Overcoming the bottleneck of platelet lysate supply in large-scale clinical expansion of adipose-derived stem cells: A comparison of fresh versus three types of platelet lysates from outdated buffy coat–derived platelet concentrates

Adipose stem cells in tissue regeneration and repair: From bench to bedside

ADSCs are a large number of mesenchymal stem cells in Adipose tissue, which can be applied to tissue engineering. ADSCs have the potential of multi-directional differentiation, and can differentiate into bone tissue, cardiac tissue, urothelial cells, skin tissue, etc. Compared with other mesenchymal stem cells, ADSCs have a multitude of promising advantages, such as abundant number, accessibility in cell culture, stable function, and less immune rejection. There are two main methods to use ADSCs for tissue repair and regeneration. One is to implant the "ADSCs-scaffold composite" into the injured site to promote tissue regeneration. The other is cell-free therapy: using ADSC-exos or ADSC-CM alone to release a large number of miRNAs, cytokines and other bioactive substances to promote tissue regeneration. The tissue regeneration potential of ADSCs is regulated by a variety of cytokines, signaling molecules, and external environment. The differentiation of ADSCs into different tissues is also induced by growth factors, ions, hormones, scaffold materials, physical stimulation, and other factors. The specific mechanisms are complex, and most of the signaling pathways need to be further explored. This article reviews and summarizes the mechanism and clinical application of ADSCs in tissue injury repair so far, and puts forward further problems that need to be solved in this field, hoping to provide directions for further research in this field.

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.

Preparation of Fibrinogen-Depleted Human Platelet Lysate to Support Heparin-Free Expansion of Umbilical Cord-Derived Mesenchymal Stem Cells

Human platelet lysate (hPL) has high levels of fibrinogen and coagulation factors, which can lead to gel and precipitate formation during storage and cell culture. Heparin derived from animals is commonly added to minimize these risks, but cannot completely eliminate them. Thus, this study proposes an alternative method to prepare fibrinogen-depleted hPL (Fd-hPL) that supports heparin-free expansion of mesenchymal stem cells (MSCs). hPL was added to heparin to prepare heparin-hPL (H-hPL), whilst Fd-hPL was prepared by adding calcium salt to hPL to remove the fibrin clot. The concentrations of calcium, fibrinogen, and growth factors in H-hPL and Fd-hPL were compared. The effects of H-hPL and Fd-hPL on umbilical cord-derived MSCs (UC-MSCs) were assessed. The results showed that Fd-hPL possessed a significantly higher calcium concentration and a lower fibrinogen level than H-hPL. The concentrations of BDNF, TGF-β1, and PDGF-BB showed no significant difference between H-hPL and Fd-hPL, but Fd-hPL had a lower VEGF concentration. Fd-hPL retained the characteristics of UC-MSCs, as it did not affect the cell viability, proliferation, multilineage differentiation potential, or surface marker expression. In conclusion, Fd-hPL effectively supported the in vitro expansion of MSCs without compromising their characteristics, positioning it as a potential substitute for FBS in MSC culture.

Fat Grafting With Expanded Adipose-Derived Stromal Cells for Breast Augmentation: A Randomized Controlled Trial

BACKGROUND

The main challenge with fat grafting is loss of some of the graft to postsurgery resorption. Previous studies suggest that adipose-derived stromal cells (ASCs) can improve the volume retention of fat grafts but there is a lack of randomized trials to support the use of ASCs in clinical practice.

OBJECTIVES

This trial aimed to investigate whether ASCs improve fat graft volume retention in patients undergoing breast augmentation with lipofilling.

METHODS

This was a double-blind, randomized controlled trial of breast augmentation with ASC-enriched fat grafting. Healthy women aged 30 to 45 years were enrolled. First, the participants underwent liposuction to obtain fat for culture expansion of ASCs. Then, the participants were randomly assigned to undergo a 300- to 350-mL breast augmentation with ASC-enriched fat grafting (10 × 106 ASCs/mL fat graft) to 1 of their breasts and placebo-enriched fat grafting of identical volume to the contralateral breast. The primary outcome was fat graft volume retention after a 1-year follow-up measured with MRI. The trial is registered at www.clinicaltrialsregister.eu (EudraCT-2014-000510-59).

RESULTS

Ten participants were included in the trial; all completed the treatment and follow-up. No serious adverse events occurred. Fat graft volume retention after 1 year was 54.0% (95% CI, 30.4%-77.6%) in the breasts treated with ASC-enriched fat grafting (n = 10) and 55.9% (95% CI, 28.9%-82.9%) in the contralateral breasts treated with placebo-enriched fat grafting (n = 10) (P = 0.566).

CONCLUSIONS

The findings of this trial do not support that ASC-enriched fat grafting is superior to standard fat grafting for breast augmentation.

LEVEL OF EVIDENCE: 2

Efficacy of mesenchymal stem cell-delivery using perpendicular multi-needle injections to the skin: Evaluation of post-ejection cellular health and dermal delivery

AIM

Mesenchymal stem cell (MSC)-therapy is increasingly being evaluated in clinical trials. Dermal delivery is not only time consuming but also unreliable, potentially hampering the therapeutic result. Therefore, qualification of cell delivery protocols is essential. This study evaluated a clinically relevant automated multi-needle injection method for cutaneous MSC-therapy, allowing the skin to be readily and timely treated, by assessing both the cellular health post-ejection and dermal delivery.

METHODS

Following dispensation through the injector (31 G needles: 9- or 5-pin) the cellular health and potency (perceived- and long-term (12 h) viability, recovery, metabolism, adherence, proliferation and IDO1-expression) of adipose-derived stem cells (10-20-50 ×10⁶ cells/ml) were assessed in vitro in addition to dermal delivery of solution in human skin.

RESULTS

No significant detrimental effect on the perceived cell viability, recovery, metabolism, adherence or IDO1-expression of either cell concentration was observed. However, the overall long-term viability and proliferation decreased significantly regardless of cell concentration, nonetheless marginally. An injection depth above 1.0 mm resulted in all needles piercing the skin with dermal delivery from up to 89% needles and minimal reflux to the skin surface, and the results were confirmed by ultrasound and histology.

CONCLUSION

The automated injector is capable of delivering dermal cell-doses with an acceptable cell quality.

Application of a deep learning-based image analysis and live-cell imaging system for quantifying adipogenic differentiation kinetics of adipose-derived stem/stromal cells

Quantitative methods for assessing differentiative potency of adipose-derived stem/stromal cells may lead to improved clinical application of this multipotent stem cell, by advancing our understanding of specific processes such as adipogenic differentiation. Conventional cell staining methods are used to determine the formation of adipose areas during adipogenesis as a qualitative representation of adipogenic potency. Staining methods such as oil-red-O are quantifiable using absorbance measurements, but these assays are time and material consuming. Detection methods for cell characteristics using advanced image analysis by machine learning are emerging. Here, live-cell imaging was combined with a deep learning-based detection tool to quantify the presence of adipose areas and lipid droplet formation during adipogenic differentiation of adipose-derived stem/stromal cells. Different detection masks quantified adipose area and lipid droplet formation at different time points indicating kinetics of adipogenesis and showed differences between individual donors. Whereas CEBPA and PPARG expression seems to precede the increase in adipose area and lipid droplets, it might be able to predict expression of ADIPOQ. The applied method is a proof of concept, demonstrating that deep learning methods can be used to investigate adipogenic differentiation and kinetics in vitro using specific detection masks based on algorithm produced from annotation of image data.

Adipose-derived stromal cells for nonhealing wounds: Emerging opportunities and challenges

Wound healing complications affect thousands of people each year, thus constituting a profound economic and medical burden. Chronic wounds are a highly complex problem that usually affects elderly patients as well as patients with comorbidities such as diabetes, cancer (surgery, radiotherapy/chemotherapy) or autoimmune diseases. Currently available methods of their treatment are not fully effective, so new solutions are constantly being sought. Cell-based therapies seem to have great potential for use in stimulating wound healing. In recent years, much effort has been focused on characterizing of adipose-derived mesenchymal stromal cells (AD-MSCs) and evaluating their clinical use in regenerative medicine and other medical fields. These cells are easily obtained in large amounts from adipose tissue and show a high proregenerative potential, mainly through paracrine activities. In this review, the process of healing acute and nonhealing (chronic) wounds is detailed, with a special attention paid to the wounds of patients with diabetes and cancer. In addition, the methods and technical aspects of AD-MSCs isolation, culture and transplantation in chronic wounds are described, and the characteristics, genetic stability and role of AD-MSCs in wound healing are also summarized. The biological properties of AD-MSCs isolated from subcutaneous and visceral adipose tissue are compared. Additionally, methods to increase their therapeutic potential as well as factors that may affect their biological functions are summarized. Finally, their therapeutic potential in the treatment of diabetic and oncological wounds is also discussed.

Influence of Human Platelet Lysate on Extracellular Matrix Deposition and Cellular Characteristics in Adipose-Derived Stem Cell Sheets

Adipose-derived stem cell (ASC) is a valuable source of cell therapy. By stimulating extracellular matrix (ECM) secretion, ASC sheets can be fabricated with enhanced regenerative capabilities. In recent years, human platelet lysate (HPL) provides an attractive alternative to fetal bovine serum (FBS) for the ex vivo expansion of ASCs for clinical use. However, the effect of HPL on ASC sheet formation has not been previously determined. In this study, we compared ECM composition and cellular characteristics of ASC sheets cultured in growth medium supplemented with either FBS or HPL. HPL supplement significantly enhanced ASC proliferation without obvious change in the expression pattern of cell surface markers. We found that culturing ASCs with HPL rendered thicker cell sheets with significantly more ECM deposition, including collagen and fibronectin. Proteomic analysis of the FBS or HPL-cultured cell sheets showed diversity in ECM composition. HPL-cultured ASC sheets exhibited up-regulation of interleukin-6 and an anti-inflammatory cytokine, C1q/tumor necrosis factor-related protein-3. Conditioned medium of HPL-cultured ASC sheets significantly enhanced fibroblast migration and tube formation of endothelial cells in vitro, while it inhibited the migration of macrophages toward stimulated macrophages in vitro. TGF-β1-stimulated fibroblasts cultured in ASC sheet-conditioned medium showed down-regulation of α-SMA and TGF-β1. By adding an anti-hepatocyte growth factor (HGF) neutralizing antibody in conditioned medium, we indicated that an anti-fibrosis effect of HPL-cultured ASC sheets is partially mediated through the increased secretion of HGF. Moreover, chick embryo chorioallantoic membrane (CAM) assay showed comparable capillary density after applying either FBS or HPL-cultured ASC sheets, both of which were significantly higher than the control. In conclusion, robust ECM formation with altered ECM composition was noted in ASC sheets cultured in HPL-supplemented medium. Their immunomodulatory and pro-angiogenesis capabilities were largely maintained. Our findings paved the way to elucidate the potential of HPL-cultured ASC sheets for clinical application in tissue regeneration.

Clinical Translational Potential in Skin Wound Regeneration for Adipose-Derived, Blood-Derived, and Cellulose Materials: Cells, Exosomes, and Hydrogels

Acute and chronic skin wounds due to burns, pressure injuries, and trauma represent a substantial challenge to healthcare delivery with particular impacts on geriatric, paraplegic, and quadriplegic demographics worldwide. Nevertheless, the current standard of care relies extensively on preventive measures to mitigate pressure injury, surgical debridement, skin flap procedures, and negative pressure wound vacuum measures. This article highlights the potential of adipose-, blood-, and cellulose-derived products (cells, decellularized matrices and scaffolds, and exosome and secretome factors) as a means to address this unmet medical need. The current status of this research area is evaluated and discussed in the context of promising avenues for future discovery.

Regulatory-compliant conditions during cell product manufacturing enhance in vitro immunomodulatory properties of infrapatellar fat pad-derived mesenchymal stem/stromal cells

BACKGROUND AIMS

Mesenchymal stem/stromal cell (MSC)-based therapies have gained attention as potential alternatives for multiple musculoskeletal indications based on their trophic and immunomodulatory properties. The infrapatellar fat pad (IFP) serves as a reservoir of MSCs, which play crucial roles modulating inflammatory and fibrotic events at the IFP and its neighboring tissue, the synovium. In an effort to comply with the existing regulatory framework regarding cell-based product manufacturing, we interrogated the in vitro immunomodulatory capacity of human-derived IFP-MSCs processed under different conditions, including a regulatory-compliant protocol, in addition to their response to the inflammatory and fibrotic environments often present in joint disease.

METHODS

Immunophenotype, telomere length, transcriptional and secretory immunomodulatory profiles and functional immunopotency assay were assessed in IFP-MSCs expanded in regular fetal bovine serum (FBS)-supplemented medium and side-by-side compared with same-donor cells processed with two media alternatives (i.e., regulatory-compliant pooled human platelet lysate [hPL] and a chemically reinforced/serum-reduced [Ch-R] formulation). Finally, to assess the effects of such formulations on the ability of the cells to respond to pro-inflammatory and pro-fibrotic conditions, all three groups were stimulated ex vivo (i.e., cell priming) with a cocktail containing TNFα, IFNγ and connective tissue growth factor (tumor-initiating cells) and compared with non-induced cohorts assessing the same outcomes.

RESULTS

Non-induced and primed IFP-MSCs expanded in either hPL or Ch-R showed distinct morphology in vitro, similar telomere dynamics and distinct phenotypical and molecular profiles when compared with cohorts grown in FBS. Gene expression of IL-8, CD10 and granulocyte colony-stimulating factor was highly enriched in similarly processed IFP-MSCs. Cell surface markers related to the immunomodulatory capacity, including CD146 and CD10, were highly expressed, and secretion of immunomodulatory and pro-angiogenic factors was significantly enhanced with both hPL and Ch-R formulations. Upon priming, the immunomodulatory phenotype was enhanced, resulting in further increase in CD146 and CD10, significant CXCR4 presence and reduction in TLR3. Similarly, transcriptional and secretory profiles were enriched and more pronounced in IFP-MSCs expanded in either hPL or Ch-R, suggesting a synergistic effect between these formulations and inflammatory/fibrotic priming conditions. Collectively, increased indoleamine-2,3-dioxygenase activity and prostaglandin E2 secretion for hPL- and Ch-R-expanded IFP-MSCs were functionally reflected by their robust T-cell proliferation suppression capacity in vitro compared with IFP-MSCs expanded in FBS, even after priming.

CONCLUSIONS

Compared with processing using an FBS-supplemented medium, processing IFP-MSCs with either hPL or Ch-R similarly enhances their immunomodulatory properties, which are further increased after exposure to an inflammatory/fibrotic priming environment. This evidence supports the adoption of regulatory-compliant practices during the manufacturing of a cell-based product based on IFP-MSCs and anticipates a further enhanced response once the cells face the pathological environment after intra-articular administration. Mechanistically, the resulting functionally enhanced cell-based product has potential utilization as a novel, minimally invasive cell therapy for joint disease through modulation of local immune and inflammatory events.

Lipoaspirate Storage Time and Temperature: Effects on Stromal Vascular Fraction Quality and Cell Composition

The adipose tissue-derived stromal vascular fraction (SVF) is a promising candidate for use in cell therapy and tissue engineering due to its regenerative and immunomodulatory properties. Some therapies are based on using the complete SVF product, whereas others depend on the expansion of adipose-derived stromal cells (ASCs) in culture. The latter application often involves a time delay between adipose tissue harvest and SVF isolation. This study investigated how storage time and temperature affected cell quality and composition. Aliquots of lipoaspirate were stored cold (4°C), at room temperature (18-20°C), or at 37°C. SVF was isolated on sequential time points over a period of 48 h, and the following were assessed: cell viability, vitality, composition, and the proliferative potential of the ASCs. When the lipoaspirate was stored cold, the viability of the SVF remained stable for up to 48 h; however, the vitality of the SVF decreased significantly after 24 h. When stored at higher temperatures (room temperature or 37°C), the vitality of the SVF decreased after 8 h. The ASC fraction in the SVF decreased rapidly after 8 h when stored at higher temperatures, whereas this change was delayed significantly when the lipoaspirate was stored cold. Tendencies towards increases in the lag phase, population doubling time (PDt), and time to reach confluency were observed when the lipoaspirate was stored at higher temperatures. The vitality of the SVF was correlated significantly with the time of the lag phase and the time required to reach confluence, whereas no correlation was observed with the PDt. Both prolonged storage time and increased temperature during lipoaspirate storage negatively affected the quality of the obtained SVF. Our results suggest that lipoaspirate should be stored for no longer than 24 h at 4°C to maintain the optimal quality for the isolation of SVF and the expansion of ASCs.

The effect of medium supplementation and serial passaging on the transcriptome of human adipose-derived stromal cells expanded in vitro

BACKGROUND

For adipose-derived stromal cells (ASCs) to be safe for use in the clinical setting, they need to be prepared using good manufacturing practices (GMPs). Fetal bovine serum (FBS), used to expand ASCs in vitro in some human clinical trials, runs the risk of xenoimmunization and zoonotic disease transmission. To ensure that GMP standards are maintained, pooled human platelet lysate (pHPL) has been used as an alternative to FBS. ASCs proliferate more rapidly in pHPL than in FBS, with no significant change in immunophenotype and differentiation capacity. However, not much is known about how pHPL affects the transcriptome of these cells.

METHODS

This study investigated the effect of pHPL and FBS on the ASC transcriptome during in vitro serial expansion from passage 0 to passage 5 (P0 to P5). RNA was isolated from ASCs at each passage and hybridized to Affymetrix HuGene 2.0 ST arrays for gene expression analysis.

RESULTS

We observed that the transcriptome of ASCs expanded in pHPL (pHPL-ASCs) and FBS (FBS-ASCs) had the greatest change in gene expression at P2. Gene ontology revealed that genes upregulated in pHPL-ASCs were enriched for cell cycle, migration, motility, and cell-cell interaction processes, while those in FBS-ASCs were enriched for immune response processes. ASC transcriptomes were most homogenous from P2 to P5 in FBS and from P3 to P5 in pHPL. FBS- and pHPL-gene-specific signatures were observed, which could be used as markers to identify cells previously grown in either FBS or pHPL for downstream clinical/research applications. The number of genes constituting the FBS-specific effect was 3 times greater than for pHPL, suggesting that pHPL may be a milder supplement for cell expansion. A set of genes were expressed in ASCs at all passages and in both media. This suggests that a unique ASC in vitro transcriptomic profile exists that is independent of the passage number or medium used.

CONCLUSIONS

GO classification revealed that pHPL-ASCs are more involved in cell cycle processes and cellular proliferation when compared to FBS-ASCs, which are involved in more specialized or differentiation processes like cardiovascular and vascular development. This makes pHPL a potential superior supplement for expanding ASCs as they retain their proliferative capacity, remain untransformed and pHPL does not affect the genes involved in differentiation in specific developmental processes.

Human Platelet Lysate as a Functional Substitute for Fetal Bovine Serum in the Culture of Human Adipose Derived Stromal/Stem Cells

INTRODUCTION

Adipose derived stromal/stem cells (ASCs) hold potential as cell therapeutics for a wide range of disease states; however, many expansion protocols rely on the use of fetal bovine serum (FBS) as a cell culture nutrient supplement. The current study explores the substitution of lysates from expired human platelets (HPLs) as an FBS substitute.

METHODS

Expired human platelets from an authorized blood center were lysed by freeze/thawing and used to examine human ASCs with respect to proliferation using hematocytometer cell counts, colony forming unit-fibroblast (CFU-F) frequency, surface immunophenotype by flow cytometry, and tri-lineage (adipocyte, chondrocyte, osteoblast) differentiation potential by histochemical staining.

RESULTS

The proliferation assays demonstrated that HPLs supported ASC proliferation in a concentration dependent manner, reaching levels that exceeded that observed in the presence of 10% FBS. The concentration of 0.75% HPLs was equivalent to 10% FBS when utilized in cell culture media with respect to proliferation, immunophenotype, and CFU-F frequency. When added to osteogenic, adipogenic, and chondrogenic differentiation media, both supplements showed appropriate differentiation by staining.

CONCLUSION

HPLs is an effective substitute for FBS in the culture, expansion and differentiation of human ASCs suitable for pre-clinical studies; however, additional assays and analyses will be necessary to validate HPLs for clinical applications and regulatory approval.

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.

Perspectives for Clinical Translation of Adipose Stromal/Stem Cells

Adipose stromal/stem cells (ASCs) are an ideal cell type for regenerative medicine applications, as they can easily be harvested from adipose tissue in large quantities. ASCs have excellent proliferation, differentiation, and immunoregulatory capacities that have been demonstrated in numerous studies. Great interest and investment have been placed in efforts to exploit the allogeneic use and immunomodulatory and anti-inflammatory effects of ASCs. However, bridging the gap between in vitro and in vivo studies and moving into clinical practice remain a challenge. For the clinical translation of ASCs, several issues must be considered, including how to characterise such a heterogenic cell population and how to ensure their safety and efficacy. This review explores the different phases of in vitro and preclinical ASC characterisation and describes the development of appropriate potency assays. In addition, good manufacturing practice requirements are discussed, and cell-based medicinal products holding marketing authorisation in the European Union are reviewed. Moreover, the current status of clinical trials applying ASCs and the patent landscape in the field of ASC research are presented. Overall, this review highlights the applicability of ASCs for clinical cell therapies and discusses their potential.

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.

Impact of incubation method on the release of growth factors in non-Ca2+-activated PRP, Ca2+-activated PRP, PRF and A-PRF

The aim of this study was to investigate the influence of different incubation methods on the growth factor content of lysates of platelet-rich fibrin (PRF), advanced-platelet-rich fibrin (A-PRF) and platelet-rich plasma (PRP) products. A comparison of related studies suggests that the method of sample preparation has a significant influence on growth factor content. There are few reports on the comparison of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, A-PRF, and PRF, along with a lack of information on the release of PDGF-BB, TGF-β1, and VEGF among the different incubation methods. The lysate preparation was made of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, PRF, and A-PRF, using a room-temperature, 37 °C, or freeze-thaw-freeze incubation method. Afterwards the VEGF, PDGF-BB, and TGF-β1 content was investigated by running ELISA tests. Growth factor levels were significantly increased in the non-Ca²⁺-activated PRP with freeze-thaw-freeze incubation, and in the PRF preparation there was a significant disadvantage to using room temperature incubation for releasing growth factors. In conclusion, the freeze-thaw-freeze method is sufficient for releasing growth factors, and calcium activation is not necessary. Finally, the study demonstrates the possibility of preparing PRP products from platelet concentrates, so that preoperative blood sampling might not be required.

A contemporary view of platelet-rich plasma therapies: moving toward refined clinical protocols and precise indications

The positive extensive clinical experience with platelet-rich plasma (PRP) in different medical areas has prompted researchers to explore clinical opportunities for optimized PRP therapies. PRP is safe but we have to make it more effective. The growing diversity of formulations and presentations enrich the field of PRP research and offer hope to refine clinical indications. Moving toward targeting the right disease phenotypes with the right PRP formulation or combination product (PRP + cell products) can offer opportunities to change treatment options in osteoarthritis and nonhealing wounds. Both are active areas of research that could offer opportunities, although cost efficacy is still an open question. Our position is to believe that these serious disease areas are likely to benefit from PRP therapies.

A Novel Porcine Model for Future Studies of Cell-enriched Fat Grafting

Supplemental Digital Content is available in the text.

Background:

Cell-enriched fat grafting has shown promising results for improving graft survival, although many questions remain unanswered. A large animal model is crucial for bridging the gap between rodent studies and human trials. We present a step-by-step approach in using the Göttingen minipig as a model for future studies of cell-enriched large volume fat grafting.

Methods:

Fat grafting was performed as bolus injections and structural fat grafting. Graft retention was assessed by magnetic resonance imaging after 120 days. The stromal vascular fraction (SVF) was isolated from excised fat and liposuctioned fat from different anatomical sites and analyzed. Porcine adipose-derived stem/stromal cells (ASCs) were cultured in different growth supplements, and population doubling time, maximum cell yield, expression of surface markers, and differentiation potential were investigated.

Results:

Structural fat grafting in the breast and subcutaneous bolus grafting in the abdomen revealed average graft retention of 53.55% and 15.28%, respectively, which are similar to human reports. Liposuction yielded fewer SVF cells than fat excision, and abdominal fat had the most SVF cells/g fat with SVF yields similar to humans. Additionally, we demonstrated that porcine ASCs can be readily isolated and expanded in culture in allogeneic porcine platelet lysate and fetal bovine serum and that the use of 10% porcine platelet lysate or 20% fetal bovine serum resulted in population doubling time, maximum cell yield, surface marker profile, and trilineage differentiation that were comparable with humans.

Conclusions:

The Göttingen minipig is a feasible and cost-effective, large animal model for future translational studies of cell-enriched fat grafting.

Comparison of human platelet lysate alternatives using expired and freshly isolated platelet concentrates for adipose-derived stromal cell expansion

Pooled human platelet lysate (pHPL) has been used to expand adipose-derived stromal cells (ASCs) and can be formulated using fresh or expired buffy coats (BCs) which are then resuspended in either plasma or an additive solution. Not much is known about the effects that expired products and additive solutions have on ASC expansion, and the need for quality control and release criteria has been expressed. This pilot study compared proliferation, cell size, morphology and immunophenotype of ASCs expanded in the different pHPL alternatives versus foetal bovine serum (FBS). Quality control criteria were assessed prior to and during the manufacture of the pHPL alternatives. ASCs were then expanded in 1%, 2.5%, 5% or 10% of the different pHPL alternatives or in 10% FBS. Cell size, morphology, cell number and immunophenotype were measured using microscopy and flow cytometry. The majority of the pHPL alternatives were within the recommended ranges for the quality control criteria. ASCs expanded in the pHPL alternatives were smaller in size, displayed a tighter spindle-shaped morphology, increased cell growth and had a similar immunophenotype (with the exception of CD34 and CD36) when compared to ASCs expanded in FBS. Here we report on the effects that expired BC products and additive solutions have on ASC expansion. When taken together, our findings indicate that all of the pHPL alternatives can be considered to be suitable replacements for FBS for ASC expansion, and that expired BC products can be used as an alternative to fresh BC products.

Safety and Efficacy of Mesenchymal Stem Cells for Radiation-Induced Xerostomia: A Randomized, Placebo-Controlled Phase 1/2 Trial (MESRIX)

BACKGROUND

Salivary gland hypofunction and xerostomia are major complications to head and neck radiotherapy. This trial assessed the safety and efficacy of adipose tissue-derived mesenchymal stem cell (ASC) therapy for radiation-induced xerostomia.

PATIENT AND METHODS

This randomized, placebo-controlled phase 1/2 trial included 30 patients, randomized in a 1:1 ratio to receive ultrasound-guided transplantation of ASCs or placebo to the submandibular glands. Patients had previously received radiotherapy for a T1-2, N0-2A, human papillomavirus-positive, oropharyngeal squamous cell carcinoma. The primary outcome was the change in unstimulated whole salivary flow rate, measured before and after the intervention. All assessments were performed one month prior (baseline) and one and four months following ASC or placebo administration.

RESULTS

No adverse events were detected. Unstimulated whole salivary flow rates significantly increased in the ASC-arm at one (33%; P = .048) and four months (50%; P = .003), but not in the placebo-arm (P = .6 and P = .8), compared to baseline. The ASC-arm symptom scores significantly decreased on the xerostomia and VAS questionnaires, in the domains of thirst (-22%, P = .035) and difficulties in eating solid foods (-2%, P = .008) after four months compared to baseline. The ASC-arm showed significantly improved salivary gland functions of inorganic element secretion and absorption, at baseline and four months, compared to the placebo-arm. Core-needle biopsies showed increases in serous gland tissue and decreases in adipose and connective tissues in the ASC-arm compared to the placebo-arm (P = .04 and P = .02, respectively). MRIs showed no significant differences between groups in gland size or intensity (P < .05).

CONCLUSIONS

ASC therapy for radiation-induced hypofunction and xerostomia was safe and significantly improved salivary gland functions and patient-reported outcomes. These results should encourage further exploratory and confirmatory trials.

Human platelet lysate supports the formation of robust human periodontal ligament cell sheets

The use of stem cell-derived sheets has become increasingly common in a wide variety of biomedical applications. Although substantial evidence has demonstrated that human platelet lysate (PL) can be used for therapeutic cell expansion, either as a substitute for or as a supplement to xenogeneic fetal bovine serum (FBS), its impact on cell sheet production remains largely unexplored. In this study, we manufactured periodontal ligament stem cell (PDLSC) sheets in vitro by incubating PDLSCs in sheet-induction media supplemented with various ratios of PL and FBS, i.e. 10% PL without FBS, 7.5% PL + 2.5% FBS, 5% PL + 5% FBS, 2.5% PL + 7.5% FBS or 10% FBS without PL. Cultures with the addition of all the designed supplements led to successful cell sheet production. In addition, all the resultant cellular materials exhibited similar expression profiles of matrix-related genes and proteins, such as collagen I, fibronectin and integrin β1. Interestingly, the cell components within sheets generated by media containing both PL and FBS exhibited improved osteogenic potential. Following in vivo transplantation, all sheets supported significant new bone formation. Our data suggest that robust PDLSC sheets can be produced by applying PL as either an alternative or an adjuvant to FBS. Further examination of the relevant influences of human PL that benefit cell behaviour and matrix production will pave the way towards optimized and standardized conditions for cell sheet production.

Tissue Source and Cell Expansion Condition Influence Phenotypic Changes of Adipose-Derived Stem Cells

Stem cells derived from the subcutaneous adipose tissue of debrided burned skin represent an appealing source of adipose-derived stem cells (ASCs) for regenerative medicine. Traditional tissue culture uses fetal bovine serum (FBS), which complicates utilization of ASCs in human medicine. Human platelet lysate (hPL) is one potential xeno-free, alternative supplement for use in ASC culture. In this study, adipogenic and osteogenic differentiation in media supplemented with 10% FBS or 10% hPL was compared in human ASCs derived from abdominoplasty (HAP) or from adipose associated with debrided burned skin (BH). Most (95–99%) cells cultured in FBS were stained positive for CD73, CD90, CD105, and CD142. FBS supplementation was associated with increased triglyceride content and expression of adipogenic genes. Culture in hPL significantly decreased surface staining of CD105 by 31% and 48% and CD142 by 27% and 35% in HAP and BH, respectively (p < 0.05). Culture of BH-ASCs in hPL also increased expression of markers of osteogenesis and increased ALP activity. These data indicate that application of ASCs for wound healing may be influenced by ASC source as well as culture conditions used to expand them. As such, these factors must be taken into consideration before ASCs are used for regenerative purposes.