Pathogen reduction through additive-free short-wave UV light irradiation retains the optimal efficacy of human platelet lysate for the expansion of human bone marrow mesenchymal stem cells

Towards standardized human platelet lysate production in Europe: An initiative of the European Blood Alliance

Human platelet lysate (hPL) is a supplement for cell culture media that can be derived from platelet concentrates. As not-for-profit blood establishments, we endorse the evolution of maximally exploiting the potential of donated blood and its derived components, including platelets. The decision to use platelet concentrates to supply hPL as a cell culture supplement should align with the principles and values that blood establishments hold towards the use of donated blood components in transfusion. As a consequence, questions on ethics, practical standardization of hPL production and logistics as well as on assuring hPL quality and safety need careful consideration. We therefore propose an opinion on some of these matters based on available literature and on discussions within the proceedings of the Working Group on Innovation and New Products of the European Blood Alliance. In addition, we propose collaboration among European blood establishments to streamline efforts of hPL supply to maximize the potential of hPL and its application in the wider field of medicine.

Expanding applications of allogeneic platelets, platelet lysates, and platelet extracellular vesicles in cell therapy, regenerative medicine, and targeted drug delivery

Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell-cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

Inactivation of human plasma alters the structure and biomechanical properties of engineered tissues

Fibrin is widely used for tissue engineering applications. The use of blood derivatives, however, carries a high risk of transmission of infectious agents, necessitating the application of pathogen reduction technology (PRT). The impact of this process on the structural and biomechanical properties of the final products is unknown. We used normal plasma (PLc) and plasma inactivated by riboflavin and ultraviolet light exposure (PLi) to manufacture nanostructured cellularized fibrin-agarose hydrogels (NFAHs), and then compared their structural and biomechanical properties. We also measured functional protein C, prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and coagulation factors [fibrinogen, Factor (F) V, FVIII, FX, FXI, FXIII] in plasma samples before and after inactivation. The use of PLi to manufacture cellularized NFAHs increased the interfibrillar spacing and modified their biomechanical properties as compared with cellularized NFAH manufactured with PLc. PLi was also associated with a significant reduction in functional protein C, FV, FX, and FXI, and an increase in the international normalized ratio (derived from the PT), APTT, and TT. Our findings demonstrate that the use of PRT for fibrin-agarose bioartificial tissue manufacturing does not adequately preserve the structural and biomechanical properties of the product. Further investigations into PRT-induced changes are warranted to determine the applications of NFAH manufactured with inactivated plasma as a medicinal product.

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Inactivation of human plasma alters the structure and biomechanical properties of engineered tissues

Fibrin is widely used for tissue engineering applications. The use of blood derivatives, however, carries a high risk of transmission of infectious agents, necessitating the application of pathogen reduction technology (PRT). The impact of this process on the structural and biomechanical properties of the final products is unknown. We used normal plasma (PLc) and plasma inactivated by riboflavin and ultraviolet light exposure (PLi) to manufacture nanostructured cellularized fibrin-agarose hydrogels (NFAHs), and then compared their structural and biomechanical properties. We also measured functional protein C, prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and coagulation factors [fibrinogen, Factor (F) V, FVIII, FX, FXI, FXIII] in plasma samples before and after inactivation. The use of PLi to manufacture cellularized NFAHs increased the interfibrillar spacing and modified their biomechanical properties as compared with cellularized NFAH manufactured with PLc. PLi was also associated with a significant reduction in functional protein C, FV, FX, and FXI, and an increase in the international normalized ratio (derived from the PT), APTT, and TT. Our findings demonstrate that the use of PRT for fibrin-agarose bioartificial tissue manufacturing does not adequately preserve the structural and biomechanical properties of the product. Further investigations into PRT-induced changes are warranted to determine the applications of NFAH manufactured with inactivated plasma as a medicinal product.

Umbilical cord mesenchymal stem/stromal cells potential to treat organ disorders; an emerging strategy

Currently, mesenchymal stem/stromal cells (MSCs) have attracted growing attention in the context of cell-based therapy in regenerative medicine. Following the first successful procurement of human MSCs from bone marrow (BM), these cells isolation has been conducted from various origins, in particular, the umbilical cord (UC). Umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs) can be acquired by a non-invasive plan and simply cultured, and thereby signifies their superiority over MSCs derived from other sources for medical purposes. Due to their unique attributes, including self-renewal, multipotency, and accessibility concomitant with their immunosuppressive competence and lower ethical concerns, UC-MSCs therapy is described as encouraging therapeutic options in cell-based therapies. Regardless of their unique aptitude to adjust inflammatory response during tissue recovery and delivering solid milieu for tissue restoration, UC-MSCs can be differentiated into a diverse spectrum of adult cells (e.g., osteoblast, chondrocyte, type II alveolar, hepatocyte, and cardiomyocyte). Interestingly, they demonstrate a prolonged survival and longer telomeres compared with MSCs derived from other sources, suggesting that UC-MSCs are desired source to use in regenerative medicine. In the present review, we deliver a brief review of UC-MSCs isolation, expansion concomitantly with immunosuppressive activities, and try to collect and discuss recent pre-clinical and clinical researches based on the use of UC-MSCs in regenerative medicine, focusing on with special focus on in vivo researches.

Human Platelet Lysate for Good Manufacturing Practice-Compliant Cell Production

Numerous cell-based therapeutics are currently being tested in clinical trials. Human platelet lysate (HPL) is a valuable alternative to fetal bovine serum as a cell culture medium supplement for a variety of different cell types. HPL as a raw material permits animal serum-free cell propagation with highly efficient stimulation of cell proliferation, enabling humanized manufacturing of cell therapeutics within a reasonable timeframe. Providers of HPL have to consider dedicated quality issues regarding identity, purity, potency, traceability and safety. Release criteria have to be defined, characterizing the suitability of HPL batches for the support of a specific cell culture. Fresh or expired platelet concentrates from healthy blood donors are the starting material for HPL preparation, according to regulatory requirements. Pooling of individual platelet lysate units into one HPL batch can balance donor variation with regard to essential platelet-derived growth factors and cytokines. The increasingly applied pathogen reduction technologies will further increase HPL safety. In this review article, aspects and regulatory requirements of whole blood donation and details of human platelet lysate manufacturing are presented. International guidelines for raw materials are discussed, and defined quality controls, as well as release criteria for safe and GMP-compliant HPL production, are summarized.

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.

Human platelet lysate to substitute fetal bovine serum in hMSC expansion for translational applications: a systematic review

BACKGROUND

Foetal bovine serum (FBS), is the most commonly used culture medium additive for in vitro cultures, despite its undefined composition, its potential immunogenicity and possible prion/zoonotic transmission. For these reasons, significant efforts have been targeted at finding a substitute, such as serum free-media or human platelet-lysates (hPL). Our aim is to critically appraise the state-of-art for hPL in the published literature, comparing its impact with FBS.

MATERIALS AND METHODS

In June 2019 a systematic search of the entire Web of Science, Medline and PubMed database was performed with the following search terms: (mesenchymal stem cells) AND (fetal bovine serum OR fetal bovine calf) AND (human platelet lysate). Excluded from this search were review articles that were published before 2005, manuscripts in which mesenchymal stem cells (MSCs) were not from human sources, and when the FBS controls were missing.

RESULTS

Based on our search algorithm, 56 papers were selected. A review of these papers indicated that hMSCs cultured with hPL showed a spindle-shaped elongated morphology, had higher proliferation indexes, similar cluster of differentiation (CD) markers and no significant variation in differentiation lineage (osteocyte, adipocyte, and chondrocyte) compared to those cultured with FBS. Main sources of primary hMSCs were either fat tissue or bone marrow; in a few studies cells isolated from alternative sources showed no relevant difference in their response.

CONCLUSION

Despite the difference in medium choice and a lack of standardization of hPL manufacturing, the majority of publications support that hPL was at least as effective as FBS in promoting adhesion, survival and proliferation of hMSCs. We conclude that hPL should be considered a viable alternative to FBS in hMSCs culture-especially with a view for their clinical use.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Nanofiltration of growth media supplemented with human platelet lysates for pathogen-safe xeno-free expansion of mesenchymal stromal cells

Background aims

Human platelet lysate can replace fetal bovine serum (FBS) for xeno-free ex vivo expansion of mesenchymal stromal cells (MSCs), but pooling of platelet concentrates (PCs) increases risks of pathogen transmission. We evaluated the feasibility of performing nanofiltration of platelet lysates and determined the impact on expansion of bone marrow–derived MSCs.

Methods

Platelet lysates were prepared by freeze-thawing of pathogen-reduced (Intercept) PCs suspended in 65% storage solution (SPP+) and 35% plasma, and by serum-conversion of PCs suspended in 100% plasma. Lysates were added to the MSC growth media at 10% (v/v), filtered and subjected to cascade nanofiltration on 35- and 19-nm Planova filters. Media supplemented with 10% starting platelet lysates or FBS were used as the controls. Impacts of nanofiltration on the growth media composition, removal of platelet extracellular vesicles (PEVs) and MSC expansion were evaluated.

Results

Nanofiltration did not detrimentally affect contents of total protein and growth factors or the biochemical composition. The clearance factor of PEVs was >3 log values. Expansion, proliferation, membrane markers, differentiation potential and immunosuppressive properties of cells in nanofiltered media were consistently better than those expanded in FBS-supplemented media. Compared with FBS, chondrogenesis and osteogenesis genes were expressed more in nanofiltered media, and there were fewer senescent cells over six passages.

Conclusions

Nanofiltration of growth media supplemented with two types of platelet lysates, including one prepared from pathogen-reduced PCs, is technically feasible. These data support the possibility of developing pathogen-reduced xeno-free growth media for clinical-grade propagation of human cells.

Effects of amotosalen treatment on human platelet lysate bioactivity: A proof-of-concept study

BACKGROUND

Clinical application of mesenchymal stromal cells (MSCs) usually requires an in vitro expansion step to reach clinically relevant numbers. In vitro cell expansion necessitates supplementation of basal mammalian cell culture medium with growth factors. To avoid using supplements containing animal substances, human platelet lysates (hPL) produced from expired and pathogen inactivated platelet concentrates can be used in place of fetal bovine serum. However, globally, most transfusion units are currently not pathogen inactivated. As blood banks are the sole source of platelet concentrates for hPL production, it is important to ensure product safety and standardized production methods. In this proof-of-concept study we assessed the feasibility of producing hPL from expired platelet concentrates with pathogen inactivation applied after platelet lysis by evaluating the retention of growth factors, cytokines, and the ability to support MSC proliferation and tri-lineage differentiation.

METHODOLOGY/PRINCIPAL FINDINGS

Bone marrow-derived MSCs (BM-MSCs) were expanded and differentiated using hPL derived from pathogen inactivated platelet lysates (hPL-PIPL), with pathogen inactivation by amotosalen/ultraviolet A treatment applied after lysis of expired platelets. Results were compared to those using hPL produced from conventional expired pathogen inactivated platelet concentrates (hPL-PIPC), with pathogen inactivation applied after blood donation. hPL-PIPL treatment had lower concentrations of soluble growth factors and cytokines than hPL-PIPC treatment. When used as supplementation in cell culture, BM-MSCs proliferated at a reduced rate, but more consistently, in hPL-PIPL than in hPL-PIPC. The ability to support tri-lineage differentiation was comparable between lysates.

CONCLUSION/SIGNIFICANCE

These results suggest that functional hPL can be produced from expired and untreated platelet lysates by applying pathogen inactivation after platelet lysis. When carried out post-expiration, pathogen inactivation may provide a valuable solution for further standardizing global hPL production methods, increasing the pool of starting material, and meeting future demand for animal-free supplements in human cell culturing.

Adipose-Derived Stem Cells from Systemic Sclerosis Patients Maintain Pro-Angiogenic and Antifibrotic Paracrine Effects In Vitro

Innovative therapies based on autologous adipose-derived stem/stromal cells (ASC) are currently being evaluated for treatment of systemic sclerosis (SSc). Although paracrine angiogenic and antifibrotic effects are considered the predominant mechanisms of ASC therapeutic potential, the impact of SSc on ASC paracrine functions remains controversial. In this study, phenotype, senescence, differentiation potential, and molecular profile were determined in ASC from SSc patients (SSc-ASC) (n = 7) and healthy donors (HD-ASC) (n = 7). ASC were co-cultured in indirect models with dermal fibroblasts (DF) from SSc patients or endothelial cells to assess their pro-angiogenic and antifibrotic paracrine effects. The angiogenic activity of endothelial cells was measured in vitro using tube formation and spheroid assays. DF collagen and alpha smooth muscle actin (αSMA) content were quantified after five days of co-culture with ASC. Differentiation capacity, senescence, and mRNA profiles did not differ significantly between SSc-ASC and HD-ASC. SSc-ASC retained the ability to stimulate angiogenesis through paracrine mechanisms; however, functional assays revealed reduced potential compared to HD-ASC. DF fibrosis markers were significantly decreased after co-culture with SSc-ASC. Together, these results indicate that SSc effects do not significantly compromise the angiogenic and the antifibrotic paracrine properties of ASC, thereby supporting further development of ASC-based autologous therapies for SSc treatment.

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.

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.

Human Platelet Lysate Media Supplement Supports Lentiviral Transduction and Expansion of Human T Lymphocytes While Maintaining Memory Phenotype

Immune cell therapy has emerged as a promising approach to treat malignancies that were up until recently only treated on a palliative basis. Chimeric antigen receptor- (CAR-) modified T lymphocytes (T cells) in particular have proven to be very effective for certain hematological malignancies. The production of CAR T cells usually involves viral transduction and ex vivo culture of T cells. The aim of this study was to explore the use of human platelet lysate (HPL) compared to two commonly used supplements, human AB serum (ABS) and fetal bovine serum (FBS), for modified T cell production. For studying transduction, activated T cells were transduced with lentivirus to deliver GFP transgenes with three different promoters. Transduction efficiency (percent GFP) was similar among the supplements, and a modest increase in the transgene product (mean fluorescence intensity) was observed when HPL was used as a supplement compared to ABS. To study the effect of supplements on expansion, peripheral blood mononuclear cells (PBMCs) were activated and expanded in the presence of interleukin 2 (IL2) for fourteen days. T cell expansions using HPL and ABS were comparable and slightly less than the expansion obtained with FBS. Interestingly, cells expanded in media supplemented with HPL showed a higher percentage of T cells with a central memory phenotype compared to those expanded in ABS or FBS. Protein profiling revealed that the phenotypic differences may be explained by elevated levels of several cytokines in HPL, including IL7. The results suggest that the use of HPL as a cell culture supplement during the production of modified T cells is a reasonable alternative to ABS. Furthermore, the use of HPL may enhance in vivo performance of the final product by enriching for central memory T cells that are associated with long-term persistence following adoptive transfer.

The effect of culture media on large-scale expansion and characteristic of adipose tissue-derived mesenchymal stromal cells

Background

Adipose tissue-derived mesenchymal stromal cells (ASCs) have been shown to exhibit some promising properties of their use in regenerative medicine as advanced therapy medicinal products (ATMP). However, different sources of their origin, methods of isolation, and expansion procedures cause the laboratory and clinical results difficult to compare.

Methods

ASCs were isolated from lipoaspirates and cultured in three different medium formulations: αMEM and DMEM as a basal medium supplemented with 10% of human platelet lysate (hPL) and DMEM supplemented with 20% fetal bovine serum (FBS) and bFGF as a gold standard medium. Subsequently, the impact of culture media on ASCs growth kinetics, their morphology and immunophenotype, ability to differentiate, clonogenic potential, and secretion profile was evaluated.

Results

All cultured ASCs lines showed similar morphology and similar clonogenic potential and have the ability to differentiate into three lines: adipocytes, osteoblasts, and chondroblasts. The immunophenotype of all cultured ASCs was consistent with the guidelines of the International Society for Cell Therapy (ISCT) allowing to define cells as mesenchymal stromal cell (MSC) (≥ 95% CD105, CD73, CD90 and ≤ 2% CD45, CD34, CD14, CD19, HLA-DR). The immunophenotype stabilized after the second passage and did not differ between ASCs cultured in different conditions. The exception was the ASCs grown in the presence of FBS and bFGF, which expressed CD146 antigens. The secretion profile of ASCs cultured in different media was similar. The main secreted cytokine was IL-6, and its level was donor-specific. However, we observed a strong influence of the medium formulation on ASCs growth kinetics. The proliferation rate of ASCs in medium supplemented with hPL was the highest.

Conclusions

Culture media that do not contain animal-derived antigens (xeno-free) can be used to culture cells defined as MSC. Xeno-free medium is a safe alternative for the production of clinical-grade MSC as an advanced therapy medicinal product. Additionally, in such culture conditions, MSC can be easily expanded in accordance with the Good Manufacturing Process (GMP) requirements to a desired amount of cells for clinical applications.

Production and Quality Requirements of Human Platelet Lysate: A Position Statement from the Working Party on Cellular Therapies of the International Society of Blood Transfusion

Human platelet lysate (HPL), rich in growth factors, is an efficient alternative supplement to fetal bovine serum (FBS) for ex vivo propagation of stromal cell-based medicinal products. Since 2014, HPL has been a focus of the Working Party for Cellular Therapies of the International Society of Blood Transfusion (ISBT). Currently, as several Good Manufacturing Practice (GMP)-compliant manufacturing protocols exist, an international consensus defining the optimal modes of industrial production, product specification, pathogen safety, and release criteria of this ancillary material (AM) is needed. This opinion article by the ISBT Working Party summarizes the current knowledge on HPL production and proposes recommendations on manufacturing and quality management in line with current technological innovations and regulations of biological products and advanced therapy medicinal products.

Gaps in the knowledge of human platelet lysate as a cell culture supplement for cell therapy: a joint publication from the AABB and the International Society for Cell & Gene Therapy

Fetal bovine serum (FBS) is used as a growth supplement in a wide range of cell culture applications for cell-based research and therapy. However, as a xenogenic product, FBS can potentially transmit prions and adventitious viruses as well as induce undesirable immunologic reactions. In addition, the use of bovine fetuses for FBS production raises concerns as society looks for ways to replace animal testing and reduce the use of animal products for scientific purposes, in particular for the manufacture of clinical products intended for human use. Until chemically defined media are available for these purposes, human platelet lysate (hPL) has been introduced as an attractive alternative for replacing FBS as a cell culture supplement. hPL is a human product that can be produced from outdated platelets avoiding ethical, medical and animal welfare concerns. An increasing number of studies demonstrate that hPL can promote cell growth similarly or even better than FBS in specific cell types. Due to increasing interest in hPL, the AABB and the International Society of Cell Therapy (ISCT) established a joint working group to address its potential. With this article, we aim to present an overview of hPL, identifying the gaps in information on how hPL is produced and tested and the barriers to its translational use in the production of clinical-grade cell therapy products.

A highly standardized and characterized human platelet lysate for efficient and reproducible expansion of human bone marrow mesenchymal stromal cells

BACKGROUND

Human platelet lysate (hPL) represents a powerful alternative to fetal bovine serum (FBS) for human mesenchymal stromal cell (hMSC) expansion. However, the large variability in hPL sources and production protocols gives rise to discrepancies in product quality, characterization and poor batch-to-batch standardization.

METHODS

hPL prepared with more than 200 donors (200+DhPL) or with five donors (5DhPL) were compared in terms of growth factor (GF) contents and biochemical analysis. A multiple protein assay and proteomic analysis were performed to further characterize 200+DhPL batches. We also compared the phenotypic and functional characteristics of bone marrow (BM)-hMSCs grown in 200+DhPL versus FBS+basic fibroblast growth factor (bFGF).

RESULTS

By contrast to 5DhPL, industrial 200+DhPL displayed a strong standardization of GF contents and biochemical characteristics. We identified specific plasmatic components and platelet-released factors as the most relevant markers for the evaluation of the standardization of hPL batches. We used a multiplex assay and proteomic analysis of 200+DhPL to establish a proteomic signature and demonstrated the robust standardization of batches. 200+DhPL was shown to improve and standardize BM-hMSC expansion compared with FBS+bFGF. The levels of expression of BM-hMSC membrane markers were found to be much more homogeneous between batches when cells were cultured in 200+DhPL. BM-hMSCs cultured in parallel under both conditions displayed similar adipogenic and osteogenic differentiation potential and immunosuppressive properties.

CONCLUSIONS

We report a standardization of hPL and the importance of such standardization for the efficient amplification of more homogeneous and reproducible cell therapy products.

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.

A double-virally-inactivated (Intercept-solvent/detergent) human platelet lysate for in vitro expansion of human mesenchymal stromal cells

BACKGROUND

Pooled human platelet lysate (HPL) can replace fetal bovine serum (FBS) as xeno-free supplement for ex vivo expansion of mesenchymal stromal cells (MSCs). We evaluate here whether a double-virally-inactivated HPL (DVI-HPL) prepared from expired Intercept-treated platelet concentrates (PCs) and treated by solvent/detergent (S/D) can be used for MSC expansion.

STUDY DESIGN AND METHODS

Expired Intercept-treated PCs in 65% platelet (PLT) additive solution were pooled and subjected to a 1% tri-n-butyl phosphate/1% Triton X-45 treatment followed by soybean oil, hydrophobic interaction chromatography purification, and sterile filtration. Bone marrow-derived MSCs (BM-MSCs) were expanded for four passages in growth medium containing 10% DVI-HPL, I-HPL (from Intercept-PC only), untreated HPL, and FBS. MSC morphology, doubling time, immunophenotype, immunosuppressive activity, and differentiation capacity were compared.

RESULTS

Expanded cells had typical spindle morphology and showed higher viability in all HPL conditions than in FBS. The DVI-HPL and FBS-expanded cells were morphologically larger than in I-HPL and HPL supplements. The cumulative population doubling was lower using DVI-HPL than with HPL and I-HPL, but significantly higher than using FBS. Immunophenotype was not affected by the supplements used. Immunosuppressive activity was maintained with all supplements. Differentiation capacity into chondrocytes and osteocytes was more effective in DVI-HPL but less toward adipocytes compared to other supplements.

CONCLUSIONS

Human PLT lysate made from Intercept-PCs subjected to S/D treatment may be an alternative to untreated HPL and to I-HPL for BM-MSC expansion. This finding reinforces the potential of HPL as a virally safe alternative to FBS for clinical grade MSC expansion protocols.

Viral inactivation of human platelet lysate by gamma irradiation preserves its optimal efficiency in the expansion of human bone marrow mesenchymal stromal cells

BACKGROUND

Human platelet lysate (hPL) represents a powerful medium supplement for human mesenchymal stromal cell (hMSC) expansion. The recently published general chapters of the Pharmacopeia require the addition of a step of viral inactivation during the production process of such raw biological material used for cell-based medicinal products.

STUDY DESIGN AND METHODS

The ability of gamma irradiation to inactivate viruses from a panel representative of the virus diversity was evaluated. The impact of gamma irradiation on hPL composition and efficiency as a supplement for hMSC culture was evaluated.

RESULTS

An efficient inactivation of all the viruses tested was demonstrated, with the minimum reduction factors obtained being superior to 4.5 log₁₀ for human immunodeficiency virus (HIV) and hepatitis A virus (HAV) and superior to 5 log₁₀ for bovine viral diarrhea virus (BVDV), pseudorabies virus (PRV) and porcine parvovirus (PPV). The gamma irradiation did not affect the content in interesting biochemical factors for cell culture or in growth factors (GF), except to basic fibroblast GF (bFGF) whereas it highly impacted the contents in the factors involved in the coagulation cascade. Finally, gamma irradiated hPL remained as efficient as non-irradiated hPL for the proliferation, clonogenic potential, differentiation potential, and immunosuppressive properties of hMSCs.

CONCLUSION

The feasibility of using gamma irradiation to efficiently inactivate viruses in hPL while maintaining its optimal efficacy as a supplement for hMSC expansion was demonstrated. Such an inactivated hPL represents a very attractive raw material for the efficient production of safe cellular therapy products.

Four types of human platelet lysate, including one virally inactivated by solvent-detergent, can be used to propagate Wharton jelly mesenchymal stromal cells

There is accumulating experimental evidence that human platelet lysate (HPL) made from platelet concentrates can replace fetal bovine serum (FBS) as a xeno-free clinical-grade supplement of growth media to expand mesenchymal stromal cells (MSCs). However, uncertainties exist in regard to impacts that various manufacturing methods of HPL can exert on the expansion and differentiation capacity of MSCs. In particular, there is a need to evaluate the possibility of implementing virus-inactivation treatment during HPL production to ensure optimal safety of industrial HPL pools. Expired human platelet concentrates from four different donors were pooled and subjected to freeze-thaw cycles (-80/+37 °C), followed or not by serum-conversion by calcium chloride, heat-treatment at 56 °C for 30 min, or solvent-detergent (S/D) virus inactivation. The concentrations of total proteins, growth factors and fibrinogen, and the chemical compositions of the HPLs were characterized. The impact of HPL supplementation on the cell morphology, doubling time, immunophenotype and trilineage differentiation capacity of Wharton jelly MSCs (WJMSCs) were compared over five passages, using FBS as a control and normalizing the protein content. Data showed that WJMSCs expanded equally well, exhibited a typical fibroblast morphology, had short doubling times, maintained their immunophenotypes, and differentiated into chondrocyte, osteocyte, and adipocyte lineages in all HPL-supplemented media, all of which were more effective than FBS. In conclusion, we found minimal detectable impact of the HPL manufacturing process, including S/D virus inactivation, on the suitability of expanding WJMSCs in vitro.

Human serum and platelet lysate are appropriate xeno-free alternatives for clinical-grade production of human MuStem cell batches

BACKGROUND

Canine MuStem cells have demonstrated regenerative efficacy in a dog model of muscular dystrophy, and the recent characterization of human counterparts (hMuStem) has highlighted the therapeutic potential of this muscle-derived stem cell population. To date, these cells have only been generated in research-grade conditions. However, evaluation of the clinical efficacy of any such therapy will require the production of hMuStem cells in compliance with good manufacturing practices (GMPs). Because the current use of fetal bovine serum (FBS) to isolate and expand hMuStem cells raises several ethical, safety, and supply concerns, we assessed the use of two alternative xeno-free blood derivatives: human serum (HS) and a human platelet lysate (hPL).

METHODS

hMuStem cells were isolated and expanded in vitro in either HS-supplemented or hPL-supplemented media and the proliferation rate, clonogenicity, myogenic commitment potential, and oligopotency compared with that observed in FBS-supplemented medium. Flow cytometry and high-throughput 3'-digital gene expression RNA sequencing were used to characterize the phenotype and global gene expression pattern of hMuStem cells cultured with HS or hPL.

RESULTS

HS-supplemented and hPL-supplemented media both supported the isolation and long-term proliferation of hMuStem cells. Compared with FBS-based medium, both supplements enhanced clonogenicity and allowed for a reduction in growth factor supplementation. Neither supplement altered the cell lineage pattern of hMuStem cells. In vitro differentiation assays revealed a decrease in myogenic commitment and in the fusion ability of hMuStem cells when cultured with hPL. In return, this reduction of myogenic potential in hPL-supplemented cultures was rapidly reversed by substitution of hPL with HS or fibrinogen-depleted hPL. Moreover, culture of hMuStem cells in hPL hydrogel and fibrinogen-depleted hPL demonstrated that myogenic differentiation potential is maintained in heparin-free hPL derivatives.

CONCLUSIONS

Our findings indicate that HS and hPL are efficient and viable alternatives to FBS for the preparation of hMuStem cell batches in compliance with GMPs.

Manufacture of endothelial colony-forming progenitor cells from steady-state peripheral blood leukapheresis using pooled human platelet lysate

BACKGROUND

Endothelial colony-forming progenitor cells (ECFCs) are promising candidates for cell therapies. However, ECFC translation to the clinic requires optimized isolation and manufacture technologies according to good manufacturing practice (GMP).

STUDY DESIGN AND METHODS

ECFCs were manufactured from steady-state peripheral blood (PB) leukapheresis (11 donors), using GMP-compliant technologies including pooled human platelet (PLT) lysate, and compared to human umbilical cord endothelial cells, human aortic endothelial cells, and human cerebral microvascular endothelial cells. Specific variables assessed were growth kinetics, phenotype, trophic factors production, stimulation of tube formation, and Dil-AcLDL uptake.

RESULTS

ECFCs could be isolated from PB leukapheresis units with mean processed volume of 5411 mL and mean white blood cell (WBC) concentration factor of 8.74. The mean frequency was 1.44 × 10^-8 ECFCs per WBC, corresponding to a mean of 177.8 ECFCs per apheresis unit. Expandable for up to 12 cumulative population doublings, calculated projection showed that approximately 730 × 10³ ECFCs could be manufactured from 1 apheresis unit. ECFCs produced epidermal growth factor, hepatocyte growth factor, vascular endothelial growth factor (VEGF)-A, PLT-derived growth factor-B, interleukin-8, and monocyte chemoattractant protein-1, featured high potential for capillary-like tubes formation, and showed no telomerase activity. They were characterized by CD29, CD31, CD44, CD105, CD117, CD133, CD144, CD146, and VEGF-R2 expression, with the most common subpopulation CD34+CD117-CD133-. Compared to controls, ECFCs featured greater Dil-AcLDL uptake and higher expression of CD29, CD31, CD34, CD44, CD144, and VEGF-R2.

CONCLUSIONS

Here we show that isolation of ECFCs with proangiogenic profile from steady-state PB leukapheresis is feasible, marking a first step toward ECFC product manufacture according to GMP.