Blood-derived biomaterials and platelet growth factors in regenerative medicine

Nanotechnological approach to delivering nutraceuticals as promising drug candidates for the treatment of atherosclerosis

Atherosclerosis is Caesar's sword, which poses a huge risk to the present generation. Understanding the atherosclerotic disease cycle would allow ensuring improved diagnosis, better care, and treatment. Unfortunately, a highly effective and safe way of treating atherosclerosis in the medical community remains a continuous challenge. Conventional treatments have shown considerable success, but have some adverse effects on the human body. Natural derived medications or nutraceuticals have gained immense popularity in the treatment of atherosclerosis due to their decreased side effects and toxicity-related issues. In hindsight, the contribution of nutraceuticals in imparting enhanced clinical efficacy against atherosclerosis warrants more experimental evidence. On the other hand, nanotechnology and drug delivery systems (DDS) have revolutionized the way therapeutics are performed and researchers have been constantly exploring the positive effects that DDS brings to the field of therapeutic techniques. It could be as exciting as ever to apply nano-mediated delivery of nutraceuticals as an additional strategy to target the atherosclerotic sites boasting high therapeutic efficiency of the nutraceuticals and fewer side effects.

Human Platelet Lysate as an Alternative to Autologous Serum for Human Chondrocyte Clinical Use

OBJECTIVE

A pivotal aspect of cartilage tissue engineering resides in cell culture medium supplementation, in view of maximizing in vitro cell proliferation and preserving cellular functionality. Autologous human serum (aHS) is commonly used as an inducive supplement for safe human articular chondrocyte (HAC) proliferation prior to clinical implantation. However, practical clinical use of aHS is hindered by constraining manufacturing requirements and quality assurance-driven downstream processing. The present study investigated potential alternative use of commercial human platelet lysate (hPL) supplements in HAC manufacturing workflows related to clinical therapeutic pathways.

DESIGN

Differential effects of hPL, aHS, and fetal bovine serum were assessed on primary cultured HAC parameters (viability, proliferative rates, and morphology) in 2-dimensional in vitro systems. A 3-dimensional HAC pellet model served for postexpansion assessment of cellular functionality, by visualizing proteoglycan production (Alcian blue staining), and by using qRT-PCR relative quantification of chondrogenic marker (SOX9, COL2-A1, and ACAN) genetic expression.

RESULTS

We found that monolayer HAC culture with hPL or aHS supplements presented similar characteristics (elongated cell morphology and nearly identical growth kinetics). Chondrogenic activity appeared as conserved in HACs expanded with human or bovine supplements, wherein histologic analysis indicated a progressive sGAG accumulation and SOX9, COL2-A1, ACAN gene expression was upregulated in 3-dimensional HAC pellet models.

CONCLUSION

This study therefore supports the use of hPL as a functional equivalent and alternative to aHS for cultured HAC batch preparation, with the potential to effectively alleviate pressure on clinical and manufacturing bottlenecks in cell therapy approaches for cartilage regeneration.

Human platelet lysate biotherapy for traumatic brain injury: preclinical assessment

Traumatic brain injury (TBI) leads to major brain anatomopathological damages underlined by neuroinflammation, oxidative stress and progressive neurodegeneration, ultimately leading to motor and cognitive deterioration. The multiple pathological events resulting from TBI can be addressed not by a single therapeutic approach, but rather by a synergistic biotherapy capable of activating a complementary set of signalling pathways and providing synergistic neuroprotective, anti-inflammatory, antioxidative, and neurorestorative activities. Human platelet lysate might fulfil these requirements as it is composed of a plethora of biomolecules readily accessible as a TBI biotherapy. In the present study, we tested the therapeutic potential of human platelet lysate using in vitro and in vivo models of TBI. We first prepared and characterized platelet lysate from clinical-grade human platelet concentrates. Platelets were pelletized, lysed by three freeze-thaw cycles, and centrifuged. The supernatant was purified by 56°C 30 min heat treatment and spun to obtain the heat-treated platelet pellet lysate that was characterized by ELISA and proteomic analyses. Two mouse models were used to investigate platelet lysate neuroprotective potential. The injury was induced by an in-house manual controlled scratching of the animals' cortex or by controlled cortical impact injury. The platelet lysate treatment was performed by topical application of 60 µl in the lesioned area, followed by daily 60 µl intranasal administration from Day 1 to 6 post-injury. Platelet lysate proteomics identified over 1000 proteins including growth factors, neurotrophins, and antioxidants. ELISA detected several neurotrophic and angiogenic factors at ∼1-50 ng/ml levels. We demonstrate, using two mouse models of TBI, that topical application and intranasal platelet lysate consistently improved mouse motor function in the beam and rotarod tests, mitigated cortical neuroinflammation, and oxidative stress in the injury area, as revealed by downregulation of pro-inflammatory genes and the reduction in reactive oxygen species levels. Moreover, platelet lysate treatment reduced the loss of cortical synaptic proteins. Unbiased proteomic analyses revealed that heat-treated platelet pellet lysate reversed several pathways promoted by both controlled cortical impact and cortical brain scratch and related to transport, postsynaptic density, mitochondria or lipid metabolism. The present data strongly support, for the first time, that human platelet lysate is a reliable and effective therapeutic source of neurorestorative factors. Therefore, brain administration of platelet lysate is a therapeutical strategy that deserves serious and urgent consideration for universal brain trauma treatment.

Effects of Combination of BMP7, PFG, and Autograft on Healing of the Experimental Critical Radial Bone Defect by Induced Membrane (Masquelet) Technique in Rabbit

Background

Healing of large segmental bone defects can be challenging for orthopedic surgeons. This research was conducted to provide further insight into the effects of BMP7 in combination with autograft and platelet fibrin glue (PFG) on bone regeneration by Masquelet technique (MT).

Methods

Twenty five domestic male rabbits, more than 6 months old, weighing 2.00±0.25 kg were randomly divided into five equal groups as follows: MT-blank cavity (without any biological or synthetic materials) (1), blank cavity (2), MT-autograft (3), MT-autograft-BMP7 (4), and MT-BMP7-PFG (5). A 20 mm segmental defect was made in radial bone in both forelimbs. The Masquelet technique was done in all groups except group 2. The study was evaluated by radiology, biomechanics, histopathology and scanning electron microscopy.

Results

The results showed that Masquelet technique enhanced the healing process, as, the structural and functional criteria of the injured bone showed significantly improved bone healing (P<0.05). Treatment by PFG-BMP7, Autograft-BMP7, and autograft demonstrated beneficial effects on bone healing. However, Autograft-BMP7 was more effective than autograft in healing of the radial defect in rabbits.

Conclusion

Our findings introduce the osteogenic materials in combination with Masquelet technique as an alternative for reconstruction of the big diaphyseal defects in the long bones in animal models. Our findings may be useful for clinical application in future.

Healing through the lens of immunothrombosis: Biology-inspired, evolution-tailored, and human-engineered biomimetic therapies

Evolution, from invertebrates to mammals, has yielded and shaped immunoclotting as a defense and repair response against trauma and infection. This mosaic of immediate and local wound-sealing and pathogen-killing mechanisms results in survival, restoration of homeostasis, and tissue repair. In mammals, immunoclotting has been complemented with the neuroendocrine system, platelets, and contact system among other embellishments, adding layers of complexity through interconnecting blood-born proteolytic cascades, blood cells, and the neuroendocrine system. In doing so, immunothrombosis endows humans with survival advantages, but entails vulnerabilities in the current unprecedented and increasingly challenging environment. Immunothrombosis and tissue repair appear to go hand in hand with common mechanisms mediating both processes, a fact that is underlined by recent advances that are deciphering the mechanisms of the repair process and of the biochemical pathways that underpins coagulation, hemostasis and thrombosis. This review is intended to frame both the universal aspects of tissue repair and the therapeutic use of autologous fibrin matrix as a biology-as-a-drug approach in the context of the evolutionary changes in coagulation and hemostasis. In addition, we will try to shed some light on the molecular mechanisms underlying the use of the autologous fibrin matrix as a biology-inspired, evolution-tailored, and human-engineered biomimetic therapy.

Hyaluronic acid nanofiber mats loaded with antimicrobial peptide towards wound dressing applications

Chronic wounds are highly susceptible to bacterial infections. Previously, we loaded a natural antimicrobial peptide of low cost and high safety, ε-polylysine (EPL), into the electrospun nanofiber mat of starch. The mat showed comparable antibacterial activity but markedly better biocompatibility than the commercial silver-containing dressing. To further optimize material property, in this paper, we use hyaluronic acid (HA) to replace starch. Results show that EPL-loaded HA nanofiber mats (OHA-EPL) have suitable water vapor permeability, good biocompatibility and broad-spectrum antibacterial property similar to that of EPL-loaded starch nanofiber mat (Starch-EPL). Differently, the content of EPL in OHA-EPL nanofiber mats increases from 19.2% to 27.9%, the tensile strength rises from 0.3 MPa to 0.6 MPa, the elongation grows from 62.0% to 130.0%, and the fiber degradation and EPL release accelerates. In addition, OHA-EPL can absorb up to 26.3-times exudate, which is much higher than Starch-EPL (15.1 times). Combined with the excellent biological activity of HA, OHA-EPL may produce better therapeutic effects than Starch-EPL.

A purified human platelet pellet lysate rich in neurotrophic factors and antioxidants repairs and protects corneal endothelial cells from oxidative stress

Human platelet lysate (HPL) is a complex mixture of potent bioactive molecules instrumental in tissue repair and regeneration. Due to their remarkable safety, cost-effective production, and availability at global level from collected platelet concentrates, HPLs can become a powerful biotherapy for various therapeutic applications, if standardized and carefully validated through pre-clinical and clinical studies. In this work, the possibility to use a tailor-made HPL as a corneal transplant alternative to treat the gradual decrease in the number of corneal endothelial cells (CECs) associated with aging, was evaluated. The HPL preparation was thoroughly characterized using various proteomics tools that revealed a remarkable richness in multiple growth factors and antioxidants. Treatment of B4G12 and BCE C/D-1b CECs with the HPL increased their viability, enhanced the wound closure rate, and maintained cell growth and typical hexagonal morphology. Besides, this HPL significantly protected against tert-butyl hydroperoxide (TBHP)-induced oxidative stress as evidenced by increasing CEC viability, decreased cell death and reactive oxygen species formation, and enhanced antioxidant capacity. Proteomics analysis of treated CECs confirmed that HPL treatment triggered the corneal healing pathway and enhanced oxidative stress. These data strongly support further pre-clinical evaluation of this tailor-made HPL as a novel CEC regeneration biotherapy. HPL treatment may eventually represent a pragmatic and cost-effective alternative to corneal transplant to treat damages of the corneal endothelium which is a major cause of blindness worldwide.

Elastin-Plasma Hybrid Hydrogels for Skin Tissue Engineering

Dermo-epidermal equivalents based on plasma-derived fibrin hydrogels have been extensively studied for skin engineering. However, they showed rapid degradation and contraction over time and low mechanical properties which limit their reproducibility and lifespan. In order to achieve better mechanical properties, elasticity and biological properties, we incorporated a elastin-like recombinamer (ELR) network, based on two types of ELR, one modified with azide (SKS-N₃) and other with cyclooctyne (SKS-Cyclo) chemical groups at molar ratio 1:1 at three different SKS (serine-lysine-serine sequence) concentrations (1, 3, and 5 wt.%), into plasma-derived fibrin hydrogels. Our results showed a decrease in gelation time and contraction, both in the absence and presence of the encapsulated human primary fibroblasts (hFBs), higher mechanical properties and increase in elasticity when SKSs content is equal or higher than 3%. However, hFBs proliferation showed an improvement when the lowest SKS content (1 wt.%) was used but started decreasing when increasing SKS concentration at day 14 with respect to the plasma control. Proliferation of human primary keratinocytes (hKCs) seeded on top of the hybrid-plasma hydrogels containing 1 and 3% of SKS showed no differences to plasma control and an increase in hKCs proliferation was observed for hybrid-plasma hydrogels containing 5 wt.% of SKS. These promising results showed the need to achieve a balance between the reduced contraction, the better mechanical properties and biological properties and indicate the potential of using this type of hydrogel as a testing platform for pharmaceutical products and cosmetics, and future work will elucidate their potential.

Angiogenic Properties of Concentrated Growth Factors (CGFs): The Role of Soluble Factors and Cellular Components

Blood-derived concentrated growth factors (CGFs) represent a novel autologous biomaterial with promising applications in regenerative medicine. Angiogenesis is a key factor in tissue regeneration, but the role played by CGFs in vessel formation is not clear. The purpose of this study was to characterize the angiogenic properties of CGFs by evaluating the effects of its soluble factors and cellular components on the neovascularization in an in vitro model of angiogenesis. CGF clots were cultured for 14 days in cell culture medium; after that, CGF-conditioned medium (CGF-CM) was collected, and soluble factors and cellular components were separated and characterized. CGF-soluble factors, such as growth factors (VEGF and TGF-β1) and matrix metalloproteinases (MMP-2 and -9), were assessed by ELISA. Angiogenic properties of CGF-soluble factors were analyzed by stimulating human cultured endothelial cells with increasing concentrations (1%, 5%, 10%, or 20%) of CGF-CM, and their effect on cell migration and tubule-like formation was assessed by wound healing and Matrigel assay, respectively. The expression of endothelial angiogenic mediators was determined using qRT-PCR and ELISA assays. CGF-derived cells were characterized by immunostaining, qRT-PCR and Matrigel assay. We found that CGF-CM, consisting of essential pro-angiogenic factors, such as VEGF, TGF-β1, MMP-9, and MMP-2, promoted endothelial cell migration; tubule structure formation; and endothelial expression of multiple angiogenic mediators, including growth factors, chemokines, and metalloproteinases. Moreover, we discovered that CGF-derived cells exhibited features such as endothelial progenitor cells, since they expressed the CD34 stem cell marker and endothelial markers and participated in the neo-angiogenic process. In conclusion, our results suggest that CGFs are able to promote endothelial angiogenesis through their soluble and cellular components and that CGFs can be used as a biomaterial for therapeutic vasculogenesis in the field of tissue regeneration.

Resumed ovarian function and pregnancy in early menopausal women by whole dimension subcortical ovarian administration of platelet-rich plasma and gonadotropins

OBJECTIVE

This study was designed to investigate if whole dimension subcortical ovarian administration of platelet-rich plasma with gonadotropin, in proximity to most ovarian follicles, is effective in restoring ovarian functions in women during early menopause.

METHODS

Platelet-rich plasma, prepared from 40 mL of autologous peripheral blood using the buffy coat method, was injected into extended subcortical area of bilateral ovaries along with recombinant follicle-stimulating hormone (rFSH) (Gonal-F 300IU) under laparoscopic guidance. The posttreatment ovarian folliculogenesis and serum levels of FSH, luteinizing hormone (LH), and estradiol were followed up for 6 months at weekly to monthly intervals. IVF was carried out in women resuming ovulatory functions.

RESULTS

Twelve early menopausal women with mean age of 44.42 ± 2.84 were enrolled. After treatment, 11 women resumed their menstrual period in 37.1 ± 23.5 days. Their average serum FSH was 70.47 ± 20.92 and 26.22 ± 17.55 IU/L, luteinizing hormone was 34.81 ± 11.86 and 14.3 ± 12.8 IU/L, before and after treatment, respectively. The mid-cycle E2 was 251.1 ± 143.8 pg/mL. Ten oocyte retrievals were carried out among six participants, four of them received controlled ovarian stimulation and another two using natural ovulation cycles. Thirteen mature eggs were retrieved which were then ICSI fertilized to obtain 10 normally fertilized 2PN oocytes. Two participants had cleavage stage embryos transferred of which one achieved clinical pregnancy.

CONCLUSIONS

Whole dimension subcortical ovarian administration of platelet-rich plasma with gonadotropin was shown to restore ovarian functions, at least temporarily, and could increase the probability of pregnancy using autologous oocytes in women with early menopause.

Will stem cells from fat and growth factors from blood bring new hope to female patients with reproductive disorders?

Female reproductive system disorders (FRSD) with or without infertility are prevalent women's health problems with a variety of treatment approaches including surgery and hormone therapy. It currently considering to sub-branch of regenerative medicine including stem cells or growth factors injection-based delivery treatment might be improved female reproductive health life. The most common products used for these patients treatment are autologous cell or platelet-based products from patients, including platelet-rich plasma, plasma rich in growth factor, platelet-rich fibrin, and stromal vascular fraction. In this review, we discuss each of the above products used in treatment of FRSD and critically evaluate the clinical outcome.

Cocktail Protocol for Preparation of Platelet-Rich Fibrin Glue for Autologous Use

Background

Biomaterials containing platelets have been used to promote healing of ulcers and burns, as well as in implantology and maxillofacial and plastic surgery to achieve wound healing and tissue repair. Commercial devices to prepare autologous biomaterials involve diverse preparation methods that can have high production costs and low yields. Hence, we designed a protocol for preparation of large amounts of autologous platelet-rich fibrin (PRF) glue using conventional processing techniques for blood components.

Methods

Autologous whole blood collected 72 h before surgery was processed to prepare platelet concentrates and cryoprecipitate. In a closed system, calcium was added to the cryoprecipitate to release autologous thrombin and generate a firm fibrin clot. The fibrin clot, platelets and calcium were then placed in a conical flask in which a PRF glue formed. The protocol was validated through determination of pre- and post-platelet counts and fibrinogen amounts in the product.

Results

Platelets were recovered with 68% efficiency during the preparation. Essentially no platelets or fibrinogen were found in the supernatant of the PRF glue, suggesting that nearly all had been incorporated in a PRF glue having a relatively large (8 cm × 10 cm) size.

Conclusion

The protocol described here is a cost-effective, simple and closed system that can be used to produce large-size PRF glue to promote repair of major surgical defects.

Application of Platelet Rich Fibrin in Tissue Engineering: Focus on Bone Regeneration

Bone tissue engineering (BTE) is a strategy for reconstructing bone lesions, which is rapidly developing in response to higher demands for bone repairing. Recently, this method, along with the emergence of functionally graded, biocompatible and biodegradable materials, has been expanded. Moreover, scaffolds with chemical, physical and external patterns have induced bone regeneration. However, the maintenance of healthy bone and its regeneration in the human body needs a series of complex and accurate processes. Hence, many studies have been accompanied for reconstructing bone by using blood-derived biomaterials, especially platelet-rich fabricates. The most important reason for using platelet-rich formulations in bone regeneration is based on releasing growth factors from alpha granules in platelets, which can induce osteogenesis. Moreover, the presence of fibrin nano-fiber structures as a constituent can provide a good substrate for cell attachments. This study attempts to review the history, structure, and biology of platelet-rich fibrin (PRF) as well as in vitro, pre-clinical, and clinical studies on the use of PRF for bone regeneration.

An Optimized Extract, Named Self-Growth Colony, from Platelet-Rich Plasma Shows Robust Skin Rejuvenation and Anti-Ageing Properties: A Novel Technology in Development of Cosmetics

INTRODUCTION

Inspired by application of platelet-rich plasma (PRP) in skin treatment during injuries, an extracting method was developed here to recover high amounts of cytokines and growth factors from PRP; this prepared extract was named as self-growth colony (SGC).

METHODS

In optimization of SGC preparation, various parameters were tested, for example, centrifugation force, freeze-thaw, sonication, and inclusion of calcium chelator. The amounts of cytokines and growth factors, including platelet factor 4, β-thromboglobulin, epidermal growth factor, vascular endothelial growth factor, platelet-derived growth factor, were measured by ELISA assay.

RESULTS

By comparing to PRP, the prepared SGC contained a significant higher amount of measured growth factors. In addition, the degradation of growth factors within SGC during the storage was calibrated, which showed better stability as compared to that of PRP preparation. Having possible application in skin care, the optimized SGC was chemically standardized by using the enrichment of growth factors. Application of SGC in cultured keratinocytes stimulated the wound healing of injured cultures. In line to this notion, SGC was applied onto human skin, and thereafter the robust improvement of skin properties was revealed.

CONCLUSIONS

The potential application of SGC in treating skin rejuvenation and ageing, as well as its elaborated application for medical purpose, that is, wound healing, was illustrated.

Platelet lysate: a promising candidate in regenerative medicine

Human platelet lysate has attracted much interest from many researchers as it is growth-factor rich for cell expansion, which is employed as a new therapeutic strategy. Not only are human platelet lysates used for cell therapy, but they are also used for the completion of basal media in mesenchymal stem cell cultures. Due to the presence of a large number of growth factors, platelet lysates have potential roles in wound healing, treatment of ocular graft-versus-host disease, osteoarthritis, Parkinson's disease, tendon regeneration, infertility, androgenetic alopecia, nerve repair and regenerative tissue, such as bone regeneration. In this review, we summarize that platelet lysates could be valuable candidates for the treatment of a variety of diseases in regenerative medicine.

Platelet lysates-based hydrogels incorporating bioactive mesoporous silica nanoparticles for stem cell osteogenic differentiation

Scaffolds for bone tissue regeneration should provide the right cues for stem cell adhesion and proliferation, but also lead to their osteogenic differentiation. Hydrogels of modified platelet lysates (PLMA) show the proper mechanical stability for cell encapsulation and contain essential bioactive molecules required for cell maintenance. We prepared a novel PLMA-based nanocomposite for bone repair and regeneration capable of releasing biofactors to induce osteogenic differentiation. Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) were encapsulated in PLMA hydrogels containing bioactive mesoporous silica nanoparticles previously loaded with dexamethasone and functionalized with calcium and phosphate ions. After 21 d of culture, hBM-MSCs remained viable, presented a stretched morphology, and showed signs of osteogenic differentiation, namely the presence of significant amounts of alkaline phosphatase, bone morphogenic protein-2 and osteopontin, hydroxyapatite, and calcium nodules. Developed for the first time, PLMA/MSNCaPDex nanocomposites were able to guide the differentiation of hBM-MSCs without any other osteogenic supplementation.

Biomaterials Regulating Bone Hematoma for Osteogenesis

Blood coagulation in tissue healing not only prevents blood loss, but also forms a natural scaffold for tissue repair and regeneration. As blood clot formation is the initial and foremost phase upon bone injury, and the quality of blood clot (hematoma) orchestrates the following inflammatory and cellular processes as well as the subsequent callus formation and bone remodeling process. Inspired by the natural healing hematoma, tissue-engineered biomimic scaffold/hydrogels and blood prefabrication strategies attract significant interests in developing functional bone substitutes. The alteration of the fracture hematoma ca significantly accelerate or impair the overall bone healing process. This review summarizes the impact of biomaterials on blood coagulation and provides evidence on fibrin network structure, growth factors, and biomolecules that contribute to bone healing within the hematoma. The aim is to provide insights into the development of novel implant and bone biomaterials for enhanced osteogenesis. Advances in the understanding of biomaterial characteristics (e.g., morphology, chemistry, wettability, and protein adsorption) and their effect on hematoma properties are highlighted. Emphasizing the importance of the initial healing phase of the hematoma endows the design of advanced biomaterials with the desired regulatory properties for optimal coagulation and hematoma properties, thereby facilitating enhanced osteogenesis and ideal therapeutic effects.

Human platelet lysates for human cell propagation

A pathogen-free and standardized xeno-free supplement of growth media is required for the ex vivo propagation of human cells used as advanced therapeutic medicinal products and for clinical translation in regenerative medicine and cell therapies. Human platelet lysate (HPL) made from therapeutic-grade platelet concentrate (PC) is increasingly regarded as being an efficient xeno-free alternative growth medium supplement to fetal bovine serum (FBS) for clinical-grade isolation and/or propagation of human cells. Most experimental studies establishing the superiority of HPL over FBS were conducted using mesenchymal stromal cells (MSCs) from bone marrow or adipose tissues. Data almost unanimously concur that MSCs expanded in a media supplemented with HPL have improved proliferation, shorter doubling times, and preserved clonogenicity, immunophenotype, in vitro trilineage differentiation capacity, and T-cell immunosuppressive activity. HPL can also be substituted for FBS when propagating MSCs from various other tissue sources, including Wharton jelly, the umbilical cord, amniotic fluid, dental pulp, periodontal ligaments, and apical papillae. Interestingly, HPL xeno-free supplementation is also proving successful for expanding human-differentiated cells, including chondrocytes, corneal endothelium and corneal epithelium cells, and tenocytes, for transplantation and tissue-engineering applications. In addition, the most recent developments suggest the possibility of successfully expanding immune cells such as macrophages, dendritic cells, and chimeric antigen receptor-T cells in HPL, further broadening its use as a growth medium supplement. Therefore, strong scientific rationale supports the use of HPL as a universal growth medium supplement for isolating and propagating therapeutic human cells for transplantation and tissue engineering. Efforts are underway to ensure optimal standardization and pathogen safety of HPL to secure its reliability for clinical-grade cell-therapy and regenerative medicine products and tissue engineering.

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.

Growth factors-based beneficial effects of platelet lysate on umbilical cord-derived stem cells and their synergistic use in osteoarthritis treatment

Poor viability of mesenchymal stem cells (MSCs) at the transplanted site often hinders the efficacy of MSCs-based therapy. Platelet lysate (PL) contains rich amounts of growth factors, which benefits cell growth. This study aimed to explore how human PL benefits umbilical cord-derived MSCs (huc-MSCs), and whether they have synergistic potential in osteoarthritis (OA) treatment. As quality control, flow cytometry and specific staining were performed to identify huc-MSCs, and ELISA was used to quantify growth factors in PL. CCK-8 and flow cytometry assays were performed to evaluate the effects of PL on the cell viability and cell cycle progression of huc-MSCs. Wound healing and transwell assays were conducted to assess the migration of huc-MSCs. RNA sequencing, real time PCR, and Western blot assays were conducted to explore the growth factors-based mechanism of PL. The in vitro results showed that PL significantly promoted the proliferation, cell cycle, and migration of huc-MSCs by upregulating relevant genes/proteins and activating beclin1-dependent autophagy via the AMPK/mTOR signaling pathway. The main growth factors (PDGF-AA, IGF-1, TGF-β, EGF, and FGF) contributed to the effects of PL in varying degrees. The in vivo data showed that combined PL and huc-MSCs exerted significant synergistic effect against OA. The overall study determined the beneficial effects and mechanism of PL on huc-MSCs and indicated PL as an adjuvant for huc-MSCs in treating OA. This is the first report on the growth factors-based mechanism of PL on huc-MSCs and their synergistic application. It provides novel knowledge of PLʹs roles and offers a promising strategy for stem cell-based OA therapy by combining PL and huc-MSCs.

Evaluation of Autologously Derived Biomaterials and Stem Cells for Bone Tissue Engineering

Despite progress, clinical translation of tissue engineering (TE) products/technologies is limited. A significant effort is underway to develop biomaterials and cells through a minimally modified process for clinical translation of TE products. Recently, bone marrow aspirate (BMA) was identified as an autologous source of cells for TE applications and is currently being tested in clinical therapies, but the isolation methods need improvement to avoid potential for contamination and increase progenitor cell yield. To address these issues, we reproducibly processed human peripheral blood (PB) and BMA to develop autologously derived biomaterials and cells. We demonstrated PB-derived biomaterial/gel cross-linking and fibrin gel formation with varied gelation times as well as biocompatibility through support of human bone marrow-derived stem cell survival and growth in vitro. Next, we established a plastic culture-free process that concentrates and increases the yield of CD146+/CD271+ early mesenchymal progenitor cells in BMA (concentrated BMA [cBMA]). cBMA exhibited increased colony formation and multipotency (including chondrogenic differentiation) in vitro compared with standard BMA. PB-derived gels encapsulated with cBMA also demonstrated increased cell proliferation and enhanced mineralization when assessed for bone TE in vitro. This strategy can potentially be developed for use in any tissue regeneration application; however, bone regeneration was used as a test bed for this study.

Washed Equine Platelet Extract as an Anti-Inflammatory Biologic Pharmaceutical

Mammalian platelets participate in the immediate tissue injury response by initiating coagulation and further promoting tissue injury mitigation and repair. The latter properties are deployed following platelet release of presynthetized morphogens, cytokines, and growth and chemotactic factors, which launch a tissue regenerative, angiogenic, and anti-inflammatory program. Several blood-derived biologic products, like platelet-rich plasma (PRP) and platelet lysate (PL), are currently on the market to allow proper healing and tissue regeneration. However, not all growth factors are released from the platelets and the final products contain plasma proteins such as albumin, fibrinogen, complement, and immunoglobulins, increasing the risks of serum sickness or allergic reaction. To address this problem, we developed a new platelet extract where equine blood platelets are concentrated, washed, and thereafter lysed by detergent Triton X-114. Distinct from PRP, this extract is devoid of albumin, fibrinogen, and immunoglobulins and is 266-fold enriched in platelet-derived growth factor content relative to PRP. Washed equine platelet extract (WEPLEX) is amenable to lyophilization without loss of biological activity. In vitro, WEPLEX significantly inhibits human and equine T cell proliferative response to phytohemagglutinin and also polarizes murine CD45⁺/CD11b⁺ peritoneal macrophages to an IL-10⁺ M2-like phenotype. In vivo, WEPLEX substantially improves clinical outcome of murine experimental dextran sulfate sodium colitis. We propose that equine-sourced, zoonosis-free WEPLEX may serve as an anti-inflammatory biological therapy across mammalian species.

Cell-derived biomimetic nanoparticles as a novel drug delivery system for atherosclerosis: predecessors and perspectives

Atherosclerosis is a key mechanism underlying the pathogenesis of cardiovascular disease, which is associated with high morbidity and mortality. In the field of precision medicine for the treatment of atherosclerosis, nanoparticle (NP)-mediated drug delivery systems have great potential, owing to their ability to release treatment locally. Cell-derived biomimetic NPs have attracted extensive attention at present due to their excellent targeting to atherosclerotic inflammatory sites, low immunogenicity and long blood circulation time. Here, we review the utility of cell-derived biomimetic NPs, including whole cells, cell membranes and extracellular vesicles, in the treatment of atherosclerosis.

Platelet-rich plasma counteracts detrimental effect of high-glucose concentrations on mesenchymal stem cells from Bichat fat pad

Diabetic patients display increased risk of periodontitis and failure in bone augmentation procedures. Mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) represent a relevant advantage in tissue repair process and regenerative medicine. We isolated MSCs from Bichat's buccal fat pad (BFP) and measured the effects of glucose and PRP on cell number and osteogenic differentiation potential. Cells were cultured in the presence of 5.5-mM glucose (low glucose [LG]) or 25-mM glucose (high glucose [HG]). BFP-MSC number was significantly lower when cells were cultured in HG compared with those in LG. Following osteogenic differentiation procedures, calcium accumulation, alkaline phosphatase activity, and expression of osteogenic markers were significantly lower in HG compared with LG. Exposure of BFP-MSC to PRP significantly increased cell number and osteogenic differentiation potential, reaching comparable levels in LG and in HG. Thus, high-glucose concentrations impair BFP-MSC growth and osteogenic differentiation. However, these detrimental effects are largely counteracted by PRP.

Clinical-grade cryopreserved doxorubicin-loaded platelets: role of cancer cells and platelet extracellular vesicles activation loop

BACKGROUND

Human platelets (PLT) and PLT-extracellular vesicles (PEV) released upon thrombin activation express receptors that interact with tumour cells and, thus, can serve as a delivery platform of anti-cancer agents. Drug-loaded nanoparticles coated with PLT membranes were demonstrated to have improved targeting efficiency to tumours, but remain impractical for clinical translation. PLT and PEV targeted drug delivery vehicles should facilitate clinical developments if clinical-grade procedures can be developed.

METHODS

PLT from therapeutic-grade PLT concentrate (PC; N > 50) were loaded with doxorubicin (DOX) and stored at - 80 °C (DOX-loaded PLT) with 6% dimethyl sulfoxide (cryopreserved DOX-loaded PLT). Surface markers and function of cryopreserved DOX-loaded PLT was confirmed by Western blot and thromboelastography, respectively. The morphology of fresh and cryopreserved naïve and DOX-loaded PLT was observed by scanning electron microscopy. The content of tissue factor-expressing cancer-derived extracellular vesicles (TF-EV) present in conditioned medium (CM) of breast cancer cells cultures was measured. The drug release by fresh and cryopreserved DOX-loaded PLT triggered by various pH and CM was determined by high performance liquid chromatography. The thrombin activated PEV was analyzed by nanoparticle tracking analysis. The cellular uptake of DOX from PLT was observed by deconvolution microscopy. The cytotoxicities of DOX-loaded PLT, cryopreserved DOX-loaded PLT, DOX and liposomal DOX on breast, lung and colon cancer cells were analyzed by CCK-8 assay.

RESULTS

15~36 × 106 molecules of DOX could be loaded in each PLT within 3 to 9 days after collection. The characterization and bioreactivity of cryopreserved DOX-loaded PLT were preserved, as evidenced by (a) microscopic observations, (b) preservation of important PLT membrane markers CD41, CD61, protease activated receptor-1, (c) functional activity, (d) reactivity to TF-EV, and (e) efficient generation of PEV upon thrombin activation. The transfer of DOX from cryopreserved PLT to cancer cells was achieved within 90 min, and stimulated by TF-EV and low pH. The cryopreserved DOX-loaded PLT formulation was 7~23-times more toxic to three cancer cells than liposomal DOX.

CONCLUSIONS

Cryopreserved DOX-loaded PLT can be prepared under clinically compliant conditions preserving the membrane functionality for anti-cancer therapy. These findings open perspectives for translational applications of PLT-based drug delivery systems.

Hard-to-heal wounds, biofilm and wound healing: an intricate interrelationship

Hard-to-heal wounds are a major public health problem that incur high economic costs. A major source of morbidity, they can have an overwhelming impact on patients, caregivers and society. In contrast to acute wound healing, which follows an 'orderly and timely reparative process', the healing of hard-to-heal wounds is delayed because the usual biological progression is interrupted. This article discusses hard-to-heal wounds, the impact they have on patients and healthcare systems, and how biofilms and other factors affect the wound-healing process. Controlling and preventing infection is of utmost importance for normal wound healing. Rational use of anti-infectious agents is crucial and is particularly relevant in the context of rising healthcare costs. Knowledge of the complex relationship between hard-to-heal wounds, biofilm formation and wound healing is vital for efficient management of hard-to-heal wounds.

Heat-treated human platelet pellet lysate modulates microglia activation, favors wound healing and promotes neuronal differentiation in vitro

The neurorestorative efficacy of human platelet lysates in neurodegenerative disorders is still under investigation. Platelets prepared from standard and pathogen reduced platelet concentrates were pelletized, washed, concentrated, and subjected to freeze-thawing. The lysate was heated to 56°C for 30 min and characterized. Toxicity was evaluated using SH-SY5Y neuroblastoma, BV-2 microglial, and EA-hy926 endothelial cells. Inflammatory activity was tested by examining tumor necrosis factor (TNF) and cyclooxygenase (COX)-2 expressions by BV-2 microglia with or without stimulation by lipopolysaccharides (LPS). The capacity to stimulate wound healing was evaluated by a scratch assay, and the capacity to differentiate SH-SY5Y into neurons was also examined. Platelet lysates contained a range of neurotrophins. They were not toxic to SH-SY5Y, EA-hy926, or BV-2 cells, did not induce the expression of TNF or COX-2 inflammatory markers by BV-2 microglia, and decreased inflammation after LPS stimulation. They stimulated the wound closure in the scratch assay and induced SH-SY5Y differentiation as revealed by the increased length of neurites as well as β3-tubulin and neurofilament staining. These data confirm the therapeutic potential of platelet lysates in the treatment of disorders of the central nervous system and support further evaluation as novel neurorestorative biotherapy in preclinical models.

Endothelial response boosted by platelet lysate: the involvement of calcium toolkit

Wound repair is a dynamic process during which crucial signaling pathways are regulated by growth factors and cytokines released by several kinds of cells directly involved in the healing process. However, the limited applications and heterogeneous clinical results of single growth factors in wound healing encouraged the use of a mixture of bioactive molecules such as platelet derivatives for best results in wound repair. An interesting platelet derivative, obtained from blood samples, is platelet lysate (PL), which has shown potential clinical application. PL is obtained from freezing and thawing of platelet-enriched blood samples. Intracellular calcium (Ca²⁺) signals play a central role in the control of endothelial cell survival, proliferation, motility, and differentiation. We investigated the role of Ca²⁺ signaling in the PL-driven endothelial healing process. In our experiments, the functional significance of Ca²⁺ signaling machinery was highlighted performing the scratch wound assay in presence of different inhibitors or specific RNAi. We also pointed out that the PL-induced generation of intracellular ROS (reactive oxygen species) via NOX4 (NADPH oxidase 4) is necessary for the activation of TRPM2 and the resulting Ca²⁺ entry from the extracellular space. This is the first report of the mechanism of wound repair in an endothelial cell model boosted by the PL-induced regulation of [Ca²⁺]_i.

Non-pooled Human Platelet Lysate: A Potential Serum Alternative for In Vitro Cell Culture

Serum supplementation is crucial in in vitro cell culture to provide all the essential nutrients needed for cellular processes. Fetal bovine serum (FBS) is considered the 'gold standard', but its production raises serious ethical concerns. Human-derived alternatives to FBS exist in the form of human platelet lysates (hPLs) or human AB serum (ABS). However, these serum products are usually pooled from several donors, in order to have a standardised product without patient-specific deviations. Nevertheless, the use of patient-specific serum in cell culture might be the key to successful transplantation of the cultured cells in medical applications, particularly as it avoids the transmission of infectious components or xenogenic proteins. In addition, the production of non-pooled hPL from single donors is likely to be a cost-effective and time-saving method. The current study used hPL units isolated from single donors and tested their performance as medium supplements for cell culture in comparison with FBS or ABS. This proof-of-concept study aimed to assess the potential of non-pooled hPL for personalised serum supplementation, and thus optimise in vitro models by making them more relevant to human physiology. We showed that A549, HepG2 and Caco-2 human cell lines were generally able to adapt to the new culture conditions and maintain viability, morphology and certain cell-specific characteristics. These results indicate that non-pooled, single patient-derived hPL could be a suitable alternative for in vitro serum supplementation.

The effect of human platelet lysate on the differentiation ability of human adipose-derived stem cells cultured on ECM-coated surfaces

Human mesenchymal stem cells (hMSCs), such as human adipose-derived stem cells (hADSCs), present heterogeneous characteristics, including varying differentiation abilities and genotypes. hADSCs isolated under different conditions exhibit differences in stemness. We isolated hADSCs from human fat tissues via culture on different cell culture biomaterials including tissue culture polystyrene (TCPS) dishes and extracellular matrix protein (ECM)-coated dishes in medium supplemented with 5% or 10% serum-converted human platelet lysate (hPL) or 10% fetal bovine serum (FBS) as a control. Currently, it is not clear whether xeno-free hPL in the cell culture medium promotes the ability of hMSCs such as hADSCs to differentiate into several cell lineages compared to the xenomaterial FBS. We investigated whether a synchronized effect of ECM (Matrigel, fibronectin, and recombinant vitronectin) coatings on TCPS dishes for efficient hADSC differentiation could be observed when hADSCs were cultured in hPL medium. We found that Matrigel-coated dishes promoted hADSC differentiation into osteoblasts and suppressed differentiation into chondrocytes in 10% hPL medium. Recombinant vitronectin- and fibronectin-coated dishes greatly promoted hADSC differentiation into osteoblasts and chondrocytes in 5% and 10% hPL media. hPL promoted hADSC differentiation into osteoblasts and chondrocytes compared to FBS on the fibronectin-coated surface and recombinant vitronectin-coated surface.

Past and Future of Neurotrophic Growth Factors Therapies in ALS: From Single Neurotrophic Growth Factor to Stem Cells and Human Platelet Lysates

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that typically results in death within 3–5 years after diagnosis. To date, there is no curative treatment and therefore an urgent unmet need of neuroprotective and/or neurorestorative treatments. Due to their spectrum of capacities in the central nervous system—e.g., development, plasticity, maintenance, neurogenesis—neurotrophic growth factors (NTF) have been exploited for therapeutic strategies in ALS for decades. In this review we present the initial strategy of using single NTF by different routes of administration to the use of stem cells transplantation to express a multiple NTFs-rich secretome to finally focus on a new biotherapy based on the human platelet lysates, the natural healing system containing a mix of pleitropic NTF and having immunomodulatory function. This review highlights that this latter treatment may be crucial to power the neuroprotection and/or neurorestoration therapy requested in this devastating disease.

Plasma-based fast-gelling biohybrid gels for biomedical applications

Blood based biomaterials are widely researched and used in different biomedical applications including cell therapy, drug delivery, sealants etc. due to their biocompatibility and biodegradability. Blood derived gels are successfully used in clinical studies due to the presence of fibrinogen and several platelet growth factors. In spite of their wide applications, it is challenging to use blood-based biomaterials due to their low mechanical stability, poor adhesive property and contamination risk. In this study, we used porcine plasma to form gel in presence of biodegradable synthetic crosslinkers. Mechanical strength of this plasma gel could be tailored by altering the amount of crosslinkers for any desired biomedical applications. These plasma gels, formed by the synthetic crosslinkers, were utilized as a drug delivery platform for wound healing due to their low cytotoxicity. A model drug release study with these plasma gels indicated slow and sustained release of the drugs.

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

Hemoderivative materials are used to treat different diseases. These derivatives include platelet-rich plasma, serum, platelet gel, and platelet lysate (PL). Among them, PL contains more growth factors than the others and its production is inexpensive and easy. PL is one of the proper sources of platelet release factors. It is used in cells growth and proliferation and is a good alternative to fetal bovine serum. In recent years, the clinical use of PL has gained more appeal by scientists. PL is a solution saturated by growth factors, proteins, cytokines, and chemokines and is administered to treat different diseases such as wound healing, bone regeneration, alopecia, oral mucositis, radicular pain, osteoarthritis, and ocular diseases. In addition, it can be used in cell culture for cell therapy and tissue transplantation purposes. Platelet-derived growth factor, fibroblast growth factor, insulin-like growth factor, transforming growth factor β, and vascular endothelial growth factor are key PL growth factors playing a major role in cell proliferation, wound healing, and angiogenesis. In this paper, we scrutinized recent advances in using PL and PL-derived growth factors to treat diseases and in regenerative medicine, and the ability to replace PL with other hemoderivative materials.

Platelet rich plasma hydrogels promote in vitro and in vivo angiogenic potential of adipose-derived stem cells

Despite great advances in skin wound care utilizing grafting techniques, the resulting severe scarring, deformity and ineffective vascularization remains a challenge. Alternatively, tissue engineering of new skin using patient-derived stem cells and scaffolding materials promises to greatly increase the functional and aesthetic outcome of skin wound healing. This work focused on the optimization of a polyethylene glycol modified (PEGylated) platelet-rich plasma (PRP) hydrogel for the protracted release of cytokines, growth factors, and signaling molecules and also the delivery of a provisional physical framework for stem cell angiogenesis. Freshly collected whole blood was utilized to synthesize PEGylated PRP hydrogels containing platelet concentrations ranging from 0 to 200,000 platelets/µl. Hydrogels were characterized using thromboelastography and impedance aggregometry for platelet function and were visualized using scanning electron microscopy. To assess the effects of PEGylated PRP hydrogels on cells, PRP solutions were seeded with human adipose-derived stem cells (ASCs) prior to gelation. Following 14 days of incubation in vitro, increased platelet concentrations resulted in higher ASC proliferation and vascular gene and protein expression (assessed via RT-PCR, ELISA, and immunochemistry). Using a rat skin excision model, wounds treated with PRP + ASC hydrogels increased the number of vessels in the wound by day 8 (80.2 vs. 62.6 vessels/mm²) compared to controls. In conclusion, the proposed PEGylated PRP hydrogel promoted both in vitro and transient in vivo angiogenesis of ASCs for improved wound healing. STATEMENT OF SIGNIFICANCE: Our findings support an innovative means of cellular therapy intervention to improve surgical wound healing in a normal wound model. ASCs seeded within PEGylated PRP could be an efficacious and completely autologous therapy for treating patients who have poorly healing wounds caused by vascular insufficiency, previous irradiation, or full-thickness burns. Because wound healing is a dynamic and complex process, the application of more than one growth factor with ASCs demonstrates an advantageous way of improving healing.

Platelet Rich Plasma Enhancement of Skin Regeneration in an ex-vivo Human Experimental Model

This study reports on the development of an original, ex-vivo wounded skin culture protocol using autologous Platelet Rich Plasma (PRP) and enriched Dulbecco's Modified Eagle's Medium (DMEM). Human skin samples obtained from specimens harvested during reduction mammoplasty procedures, were injured in their central portion—to create a standard wound—and cultured under three different conditions:

– enriched DMEM with saline solution in the central wound (control)

– enriched DMEM with the same medium in the central wound

– enriched DMEM plus 2.5% autologous PRP, with the same PRP added medium in the central wound.

Morphological analysis was carried out at 0 h (T₀) and on days 1, 3, 5 and 10 (T₁-T₃-T₅-T₁₀) using Hematoxylin and Eosin; Masson's trichrome staining; Weigert staining and Ki-67 staining to identify the skin histological features in the different experimental conditions. The combination of DMEM and PRP allowed a favorable modulation of the epithelial cells and fibroblasts proliferation, and a relevant anti-inflammatory action. PRP also demonstrated an inhibitory effect on both the collagen and elastic fibers' de-structuration and a favorable modulation of the re-organization of these fibers. The step by step histological and immune-histo-chemical regenerative effects of PRP on human skin wound repair and regeneration process was observed over a period of 10 days.

Photopolymerizable Platelet Lysate Hydrogels for Customizable 3D Cell Culture Platforms

3D cell culture platforms have emerged as a setting that resembles in vivo environments replacing the traditional 2D platforms. Over the recent years, an extensive effort has been made on the development of more physiologically relevant 3D cell culture platforms. Extracellular matrix-based materials have been reported as a bioactive and biocompatible support for cell culture. For example, human plasma derivatives have been extensively used in cell culture. Despite all the promising results, in most cases these types of materials have poor mechanical properties and poor stability in vitro. Here plasma-based hydrogels with increased stability are proposed. Platelet lysates are modified by addition of methacryloyl groups (PLMA) that polymerize in controlled geometries upon UV light exposure. The hydrogels could also generate porous scaffolds after lyophilization. The results show that PLMA materials have increased mechanical properties that can be easily adjusted by changing PLMA concentration or modification degree. Cells readily adhere, proliferate, and migrate, exhibiting high viability when encapsulated in PLMA hydrogels. The innovation potential of PLMA materials is based on the fact that it is a complete xeno-free solution for human cell culture, thus an effective alternative to the current gold standards for 3D cell culture based on animal products.

Blood Plasma Derivatives for Tissue Engineering and Regenerative Medicine Therapies

Platelet-rich plasma (PRP) and its derivatives have been investigated and applied in regenerative medicine. The use of PRP as a supplement of cell culture media has consistently shown to potentiate stem cell proliferation, migration, and differentiation. In addition, the clinical utility of PRP is supported by evidence that PRP contains high concentrations of growth factors (GFs) and proteins which contribute to the regenerative process. PRP based therapies are cost effective and also benefit from the accessibility and safety of using the patient's own GFs. In the last years, a great development has been witnessed on PRP based biomaterials, with both structural and functional purposes. In this study we overview the most relevant PRP applications encompassing PRP based materials for tissue engineering and regenerative medicine. This review also summarizes the challenges in the fields of tissue engineering and regenerative medicine and provides a perspective on future directions.

Therapeutic implication of platelets in liver regeneration -hopes and hues

Mounting evidence highlights platelet involvement in liver regeneration via interaction with liver cells, growth factors release, and signaling contributions. Existing research suggests a compelling biological rationale for utilizing platelet biology, with the goal of improving liver function and accelerating its regenerative potential. Despite its expanding application in several clinical areas, the contribution of the platelet and its therapeutic implementation in liver regeneration so far has not yet fulfilled the initial high expectations. Areas covered: This review scrutinizes the progress, current updates, and discusses how recent understanding - particularly in the clinical implications of platelet-based therapy - may enable strategies to introduce and harness the therapeutic potential of the platelet during liver regeneration. Expert commentary: Several clinical and translational studies have facilitated a platform for the development of platelet-based therapy to enhance liver regeneration. While some of these therapies are effective to augment liver regeneration, the others have had some detrimental outcomes. The existing evidence represents a challenge for future projects that are focused on directly incorporating platelet-based therapies to induce liver regeneration.

Autologous fibrin scaffolds: When platelet- and plasma-derived biomolecules meet fibrin

The healing of vascularized mammalian tissue injuries initiate with hemostasis and clotting as part of biological defense system leading to the formation of a fibrin clot in which activated platelets are trapped to quickly stop bleeding and destroy microbials. In order to harness the therapeutic potential of biomolecules secreted by platelets and stemmed from plasma, blood deconstruction has allowed to yield autologous platelet-and plasma-derived protein fibrin scaffold. The autologous growth factors and microparticles stemmed from platelets and plasma, interact with fibrin, extracellular matrix, and tissue cells in a combinatorial, synergistic, and multidirectional way on mechanisms governing tissue repair. This interplay will induce a wide range of cell specifications during inflammation and repair process including but not limited to fibrogenesis, angiogenesis, and immunomodulation. As biology-as-a-drug approach, autologous platelet-and plasma-derived protein fibrin scaffold is emerging as a safe and efficacious natural human-engineered growth factor delivery system to repair musculoskeletal tissues, and skin and corneal ulcers and burns. In doing so, it acts as therapeutic agent not perfect but close to biological precision. However, this autologous, biocompatible, biodegradable, and long in vivo lasting strategy faces several challenges, including its non-conventional single dose-response effect, the lack of standardization in its preparation and application, and the patient's biological features. In this review, we give an account of the main events of tissue repair. Then, we describe the procedure to prepare autologous platelet-and plasma-derived protein fibrin scaffolds, and the rationale behind these biomaterials, and finally, we highlight the significance of strategic accuracy in their application.

Human-based fibrillar nanocomposite hydrogels as bioinstructive matrices to tune stem cell behavior

The extracellular matrix (ECM)-biomimetic fibrillar structure of platelet lysate (PL) gels along with their enriched milieu of biomolecules has drawn significant interest in regenerative medicine applications. However, PL-based gels have poor structural stability, which severely limits their performance as a bioinstructive biomaterial. Here, rod-shaped cellulose nanocrystals (CNC) are used as a novel approach to modulate the physical and biochemical microenvironment of PL gels enabling their effective use as injectable human-based cell scaffolds with a level of biomimicry that is difficult to recreate with synthetic biomaterials. The incorporation of CNC (0 to 0.61 wt%) into the PL fibrillar network during the coagulation cascade leads to decreased fiber branching, increased interfiber porosity (from 66 to 83%) and modulates fiber (from 1.4 ± 0.7 to 27 ± 12 kPa) and bulk hydrogel (from 18 ± 4 to 1256 ± 82 Pa) mechanical properties. As a result of these physicochemical alterations, nanocomposite PL hydrogels resist the typical extensive clot retraction (from 76 ± 1 to 24 ± 3 at day 7) and show favored retention of PL bioactive molecules. The feedback of these cues on the fate of human adipose-derived stem cells is evaluated, showing how it can be explored to modulate the commitment of encapsulated stem cells toward different genetic phenotypes without the need for additional external biological stimuli. These fibrillar nanocomposite hydrogels allow therefore the exploration of the outstanding biological properties of human-based PL as an efficient engineered ECM which can be tailored to trigger specific regenerative pathways in minimal invasive strategies.

Abundant proteins in platelet-rich fibrin and their potential contribution to wound healing: An explorative proteomics study and review of the literature

Background/purpose

It is well-known that diverse types of blood proteins contribute to healing process via different mechanisms. Presence and potential involvements of blood-derived abundant proteins in the platelet-rich fibrin (PRF) to its regenerative capacity have not been sufficiently emphasized in the literature. The aim of this paper was to analyze the abundant proteome content of PRF and summarize previously reported effects of identified proteins on wound healing via a literature review.

Materials and methods

The PRF samples obtained from non-smoking, systemically healthy volunteers were subjected to 2D gel electrophoresis after extracting the proteins from fibrin matrices. All matching spots were excised from the gels and identified by MALDI TOF/TOF MS/MS analysis. A literature review was conducted to reveal possible contributions of identified proteins to wound healing.

Results

Totally, thirty-five blood proteins were commonly identified among all studied samples. These proteins included serine protease inhibitors, such as alpha-1-antitrypsin, alpha-1-antichymotrypsin, alpha-1-acid glycoprotein, inter-alpha-trypsin-inhibitor, protease C1 inhibitor, and complement proteins. In addition, abundant presence of immunoglobulin G was observed. The abundance of albumin, haptoglobin, ceruloplasmin vitronectin, fetuin-A, ficolin-3 and transthyretin was also detected.

Conclusion

The results of this study indicated that PRF abundantly contains blood-origin actors which were previously reported for their direct contribution to wound healing. Further studies exploring the protein content of PRF are needed to reveal its undisclosed potential roles in the healing process.

Hyperacute serum has markedly better regenerative efficacy than platelet-rich plasma in a human bone oxygen-glucose deprivation model

AIM

Platelet-rich plasma (PRP) and hyperacute serum (HAS) were compared in a novel human model of ex vivo bone damage induced by oxygen-glucose deprivation (OGD).

MATERIALS & METHODS

Osteoarthritic subchondral bone pieces were harvested from discarded femoral heads during hip replacement surgery and subjected to transient OGD.

RESULTS

Proteome profiling revealed that PRP is more angiopoietic, whereas HAS is more antiangiopoietic in composition. However, treatment of OGD-exposed bone with multiple PRP preparations had no effect on cell counts, whereas HAS restored cell proliferation capacity and rescued viable cell number following OGD.

CONCLUSION

A similar pro-proliferation effect was observed with recombinant growth factors, indicating that HAS may be an alternative agent for enhancing the regeneration of damaged bone cells.