Immunoregulatory role of platelet derivatives in the macrophage-mediated immune response.

Background: Macrophages are innate immune cells that display remarkable phenotypic heterogeneity and functional plasticity. Due to their involvement in the pathogenesis of several human conditions, macrophages are considered to be an attractive therapeutic target. In line with this, platelet derivatives have been successfully applied in many medical fields and as active participants in innate immunity, cooperation between platelets and macrophages is essential. In this context, the aim of this review is to compile the current evidence regarding the effects of platelet derivatives on the phenotype and functions of macrophages to identify the advantages and shortcomings for feasible future clinical applications. Methods: A total of 669 articles were identified during the systematic literature search performed in PubMed and Web of Science databases. Results: A total of 27 articles met the inclusion criteria. Based on published findings, platelet derivatives may play an important role in inducing a dynamic M1/M2 balance and promoting a timely M1-M2 shift. However, the differences in procedures regarding platelet derivatives and macrophages polarization and the occasional lack of information, makes reproducibility and comparison of results extremely challenging. Furthermore, understanding the differences between human macrophages and those derived from animal models, and taking into account the peculiarities of tissue resident macrophages and their ontogeny seem essential for the design of new therapeutic strategies. Conclusion: Research on the combination of macrophages and platelet derivatives provides relevant information on the function and mechanisms of the immune response.

Human Platelet Lysate-Derived Nanofibrils as Building Blocks to Produce Free-Standing Membranes for Cell Self-Aggregation.

Amyloid-like fibrils are garnering keen interest in biotechnology as supramolecular nanofunctional units to be used as biomimetic platforms to control cell behavior. Recent insights into fibril functionality have highlighted their importance in tissue structure, mechanical properties, and improved cell adhesion, emphasizing the need for scalable and high-kinetics fibril synthesis. In this study, we present the instantaneous and bulk formation of amyloid-like nanofibrils from human platelet lysate (PL) using the ionic liquid cholinium tosylate as a fibrillating agent. The instant fibrillation of PL proteins upon supramolecular protein-ionic liquid interactions was confirmed from the protein conformational transition toward cross-ß-sheet-rich structures. These nanofibrils were utilized as building blocks for the formation of thin and flexible free-standing membranes via solvent casting to support cell self-aggregation. These PL-derived fibril membranes reveal a nanotopographically rough surface and high stability over 14 days under cell culture conditions. The culture of mesenchymal stem cells or tumor cells on the top of the membrane demonstrated that cells are able to adhere and self-organize in a three-dimensional (3D) spheroid-like microtissue while tightly folding the fibril membrane. Results suggest that nanofibril membrane incorporation in cell aggregates can improve cell viability and metabolic activity, recreating native tissues' organization. Altogether, these PL-derived nanofibril membranes are suitable bioactive platforms to generate 3D cell-guided microtissues, which can be explored as bottom-up strategies to faithfully emulate native tissues in a fully human microenvironment.

Autologous peripheral blood-derived orthobiologics: Different types and their effectiveness in managing knee osteoarthritis.

Knees are the most commonly impacted weight-bearing joints in osteoarthritis (OA), affecting millions of people worldwide. With increasing life spans and obesity rates, the incidence of knee OA will further increase, leading to a significant increase in the economic burden. Conventional treatment modalities utilized to manage knee OA have limitations. Over the last decade, the role of various autologous peripheral blood-derived orthobiologics (APBOs) for the treatment of knee OA has been extensively investigated. This editorial provided an overview and focused on defining and shedding light on the current state of evidence based on the most recent published clinical studies concerning the use of APBO for the management of knee OA. While numerous studies have demonstrated promising results for these preparations, a notable gap exists in the comparative analysis of these diverse formulations. This absence of head-to-head studies poses a considerable challenge for physicians/surgeons in determining the optimal preparation for managing knee OA and achieving sustained long-term results. Thus, more adequately powered, multicenter, prospective, double-blind, randomized controlled trials with longer follow-ups are needed to establish the long-term efficacy and to aid physicians/surgeons in determining the optimal APBO for the management of knee OA.

Platelet lysate for the treatment of osteoarthritis: a systematic review of preclinical and clinical studies.

Intra-articular injection-based therapy is often used aside conservative treatment and lifestyle modifications to manage knee osteoarthritis (KO) patients. Conventional injections contain steroids and hyaluronic acid, while more recently multipotential adult stem cell, platelet-rich plasma (PRP), and platelet lysate (PL) injections have been used to promote cartilage regeneration or repair. The aim of the current study is to analyse current evidence on PL injections for the treatment of KO and to determine if these are effective and how these perform compared to other injection regimens. The databases of Scopus, Embase, PubMed, Web of Science, and Cochrane Library were searched on 30 June 2023. Risk of bias was assessed using the SYRCLE tool for animal studies and Cochrane RoB 2 as well as ROBINS-I tool for human studies. Studies were included if these were in English, any year, and regarded animals with osteoarthritis (OA) or human adult patients with OA. In vitro trials and non-adult human studies were excluded. Results on OA symptom stage and severity, and pain were recorded. The research retrieved three human studies (n = 48, n = 25, n = 58) and four animal studies: one rabbit, two studies, and one rat study. PL was found to decrease KO symptoms at follow-up ≤ 1 year with respect to baseline levels and when compared to hyaluronic acid or platelet-rich plasma. Symptoms returned 6 months-1 year after the final administration, with studies showing peak efficacy at approximately 6 months. Animal studies showed clinical improvements, reduction of lameness, and partial effect on the cartilage regeneration of the seven studies, two had a high risk of bias, four were associated to some concerns, and one had low risk. A major source of bias in these studies was the use of questionnaires and scoring that could be subject to interpretation. Overall, PL was well-tolerated and showed efficacy comparable to PRP; when pain control was assessed, it showed similar efficacy compared to hyaluronic acid. These findings may support its use in clinical trials to confirm these initial findings; future research should also focus on the comparison with other non-surgical treatments, on a more detail of the potential regenerative properties, and to optimise the treatment schedule.

Low-density cultured cartilage cells expanded in platelet lysate present distinct features to develop an innovative clinical treatment for diffuse cartilage lesions.

PURPOSE: Chondrocyte-based cell therapies are effective for the treatment of chondral lesions, but remain poorly indicated for diffuse lesions in the context of early osteoarthritis (OA). The aim of this study was to develop a protocol to obtain chondroprogenitor cells suitable for the treatment of diffuse chondral lesions within early OA. METHODS: Cartilage cells were expanded at low density in human platelet lysate (hPL). A test was performed to exclude senescence. The expression of surface cluster of differentiation 146, cluster of differentiation 166, major histocompatibility complex (MHC)-I and MHC-II and of genes of interest were evaluated, as well as the trophic potential of these cells, by the assessment of lubricin and matrix production. The immunomodulatory potential was assessed through their co-culture with macrophages. RESULTS: Cartilage cells expanded at low density in hPL showed higher proliferation rate than standard-density cells, no replicative senescence, low immunogenicity and expression of lubricin. Moreover, they presented an increased expression of chondrogenic and antihypertrophic markers, as well as a superior matrix deposition if compared to cells cultured at standard density. Cartilage cells induced on macrophages an upregulation of CD206, although a higher increase of CD163 expression was observed in the presence of low-density cells. CONCLUSIONS: These findings lay the grounds to explore the clinical usefulness of low-density cultured cartilage cells to treat diffuse lesions in early OA joints for both autologous and allogenic use. LEVEL OF EVIDENCE: Not applicable.

Impact of platelet lysate on immunoregulatory characteristics of equine mesenchymal stromal cells.

Multipotent mesenchymal stromal cells (MSC) play an increasing role in the treatment of immune-mediated diseases and inflammatory processes. They regulate immune cells via cell-cell contacts and by secreting various anti-inflammatory molecules but are in turn influenced by many factors such as cytokines. For MSC culture, platelet lysate (PL), which contains a variety of cytokines, is a promising alternative to fetal bovine serum (FBS). We aimed to analyze if PL with its cytokines improves MSC immunoregulatory characteristics, with the perspective that PL could be useful for priming the MSC prior to therapeutic application. MSC, activated peripheral blood mononuclear cells (PBMC) and indirect co-cultures of both were cultivated in media supplemented with either PL, FBS, FBS+INF-γ or FBS+IL-10. After incubation, cytokine concentrations were measured in supernatants and control media. MSC were analyzed regarding their expression of immunoregulatory genes and PBMC regarding their proliferation and percentage of FoxP3+ cells. Cytokines, particularly IFN-γ and IL-10, remained at high levels in PL control medium without cells but decreased in cytokine-supplemented control FBS media without cells during incubation. PBMC released IFN-γ and IL-10 in various culture conditions. MSC alone only released IFN-γ and overall, cytokine levels in media were lowest when MSC were cultured alone. Stimulation of MSC either by PBMC or by PL resulted in an altered expression of immunoregulatory genes. In co-culture with PBMC, the MSC gene expression of COX2, TNFAIP6, IDO1, CXCR4 and MHC2 was upregulated and VCAM1 was downregulated. In the presence of PL, COX2, TNFAIP6, VCAM1, CXCR4 and HIF1A were upregulated. Functionally, while no consistent changes were found regarding the percentage of FoxP3+ cells, MSC decreased PBMC proliferation in all media, with the strongest effect in FBS media supplemented with IL-10 or IFN-γ. This study provides further evidence that PL supports MSC functionality, including their immunoregulatory mechanisms. The results justify to investigate functional effects of MSC cultured in PL-supplemented medium on different types of immune cells in more detail.

Evaluation of Human Platelet Lysate as an Alternative to Fetal Bovine Serum for Potential Clinical Applications of Stem Cells from Human Exfoliated Deciduous Teeth.

In recent years, there has been a surge in demand for and research focus on cell therapy, driven by the tissue-regenerative and disease-treating potentials of stem cells. Among the candidates, dental pulp stem cells (DPSCs) or human exfoliated deciduous teeth (SHED) have garnered significant attention due to their easy accessibility (non-invasive), multi-lineage differentiation capability (especially neurogenesis), and low immunogenicity. Utilizing these stem cells for clinical purposes requires careful culture techniques such as excluding animal-derived supplements. Human platelet lysate (hPL) has emerged as a safer alternative to fetal bovine serum (FBS) for cell culture. In our study, we assessed the impact of hPL as a growth factor supplement for culture medium, also conducting a characterization of SHED cultured in hPL-supplemented medium (hPL-SHED). The results showed that hPL has effects in enhancing cell proliferation and migration and increasing cell survivability in oxidative stress conditions induced by H2O2. The morphology of hPL-SHED exhibited reduced size and elongation, with a differentiation capacity comparable to or even exceeding that of SHED cultured in a medium supplemented with fetal bovine serum (FBS-SHED). Moreover, no evidence of chromosome abnormalities or tumor formation was detected. In conclusion, hPL-SHED emerges as a promising candidate for cell therapy, exhibiting considerable potential for clinical investigation.

Calcium chloride declotted human platelet lysate promotes the expansion of mesenchymal stromal cells and allows manufacturing of immunomodulatory active extracellular vesicle products.

BACKGROUND: Mesenchymal stromal cells (MSCs) exert immunomodulatory effects, primarily through released extracellular vesicles (EVs). For the clinical-grade manufacturing of MSC-EV products culture conditions need to support MSC expansion and allow the manufacturing of potent MSC-EV products. Traditionally, MSCs are expanded in fetal bovine serum-supplemented media. However, according to good manufacturing practice (GMP) guidelines the use of animal sera should be avoided. To this end, human platelet lysate (hPL) has been qualified as an animal serum replacement. Although hPL outcompetes animal sera in promoting MSC expansion, hPL typically contains components of the coagulation system that need to be inhibited or removed to avoid coagulation reactions in the cell culture. Commonly, heparin is utilized as an anticoagulant; however, higher concentrations of heparin can negatively impact MSC viability, and conventional concentrations alone do not sufficiently prevent clot formation in prepared media. METHODS: To circumvent unwanted coagulation processes, this study compared various clotting prevention strategies, including different anticoagulants and calcium chloride (CaCl2)-mediated declotting methods, which in combination with heparin addition was found effective. We evaluated the influence of the differently treated hPLs on the proliferation and phenotype of primary bone marrow-derived MSCs and identified the CaCl2-mediated declotting method as the most effective option. To determine whether CaCl2 declotted hPL allows the manufacturing of immunomodulatory MSC-EV products, EVs were prepared from conditioned media of MSCs expanded with either conventional or CaCl2 declotted hPL. In addition to metric analyses, the immunomodulatory potential of resulting MSC-EV products was assessed in a recently established multi-donor mixed lymphocyte reaction assay. RESULTS AND CONCLUSIONS: Our findings conclusively show that CaCl2-declotted hPLs support the production of immunomodulatory-active MSC-EV products.

Treatment with Umbilical Cord Blood Platelet Lysate Gel Improves Healing of Diabetic Foot Ulcer.

BACKGROUND: This study was conducted to examine the hypothesis that umbilical cord blood platelet lysate (UCB-PL) gel has a significant impact on the healing rate of DFU. Μethods: In this open-labeled, randomized controlled trial, 110 patients were randomized to treatment with UCB-PL gel (UCB-PL group, n = 52) every three days for one month or dressing with normal saline (control group, n = 58). All participants were followed up for 20 weeks post treatment. Ulcer surface area was assessed with the imitoMeasure application at two, four, and six weeks, and two, four and six months. This study's main outcome was the reduction in ulcer size over the six-month study period. RESULTS: The mean ulcer area at baseline was 4.1 cm2 in the UCB-PL group and 1.7 cm2 in the control group. At six months post treatment, patients on the UCB-PL treatment displayed a significant reduction in ulcer size compared to baseline 0.12 (0-8.16) in contrast to a more modest change in the control group 1.05 (0-24.7). The ulcer area was decreased at the end of the study in 40 patients (97.6%) in the UCB-PL group and 27 (73%) in the control group (Fisher's p = 0.002). CONCLUSIONS: The application of UCB-PL gel in DFU resulted in a significant reduction in ulcer size compared to regular saline dressing.

Using Macrophage Polarization in Human Platelet Lysate to Test the Immunomodulatory Potential of Cells for Clinical Use.

Macrophage-based co-cultures are used to test the immunomodulatory function of candidate cells for clinical use. This study aimed to characterize a macrophage polarization model using human platelet lysate (hPL) as a GMP-compliant alternative to Fetal Bovine Serum (FBS). Primary human monocytes were differentiated into unpolarized (M0) or polarized (M1, M2a, and M2c) macrophages in an hPL- or FBS-based medium. The protein secretion profiles and expression of phenotypic markers (CD80 for M1, CD206 for M2a, and CD163 for M2c) were analyzed. Subsequently, chondrocytes were tested in an hPL-based co-culture model to assess their immunomodulatory function in view of their possible use in patients with osteoarthritis. The results showed similar marker regulation between hPL and FBS cultures, but lower basal levels of CD206 and CD163 in hPL-cultured macrophages. Functional co-culture experiments with chondrocytes revealed increased CD206 expression both in hPL and in FBS, indicating an interaction between macrophages and chondrocytes. While markers in FBS-cultured macrophages were confirmed in hPL-cultured cells, the interpretation of marker modulation in immunomodulatory assays with hPL-based cultures should be carried out cautiously due to the observed differences in the basal marker levels for CD206 and CD163. This research underscores the utility of hPL as a GMP-compliant alternative to FBS for macrophage-based co-cultures and highlights the importance of understanding marker expressions in different culture conditions.

Differentiation of placenta-derived MSCs cultured in human platelet lysate: a xenofree supplement.

In the last few decades, mesenchymal stem cells (MSCs)-based regenerative therapies in clinical applications have gradually become a hot topic due to their long-term self-renewal and multilineage differentiation ability. In this scenario, placenta (p) has been considered as a good source of MSCs. As a tissue of fetal origin with abundant number of stem cells compared to other sources, their non-invasive acquisition, strong immunosuppression, and lack of ethical concerns make placenta an indispensable source of MSC in stem cell research and therapy. The mesenchymal stem cells were derived from human term placenta (p-MSCs) in xenofree condition using platelet lysate (PL) as a suitable alternative to fetal bovine serum (FBS). Upon isolation, p-MSCs showed plastic adherence with spindle-shaped, fibroblast-like morphology under microscope. p-MSCs flourished well in PL-containing media. Immunophenotyping showed classical MSC markers (> 90%) and lack expression of hematopoietic and HLA-DR (< 1%). Surprisingly, differentiation study showed differentiation of p-MSCs to mature adipocytes in both induced cells and control (spontaneous differentiation), as observed via oil red staining. This is in line with gene expression data where both control and induced cells were positive for visfatin and leptin. Thus, we propose that p-MSCs can be used for clinical applications in the treatment of various chronic and degenerative diseases.

Biogelx-IKVAV Is An Innovative Human Platelet Lysate-Adipose-Derived Stem Cells Delivery Strategy to Improve Peripheral Nerve Repair.

Adipose-derived stem cells (ADSC) are nowadays one of the most exploited cells in regenerative medicine. They are fast growing, capable of enhancing axonal elongation, support and locally stimulate Schwann cells (SCs), and protect de-innervated muscles from atrophy after a peripheral nerve injury. With the aim of developing a bio-safe, clinically translatable cell-therapy, we assessed the effect of ADSC pre-expanded with human platelet lysate in an in vivo rat model, delivering the cells into a 15 mm critical-size sciatic nerve defect embedded within a laminin-peptide-functionalized hydrogel (Biogelx-IKVAV) wrapped by a poly-ɛ-caprolactone (PCL) nerve conduit. ADSC retained their stemness, their immunophenotype and proliferative activity when tested in vitro. At 6 weeks post-implantation, robust regeneration was observed across the critical-size gap as evaluated by both the axonal elongation (anti-NF 200) and SC proliferation (anti-S100) within the human ADSC-IKVAV filled PCL conduit. All the other experimental groups manifested significantly lower levels of growth cone elongation. The histological gastrocnemius muscle analysis was comparable with no quantitative significant differences among the experimental groups. Taken together, these results suggest that ADSC encapsulated in Biogelx-IKVAV are a potential path to improve the efficacy of nerve regeneration. New perspectives can be pursued for the development of a fully synthetic bioengineered nerve graft for the treatment of peripheral nerve injury.

Human platelet lysate enhances in vivo activity of CAR-Vδ2 T cells by reducing cellular senescence and apoptosis.

BACKGROUND AIMS: Vγ9Vδ2 T cells are an attractive cell platform for the off-the-shelf cancer immunotherapy as the result of their lack of alloreactivity and inherent multi-pronged cytotoxicity, which could be further amplified with chimeric antigen receptors (CARs). In this study, we sought to enhance the in vivo longevity of CAR-Vδ2 T cells by modulating ex vivo manufacturing conditions and selecting an optimal CAR costimulatory domain. METHODS: Specifically, we compared the anti-tumor activity of Vδ2 T cells expressing anti-CD19 CARs with costimulatory endodomains derived from CD28, 4-1BB or CD27 and generated in either standard fetal bovine serum (FBS)- or human platelet lysate (HPL)-supplemented medium. RESULTS: We found that HPL supported greater expansion of CAR-Vδ2 T cells with comparable in vitro cytotoxicity and cytokine secretion to FBS-expanded CAR-Vδ2 T cells. HPL-expanded CAR-Vδ2 T cells showed enhanced in vivo anti-tumor activity with longer T-cell persistence compared with FBS counterparts, with 4-1BB costimulated CAR showing the greatest activity. Mechanistically, HPL-expanded CAR Vδ2 T cells exhibited reduced apoptosis and senescence transcriptional pathways compared to FBS-expanded CAR-Vδ2 T cells and increased telomerase activity. CONCLUSIONS: This study supports enhancement of therapeutic potency of CAR-Vδ2 T cells through a manufacturing improvement.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications.

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor ß, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

The Use of Human Platelet Lysate as a Coating Substance for Adipose-Derived Stem Cell Expansion.

BACKGROUND: Large-scale production of mesenchymal stromal cells is essential for sufficient therapeutic doses in regenerative medicine. However, long-term cultivation encounters limited cell growth and cellular aging. Therefore, an alternative cell culture approach that promotes proliferation and attenuates cell senescence is required. Human platelet lysate (HPL) is a potent supplement for in vitro cell expansion. Applying HPL as a coating material can potentially improve mesenchymal stromal cell cultures. METHOD: To examine the capacity of HPL, it was used to pre-coat a tissue culture plate for in vitro adipose-derived mesenchymal stromal cell expansion. Alterations in biological features of adipose-derived stem cells (ADSCs) were investigated, including cell adhesion assays, cell proliferation, population doubling time, and cellular senescence. RESULTS: ADSCs cultured on HPL-coated plates significantly increased cell adhesion rate, shortened population doubling time, and stimulated cell growth. The senescent cells were significantly decreased in ADSCs cultured in an HPL-coated plate, and the expression levels of senescence-associated genes, including p16, p21, and p53, were downregulated. Furthermore, Western blotting analysis revealed that HPL was enriched with fibronectin and vitronectin, essential cell adhesive proteins. CONCLUSIONS: HPL was effectively used as a coating material for ADSC expansions. Cellular cultivation on the HPL coating is an alternative approach for producing mesenchymal stromal cells.

Advanced Platelet Lysate Aerogels: Biomaterials for Regenerative Applications.

Human platelet lysate (HPL), rich in growth factors, is increasingly recognized for its potential in tissue engineering and regenerative medicine. However, its use in liquid or gel form is constrained by limited stability and handling difficulties. This study aimed to develop dry and porous aerogels from HPL hydrogel using an environmentally friendly supercritical CO2-based shaping process, specifically tailored for tissue engineering applications. The aerogels produced retained their three-dimensional structure and demonstrated significant mechanical robustness and enhanced manageability. Impressively, they exhibited high water absorption capacity, absorbing 87% of their weight in water within 120 min. Furthermore, the growth factors released by these aerogels showed a sustained and favourable biological response in vitro. They maintained the cellular metabolic activity of fibroblasts (BALB-3T3) at levels akin to conventional culture conditions, even after prolonged storage, and facilitated the migration of human umbilical vein endothelial cells (HUVECs). Additionally, the aerogels themselves supported the adhesion and proliferation of murine fibroblasts (BALB-3T3). Beyond serving as excellent matrices for cell culture, these aerogels function as efficient systems for the delivery of growth factors. Their multifunctional capabilities position them as promising candidates for various tissue regeneration strategies. Importantly, the developed aerogels can be stored conveniently and are considered ready to use, enhancing their practicality and applicability in regenerative medicine.

Intra-articular injection of platelet lysate-derived extracellular vesicles recovers from knee osteoarthritis in an in vivo rat model.

Objective: MSCs and Platelet-Rich Plasma are the main focus in the study of new regenerative treatments aimed to reverse Osteoarthritis (OA). However, extracellular vesicles (EVs) present several advantages to cell-based treatments. Thus, the aim of this study was to compare and evaluate the regenerative potential of MSC-derived EVs (cEVs) and platelet-derived EVs (pEVs) in an OA cartilage rat model. Design: OA in vivo model was established through injection of 6 mg MIA in the rat knee joints. After 14 and 21 days, OA knee joints were treated with 1 × 1010 particles of pEVs or cEVs. At day 28, the animals were sacrificed, plasma was collected to quantify CTX-II and knee joints were excised to be evaluated by Cone Beam Computed Tomography (CBCT). After decalcification, histology was used to determine the OARSI score and to visualize collagen and glycosaminoglycan content. Results: pEVs and cEVs samples did not show significant differences per se but they did in terms of regenerative effects on OA knee joints. pEVs-treated knee joints showed better subchondral bone integrity in CT-analysed parameters when compared to cEVs or OA group, showing similar values to the healthy control group. Moreover, OARSI score indicated that pEVs showed a greater OA reversion in knee joints, especially in female rats, and so indicated the analysed histological images. Conclusions: pEVs are proposed as a viable regeneration treatment for OA since they are not only capable of exerting their regenerative potential on osteoarthritic cartilage, but also outperform cEVs in terms of efficacy, particularly in females. Significance statement: Osteoarthritis (OA) is one of the most age-related diseases. It is estimated that 500 million people suffer from OA worldwide, representing the principal cause of chronic disability in adults. In the present study we evaluated the therapeutic effect of extracellular vesicles (EVs) from different sources (platelet lysate and human umbilical cord mesenchymal stromal cells) in an in vivo rat model. Our results demonstrate that platelet-derived EVs (pEVs) induce an OA reversion in knee joints, thus evidencing the therapeutic potential of pEVs as cell-free regenerative agents for OA treatment. The translational potential of this article: Platelet-derived extracellular vesicles (pEVs) offer a promising cell-free therapy option for OA treatment. Their production could be easily standardized and reproduced without extensive platelet harvesting and amplification, thus paving the way for their clinical translation.

Biomimetic mineralization of platelet lysate/oxidized dextran cryogel as a macroporous 3D composite scaffold for bone repair.

Scaffold development approaches using autologous sources for tissue repair are of great importance in obtaining bio-active/-compatible constructs. Platelet-rich plasma (PRP) containing various growth factors and platelet lysate (PL) derived from PRP are autologous products that have the potential to accelerate the tissue repair response by inducing a transient inflammatory event. Considering the regenerative capacity of PRP and PL, PRP/PL-based scaffolds are thought to hold great promise for tissue engineering as a natural source of autologous growth factors and a provider of mechanical support for cells. Here, a bio-mineralized PRP-based scaffold was developed using oxidized dextran (OD) and evaluated for future application in bone tissue engineering. Prepared PL/OD scaffolds were incubated in simulated body fluid (SBF) for 7, 14 and 21 d periods. Mineralized PL/OD scaffolds were characterized using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, porosity and compression tests. SEM and energy-dispersive x-ray spectroscopy analyses revealed mineral accumulation on the PL/OD scaffold as a result of SBF incubation.In vitrocytotoxicity andin vitrohemolysis tests revealed that the scaffolds were non-toxic and hemocompatible. Additionally, human osteoblasts (hOBs) exhibited good attachment and spreading behavior on the scaffolds and maintained their viability throughout the culture period. The alkaline phosphatase activity assay and calcium release results revealed that PL/OD scaffolds preserved the osteogenic properties of hOBs. Overall, findings suggest that mineralized PL/OD scaffold may be a promising scaffold for bone tissue engineering.

Exploring the Hemostatic Effects of Platelet Lysate-Derived Vesicles: Insights from Mouse Models.

Platelet transfusion has various challenges, and platelet-derived extracellular vesicles have been reported to have more significant procoagulant activity than platelets themselves. Furthermore, platelet products derived from platelet-rich plasma and platelet lysates (PLs) have gained attention for their physiological activity and potential role as drug delivery vehicles owing to the properties of their membranes. We aimed to investigate the characteristics of the fractions isolated through ultracentrifugation from mouse-washed PLs and assess the potential clinical applications of these fractions as a therapeutic approach for bleeding conditions. We prepared PLs from C57BL/6 mouse-washed platelets and isolated three different fractions (20K-vesicles, 100K-vesicles, and PLwo-vesicles) using ultracentrifugation. There was a notable difference in particle size distribution between 20K-vesicles and 100K-vesicles, particularly in terms of the most frequent diameter. The 20K-vesicles exhibited procoagulant activity with concentration dependence, whereas PLwo-vesicles exhibited anticoagulant activity. PLwo-vesicles did not exhibit thrombin generation capacity, and the addition of PLwo-vesicles to Microparticle Free Plasma extended the time to initiate thrombin generation by 20K-vesicles and decreased the peak thrombin value. In a tail-snip bleeding assay, pre-administration of 20K-vesicles significantly shortened bleeding time. PL-derived 20K-vesicles exhibited highly potent procoagulant activity, making them potential alternatives to platelet transfusion.

Comparison between Platelet Lysate, Platelet Lysate Serum, and Fetal Bovine Serum as Supplements for Cell Culture, Expansion, and Cryopreservation.

As cell culture supplements, human platelet lysate (PL) and human platelet lysate serum (PLS) are alternatives to fetal bovine serum (FBS) due to FBS-related issues such as ethical concerns, variability between batches, and the possible introduction of xenogenic contaminants. This study compared the composition and efficacy of PL, PLS, and FBS as supplements in the culture and cryopreservation of human dermal fibroblasts, Wharton's jelly-derived mesenchymal stem cells (WJ-MCS), and adipose tissue (AdMSC). Biochemical components, some growth factors, and cytokines present in each of them were analyzed; in addition, the cells were cultured in media supplemented with 5% PL, 5% PLS, and 10% FBS and exposed to different freezing and thawing solutions with the supplements under study. Biochemical parameters were found to be similar in PL and PLS compared to FBS, with some differences in fibrinogen and calcium concentration. Growth factors and cytokines were higher in PL and PLS compared to FBS. Cell proliferation and morphology showed no significant differences between the three culture media. Regarding the cryopreservation and thawing of cells, better results were obtained with PLS and FBS. In conclusion, PL and PLS are an excellent choice to replace the standard supplement of animal origin (FBS) in the media used for the culture and cryopreservation of fibroblasts, WJ-MSC, and AdMSC.