for OA meet the Food and Drug Administration’s (FDA’s) definition of a drug; however, researchers must consider their approach to veterinary cell-based research to meet future regulatory demands. This review explains the USA’s FDA guidelines as an example pathway for cell-based therapies to demonstrate safety, effectiveness, and manufacturing consistency. An understanding of the variation in production consistency, effectiveness, and regulatory concerns is essential for practitioners and researchers to determine what products are indicated for the treatment of joint disease and tactics to improve the quality of future research.

Implications of anticoagulants and gender on cell counts and growth factor concentration in platelet-rich plasma and platelet-rich gel supernatants from rabbits

Objectives: Our objectives were as follows: 1) to validate a protocol for producing rabbit platelet-rich plasma (PRP); 2) to determine the influence of two anticoagulants, sodium citrate and acid-citrate-dextrose solution A, and gender on cell count in PRP and growth factor concentration in pure platelet-rich gel supernatants; 3) to correlate the variables evaluated.

Methods: Whole blood from 18 New Zealand rabbits (9 males and 9 females) was obtained with sodium citrate and acid- citrate-dextrose solution A for processing PRP fractions (A and B), which were evaluated for haematology. The PRP fractions were either activated with calcium gluconate or lysated with a detergent. The concentrations of transforming growth factor beta 1 and platelet-derived growth factor BB were assayed by ELISA.

Results: The sodium citrate PRP-B had significantly higher counts of platelets in comparison to PRP-A and whole blood obtained with the same anticoagulant and the homologous acid-citrate-dextrose solution A PRP fraction. The sodium citrate PRP-A had a significantly higher count of leukocytes compared to the homologous acid-citrate-dextrose solution A fraction. All the PRP fractions had a significant leuko-reduction when compared to whole blood. The sodium citrate PRP-A fraction from female rabbits had significantly lower platelet counts and significantly higher leukocyte counts than the same acid-citrate-dextrose solution A fraction. Growth factor concentration was not affected by the type of anticoagulant or gender.

Clinical significance: The type of anticoagulant and gender affected the cell counts in PRP, but they did not influence the growth factor concentration. More complete rabbit PRP studies should be performed before evaluating this type of substance in models of disease.

Comparative evaluation of leukocyte- and platelet-rich plasma and pure platelet-rich plasma for cartilage regeneration

Platelet-rich plasma (PRP) has gained growing popularity in the treatment of articular cartilage lesions in the last decade. However, the potential harmful effects of leukocytes in PRP on cartilage regeneration have seldom been studied in vitro, and not at all in vivo yet. The objective of the present study is to compare the effects of leukocyte- and platelet-rich plasma (L-PRP) and pure platelet-rich plasma (P-PRP) on cartilage repair and NF-κB pathway, in order to explore the mechanism underlying the function of leukocytes in PRP in cartilage regeneration. The constituent analysis showed that P-PRP had significantly lower concentrations of leukocytes and pro-inflammatory cytokines compared with L-PRP. In addition, cell proliferation and differentiation assays indicated P-PRP promoted growth and chondrogenesis of rabbit bone marrow mesenchymal stem cells (rBMSC) significantly compared with L-PRP. Despite similarity in macroscopic appearance, the implantation of P-PRP combining rBMSC in vivo yielded better cartilage repair results than the L-PRP group based on histological examination. Importantly, the therapeutic effects of PRP on cartilage regeneration could be enhanced by removing leukocytes to avoid the activation of the NF-κB pathway. Thus, PRP without concentrated leukocytes may be more suitable for the treatment of articular cartilage lesions.

Dendritic polyglycerol anions for the selective targeting of native and inflamed articular cartilage

Dye-conjugated polyanions show high affinities toward native and inflamed cartilage dependent on the anionic moiety and the condition of the tissue.

In vitro effects of platelet-rich gel supernatants on histology and chondrocyte apoptosis scores, hyaluronan release and gene expression of equine cartilage explants challenged with lipopolysaccharide

Background

Platelet-rich plasma (PRP) preparations are a common treatment in equine osteoarthritis (OA). However, there are controversies regarding the ideal concentration of platelets and leukocytes in these biological substances necessary to induce an adequate anti-inflammatory and anabolic response in articular cartilage. The aims were to study the influence of leukocyte- and platelet-rich gel (L-PRG) and pure platelet-rich gel (P-PRG) supernatants on the histological changes of cartilage, the degree of chondrocyte apoptosis, the production of hyaluronan (HA) and the gene expression of nuclear factor kappa beta (NFkβ), matrix metalloproteinase 13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4), collagen type I alpha 1 (COL1A1), collagen type II alpha 1 (COL2A1) and cartilage oligomeric matrix protein (COMP) in normal cartilage explants (CEs) challenged with lipopolysaccharide (LPS).

Results

Overall, 25 % L-PRG supernatant (followed in order of importance by, 50 % P-PRG, 25 % P-PRG and 50 % L-PRG) represented the substance with the most important anti-inflammatory and anabolic effect. 25 % P-PRG supernatant presented important anabolic effects, but it induced a more severe chondrocyte apoptosis than the other evaluated substances.

Conclusions

25 % L-PRG supernatant presented the best therapeutic profile. Our results demonstrate that the biological variability of PRP preparations makes their application rather challenging. Additional in vivo research is necessary to know the effect of PRP preparations at different concentrations.

Effects over time of two platelet gel supernatants on growth factor, cytokine and hyaluronan concentrations in normal synovial membrane explants challenged with lipopolysaccharide

BACKGROUND

Platelet-rich plasma (PRP) preparations are a common treatment in osteoarthritis (OA) and inflammatory synovitis. However, there is ambiguity regarding the ideal concentration of leukocytes and platelets in these preparations necessary to induce an adequate anti-inflammatory and anabolic response in joint tissues, such as the synovial membrane. This research aimed to study, in normal synovial membrane explants (SME) challenged with lipopolysaccharide (LPS), the temporal effects (at 48 and 96h) of leukocyte- and platelet-rich gel (L-PRG) and pure platelet-rich gel (P-PRG) supernatants on the production and degradation of platelet associated growth factors (GF) (platelet derived GF isoform BB (PDGF-BB) and transforming growth factor beta-1 (TGF-β1)), pro-inflammatory (tumour necrosis factor alpha (TNF-α)) and anti-inflammatory cytokines (interleukin 4 (IL-4) and IL-1 receptor antagonists (IL-1ra)) and hyaluronan (HA).

METHODS

Synovial membrane explants (SMEs) from 6 horses were challenged with LPS and cultured for 96h with L-PRG and P-PRG supernatants at concentrations of 25 and 50 %, respectively. The SME culture medium was changed every 48h and used for determination by ELISA of PDGF-BB, TGF-β1, TNF-α, IL-4, IL-1ra and HA. These molecules were also determined in synovial fluid from the horses.

RESULTS

Both the 25 and 50 % PRG supernatants produced a molecular profile in the culture media unlike that of the SME challenged with LPS only. They presented GF, cytokine and HA concentrations very near to the concentrations of these molecules in normal synovial fluid when compared with the SME control groups (either with LPS or without LPS). However, in comparison with the rest of the SME treated groups, the 25 % L-PRG produced the most IL-1ra, and the 50 % P-PRG induced the sustained production of IL-4 and HA.

CONCLUSIONS

These in vitro findings suggest that anabolic and anti-inflammatory joint responses depend on the leukocyte and platelet concentration of the PRP preparation and on the volume of this substance injected. Moreover, it is possible, that leukoreduced PRP preparations are more effective for the medical treatment of patients with OA and inflammatory synovitis.

Platelet-Rich Gel Supernatants Stimulate the Release of Anti-Inflammatory Proteins on Culture Media of Normal Equine Synovial Membrane Explants

The aims were as follows: (1) to evaluate the effects at 48 and 96 h of two concentrations (25 and 50%) of leukocyte and platelet-rich gel (L-PRG) and pure PRG (P-PRG) supernatants on the production/degradation in normal equine synovial membrane explants (SME) of platelet derived growth factor isoform BB, transforming growth factor beta-1, tumor necrosis factor alpha, interleukin (IL-) 4 (IL-4), IL-1 receptor antagonist (IL-1ra), and hyaluronan (HA) synthesis and (2) to correlate these molecules with their respective PRG supernatant treatments. SME from 6 horses were cultured for 96 h with L-PRG and P-PRG supernatants at 25 and 50% concentrations, respectively. SME culture media were changed each 48 h and used for determination by ELISA of the molecules, which were also determined in synovial fluid. 25% L-PRG supernatant produced a sustained release over time of IL-1ra and a gradual release of HA, whereas 50% L-PRG supernatant produced a sustained increase over time of IL-4 and HA. 50% P-PRG supernatant produced an increased and sustained production of IL-1ra and IL-4. The cellular composition and the articular concentration (volume) of a platelet-rich plasma preparation could affect the anti-inflammatory and anabolic joint responses in horses with osteoarthritis.

Morphogen and proinflammatory cytokine release kinetics from PRGF-Endoret fibrin scaffolds: evaluation of the effect of leukocyte inclusion

The potential influence of leukocyte incorporation in the kinetic release of growth factors from platelet-rich plasma (PRP) may explain the conflicting efficiency of leukocyte platelet-rich plasma (L-PRP) scaffolds in tissue regeneration. To assess this hypothesis, leukocyte-free (PRGF-Endoret) and L-PRP fibrin scaffolds were prepared, and both morphogen and proinflammatory cytokine release kinetics were analyzed. Clots were incubated with culture medium to monitor protein release over 8 days. Furthermore, the different fibrin scaffolds were morphologically characterized. Results show that leukocyte-free fibrin matrices were homogenous while leukocyte-containing ones were heterogeneous, loose and cellular. Leukocyte incorporation produced a significant increase in the contents of proinflammatory cytokines interleukin (IL)-1β and IL-16 but not in the platelet-derived growth factors release (<1.5-fold). Surprisingly, the availability of vascular endothelial growth factor suffered an important decrease after 3 days of incubation in the case of L-PRP matrices. While the release of proinflammatory cytokines was almost absent or very low from PRGF-Endoret, the inclusion of leukocytes induced a major increase in these cytokines, which was characterized by the presence of a latent period. The PRGF-Endoret matrices were stable during the 8 days of incubation. The inclusion of leukocytes alters the growth factors release profile and also increased the dose of proinflammatory cytokines.

Application of Platelet-Rich Plasma to Disorders of the Knee Joint

IMPORTANCE

The promising therapeutic potential and regenerative properties of platelet-rich plasma (PRP) have rapidly led to its widespread clinical use in musculoskeletal injury and disease. Although the basic scientific rationale surrounding PRP products is compelling, the clinical application has outpaced the research.

OBJECTIVE

The purpose of this article is to examine the current concepts around the basic science of PRP application, different preparation systems, and clinical application of PRP in disorders in the knee.

EVIDENCE ACQUISITION

A systematic search of PubMed for studies that evaluated the basic science, preparation and clinical application of platelet concentrates was performed. The search used terms, including platelet-rich plasma or PRP preparation, activation, use in the knee, cartilage, ligament, and meniscus. Studies found in the initial search and related studies were reviewed.

RESULTS

A comprehensive review of the literature supports the potential use of PRP both nonoperatively and intraoperatively, but highlights the absence of large clinical studies and the lack of standardization between method, product, and clinical efficacy. Conclusions and Relevance. In addition to the call for more randomized, controlled clinical studies to assess the clinical effect of PRP, at this point, it is necessary to investigate PRP product composition and eventually have the ability to tailor the therapeutic product for specific indications.