Novel therapeutic approaches in utilizing platelet lysate in regenerative medicine: Are we ready for clinical use?

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.

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.

A systematic review and meta-analysis of the efficacy of platelet-rich plasma products for treatment of equine joint disease

BACKGROUND

Equine joint disease including septic arthritis (SA) and osteoarthritis (OA) is a critical cause of equine lameness. Platelet-rich plasma (PRP) is one of the most popular regenerative therapies to treat equine OA, even SA, but the evidence in support of the treatment is conflicting.

OBJECTIVES

The aim of the study was to systematically review the current evidence on PRP products used for SA and OA, as well as the efficacy of PRP products as treatment for OA on the basis of a meta-analysis of the available literature.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A systematic search of relevant databases (PubMed, Web of Science, Scopus) was performed to identify studies published from 2013 to 2023, in accordance with the PRISMA guidelines. Randomised controlled trials, non-randomised trials and controlled laboratory studies that used at least one type of PRP products were included. Dichotomous outcomes were presented using odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

A total of 21 publications were identified in the systematic review and 5 of them in the meta-analysis. These publications involved various types of PRP products and reported different outcomes. Although most of the studies were associated with a high risk of bias, the overall estimated effect was consistent with a significant improvement in the PRP products treatment group compared with the control group (OR: 15.32; 95% CI: 3.00-78.15; p < 0.05). There was a significant improvement in clinical performance outcomes between the groups (OR: 36.64; 95% CI: 3.69-364.30; p < 0.05).

CONCLUSION

PRP products as intra-articular treatment are likely efficacious for treatment of equine OA and have potential for treating SA. These conclusions might be affected by the limited number of randomised controlled studies and high variability of different types of PRP products. To better evaluate the efficacy of PRP, a widely recognised classification system and the utilisation of randomised, blinded, equivalency or non-inferiority trials are required.

Platelet lysate for expansion or osteogenic differentiation of bone marrow mesenchymal stem cells for 3D tissue constructs

Background

The use of mesenchymal stem cells (MSCs) for the development of tissue-engineered constructs has advanced in recent years. However, future clinically approved products require following good manufacturing practice (GMP) guidelines. This includes using alternatives to xenogeneic-derived cell culture supplements to avoid rejection of the transplants. Consequently, human platelet lysate (PLT) has been adopted as an affordable and effective alternative to foetal bovine serum (FBS) in traditional 2D cultures. However, little is known about its effect in more advanced 3D culture systems.

Methods

We evaluated bone marrow MSCs (BMSCs) proliferation and CD marker expression in cells expanded in FBS or PLT-supplemented media. Differentiation capacity of the BMSCs expanded in the presence of the different supplements was evaluated in 3D type I collagen hydrogels. Furthermore, the effects of the supplements on the process of differentiation were analyzed by using qPCR and histological staining.

Results

Cell proliferation was greater in PLT-supplemented media versus FBS. BMSCs expanded in PLT showed similar osteogenic differentiation capacity in 3D compared with FBS expanded cells. In contrast, when cells were 3D differentiated in PLT they showed lower osteogenesis versus the traditional FBS protocol. This was also the case for adipogenic differentiation, in which FBS supplementation was superior to PLT.

Conclusions

PLT is a superior alternative to FBS for the expansion of MSCs without compromising their subsequent differentiation capacity in 3D. However, differentiation in PLT is impaired. Thus, PLT can be used to reduce the time required to expand the necessary cell numbers for development of 3D tissue engineered MSC constructs.

Calvaria defect regeneration via human periodontal ligament stem cells and prevascularized scaffolds in athymic rats

BACKGROUND

Vascularization plays an important role in dental and craniofacial regenerations. Human periodontal ligament stem cells (hPDLSCs) are a promising cell source and, when co-cultured with human umbilical vein endothelial cells (hUVECs), could promote vascularization. The objectives of this study were to develop a novel prevascularized hPDLSC-hUVEC-calcium phosphate construct, and investigate the osteogenic and angiogenic efficacy of this construct with human platelet lysate (hPL) in cranial defects in rats for the first time.

METHODS

hPDLSCs and hUVECs were co-cultured on calcium phosphate cement (CPC) scaffolds with hPL. Cell proliferation, angiogenic gene expression, angiogenesis, alkaline phosphatase activity, and cell-synthesized minerals were determined. Bone and vascular regenerations were investigated in rat critical-sized cranial defects in vivo.

RESULTS

hPDLSC-hUVEC-CPC-hPL group had 2-fold greater angiogenic expressions and cell-synthesized mineral synthesis than hPDLSC-hUVEC-CPC group (p < 0.05). Microcapillary-like structures were formed on scaffolds in vitro. hPDLSC-hUVEC-CPC-hPL group had more vessels than hPDLSC-hUVEC-CPC group (p < 0.05). In cranial defects in rats, hPDLSC-hUVEC-CPC-hPL group regenerated new bone amount that was 2.1 folds and 4.0 folds, respectively, that of hPDLSC-hUVEC-CPC group and CPC control (p < 0.05). New blood vessel density of hPDLSC-hUVEC-CPC-hPL group was 2 folds and 7.9 folds, respectively, that of hPDLSC-hUVEC-CPC group and CPC control (p < 0.05).

CONCLUSION

The hPL pre-culture method is promising to enhance bone regeneration via prevascularized CPC. Novel hPDLSC-hUVEC-CPC-hPL prevascularized construct increased new bone formation and blood vessel density by 4-8 folds over CPC control.

CLINICAL SIGNIFICANCE

Novel hPDLSC-hUVEC-hPL-CPC prevascularized construct greatly increased bone and vascular regeneration in vivo and hence is promising for a wide range of craniofacial applications.

Tunable Double-Network GelMA/Alginate Hydrogels for Platelet Lysate-Derived Protein Delivery

Hydrogels (gels) are attractive tools for tissue engineering and regenerative medicine due to their potential for drug delivery and ECM-like composition. In this study, we use rheology to characterize GelMA/alginate gels loaded with human platelet lysate (PL). We then characterize these gels from a physicochemical perspective and evaluate their ability to transport PL proteins, their pore size, and their rate of degradation. Finally, their biocompatibility is evaluated. We describe how alginate changes the mechanical behavior of the gels from elastic to viscoelastic after ionic (calcium-mediated) crosslinking. In addition, we report the release of ~90% of PL proteins from the gels and relate it to the degradation profile of the gels. Finally, we evaluated the biocompatibility of the gels. Thus, the developed gels represent attractive substrates for both cell studies and as bioactive materials.

Combination therapy along with mesenchymal stem cells in wound healing; the state of the art

Mesenchymal stem cells (MSCs) are being increasingly used in various therapeutic applications including skin tissue repair and wound healing. The positive effects of the MSCs therapy are largely elicited by immunomodulation, increasing angiogenesis, supporting extracellular matrix (ECM) and thus favoring skin structure. However, the therapeutic competences of MSC-based therapies are somewhat hindered by their apparent modest clinical merits, conferring the need for methods that would rise the efficacy of such therapies. A plethora of reports have shown that therapeutic properties of MSCs could be enhanced with other strategies and compounds like biomaterial and platelet-rich plasma (PRP) to target key possessions of MSCs and properties of adjacent tissues concurrently. Manipulation of cellular stress-response mechanisms to improve cell resistance to oxidative stress prior to or during MSC injection could also improve therapeutic efficacy of MSCs. In the current review, we shed light on the recent advances in MSCs combination therapy with other ingredients and procedures to sustain MSCs-mediated effects in wound healing.

Anti-Aging Potential of Platelet Rich Plasma (PRP): Evidence from Osteoarthritis (OA) and Applications in Senescence and Inflammaging

Aging and age-related changes impact the quality of life (QOL) in elderly with a decline in movement, cognitive abilities and increased vulnerability towards age-related diseases (ARDs). One of the key contributing factors is cellular senescence, which is triggered majorly by DNA damage response (DDR). Accumulated senescent cells (SCs) release senescence-associated secretory phenotype (SASP), which includes pro-inflammatory cytokines, matrix metalloproteinases (MMPs), lipids and chemokines that are detrimental to the surrounding tissues. Chronic low-grade inflammation in the elderly or inflammaging is also associated with cellular senescence and contributes to ARDs. The literature from the last decade has recorded the use of platelet rich plasma (PRP) to combat senescence and inflammation, alleviate pain as an analgesic, promote tissue regeneration and repair via angiogenesis-all of which are essential in anti-aging and tissue regeneration strategies. In the last few decades, platelet-rich plasma (PRP) has been used as an anti-aging treatment option for dermatological applications and with great interest in tissue regeneration for orthopaedic applications, especially in osteoarthritis (OA). In this exploration, we connect the intricate relationship between aging, ARDs, senescence and inflammation and delve into PRP's properties and potential benefits. We conduct a comparative review of the current literature on PRP treatment strategies, paying particular attention to the instances strongly linked to ARDs. Finally, upon careful consideration of this interconnected information in the context of aging, we suggest a prospective role for PRP in developing anti-aging therapeutic strategies.

The Effect of Advanced Platelet-Rich Fibrin in Tissue Regeneration in Reconstructive and Graft Surgery: Systematic Review

This systematic review answered the guiding question using the PICO system: "What are the effects of advanced platelet-rich fibrin (A-PRF) on alveolar ridge preservation and tissue gain in reconstructive and jaw graft surgery?" Searches were performed in the PubMed|MEDLINE, Scopus, Embase, Web of Science, Cochrane Library, and LILACS|bvs databases. In total, 573 articles were found in the initial search, and 564 were evaluated after the removal of duplicates, of which 5 randomized controlled trials met the eligibility criteria and were included 2 studies investigated the effect of A-PRF on the preservation of the bone ridge, 1 study evaluated the tissue repair after tooth extraction with A-PRF, 1 evaluated the peri-implant gap filling with A-PRF-xenograft mixture, and other the A-PRF on the treatment of alveolar osteitis. Advanced-PRF preparation protocol varied between the included studies from 8 to 13 minutes of centrifugation, at 1300 RPM (200 g ). The use of A-PRF provided greater dimensions of height and more favorable maintenance of the ridge profile, probing depth, and gingival margin level after extraction. Advanced-PRF also increased bone density, vital bone, epithelial healing, and control of postoperative pain and swelling after tooth extraction and in the treatment of alveolar osteitis.

Platelet lysate promotes hair growth: In vitro and in vivo mechanism and randomized, controlled trial

BACKGROUND

Platelet lysate (PL), a novel platelet derivative, has been widely used in regenerative medicine and is a potential therapy for improving hair growth. It is necessary to fully clarify the potential mechanism and evaluate preliminary clinical effect of PL on hair growth.

METHODS

We used the C57BL/6 model, organ-cultured hair follicles, and RNA-seq analysis to explore the mechanisms of PL regulating hair growth. Then, we performed a randomized, controlled, double-blind study of 107 AGA patients to verify the therapeutic efficacy of PL.

RESULTS

The results confirmed that PL improved hair growth and accelerated hair cycling in mice. Organ-cultured hair follicle evaluation confirmed that PL prolonged anagen remarkably and down-regulated IL-6, C-FOS, and p-STAT5a. Clinically, diameter, hair counts, absolute anagen counts and changes from baseline in the PL group showed a significant improvement at 6 months.

CONCLUSIONS

We elucidated the specific molecular mechanism of PL action on hair growth and proved equal changes in hair follicle performance after PL vs PRP in AGA patients. This study provided novel knowledge of PL, making it ideal for AGA.

In Vitro Cell Proliferation and Migration Properties of Oral Mucosal Fibroblasts: A Comparative Study on the Effects of Cord Blood- and Peripheral Blood-Platelet Lysate

Cord blood-platelet lysate (CB-PL), containing growth factors such as a platelet-derived growth factor, has a similar efficacy to peripheral blood-platelet lysate (PB-PL) in initiating cell growth and differentiation, which makes it a unique alternative to be implemented into oral ulceration healing. This research study aimed to compare the effectiveness of CB-PL and PB-PL in promoting oral wound closure in vitro. Alamar blue assay was used to determine the optimal concentration of CB-PL and PB-PL in enhancing the proliferation of human oral mucosal fibroblasts (HOMF). The percentage of wound closure was measured using the wound-healing assay for CB-PL and PB-PL at the optimal concentration of 1.25% and 0.3125%, respectively. The gene expressions of cell phenotypic makers (Col. I, Col. III, elastin and fibronectin) were determined via qRT-PCR. The concentrations of PDGF-BB were quantified using ELISA. We found that CB-PL was as effective as PB-PL in promoting wound-healing and both PL were more effective compared to the control (CTRL) group in accelerating the cell migration in the wound-healing assay. The gene expressions of Col. III and fibronectin were significantly higher in PB-PL compared to CB-PL. The PDGF-BB concentration of PB-PL was the highest and it decreased after the wound closed on day 3. Therefore, we concluded that PL from both sources can be a beneficial treatment for wound-healing, but PB-PL showed the most promising wound-healing properties in this study.

A double-edged sword of platelet-derived extracellular vesicles in tissues, injury or repair: The current research overview

Extracellular vesicles (EVs) are vesicular bodies with a double-layered membrane structure that are detached from the cell membrane or secreted by the cells. EVs secreted by platelets account for the main part in the blood circulation, which account for about 30% or even more. Many types of cells are regulated by PEVs, including endothelial cells, leukocytes, smooth muscle cells, etc. Nevertheless, despite the growing interest in the study of extracellular vesicles, there are still only a few studies on the role of PEVs. Therefore, this overview mainly focuses on one method of isolation and the functions of PEVs in tissues found so far, including promoting tissue repair and mediating tissue damage, which can be used for researchers to continue to explore the role of PEVs in other fields.

Cytokines in equine platelet lysate and related blood products

In equine medicine, the use of regenerative therapeutics has gained growing attention, but is still a new and complex field with room for improvement. Platelet lysate (PL) can be used as therapeutic agent but is also a promising supplement for the culture of multipotent mesenchymal stromal cells. To enable a targeted use of PL both in clinic and laboratory, it is crucial to learn more details on its effective ingredients. While so far, mainly growth factor components have been analyzed in platelet-based products such as PL, the current study focuses on the content of cytokines in serum, plasma, platelet concentrate and PL. Blood was harvested from 20 clinically healthy horses and subjected to blood count and chemistry analysis, as well as to further processing to PL. Plasma and platelet concentrate were produced by a buffy-coat-based method and PL was produced from the concentrate by freeze-thawing. Samples from each horse were analyzed regarding interleukin (IL)-1β, −4, −6 and −10, interferon-γ and tumor necrosis factor-α concentrations using sandwich ELISAs. Cytokine concentrations in serum, plasma, concentrate and PL were similar and correlated significantly. However, there was a large inter-individual variability in cytokine concentrations between the different donor horses. The samples from some donor animals had overall very high cytokine concentrations, while samples from other donors had no measurable cytokine ingredient. This pattern was observed for all cytokines. There was a noticeable link between high cytokine concentrations in the blood products and abnormal findings in blood chemistry. Cytokine concentrations in samples from horses with abnormal findings were significantly higher than in samples from the remaining horses. The interindividual differences in cytokine concentrations could be highly relevant when using PL for therapy and cell culture, as the mode of action of the PL is likely changed depending on the presence of pro- and anti-inflammatory cytokines. Blood chemistry might be useful to predict cytokine concentrations in blood products.

Platelets, Protean Cells with All-Around Functions and Multifaceted Pharmacological Applications

Platelets, traditionally known for their roles in hemostasis and coagulation, are the most prevalent blood component after erythrocytes (150,000-400,000 platelets/μL in healthy humans). However, only 10,000 platelets/μL are needed for vessel wall repair and wound healing. Increased knowledge of the platelet's role in hemostasis has led to many advances in understanding that they are crucial mediators in many other physiological processes, such as innate and adaptive immunity. Due to their multiple functions, platelet dysfunction is involved not only in thrombosis, mediating myocardial infarction, stroke, and venous thromboembolism, but also in several other disorders, such as tumors, autoimmune diseases, and neurodegenerative diseases. On the other hand, thanks to their multiple functions, nowadays platelets are therapeutic targets in different pathologies, in addition to atherothrombotic diseases; they can be used as an innovative drug delivery system, and their derivatives, such as platelet lysates and platelet extracellular vesicles (pEVs), can be useful in regenerative medicine and many other fields. The protean role of platelets, from the name of Proteus, a Greek mythological divinity who could take on different shapes or aspects, is precisely the focus of this review.

Platelets Facilitate Wound Healing by Mitochondrial Transfer and Reducing Oxidative Stress in Endothelial Cells

As a critical member in wound healing, vascular endothelial cells (ECs) impaired under high levels of reactive oxygen species (ROS) would hamper neovascularization. Mitochondria transfer can reduce intracellular ROS damage under pathological condition. Meanwhile, platelets can release mitochondria and alleviate oxidative stress. However, the mechanism by which platelets promote cell survival and reduce oxidative stress damage has not been clarified. Here, first, we selected ultrasound as the best method for subsequent experiments by detecting the growth factors and mitochondria released from manipulation platelet concentrates (PCs), as well as the effect of manipulation PCs on the proliferation and migration of HUVECs. Then, we found that sonicate platelet concentrates (SPC) decreased the level of ROS in HUVECs treated with hydrogen peroxide in advance, increased mitochondrial membrane potential, and reduced apoptosis. By transmission electron microscope, we saw that two kinds of mitochondria, free or wrapped in vesicles, were released by activated platelets. In addition, we explored that platelet-derived mitochondria were transferred to HUVECs partly by means of dynamin-dependent clathrin-mediated endocytosis. Consistently, we determined that platelet-derived mitochondria reduced apoptosis of HUVECs caused by oxidative stress. What is more, we screened survivin as the target of platelet-derived mitochondria via high-throughput sequencing. Finally, we demonstrated that platelet-derived mitochondria promoted wound healing in vivo. Overall, these findings revealed that platelets are important donors of mitochondria, and platelet-derived mitochondria can promote wound healing by reducing apoptosis caused by oxidative stress in vascular endothelial cells. And survivin is a potential target. These results further expand the knowledge of the platelet function and provide new insights into the role of platelet-derived mitochondria in wound healing.

Tissue Engineering as a Promising Treatment for Glottic Insufficiency: A Review on Biomolecules and Cell-Laden Hydrogel

Glottic insufficiency is widespread in the elderly population and occurs as a result of secondary damage or systemic disease. Tissue engineering is a viable treatment for glottic insufficiency since it aims to restore damaged nerve tissue and revitalize aging muscle. After injection into the biological system, injectable biomaterial delivers cost- and time-effectiveness while acting as a protective shield for cells and biomolecules. This article focuses on injectable biomaterials that transport cells and biomolecules in regenerated tissue, particularly adipose, muscle, and nerve tissue. We propose Wharton's Jelly mesenchymal stem cells (WJMSCs), induced pluripotent stem cells (IP-SCs), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), insulin growth factor-1 (IGF-1) and extracellular vesicle (EV) as potential cells and macromolecules to be included into biomaterials, with some particular testing to support them as a promising translational medicine for vocal fold regeneration.

Platelet lysate and tendon healing: comparative analysis of autologous frozen-thawed PRP and ketorolac tromethamine in the treatment of patients with rotator cuff tendinopathy

Platelet-rich blood derivatives are being nowadays increasingly used in the treatment of tendon-related pathologies as a rich source of growth factors. We sought to ascertain if local application of platelet lysate (PL) to augment rotator cuff repair ameliorates patient outcomes compared to ketorolac tromethamine treated group. A total of forty patients, with clinical diagnosis of Rotator Cuff Tendinopathy were randomized to receive sub acromial injections of PL every week for a total of 3 injections and two injection of ketorolac tromethamine once every two weeks. Subjective assessments included VAS, SPADI and shoulder range of motion were assessed at baseline and at 1 and 6 months after injection. Taking both control and PL groups, it was vividly seen that the outcomes were identical at the initial state, as well as the short-term one; whereas, when considering the 6-month period, there is a seemingly remarkable superiority in PL group in all parameters.

Platelet Derivatives and the Immunomodulation of Wound Healing

Besides their primary role in hemostasis, platelets contain a plethora of immunomodulatory molecules that profoundly affect the entire process of wound repair. Therefore, platelet derivatives, such as platelet-rich plasma or platelet lysate, have been widely employed with promising results in the treatment of chronic wounds. Platelet derivatives provide growth factors, cytokines, and chemokines targeting resident and immigrated cells belonging to the innate and adaptive immune system. The recruitment and activation of neutrophils and macrophages is critical for pathogen clearance in the early phase of wound repair. The inflammatory response begins with the release of cytokines, such as TGF-β, aimed at damping excessive inflammation and promoting the regenerative phase of wound healing. Dysregulation of the immune system during the wound healing process leads to persistent inflammation and delayed healing, which ultimately result in chronic wound. In this review, we summarize the role of the different immune cells involved in wound healing, particularly emphasizing the function of platelet and platelet derivatives in orchestrating the immunological response.

Risks in Induction of Platelet Aggregation and Enhanced Blood Clot Formation in Platelet Lysate Therapy: A Pilot Study

Platelet concentrates (PCs) are widely used in regenerative medicine; as it is produced from freeze–thawing PC, platelet lysate (PL) has a longer shelf life. The thrombotic risk of PL therapy needs to be explored since PL and PC contain cytokines that contribute to platelet aggregation and thrombus formation. Whole blood samples of 20 healthy subjects were collected; PL was produced from PCs with expired shelf life through freeze–thawing. The direct mixing of PL with platelet-rich plasma (PRP) or whole blood was performed. In addition, rotational thromboelastometry (ROTEM) was used to investigate whether PL enhanced coagulation in vitro; the effects of fibrinogen depletion and anticoagulants were evaluated to prevent hypercoagulation. The results showed that PL induced platelet aggregation in both PRP and whole blood. In ROTEM assays, PL was shown to cause a significantly lower clotting onset time (COT) and clot formation time (CFT), and a significantly greater α angle and maximum clot firmness (MCF). Compared with the controls, which were 1:1 mixtures of normal saline and whole blood, fibrinogen depletion of PL showed no significant difference in CFT, α angle and MCF. Moreover, heparin- and rivaroxaban-added PL groups demonstrated no clot formation in ROTEM assays. Platelet lysate-induced hypercoagulability was demonstrated in vitro in the present study, which could be prevented by fibrinogen depletion or the addition of an anticoagulant.

High-Throughput Production of Microsponges from Platelet Lysate for Tissue Engineering Applications

Cell-based therapies require a large number of cells, as well as appropriate methods to deliver the cells to damaged tissue. Microcarriers provide an optimal platform for large-scale cell culture while also improving cell retention during cell delivery. However, this technology still presents significant challenges due to low-throughput fabrication methods and an inability of the microcarriers to recreate the properties of human tissue. This work proposes, for the first time, the use of methacryloyl platelet lysates (PLMA), a photocrosslinkable material derived from human platelet lysates, to produce porous microcarriers. Initially, high quantities of PLMA/alginate core-shell microcapsules are produced using coaxial electrospray. Subsequently, the microcapsules are collected, irradiated with ultraviolet light, washed, and freeze dried yielding PLMA microsponges. These microsponges are able to support the adhesion and proliferation of human adipose-derived stem cells, while also displaying potential in the assembly of autologous microtissues. Cell-laden microsponges were shown to self-organize into aggregates, suggesting possible applications in bottom-up tissue engineering applications. Impact Statement Microcarriers have increasingly been used as delivery platforms in cell therapy. Herein, the encapsulation of human-derived proteins in alginate microcapsules is proposed as a method to produce microcarriers from photopolymerizable materials. The capsules function as a template structure, which is then processed into spherical microparticles, which can be used in cell culture, cell delivery, and bottom-up assembly. As a proof of concept, this method was combined with lyophilization to process methacryloyl platelet lysates into injectable microsponges for cell delivery.

Customizing the extracellular vesicles release and effect by strategizing surface functionalization of titanium

Metallic material functionalization with Extracellular Vesicles (EVs) is a desirable therapeutic approach to improve regenerative procedures. Among the different functionalization strategies available, here we have compared drop casting on machined Ti surfaces, drop casting on nanostructured TiO₂ surfaces and polymeric entrapment with polydopamine. EVs are a heterogeneous population of communication nanovesicles released by cells that are being intensively investigated for their use in therapeutics. We have selected platelet derived EVs for Ti surface coating due to their demonstrated osteoinductive properties. Our results show that each functionalization strategy leads to differences in the size of EV populations attached to and released from the metallic implants, which, in turn, leads to variations in their osteogenic capability measured through alkaline phosphatase activity and calcium deposition. In conclusion, the functionalization strategy used has an important effect on the resulting implant functionality, probably due to the heterogeneous EVs nature. Thus, the methodological approach to metallic material functionalization should be carefully chosen when working with extracellular vesicles in order to obtain the desired therapeutic application.

Autologous Fat Plus Platelet-Rich Plasma versus Autologous Fat Alone on Sulcus Vocalis

Sulcus vocalis is a frequent cause of glottic insufficiency that leads to incomplete vocal fold closure during phonation. Type II sulcus vocalis is defined as a partial defect of the lamina propria (LP). Treatment with fillers, such as fat or hyaluronic acid (HA), in the vocal folds is widely used, but the duration of effect is variable. Platelet-rich plasma (PRP) can enhance the survival of autologous fat in fat grafting, and also is used to treat sulcus vocalis. This study aimed to compare the effectiveness of autologous fat graft versus fat graft plus PRP to treat type II sulcus vocalis. Thirty-four patients with a voice handicap index (VHI) ≥ 11 were randomized to two groups, which received LP injections of fat graft (n = 17) or fat graft plus PRP (n = 17). At 1 month and 6 months after injection, the VHI decreased significantly in both groups. The fat plus PRP group had better Jitter, Shimmer, and noise to harmonic ratio (NHR) in 1 month and 6 months after surgery. The fat plus PRP group resulted in lower VHI scores one month after surgery, and stroboscopy revealed sustained smaller gaps after six months. These results indicate that a combination of fat graft plus PRP is safe and effective for treating sulcus vocalis type II and associated vocal atrophy.

Platelet Lysate for Mesenchymal Stromal Cell Culture in the Canine and Equine Species: Analogous but Not the Same

Simple Summary

Regenerative medicine using platelet-based blood products or adult stem cells offers the prospect of better clinical outcomes with many diseases. In veterinary medicine, most progress has been made with the development and therapeutic use of these regenerative therapeutics in horses, but the clinical need is given in dogs as well. Our aim was to transfer previous advances in the development of horse regenerative therapeutics, specifically the use of platelet lysate for feeding stem cell cultures, to the dog. Here, we describe the scalable production of canine platelet lysate, which could be used in regenerative biological therapies. We also evaluated the canine platelet lysate for its suitability in feeding canine stem cell cultures in comparison to equine platelet lysate used for equine stem cell cultures. Platelet lysate production from canine blood was successful, but the platelet lysate did not support stem cell culture in dogs in the same beneficial way observed with the equine platelet lysate and stem cells. In conclusion, canine platelet lysate can be produced in large scales as described here, but further research is needed to improve the cultivation of canine stem cells.

Abstract

Platelet lysate (PL) is an attractive platelet-based therapeutic tool and has shown promise as xeno-free replacement for fetal bovine serum (FBS) in human and equine mesenchymal stromal cell (MSC) culture. Here, we established a scalable buffy-coat-based protocol for canine PL (cPL) production (n = 12). The cPL was tested in canine adipose MSC (n = 5) culture compared to FBS. For further comparison, equine adipose MSC (n = 5) were cultured with analogous equine PL (ePL) or FBS. During canine blood processing, platelet and transforming growth factor-β1 concentrations increased (p < 0.05 and p < 0.001), while white blood cell concentrations decreased (p < 0.05). However, while equine MSC showed good results when cultured with 10% ePL, canine MSC cultured with 2.5% or 10% cPL changed their morphology and showed decreased metabolic activity (p < 0.05). Apoptosis and necrosis in canine MSC were increased with 2.5% cPL (p < 0.05). Surprisingly, passage 5 canine MSC showed less genetic aberrations after culture with 10% cPL than with FBS. Our data reveal that using analogous canine and equine biologicals does not entail the same results. The buffy-coat-based cPL was not adequate for canine MSC culture, but may still be useful for therapeutic applications.

Platelet lysate converts M (IFNγ+LPS) macrophages in CD206+ TGF-β+ arginase+ M2-like macrophages that affect fibroblast activity and T lymphocyte migration

Macrophages, thanks to their extreme plasticity, exert critical roles in wound healing by orchestrating tissue defenses in the early inflammatory phase, and by promoting tissue regeneration and angiogenesis at a later time point. In parallel, platelets release a large number of preformed molecules that could affect immunocyte functions. Platelet-rich plasma and platelet lysate (PL) have been widely used as a therapeutic preside for ulcers, although little is known about the effects of platelet-derived biomolecules on macrophage functions during wound healing. In this study, we analyze the effects of PL on macrophages phenotype and functions. Monocyte-derived macrophages were cultured in the presence of interferon-γ and lipopolysaccharides to induce the M1 polarization and were further exposed to 10% PL. PL treatment reduced CD80, CD86, and PDL-1 and enhanced CD206 and CD200R expression on macrophages analyzed by cytofluorimetry. Additionally, macrophage cultures show reduced TNF-α and CXCL10, while increased arginase protein, PPAR, TGF-β, and VEGF. TGF-β secretion was paralleled by the decrease of NFkB and increase of STAT3, STAT6, and SMAD2 and SMAD4. Supernatants of PL-treated macrophages induced a significant increase of type-I collagen and to a lesser extent of type-III collagen production by fibroblasts. Finally, the supernatant of PL-treated macrophages showed significantly reduced capacity to induce the in vitro migration of T lymphocytes. Our results demonstrate that PL dampens the macrophage secretion of pro-inflammatory cytokines and induces the release of arginase, TGF-β, and VEGF that may affect angiogenesis and tissue regeneration, thus facilitating the wound healing process.

Human platelet lysate - A potent (and overlooked) orthobiologic

The knowledge of the essential role of platelets in tissue healing is gradually increasing and as regenerative medicine prompts new solutions, platelet-derived bioproducts have been proposed as a potential tool in this field. In orthopaedics and sports medicine, the use of PRP has been rapidly increasing in popularity as patients seek novel non-surgical approaches to acute and chronic musculoskeletal conditions. The concept of having platelets as a secretory organ other than a mere sponge-like coagulation component opens up new frontiers for the use of the platelet secretome. Platelet lysate is a solution saturated by growth factors, proteins, cytokines, and chemokines involved in crucial healing processes and is administered to treat different diseases such as alopecia, oral mucositis, radicular pain, osteoarthritis, and cartilage and tendon disorders. For this purpose, the abundant presence of growth factors and chemokines stored in platelet granules can be naturally released by different strategies, mostly through lyophilization, thrombin activation or ultrasound baths (ultrasonication). As a result, human platelet lysate can be produced and applied as a pure orthobiologic. This review outlines the current knowledge about human platelet lysate as a powerful adjuvant in the orthobiological use for the treatment of musculoskeletal injuries, without however failing to raise some of its most applicable basic science.

Human Platelet Lysate-Loaded Poly(ethylene glycol) Hydrogels Induce Stem Cell Chemotaxis In Vitro

Platelet lysates (PL) contain a selection of proteins and growth factors (GFs) that are known to mediate cell activity. Many of these biomolecules have been identified as chemoattractants with the capacity to induce cell migration. In order to effectively deliver and retain these biomolecules to the site of injury, a scaffold containing PL could be an option. We use poly(ethylene glycol) (PEG) hydrogels consisting of 90 vol % PL to investigate their migratory potential on human mesenchymal stem cells (hMSCs). Cells exposed to these hydrogels were tracked, resulting in cell trajectories and detailed migratory parameters (velocity, Euclidean distance, directness, and forward migration index). Volumetric swelling ratios, hydrogel mechanical properties, and the release kinetics of proteins and GFs from hydrogels were also assessed. Furthermore, hMSC spheroids were encapsulated within the hydrogels to qualitatively assess cell invasion by means of sprouting and disintegration of the spheroid. Cell spheroids encapsulated within the PL-PEG gels exhibited initial outgrowths and eventually colonized the 3D matrix successfully. Results from this study confirmed that hMSCs exhibit directional migration toward the PL-loaded hydrogel with increased velocity and directness, compared to the controls. Overall, the incorporation of PL renders the PEG hydrogel bioactive. This study demonstrates the capacity of PL-loaded hydrogel constructs to attract stem cells for endogenous tissue engineering purposes.

Platelet-Therapeutics to Improve Tissue Regeneration and Wound Healing-Physiological Background and Methods of Preparation

Besides their function in primary hemostasis, platelets are critically involved in the physiological steps leading to wound healing and tissue repair. For this purpose, platelets have a complex set of receptors allowing the recognition, binding, and manipulation of extracellular structures and the detection of pathogens and tissue damage. Intracellular vesicles contain a huge set of mediators that can be released to the extracellular space to coordinate the action of platelets as other cell types for tissue repair. Therapeutically, the most frequent use of platelets is the intravenous application of platelet concentrates in case of thrombocytopenia or thrombocytopathy. However, there is increasing evidence that the local application of platelet-rich concentrates and platelet-rich fibrin can improve wound healing and tissue repair in various settings in medicine and dentistry. For the therapeutic use of platelets in wound healing, several preparations are available in clinical practice. In the present study we discuss the physiology and the cellular mechanisms of platelets in hemostasis and wound repair, the methods used for the preparation of platelet-rich concentrates and platelet-rich fibrin, and highlight some examples of the therapeutic use in medicine and dentistry.

Using intra-articular allogenic lyophilized growth factors in primary knee osteoarthritis: a randomized pilot study

Objective: Investigating the safety in addition to clinical and structural efficacy of allogenic lyophilized growth factors (L-GFs) in patients with symptomatic primary knee osteoarthritis. Design: A prospective, open-label pilot study. A total of 31-patients randomized into non-intervention and intervention groups. Materials & methods: The intervention group received two intra-articular doses at baseline and after 2-months. Post-injection complications were documented, and the efficacy was assessed by Western Ontario and McMaster Universities Osteoarthritis Index scores and ultrasonography. Results: One dropout from the intervention group. The percentage of improvement of mean Western Ontario and McMaster Universities Osteoarthritis Index-scores and ultrasonography-detected effusion were statistically significant in the intervention group compared with the non-intervention. A brief, mild, post-injection pain was reported by all intervention group. Conclusion: This study provides the safety of intra-articular injection of allogenic L-GFs in knee osteoarthritis. The conclusion of efficacy was limited by small sample size and lack of control injection. Clinical trial registration: NCT04331327 (ClinicalTrials.gov, retrospectively registered).

[Standardized management of platelet derivatives for tissue regeneration research and applications]

Objective

To summary the standardized management in research and applications of platelet derivatives for tissue regeneration.

Methods

The related literature about bottlenecks and standardized management of platelet derivatives in recent years was reviewed and analyzed.

Results

Although the platelet derivatives are increasingly used to accelerate the regenerative processes of injured joint, skin, nerve, ligament/tendon, and alveolar bone, etc., the large variation in preparation methods, diverse nomenclature, incomplete reporting system, and lack of quantitative and standardized management of the preparation process have caused uncertainty and incomparability of research and application results. In recent years, there has been a trend towards standardized research and management of platelet derivatives.

Conclusion

The implementation of standardized research and quality management will contribute to promote the research and application of platelet derivatives in the field of tissue regeneration.

Angiogenesis Is Differentially Modulated by Platelet-Derived Products

Platelet-derived preparations are being used in clinic for their role in tissue repair and regenerative processes. The release of platelet-derived products such as autologous growth factors, cytokines and chemokines can trigger therapeutic angiogenesis. In this in vitro study, we evaluated and compared the ability of three platelet-derived preparations: platelet-rich-plasma (PRP), PRP-hyaluronic acid (PRP-HA) and platelet lysates (PL) at various concentrations (5–40%) to modulate human umbilical vein endothelial cells (HUVEC) biological effects on metabolism, viability, senescence, angiogenic factors secretion and angiogenic capacities in 2D (endothelial tube formation assay or EFTA) and in 3D (fibrin bead assay or FBA). HUVEC exocytosis was stimulated with PRP and PRP-HA. Cell viability was strongly increased by PRP and PRP-HA but mildly by PL. The three preparations inhibit HUVEC tube formation on Matrigel, while PRP enhanced the complexity of the network. In the fibrin bead assay (FBA), PRP and PRP-HA stimulated all steps of the angiogenic process resulting in massive sprouting of a branched microvessel network, while PL showed a weaker angiogenic response. Secretome profiling revealed modulation of 26 human angiogenic proteins upon treatment with the platelet derived preparations. These in vitro experiments suggest that PRP and PRP-HA are effective biological therapeutic tools when sustained therapeutic angiogenesis is needed.

Use of platelet concentrate gel in second-intention wound healing: a case report

Background

Wound healing is a complex and dynamic process. Healing of acute and chronic wounds can be impaired by patient factors (that is, comorbidities) and/or wound factors (that is, infection). Regenerative medicine products, such as autologous/homologous platelet-rich plasma gel, may speed up the healing process. Autologous/homologous platelet-rich plasma is an advanced wound therapy used for hard-to-heal acute and chronic wounds. The cytokines and growth factors contained in platelet-rich plasma play a crucial role in the healing process.

Case presentation

A 61-year-old Caucasian male patient, suffering from mental retardation following meningitis, with a transplanted kidney due to prior renal impairment, and under immunosuppressant therapy, was submitted to aneurysmectomy of his proximal left forearm arteriovenous fistula. A few days later, the patient came to our attention with substantial blood loss from the surgical site. The wound presented no signs of healing, and after fistula reparation and considering persistent infection of the surgical site (by methicillin-resistant Staphylococcus aureus), surgeons decided for second-intention healing. To favor healing, 10 mL homologous platelet concentrate gel was sequentially applied. After each application, wound was covered with nonadherent antiseptic dressing. After only seven applications of homologous platelet concentrate gel, wound completely recovered and no amputation was necessary.

Conclusions

Topical application of homologous platelet-rich plasma gel in healing wound shows beneficial results in wound size reduction and induces granulation tissue formation. Platelet-rich plasma could be a safe and cost-effective treatment for managing the cutaneous wound healing process to shorten the recovery period and thereby improve patient quality of life.

The Effect of a Polyester Nanofibrous Membrane with a Fibrin-Platelet Lysate Coating on Keratinocytes and Endothelial Cells in a Co-Culture System

Chronic wounds affect millions of patients worldwide, and it is estimated that this number will increase steadily in the future due to population ageing. The research of new therapeutic approaches to wound healing includes the development of nanofibrous meshes and the use of platelet lysate (PL) to stimulate skin regeneration. This study considers a combination of a degradable electrospun nanofibrous blend of poly(L-lactide-co-ε-caprolactone) and poly(ε-caprolactone) (PLCL/PCL) membranes (NF) and fibrin loaded with various concentrations of PL aimed at the development of bioactive skin wound healing dressings. The cytocompatibility of the NF membranes, as well as the effect of PL, was evaluated in both monocultures and co-cultures of human keratinocytes and human endothelial cells. We determined that the keratinocytes were able to adhere on all the membranes, and their increased proliferation and differentiation was observed on the membranes that contained fibrin with at least 50% of PL (Fbg + PL) after 14 days. With respect to the co-culture experiments, the membranes with fibrin with 20% of PL were observed to enhance the metabolic activity of endothelial cells and their migration, and the proliferation and differentiation of keratinocytes. The results suggest that the newly developed NF combined with fibrin and PL, described in the study, provides a promising dressing for chronic wound healing purposes.

Super Activated Platelet Lysate, a Novel Autologous Platelet Lysate, Regulates the Expression of Inflammasome and Cytokine in the Experimental Periodontitis in Rats

Purpose

The aim of the present study was to evaluate the expression of inflammasome and cytokine on experimental periodontitis with super activated platelet lysate (SPL) in rats.

Methods

Periodontitis was induced by submerging cotton ligatures on the right side of the maxillary second molar in 36 Wistar rats. The rats were divided into 3 groups randomly: the rats received no treatment (control group); local injection with sterile saline (ligature+saline group) and local injection with SPL (ligature+SPL group). After treatments, the alveolar bone level and inflammation of periodontal tissue were evaluated by micro-computed tomography (micro-CT) scanning and histological examination, respectively. The expression of inflammasome and cytokine was evaluated by real-time quantitative polymerase chain reaction (RT-qPCR) assay.

Results

Compared with the control group, the bone loss significantly increased by 0.9 mm in the ligature+saline group and 0.4 mm in the ligature+SPL group (P < 0.001). 0.5 mm reduction in the bone loss was founded in the ligature+SPL group compared with the ligature+saline group (P < 0.001). The gene expression of CCL2, CXCL2, IL-6, IL-18, IL-1α, IL-1β, CXCL10, CXCL16, CCL5 was significantly reduced in the ligature+SPL group compared with the ligature+saline group (P < 0.05). Compared with the ligature+saline group, the expression for inflammasome NLRP3, AIM2, CASP1 was both downregulated in the ligature+SPL group (P < 0.05).

Conclusion

Our present study demonstrated local injection of SPL regulated the expression of inflammasome and cytokine and had a visible effect of relieving inflammation in the experimental periodontitis in rats.

Extensive characterization of the composition and functional activities of five preparations of human platelet lysates for dedicated clinical uses

Human platelet lysates (HPLs), rich in various growth factors and cell growth-promoting molecules, encompass a new range of blood products that are being used for regenerative medicine, cell therapies, and tissue engineering. Well-characterized dedicated preparations, tailor-made to best fit specific therapeutic applications, are needed for optimal clinical efficacy and safety. Here, five types of HPL were prepared from the same platelet concentrates and extensively characterized to determine and compare their proteins, growth factors, cytokines, biochemical profiles, thrombin-generating capacities, thrombin-associated proteolytic activities, phospholipid-associated procoagulant potential, contents of extracellular vesicles expressing phosphatidylserine and tissue factor, and antioxidative properties. Our results revealed that all five HPL preparations contained detectable supraphysiological levels, in the ca. 0.1 ~ 350-ng/ml range, of all growth factors assessed, except insulin-like growth factor-1 detected only in HPL containing plasma. There were significant differences observed among these HPLs in total protein content, fibrinogen, complement components C3 and C4, albumin, and immunoglobulin G, and, most importantly, in their functional coagulant and procoagulant activities and antioxidative capacities. Our data revealed that the biochemical and functional properties of HPL preparations greatly vary depending upon their mode of production, with potential impacts on the safety and efficacy for certain clinical indications. Modes of preparation of HPLs should be carefully designed, and the product properties carefully evaluated based on the intended therapeutic use to ensure optimal clinical outcomes.

Platelet-derived extracellular vesicles promote osteoinduction of mesenchymal stromal cells

Aims

Platelet concentrates, like platelet-rich plasma (PRP) and platelet lysate (PL), are widely used in regenerative medicine, especially in bone regeneration. However, the lack of standard procedures and controls leads to high variability in the obtained results, limiting their regular clinical use. Here, we propose the use of platelet-derived extracellular vesicles (EVs) as an off-the-shelf alternative for PRP and PL for bone regeneration. In this article, we evaluate the effect of PL-derived EVs on the biocompatibility and differentiation of mesenchymal stromal cells (MSCs).

Methods

EVs were obtained first by ultracentrifugation (UC) and then by size exclusion chromatography (SEC) from non-activated PL. EVs were characterized by transmission electron microscopy, nanoparticle tracking analysis, and the expression of CD9 and CD63 markers by western blot. The effect of the obtained EVs on osteoinduction was evaluated in vitro on human umbilical cord MSCs by messenger RNA (mRNA) expression analysis of bone markers, alkaline phosphatase activity (ALP), and calcium (Ca²⁺) content.

Results

Osteogenic differentiation of MSCs was confirmed when treated with UC-isolated EVs. In order to disprove that the effect was due to co-isolated proteins, EVs were isolated by SEC. Purer EVs were obtained and proved to maintain the differentiation effect on MSCs and showed a dose-dependent response.

Conclusion

PL-derived EVs present an osteogenic capability comparable to PL treatments, emerging as an alternative able to overcome PL and PRP limitations.

Cite this article: Bone Joint Res 2020;9(10):667–674.

Platelet-Derived Products in Veterinary Medicine: A New Trend or an Effective Therapy?

Platelet-derived products (PDPs) have gained popularity, mainly due to their high concentrations of bioactive molecules such as growth factors and cytokines, which play important roles in tissue healing and regeneration. PDPs are obtained through minimally invasive procedures and their therapeutic effect has been widely recognized. In veterinary medicine, however, the lack of standard protocols to generate PDPs is a major hurdle for assessing the clinical relevance of PDP-based therapies and for their widespread usage. The aim of this review is to analyze the technical and scientific specificities of PDPs in terms of preparation methodologies, classification categorization, nomenclature, and biological proprieties to advance their future biotechnological potential in veterinary contexts.

The molecular mechanism of platelet lysate promotes transformation of non-union cells into osteoblasts

Background

Platelet lysate (PL) had a remarkable therapeutic effect on bone repair related diseases, such as delayed fracture healing, femoral head necrosis and meniscal tear. In this study, we investigated the effect of PL on patients with nonunion, cartilage repair and osteonecrosis, and to evaluate the effect of PL on nonunion cells proliferation and the effect of PL on OPG/RANKL signaling pathway in nonunion cell of male rats. To reveal the molecular mechanism of PL for bone healing.

Methods

We used different concentrations of PL to treat nonunion cells, then detected cell proliferation and protein expression levels of osteoprotegerin (OPG), RANKL, osteopontin (OPN), osteocalcin (OCN) and alkaline phosphatase (ALP).

Results

The proliferation rate of nonunion cells treated by 5% PL, was significantly higher than that of the control group (P<0.05). Surprisingly, there were no significant difference among the proliferation rates of nonunion cells treated by 8% PL, 10% FBS and the control group (P>0.05). the results of western blot analysis and immunofluorescence analysis showed that PL improved the expression of OPG, OPN, OCN and ALP proteins in nonunion cells, but PL had no effect on the expression of nuclear factor-κB ligand (RANKL) protein.

Conclusions

We found that PL had a remarkable therapeutic effect on bone repair related diseases; 5% PL significantly improved the proliferation rate of the nonunion cells; 10% PL had a significantly positive effect on improving the expression levels of osteogenic related genes.

Humanized Culture Medium for Clinical-Grade Generation of Erythroid Cells from Umbilical Cord Blood CD34+ Cells

Purpose: Transfusion of red blood cells (RBCs) is a supportive and common treatment in surgical care, trauma, and anemia. However, in vivo production of RBC seems to be a suitable alternative for blood transfusions due to the limitation of blood resources, the possibility of disease transmission, immune reactions, and the presence of rare blood groups. Cell cultures require serum-free or culture media supplemented with highly expensive animal serum, which can transmit xenoviruses. Platelet lysate (PL) can be considered as a suitable alternative containing a high level of growth factors and a low production cost.

Methods: Three-step culture media supplemented with PL or fetal bovine serum (FBS) were used for proliferation and differentiation of CD34⁺ umbilical cord blood stem cells to erythrocytes in co-culture with bone marrow mesenchymal stem cells (BM-MSCs). The cells were cultivated for 15 days and cell proliferation and expansion were assessed using cell counts at different days. Erythroid differentiation genes, CD71 and glycophorin A expression levels were evaluated.

Results: Maximum hematopoietic stem cells (HSCs) proliferation was observed on day 15 in PL-containing medium (99±17×10³-fold). Gene expression and surface markers showed higher differentiation of cells in PL-containing medium.

Conclusion: The results of this study indicate that PL can enhance erythroid proliferation and differentiation of CD34⁺ HSCs. PL can also be used as a proper alternative for FBS in the culture medium and HSCs differentiation.

Viral safety of human platelet lysate for cell therapy and regenerative medicine: Moving forward, yes, but without forgetting the past

Growth factor-rich pooled human platelet lysate (HPL), made from human platelet concentrates, is one new blood-derived bioproduct that is attracting justified interest as a xeno-free supplement of growth media for human cell propagation for cell therapy. HPL can also find potentially relevant applications in the field of regenerative medicine. Therefore, the therapeutic applications of HPL go far beyond the standard clinical applications of the traditional blood products typically used in patients suffering from life-threatening congenital or acquired deficiencies in cellular components or proteins due to severe genetic diseases or trauma. A wider population of patients, suffering from various pathologies than has traditionally been the case, is thus, now susceptible to receiving a human blood-derived product. These patients would, therefore, be exposed to the possible, but avoidable, side effects of blood products, including transfusion-transmitted infections, most specifically virus transmissions. Unfortunately, not all manufacturers, suppliers, and users of HPL may have a strong background in the blood product industry. As such, they may not be fully aware of the various building blocks that should contribute to the viral safety of HPL as is already the case for any licensed blood products. The purpose of this manuscript is to reemphasize all the measures, including in regulatory aspects, capable of assuring that HPL exhibits a sufficient pathogen safety margin, especially when made from large pools of human platelet concentrates. It is vital to remember the past to avoid that the mistakes, which happened 30 to 40 years ago and led to the contamination of many blood recipients, be repeated due to negligence or ignorance of the facts.

Association of Platelet-Rich Plasma and Auto-Crosslinked Hyaluronic Acid Microparticles: Approach for Orthopedic Application

Platelet-rich plasma (PRP) associated with high molecular weight hyaluronic acid (HA) has been clinically used for tissue regeneration in orthopedics. Despite the recognized beneficial clinical outcomes (e.g., early pain control, improvement of patients' functional limitation and longer-term effectiveness compared to PRP and HA alone in mild and moderate osteoarthritis treatments), its use is still challenging and controversial due to lack of standardization of association practical protocols. Moreover, most studies neglect the matrix structure, that generates the ultimate properties of the association among platelets, fibrin network and the microparticles. In the present work, we aimed to analyze the influence of the PRP/HA association with a controlled matrix structure on the stability, rheological behavior, release of growth factors and in vitro proliferation of human adipose-derived mesenchymal cells (h-AdMSCs). The attenuation of the negative charge of HA was also evaluated. Pure PRP (P-PRP) (i.e., plasma enriched with platelets and poor in leukocytes) was prepared by centrifugation and activated with serum and calcium chloride (_AP-PRP). Autocrosslinked hyaluronic acid (AHA) was prepared by organocatalyzed auto-esterification and structured in microparticles (_MPAHA) by shearing. The attenuation of the negative charge of _MPAHA was performed with chitosan (CHT) by polyelectrolyte complexation yielding _MPAHA-CHT. The results showed that microparticles (MPs) have viscoelastic properties, extrusion force and swelling ratio appropriate for injectable applications. The association of _AP-PRP with the controlled structure of _MPAHA and _MPAHA-CHT formed a matrix composed of platelets and of a fibrin network with fibers around 160 nm located preferably on the surface of the MPs with an average diameter of 250 μm. Moreover, _AP-PRP/_MPAHA and _AP-PRP/_MPAHA-CHT associations were non-toxic and supported controlled growth factor (PDGF-AB and TGF-β1) release and in vitro proliferation of h-AdMSC with a similar pattern to that of _AP-PRP alone. The best h-AdMSC proliferation was obtained with the _AP-PRP/_MPAHA-CHT_75:25 indicating that the charge attenuation improved the cell proliferation. Thus, the association of _AP-PRP with the controlled structure of HA can be a valuable approach for orthopedic applications.