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

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.

Donor-Matched Peripheral Blood-Derived Mesenchymal Stem Cells Combined With Platelet-Rich Plasma Synergistically Ameliorate Surgery-Induced Osteoarthritis in Rabbits: An In Vitro and In Vivo Study

BACKGROUND

Osteoarthritis (OA) is a common disease that causes joint pain and disability. Stem cell therapy is emerging as a promising treatment for OA.

PURPOSE

To evaluate the ability of peripheral blood-derived mesenchymal stem cells (PBMSCs) combined with donor-matched platelet-rich plasma (PRP) to treat OA in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

PBMSCs and donor-matched PRP were isolated and prepared from the same rabbit. PBMSCs were treated with serum-free medium, fetal bovine serum, and PRP; a series of PBMSC behaviors, including proliferation, migration, and adhesion, were compared among groups. The ability of PBMSCs or PRP alone and PBMSCs+PRP to protect chondrocytes against proinflammatory cytokine (interleukin 1β [IL-1β]) treatment was compared by analyzing reactive oxygen species (ROS)-scavenging ability and apoptosis. Real-time quantitative polymerase chain reaction and immunofluorescence were used to investigate the expression of extracellular matrix (ECM) metabolism genes and proteins, and Western blotting was used to explore the potential mechanism of the corresponding signaling pathway. In vivo, the effect of PBMSCs+PRP on cartilage and inflammation of the synovium was observed in a surgery-induced OA rabbit model via gross observation, histological and immunohistochemical staining, and enzyme-linked immunosorbent assay.

RESULTS

Proliferation, migration, and adhesion ability were enhanced in PBMSCs treated with PRP. Moreover, compared with either PBMSCs or PRP alone, PBMSCs+PRP enhanced ROS-scavenging ability and inhibited apoptosis in IL-1β-treated chondrocytes. PBMSCs+PRP also reversed the IL-1β-induced degradation of collagen type 2 and aggrecan and increased expression of matrix metalloproteinase 13, and this effect was related to increased expression of ECM synthesis and decreased expression of degradation and inflammatory genes and proteins. Mechanistically, PBMSCs+PRP reduced the phosphorylation of inhibitor of nuclear factor-κBα (IκBα), which further inhibited the phosphorylation of downstream nuclear factor-κB (NF-κB) in the NF-κB signaling pathway. In vivo, compared with PBMSCs or PRP alone, intra-articular (IA) injection of PBMSCs+PRP enhanced cartilage regeneration and attenuated synovial inflammation in OA-induced rabbits.

CONCLUSION

These results demonstrate that PRP could enhance biological activities, including viability, migration, and adhesion, in PBMSCs. PBMSCs+PRP could rescue ECM degeneration by inhibiting inflammatory signaling in IL-1β-treated OA chondrocytes. In addition, IA injection of PBMSCs+PRP effectively attenuated OA progression in a surgery-induced OA rabbit model.

CLINICAL RELEVANCE

PBMSCs+PRP may provide a promising treatment for knee OA, and this study can advance the related basic research.

Neural Differentiation of Induced Pluripotent Stem Cells for a Xenogeneic Material-Free 3D Neurological Disease Model Neurulation from Pluripotent Cells Using a Human Hydrogel

Alzheimer's Disease (AD) is characterized by synapse and neuronal loss and the accumulation of neurofibrillary tangles and Amyloid β plaques. Despite significant research efforts to understand the late stages of the disease, its etiology remains largely unknown. This is in part because of the imprecise AD models in current use. In addition, little attention has been paid to neural stem cells (NSC), which are the cells responsible for the development and maintenance of brain tissue during an individual's lifespan. Thus, an in vitro 3D human brain tissue model using induced pluripotent stem (iPS) cell-derived neural cells in human physiological conditions may be an excellent alternative to standard models to investigate AD pathology. Following the differentiation process mimicking development, iPS cells can be turned into NSCs and, ultimately, neural cells. During differentiation, the traditionally used xenogeneic products may alter the cells' physiology and prevent accurate disease pathology modeling. Hence, establishing a xenogeneic material-free cell culture and differentiation protocol is essential. This study investigated the differentiation of iPS cells to neural cells using a novel extracellular matrix derived from human platelet lysates (PL Matrix). We compared the stemness properties and differentiation efficacies of iPS cells in a PL matrix against those in a conventional 3D scaffold made of an oncogenic murine-matrix. Using well-defined conditions without xenogeneic material, we successfully expanded and differentiated iPS cells into NSCs via dual-SMAD inhibition, which regulates the BMP and TGF signaling cascades in a manner closer to human conditions. This in vitro, 3D, xenogeneic-free scaffold will enhance the quality of disease modeling for neurodegenerative disease research, and the knowledge produced could be used in developing more effective translational medicine.

Adipose-Derived Stem Cells in Reinforced Collagen Gel: A Comparison between Two Approaches to Differentiation towards Smooth Muscle Cells

Scaffolds made of degradable polymers, such as collagen, polyesters or polysaccharides, are promising matrices for fabrication of bioartificial vascular grafts or patches. In this study, collagen isolated from porcine skin was processed into a gel, reinforced with collagen particles and with incorporated adipose tissue-derived stem cells (ASCs). The cell-material constructs were then incubated in a DMEM medium with 2% of FS (DMEM_part), with added polyvinylalcohol nanofibers (PVA_part sample), and for ASCs differentiation towards smooth muscle cells (SMCs), the medium was supplemented either with human platelet lysate released from PVA nanofibers (PVA_PL_part) or with TGF-β1 + BMP-4 (TGF + BMP_part). The constructs were further endothelialised with human umbilical vein endothelial cells (ECs). The immunofluorescence staining of alpha-actin and calponin, and von Willebrand factor, was performed. The proteins involved in cell differentiation, the extracellular matrix (ECM) proteins, and ECM remodelling proteins were evaluated by mass spectrometry on day 12 of culture. Mechanical properties of the gels with ASCs were measured via an unconfined compression test on day 5. Gels evinced limited planar shrinkage, but it was higher in endothelialised TGF + BMP_part gel. Both PVA_PL_part samples and TGF + BMP_part samples supported ASC growth and differentiation towards SMCs, but only PVA_PL_part supported homogeneous endothelialisation. Young modulus of elasticity increased in all samples compared to day 0, and PVA_PL_part gel evinced a slightly higher ratio of elastic energy. The results suggest that PVA_PL_part collagen construct has the highest potential to remodel into a functional vascular wall.

Human platelet lysate enhances proliferation but not chondrogenic differentiation of pediatric mesenchymal progenitors

BACKGROUND AIMS

Cell therapies have the potential to improve reconstructive procedures for congenital craniofacial cartilage anomalies such as microtia. Adipose-derived stem cells (ADSCs) and auricular cartilage stem/progenitor cells (CSPCs) are promising candidates for cartilage reconstruction, but their successful use in the clinic will require the development of xeno-free expansion and differentiation protocols that can maximize their capacity for chondrogenesis.

METHODS

We assessed the behavior of human ADSCs and CSPCs grown either in qualified fetal bovine serum (FBS) or human platelet lysate (hPL), a xeno-free alternative, in conventional monolayer and 3-dimensional spheroid cultures.

RESULTS

We show that CSPCs and ADSCs display greater proliferation rate in hPL than FBS and express typical mesenchymal stromal cell surface antigens in both media. When expanded in hPL, both cell types, particularly CSPCs, maintain a spindle-like morphology and lower surface area over more passages than in FBS. Both media supplements support chondrogenic differentiation of CSPCs and ADSCs grown either as monolayers or spheroids. However, chondrogenesis appears less ordered in hPL than FBS, with reduced co-localization of aggrecan and collagen type II in spheroids.

CONCLUSIONS

hPL may be beneficial for the expansion of cells with chondrogenic potential and maintaining stemness, but not for their chondrogenic differentiation for tissue engineering or disease modeling.

Human nasal olfactory stem cells, purified as advanced therapy medicinal products, improve neuronal differentiation

BACKGROUND

Olfactory ecto-mesenchymal stem cells (OE-MSC) are mesenchymal stem cells derived from the lamina propria of the nasal mucosa. They display neurogenic and immunomodulatory properties and were shown to induce recovery in animal models of spinal cord trauma, hearing loss, Parkinsons's disease, amnesia, and peripheral nerve injury. As a step toward clinical practice, we sought to (i) devise a culture protocol that meets the requirements set by human health agencies and (ii) assess the efficacy of stem cells on neuron differentiation.

METHODS

Nasal olfactory mucosa biopsies from three donors were used to design and validate the good manufacturing process for purifying stem cells. All processes and procedures were performed by expert staff from the cell therapy laboratory of the public hospital of Marseille (AP-HM), according to aseptic handling manipulations. Premises, materials and air were kept clean at all times to avoid cross-contamination, accidents, or even fatalities. Purified stem cells were cultivated for 24 or 48 h and conditioned media were collected before being added to the culture medium of the neuroblastoma cell line Neuro2a.

RESULTS

Compared to the explant culture-based protocol, enzymatic digestion provides higher cell numbers more rapidly and is less prone to contamination. The use of platelet lysate in place of fetal calf serum is effective in promoting higher cell proliferation (the percentage of CFU-F progenitors is 15.5%), with the optimal percentage of platelet lysate being 10%. Cultured OE-MSCs do not show chromosomal rearrangement and, as expected, express the usual phenotypic markers of mesenchymal stem cells. When incorporated in standard culture medium, the conditioned medium of purified OE-MSCs promotes cell differentiation of Neuro2a neuroblastoma cells.

CONCLUSION

We developed a safer and more efficient manufacturing process for clinical grade olfactory stem cells. With this protocol, human OE-MSCs will soon be used in a Phase I clinical based on their autologous transplantation in digital nerves with a neglected injury. However, further studies are required to unveil the underlying mechanisms of action.

Evaluation of the Regenerative Potential of Platelet-Lysate and Platelet-Poor Plasma Derived from the Cord Blood Units in Corneal Wound Healing Applications: An In Vitro Comparative Study on Corneal Epithelial Cells

Background: Cord blood platelet lysate (CB-PL) and cord blood platelet poor plasma (CB-PPP) have been applied with success in wound healing applications. Pathologies such as Sjogrens’s Syndrome (SS) and chronic graft versus host disease (cGVHD) can lead to severe ophthalmology issues. The application of CB-PL and CB-PPP may be strongly considered for damaged cornea healing. This study aimed to the evaluation of the beneficial properties of CB-PL and CB-PPP in corneal wound healing applications. Methods: Initially, the CB-PL and CB-PPP were produced from donated cord blood units (CBUs), followed by biochemical analysis. Corneal epithelial cells (CECs) were isolated from wistar rats and then cultured with medium containing 20% v/v either of CB-PL or CB-PPP. To define the impact of CB-PL and CB-PPP, biochemical, morphological analysis, scratch-wound assays, and immunoassays in CECs were performed. Results: CB-PL and CB-PPP were characterized by good biochemical parameters, regarding their quality characteristics and biomolecule content. CECs’ morphological features did not change after their cultivation with CB-PL or CB-PPP. A scratch wound assay and molecular analysis of CECs expanded with CB-PL indicated higher migratory capacity compared to those cultured with CB-PPP. Conclusion: CB-PL and CB-PPP exhibited good properties with respect to cell migration and proliferation, and could be considered an alternative source for eye drop production, to possibly be used in cornea wound healing applications.

Human periodontal ligament stem cell encapsulation in alginate-fibrin-platelet lysate microbeads for dental and craniofacial regeneration

OBJECTIVE

Tissue engineering is promising for dental and craniofacial regeneration. The objectives of this study were to develop a novel xeno-free alginate-fibrin-platelet lysate hydrogel with human periodontal ligament stem cells (hPDLSCs) for dental regeneration, and to investigate the proliferation and osteogenic differentiation of hPDLSCs using hPL as a cell culture nutrient supplement.

METHODS

hPDLSCs were cultured with Dulbecco's modified eagle medium (DMEM), DMEM + 10% fetal bovine serum (FBS), and DMEM + hPL (1%, 2.5%, and 5%). hPDLSCs were encapsulated in alginate-fibrin microbeads (Alg+Fib), alginate-hPL microbeads (Alg+hPL), or alginate-fibrin-hPL microbeads (Alg+Fib+hPL). hPDLSCs encapsulated in alginate microbeads were induced with an osteogenic medium containing hPL or FBS. Quantitative real-time polymerase chain reaction (qRT-PCR), alkaline phosphatase (ALP) activity, ALP staining, and alizarin red (ARS) staining was investigated.

RESULTS

hPDLSCs were released faster from Alg+Fib+hPL than from Alg+hPL. At 14 days, ALP activity was 44.1 ± 7.61 mU/mg for Alg+Fib+hPL group, higher than 28.07 ± 5.15 mU/mg of Alg+Fib (p<0.05) and 0.95 ± 0.2 mU/mg of control (p<0.01). At 7 days, osteogenic genes (ALP, RUNX2, COL1, and OPN) in Alg+Fib+hPL and Alg+Fib were 3-10 folds those of control. At 21 days, the hPDLSC-synthesized bone mineral amount in Alg+Fib+hPL and Alg+Fib was 7.5 folds and 4.3 folds that of control group, respectively.

CONCLUSIONS

The 2.5% hPL was determined to be optimal for hPDLSCs. Adding hPL into alginate hydrogel improved the viability of the hPDLSCs encapsulated in the microbeads. The hPL-based medium enhanced the osteogenic differentiation of hPDLSCs in Alg+Fib+hPL construct, showing a promising xeno-free approach for delivering hPDLSCs to enhance dental, craniofacial and orthopedic regenerations.

In Vitro and Ectopic In Vivo Studies toward the Utilization of Rapidly Isolated Human Nasal Chondrocytes for Single-Stage Arthroscopic Cartilage Regeneration Therapy

Nasal chondrocytes (NCs) have a higher and more reproducible chondrogenic capacity than articular chondrocytes, and the engineered cartilage tissue they generate in vitro has been demonstrated to be safe in clinical applications. Here, we aimed at determining the feasibility for a single-stage application of NCs for cartilage regeneration under minimally invasive settings. In particular, we assessed whether NCs isolated using a short collagenase digestion protocol retain their potential to proliferate and chondro-differentiate within an injectable, swiftly cross-linked and matrix-metalloproteinase (MMP)-degradable polyethylene glycol (PEG) gel enriched with human platelet lysate (hPL). NC-hPL-PEG gels were additionally tested for their capacity to generate cartilage tissue in vivo and to integrate into cartilage/bone compartments of human osteochondral plugs upon ectopic subcutaneous implantation into nude mice. NCs isolated with a rapid protocol and embedded in PEG gels with hPL at low cell density were capable of efficiently proliferating and of generating tissue rich in glycosaminoglycans and collagen II. NC-hPL-PEG gels developed into hyaline-like cartilage tissues upon ectopic in vivo implantation and integrated with surrounding native cartilage and bone tissues. The delivery of NCs in PEG gels containing hPL is a feasible strategy for cartilage repair and now requires further validation in orthotopic in vivo models.

Posology and Serum-/Xeno-Free Engineered Adipose Stromal Cells Cell Sheets

Well-characterized adipose stem cells and chemically defined culture media are important factors that control the production of the cell sheet, used in translational medicine. In this study, we have developed and engineered multilayer adipose stem cell cell sheets (ASCCSs) using chemically defined/serum-free culture media: undifferentiated or differentiated into osteoblasts and chondrocytes. In addition, using the cell sheet transmittance, we estimated the number of cells per cell sheet. Undifferentiated ASCCSs were engineered in 10 days, using serum-free/xeno-free culture media. They were CD29⁺, CD73⁺, CD90⁺, CD105+, HLA-A+, and HLA-DR-. ASCCSs differentiated into chondrocytes and osteoblasts were also engineered using chemically defined and animal-free culture media, in only 14 days. The addition of an ROCK inhibitor improved the chondrocyte cell sheet engineering. The decrease in the cell sheet transmittance rate was higher for the osteoblast cell sheets due to the intracellular Ca²⁺ accumulation. The estimation of cell number per cell sheet was carried out with the transmittance, which will provide important information for cell sheet posology. In conclusion, three types of ASCCSs were engineered using serum-free, xeno-free culture media, expressing their specific markers. Their transmittance measurement allowed estimating the number of cells per cell sheet, with a non-invasive methodology.

Platelet-Rich Plasma Does Not Inhibit Inflammation or Promote Regeneration in Human Osteoarthritic Chondrocytes In Vitro Despite Increased Proliferation

OBJECTIVE

The aims of the study were to assess the anti-inflammatory properties of platelet-rich plasma (PRP) and investigate its regenerative potential in osteoarthritic (OA) human chondrocytes. We hypothesized that PRP can modulate the inflammatory response and stimulate cartilage regeneration.

DESIGN

Primary human chondrocytes from OA knees were treated with manually prepared PRP, after which cell migration and proliferation were assessed. Next, tumor necrosis factor-α-stimulated chondrocytes were treated with a range of concentrations of PRP. Expression of genes involved in inflammation and chondrogenesis was determined by real-time polymerase chain reaction. In addition, chondrocytes were cultured in PRP gels and fibrin gels consisting of increasing concentrations of PRP. The production of cartilage extracellular matrix (ECM) was assessed. Deposition and release of glycosaminoglycans (GAG) and collagen was quantitatively determined and visualized by (immuno)histochemistry. Proliferation was assessed by quantitative measurement of DNA.

RESULTS

Both migration and the inflammatory response were altered by PRP, while proliferation was stimulated. Expression of chondrogenic markers COL2A1 and ACAN was downregulated by PRP, independent of PRP concentration. Chondrocytes cultured in PRP gel for 28 days proliferated significantly more when compared with chondrocytes cultured in fibrin gels. This effect was dose dependent. Significantly less GAGs and collagen were produced by chondrocytes cultured in PRP gels when compared with fibrin gels. This was qualitatively confirmed by histology.

CONCLUSIONS

PRP stimulated chondrocyte proliferation, but not migration. Also, production of cartilage ECM was strongly downregulated by PRP. Furthermore, PRP did not act anti-inflammatory on chondrocytes in an in vitro inflammation model.

Adipose-derived stem cell secretome as a cell-free product for cutaneous wound healing

Chronic wounds continue to be a substantial public health concern contributing to both humanistic and economic burden worldwide. The magnitude of chronic wounds as a global healthcare crisis is likely to increase due to the rising geriatric and diabetic population, demanding novel therapeutic approaches that can restore the functionality of the skin at a reduced cost. Stem cell therapy has been widely acknowledged as a promising strategy for the repair of damaged tissues due to its regenerative potential. This potential attributes to a concoction of bioactive molecules secreted by the stem cells, collectively called the secretome, that mediates paracrine and autocrine functions. Among the stem cell types, adipose tissue-derived mesenchymal stem cells (ADMSCs) have been receiving increased attention for its ease of isolation, abundance in tissue and notable impact on improving chronic wound healing. Owing to the reported advantages of cell-free preparations like the secretome over cellular products, developing secretome as a ready-to-use product for wound healing applications seems promising. In this review, we discuss the functional benefits of adipose stem cell secretome in wound healing, the techniques to enrich the secretome and the recommendations for the scale-up and commercialization of secretome products.

Human platelet lysate - A potent (and overlooked) orthobiologic

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

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

Isolation and characterization of bone marrow-derived mesenchymal stem cells in Xenopus laevis

Mesenchymal stem cells (MSCs) are multipotent cells that exist in mesenchymal tissues such as bone marrow and are able to differentiate into osteocytes, chondrocytes, and adipocytes. MSCs are generally collected as adherent cells on a plastic dish, and are positive for markers such as CD44, CD73, CD90, CD105 and CD166, and negative for CD11b, CD14, CD19, CD31, CD34, CD45, CD79a and HLA-DR. MSCs have been established from many kinds of mammals, but MSCs from amphibians have not yet been reported. We cultured adherent cells from the bone marrow of Xenopus laevis by modifying the protocol for culturing mammalian MSCs. The morphology of these cells was similar to that of mammalian MSCs. The amphibian MSCs were positive for cd44, cd73, cd90 and cd166, and negative for cd11b, cd14, cd19, cd31, cd34, cd45, cd79a and hla-dra. Moreover, they could be induced to differentiate into osteocyte-, chondrocyte-, and adipocyte-lineage cells by cytokine induction systems that were similar to those used for mammalian MSC differentiation. Thus, they are considered to be similar to mammalian MSCs. Unlike mammals, amphibians have high regenerative capacity. The findings from the present study will allow for future research to reveal how Xenopus MSCs are involved in the amphibian regenerative capacity and to elucidate the differences in the regenerative capacity between mammals and amphibians.

Human Platelet Lysate Acts Synergistically With Laminin to Improve the Neurotrophic Effect of Human Adipose-Derived Stem Cells on Primary Neurons in vitro

Background

Despite the advancements in microsurgical techniques and noteworthy research in the last decade, peripheral nerve lesions have still weak functional outcomes in current clinical practice. However, cell transplantation of human adipose-derived stem cells (hADSC) in a bioengineered conduit has shown promising results in animal studies. Human platelet lysate (hPL) has been adopted to avoid fetal bovine serum (FBS) in consideration of the biosafety concerns inherent with the use of animal-derived products in tissue processing and cell culture steps for translational purposes. In this work, we investigate how the interplay between hPL-expanded hADSC (hADSC^hPL) and extracellular matrix (ECM) proteins influences key elements of nerve regeneration.

Methods

hADSC were seeded on different ECM coatings (laminin, LN; fibronectin, FN) in hPL (or FBS)-supplemented medium and co-cultured with primary dorsal root ganglion (DRG) to establish the intrinsic effects of cell–ECM contact on neural outgrowth. Co-cultures were performed “direct,” where neural cells were seeded in contact with hADSC expanded on ECM-coated substrates (contact effect), or “indirect,” where DRG was treated with their conditioned medium (secretome effect). Brain-derived nerve factor (BDNF) levels were quantified. Tissue culture plastic (TCPS) was used as the control substrate in all the experiments.

Results

hPL as supplement alone did not promote higher neurite elongation than FBS when combined with DRG on ECM substrates. However, in the presence of hADSC, hPL could dramatically enhance the stem cell effect with increased DRG neurite outgrowth when compared with FBS conditions, regardless of the ECM coating (in both indirect and direct co-cultures). The role of ECM substrates in influencing neurite outgrowth was less evident in the FBS conditions, while it was significantly amplified in the presence of hPL, showing better neural elongation in LN conditions when compared with FN and TCPS. Concerning hADSC growth factor secretion, ELISA showed significantly higher concentrations of BDNF when cells were expanded in hPL compared with FBS-added medium, without significant differences between cells cultured on the different ECM substrates.

Conclusion

The data suggest how hADSC grown on LN and supplemented with hPL could be active and prone to support neuron–matrix interactions. hPL enhanced hADSC effects by increasing both proliferation and neurotrophic properties, including BDNF release.

Breast Cancer Reconstruction: Design Criteria for a Humanized Microphysiological System

International regulatory agencies such as the Food and Drug Administration have mandated that the scientific community develop humanized microphysiological systems (MPS) as an in vitro alternative to animal models in the near future. While the breast cancer research community has long appreciated the importance of three-dimensional growth dynamics in their experimental models, there are remaining obstacles preventing a full conversion to humanized MPS for drug discovery and pathophysiological studies. This perspective evaluates the current status of human tissue-derived cells and scaffolds as building blocks for an "idealized" breast cancer MPS based on bioengineering design principles. It considers the utility of adipose tissue as a potential source of endothelial, lymphohematopoietic, and stromal cells for the support of breast cancer epithelial cells. The relative merits of potential MPS scaffolds derived from adipose tissue, blood components, and synthetic biomaterials is evaluated relative to the current "gold standard" material, Matrigel, a murine chondrosarcoma-derived basement membrane-enriched hydrogel. The advantages and limitations of a humanized breast cancer MPS are discussed in the context of in-process and destructive read-out assays. Impact statement Regulatory authorities have highlighted microphysiological systems as an emerging tool in breast cancer research. This has been led by calls for more predictive human models and reduced animal experimentation. This perspective describes how human-derived cells, extracellular matrices, and hydrogels will provide the building blocks to create breast cancer models that accurately reflect diversity at multiple levels, that is, patient ethnicity, pathophysiology, and metabolic status.

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.

Xeno-free approach for the expansion of human adipose derived mesenchymal stem cells for ocular therapies

To restore corneal transparency and vision loss after an injury on the ocular surface, the use of human stem cells from different origins has been recently proposed. Mesenchymal stem cells (MSCs) seem to be an appropriate adult source of autologous stem cells due to their accessibility, high proliferation rate, and multipotent capacity. In this work, we developed a simple culture system to prepare a graft based on a fibrin membrane seeded with human MSCs. A commercial kit, PRGF Endoret®, was used to prepare both, the growth factors used as culture media supplement and the fibrin membrane grafts. Adipose-derived MSCs (Ad-MSCs) were expanded, characterised by flow cytometry and their multilineage differentiation potential confirmed by inducing adipogenesis, osteogenesis and chondrogenesis. Ad-MSCs seeded on the fibrin membranes were grafted onto athymic mice showing good biocompatibility with no adverse reactions observed during the follow up period. These findings support the assumption that a system in which all the biological components (cells, grow factors and carrier) are autologous, could potentially be used for future ex vivo expansion of Ad-MSCs to treat ocular conditions such as an inflammatory milieu, traumatic scars and loss of the regenerative capacity of the corneal epithelium that compromise the quality of vision.

In Vitro Oxygen-Glucose Deprivation-Induced Stroke Models with Human Neuroblastoma Cell- and Induced Pluripotent Stem Cell-Derived Neurons

Stroke is a devastating neurological disorder and one of the leading causes of mortality and disability. To understand the cellular and molecular mechanisms of stroke and to develop novel therapeutic approaches, two different in vitro human cell-based stroke models were established using oxygen-glucose deprivation (OGD) conditions. In addition, the effect of adipose stem cells (ASCs) on OGD-induced injury was studied. In the present study, SH-SY5Y human neuroblastoma cells and human induced pluripotent stem cells (hiPSCs) were differentiated into neurons, cultured under OGD conditions (1% O₂) for 24 h, and subjected to a reperfusion period for 24 or 72 h. After OGD, ASCs were cocultured with neurons on inserts for 24 or 72 h to study the neuroprotective potential of ASCs. The effect of OGD and ASC coculture on the viability, apoptosis, and proliferation of and axonal damage to neuronal cells was studied. The results showed that OGD conditions induced cytotoxicity and apoptosis of SH-SY5Y- and hiPSC-derived neurons, although more severe damage was detected in SH-SY5Y-derived neurons than in hiPSC-derived neurons. Coculture with ASCs was protective for neurons, as the number of dead ASC-cocultured neurons was lower than that of control cells, and coculture increased the proliferation of both cell types. To conclude, we developed in vitro human cell-based stroke models in SH-SY5Y- and hiPSC-derived neurons. This was the first time hiPSCs were used to model stroke in vitro. Since OGD had different effects on the studied cell types, this study highlights the importance of using several cell types in in vitro studies to confirm the outcomes of the study. Here, ASCs exerted a neuroprotective effect by increasing the proliferation and decreasing the death of SH-SY5Y- and hiPSC-derived neurons after OGD.

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.

Human platelet lysate as a potential clinical-translatable supplement to support the neurotrophic properties of human adipose-derived stem cells

Background

The autologous nerve graft, despite its donor site morbidity and unpredictable functional recovery, continues to be the gold standard in peripheral nerve repair. Rodent research studies have shown promising results with cell transplantation of human adipose-derived stem cells (hADSC) in a bioengineered conduit, as an alternative strategy for nerve regeneration. To achieve meaningful clinical translation, cell therapy must comply with biosafety. Cell extraction and expansion methods that use animal-derived products, including enzymatic adipose tissue dissociation and the use of fetal bovine serum (FBS) as a culture medium supplement, have the potential for transmission of zoonotic infectious and immunogenicity. Human-platelet-lysate (hPL) serum has been used in recent years in human cell expansion, showing reliability in clinical applications.

Methods

We investigated whether hADSC can be routinely isolated and cultured in a completely xenogeneic-free way (using hPL culture medium supplement and avoiding collagenase digestion) without altering their physiology and stem properties. Outcomes in terms of stem marker expression (CD105, CD90, CD73) and the osteocyte/adipocyte differentiation capacity were compared with classical collagenase digestion and FBS-supplemented hADSC expansion.

Results

We found no significant differences between the two examined extraction and culture protocols in terms of cluster differentiation (CD) marker expression and stem cell plasticity, while hADSC in hPL showed a significantly higher proliferation rate when compared with the usual FBS-added medium. Considering the important key growth factors (particularly brain-derived growth factor (BDNF)) present in hPL, we investigated a possible neurogenic commitment of hADSC when cultured with hPL. Interestingly, hADSC cultured in hPL showed a statistically higher secretion of neurotrophic factors BDNF, glial cell-derived growth factor (GDNF), and nerve-derived growth factor (NFG) than FBS-cultured cells. When cocultured in the presence of primary neurons, hADSC which had been grown under hPL supplementation, showed significantly enhanced neurotrophic properties.

Conclusions

The hPL-supplement medium could improve cell proliferation and neurotropism while maintaining stable cell properties, showing effectiveness in clinical translation and significant potential in peripheral nerve research.

Influence of platelet storage time on human platelet lysates and platelet lysate-expanded mesenchymal stromal cells for bone tissue engineering

Background

Human platelet lysate (HPL) is emerging as the preferred xeno-free supplement for the expansion of mesenchymal stromal cells (MSCs) for bone tissue engineering (BTE) applications. Due to a growing demand, the need for standardization and scaling-up of HPL has been highlighted. However, the optimal storage time of the source material, i.e., outdated platelet concentrates (PCs), remains to be determined. The present study aimed to determine the optimal storage time of PCs in terms of the cytokine content and biological efficacy of HPL.

Methods

Donor-matched bone marrow (BMSCs) and adipose-derived MSCs (ASCs) expanded in HPL or fetal bovine serum (FBS) were characterized based on in vitro proliferation, immunophenotype, and multi-lineage differentiation. Osteogenic differentiation was assessed at early (gene expression), intermediate [alkaline phosphatase (ALP) activity], and terminal stages (mineralization). Using a multiplex immunoassay, the cytokine contents of HPLs produced from PCs stored for 1–9 months were screened and a preliminary threshold of 4 months was identified. Next, HPLs were produced from PCs stored for controlled durations of 0, 1, 2, 3, and 4 months, and their efficacy was compared in terms of cytokine content and BMSCs’ proliferation and osteogenic differentiation.

Results

BMSCs and ASCs in both HPL and FBS demonstrated a characteristic immunophenotype and multi-lineage differentiation; osteogenic differentiation of BMSCs and ASCs was significantly enhanced in HPL vs. FBS. Multiplex network analysis of HPL revealed several interacting growth factors, chemokines, and inflammatory cytokines. Notably, stem cell growth factor (SCGF) was detected in high concentrations. A majority of cytokines were elevated in HPLs produced from PCs stored for ≤ 4 months vs. > 4 months. However, no further differences in PC storage times between 0 and 4 months were identified in terms of HPLs’ cytokine content or their effects on the proliferation, ALP activity, and mineralization of BMSCs from multiple donors.

Conclusions

MSCs expanded in HPL demonstrate enhanced osteogenic differentiation, albeit with considerable donor variation. HPLs produced from outdated PCs stored for up to 4 months efficiently supported the proliferation and osteogenic differentiation of MSCs. These findings may facilitate the standardization and scaling-up of HPL from outdated PCs for BTE applications.

Characterization and Proteomic Analysis of Decellularized Adipose Tissue Hydrogels Derived from Lean and Overweight/Obese Human Donors

While decellularized adipose tissue (DAT) has potential as an "off-the-shelf" biomaterial product for regenerative medicine, it remains to be determined if donor-source body mass index (BMI) impacts the functionality of DAT. This study set out to comparatively characterize lean versus overweight/obese-donor derived DAT hydrogel based on proteome and to analyze their respective effects on adipose stromal/stem cell (ASC) viability, and differentiation in vitro. Decellularized adipose tissue from lean (lDAT) and overweight/obese (oDAT) donors is produced and characterized. Variability in the fibril microstructures is found, with dense fibrotic fiber clusters and large pore area uniquely present in the oDAT samples. Proteomic analysis reveals that lDAT contains a greater proportion of enriched extracellular proteins and a smaller proportion of enriched intracellular proteins relative to oDAT. Biocompatibility studies show that ASCs cultured in lDAT and oDAT hydrogels remain viable. The adipogenic and osteogenic differentiation capability of ASCs seeded in lDAT and oDAT hydrogels is confirmed by an upregulation in marker gene expression and phenotypic analysis. In conclusion, this study establishes that DAT hydrogels derived from lean and overweight/obese adipose donors present similar physicochemical profiles with some distinctive features while comparably supporting the viability and adipogenic differentiation of ASCs in vitro.

In Vitro Cultures of Adipose-Derived Stem Cells: An Overview of Methods, Molecular Analyses, and Clinical Applications

Adipose-derived stem cells (ASCs) exhibiting mesenchymal stem cell (MSC) characteristics, have been extensively studied in recent years. Because they have been shown to differentiate into lineages such as osteogenic, chondrogenic, neurogenic or myogenic, the focus of most of the current research concerns either their potential to replace bone marrow as a readily available and abundant source of MSCs, or to employ them in regenerative and reconstructive medicine. There is close to consensus regarding the methodology used for ASC isolation and culture, whereas a number of molecular analyses implicates them in potential therapies of a number of pathologies. When it comes to clinical application, there is a range of examples of animal trials and clinical studies employing ASCs, further emphasizing the advancement of studies leading to their more widespread use. Nevertheless, in vitro studies will most likely continue to play a significant role in ASC studies, both providing the molecular knowledge of their ex vivo properties and possibly serving as an important step in purification and application of those cells in a clinical setting. Therefore, it is important to consider current methods of ASC isolation, culture, and processing. Furthermore, molecular analyses and cell surface properties of ASCs are essential for animal studies, clinical studies, and therapeutic applications of the MSC properties.

Supervivencia de células fibroblásticas humanas en ausencia de suplementación

Introducción. Los fibroblastos gingivales (FGs) son células del tejido conjuntivo gingival que han tomado en los últimos años una relevancia promisoria por su probable utilización en la terapia celular, dadas sus capacidades de multipotencialidad y de autorrenovación. Objetivo. Conocer y describir el impacto de la ausencia en la suplementación de Suero Fetal Bovino (SFB) en la supervivencia de fibroblastos gingivales en cultivos. Materiales y métodos. Fibroblastos gingivales fueron aislados de tejido gingival de pacientes sanos y cultivados en medios de cultivos DMEM (Dulbecco’s Modified of Eagle Medium) en ausencia y suplementados con 0.2% de SFB a 37°C en una atmósfera húmeda con 5% de CO2. Se llevó a cabo una evaluación morfológica, de supervivencia y proliferación de los FGs, así como la identificación mediante la técnica de inmunofluorescencia de marcadores del citoesqueleto celular como la actina y mitocondrias. Resultados. Los FGs cultivados en ausencia y con suplementación de 0.2% de SFB evidenciaron una forma fusiforme, con núcleos ovalados y numerosas prolongaciones citoplasmáticas durante el tiempo de cultivo. Un leve aumento en la proliferación de FGs fue observado en aquellas células en contacto con el medio DMEM+0.2% de SFB comparadas con el medio donde estuvo ausente la suplementación. El inmunomarcaje de la actina y las mitocondrias dejó en evidencia que la ausencia y suplementación a 0.2% de SFB no afectó su localización en los FGs evaluados. Conclusión. Los fibroblastos gingivales sobreviven y proliferan en ausencia de SFB, conservando sus características morfológicas celulares.

Hopes and Limits of Adipose-Derived Stem Cells (ADSCs) and Mesenchymal Stem Cells (MSCs) in Wound Healing

Adipose tissue derived stem cells (ADSCs) are mesenchymal stem cells identified within subcutaneous tissue at the base of the hair follicle (dermal papilla cells), in the dermal sheets (dermal sheet cells), in interfollicular dermis, and in the hypodermis tissue. These cells are expected to play a major role in regulating skin regeneration and aging-associated morphologic disgraces and structural deficits. ADSCs are known to proliferate and differentiate into skin cells to repair damaged or dead cells, but also act by an autocrine and paracrine pathway to activate cell regeneration and the healing process. During wound healing, ADSCs have a great ability in migration to be recruited rapidly into wounded sites added to their differentiation towards dermal fibroblasts (DF), endothelial cells, and keratinocytes. Additionally, ADSCs and DFs are the major sources of the extracellular matrix (ECM) proteins involved in maintaining skin structure and function. Their interactions with skin cells are involved in regulating skin homeostasis and during healing. The evidence suggests that their secretomes ensure: (i) The change in macrophages inflammatory phenotype implicated in the inflammatory phase, (ii) the formation of new blood vessels, thus promoting angiogenesis by increasing endothelial cell differentiation and cell migration, and (iii) the formation of granulation tissues, skin cells, and ECM production, whereby proliferation and remodeling phases occur. These characteristics would be beneficial to therapeutic strategies in wound healing and skin aging and have driven more insights in many clinical investigations. Additionally, it was recently presented as the tool key in the new free-cell therapy in regenerative medicine. Nevertheless, ADSCs fulfill the general accepted criteria for cell-based therapies, but still need further investigations into their efficiency, taking into consideration the host-environment and patient-associated factors.

Human Adipose-Derived Hydrogel Characterization Based on In Vitro ASC Biocompatibility and Differentiation

Hydrogels serve as three-dimensional scaffolds whose composition can be customized to allow attachment and proliferation of several different cell types. Extracellular matrix-derived hydrogels are considered close replicates of the tissue microenvironment. They can serve as scaffolds for in vitro tissue engineering and are a useful tool to study cell-scaffold interaction. The aim of the present study was to analyze the effect of adipose-derived stromal/stem cells (ASCs) and decellularized adipose tissue-derived (DAT) hydrogel interaction on ASC morphology, proliferation, differentiation, and DAT hydrogel microstructure. First, the ASCs were characterized using flow cytometry, adipogenic/osteogenic differentiation, colony-forming unit fibroblast assay and doubling time. The viability and proliferation assays showed that ASCs seeded in DAT hydrogel at different concentrations and cultured for 21 days remained viable and displayed proliferation. ASCs were seeded on DAT hydrogel and cultured in stromal, adipogenic, or osteogenic media for 14 or 28 days. The analysis of adipogenic differentiation demonstrated the upregulation of adipogenic marker genes and accumulation of oil droplets in the cells. Osteogenic differentiation demonstrated the upregulation of osteogenic marker genes and mineral deposition in the DAT hydrogel. The analysis of DAT hydrogel fiber metrics revealed that ASC seeding, and differentiation altered both the diameter and arrangement of fibers in the matrix. Matrix metalloproteinase-2 (MMP-2) activity was assessed to determine the possible mechanism for DAT hydrogel remodeling. MMP-2 activity was observed in all ASC seeded samples, with the osteogenic samples displaying the highest MMP-2 activity. These findings indicate that DAT hydrogel is a cytocompatible scaffold that supports the adipogenic and osteogenic differentiation of ASCs. Furthermore, the attachment of ASCs and differentiation along adipogenic and osteogenic lineages remodels the microstructure of DAT hydrogel.