Platelet lysate supports the in vitro expansion of human periodontal ligament stem cells for cytotherapeutic use

Biomarkers for intervertebral disc and associated back pain: From diagnosis to disease prognosis and personalized treatment

Biomarkers are commonly recognized as objective indicators of a medical state or clinical outcome and have been widely used as clinical and diagnostic tools and surrogate endpoints in many pathological conditions. In the context of intervertebral disc (IVD) and associated back pain, also known as degenerative disc disease (DDD), the use of biomarkers has been poorly explored. DDD is currently diagnosed using imaging techniques and subjective pain scales, limiting an objective association between DDD and pain levels, as well as an evaluation of disease progression. There is a need for objective and reliable measurements for DDD, pain and pathology progression. DDD predictors could also help clinicians in deciding on the optimal treatment for distinct patient groups. This review addresses the current candidate biomarkers in DDD, including imaging, genetic, metabolite and protein-based parameters, both at the tissue and systemic levels, that may become a major advance in the diagnosis and prognosis of the disease, as well as in the management of therapeutic approaches to DDD.

A Review of Novel Strategies for Human Periodontal Ligament Stem Cell Ex Vivo Expansion: Are They an Evidence-Based Promise for Regenerative Periodontal Therapy?

Periodontitis is a gingiva disease sustained by microbially associated and host-mediated inflammation that results in the loss of the connective periodontal tissues, including periodontal ligament and alveolar bone. Symptoms include swollen gingiva, tooth loss and, ultimately, ineffective mastication. Clinicians utilize regenerative techniques to rebuild and recover damaged periodontal tissues, especially in advanced periodontitis. Human periodontal ligament stem cells (hPDLSCs) are considered an appealing source of stem cells for regenerative therapy in periodontium. hPDLSCs manifest the main properties of mesenchymal stem cells, including the ability to self-renew and to differentiate in mesodermal cells. Significant progress has been made for clinical application of hPDLSCs; nevertheless, some problems remain, including the small number of cells isolated from each sample. In recent decades, hPDLSC ex vivo expansion and differentiation have been improved by modifying cell culture conditions, especially with the supplementation of cytokines' or growth factors' mix, chemicals, and natural compounds, or by using the decellularized extracellular matrix. Here, we analyzed the changes in stemness properties and differentiation potential of hPDLSCs when culturing in alternative media. In addition, we focused on the possibility of replacing FBS with human emoderivates to minimize the risks of xenoimmunization or zoonotic transmission when cells are expanded for therapeutic purposes.

Human Platelet Lysate Maintains Stemness of Umbilical Cord-Derived Mesenchymal Stromal Cells and Promote Lung Repair in Rat Bronchopulmonary Dysplasia

Mesenchymal stromal cells (MSCs) show potential for treating preclinical models of newborn bronchopulmonary dysplasia (BPD), but studies of their therapeutic effectiveness have had mixed results, in part due to the use of different media supplements for MSCs expansion in vitro. The current study sought to identify an optimal culture supplement of umbilical cord-derived MSCs (UC-MSCs) for BPD therapy. In this study, we found that UC-MSCs cultured with human platelet lysate (hPL-UCMSCs) were maintained a small size from Passage 1 (P1) to P10, while UC-MSCs cultured with fetal bovine serum (FBS-UCMSCs) became wide and flat. Furthermore, hPL was associated with lower levels of senescence in UC-MSCs during in vitro expansion compared with FBS, as indicated by the results of β-galactosidase staining and measures of senescence-related genes (CDKN2A, CDKN1A, and mTOR). In addition, hPL enhanced the proliferation and cell viability of the UC-MSCs and reduced their doubling time in vitro. Compared with FBS-UCMSCs, hPL-UCMSCs have a greater potential to differentiate into osteocytes and chondrocytes. Moreover, using hPL resulted in greater expression of Nestin and specific paracrine factors (VEGF, TGF-β1, FGF2, IL-8, and IL-6) in UC-MSCs compared to using FBS. Critically, we also found that hPL-UCMSCs are more effective than FBS-UCMSCs for the treatment of BPD in a rat model, with hPL leading to improvements in survival rate, lung architecture and fibrosis, and lung capillary density. Finally, qPCR of rat lung mRNA demonstrated that hPL-UCMSCs had lower expression levels of inflammatory factors (TNF-α and IL-1β) and a key chemokine (MCP-1) at postnatal day 10, and there was significant reduction of CD68⁺ macrophages in lung tissue after hPL-UCMSCs transplantation. Altogether, our findings suggest that hPL is an optimal culture supplement for UC-MSCs expansion in vitro, and that hPL-UCMSCs promote lung repair in rat BPD disease.

Xeno-Free Spheroids of Human Gingiva-Derived Progenitor Cells for Bone Tissue Engineering

Gingiva has been identified as a minimally invasive source of multipotent progenitor cells (GPCs) for use in bone tissue engineering (BTE). To facilitate clinical translation, it is important to characterize GPCs in xeno-free cultures. Recent evidence indicates several advantages of three-dimensional (3D) spheroid cultures of mesenchymal stromal cells (MSCs) over conventional 2D monolayers. The present study aimed to characterize human GPCs in xeno-free 2D cultures, and to test their osteogenic potential in 3D cultures, in comparison to bone marrow MSCs (BMSCs). Primary GPCs and BMSCs were expanded in human platelet lysate (HPL) or fetal bovine serum (FBS) and characterized based on in vitro proliferation, immunophenotype and multi-lineage differentiation. Next, 3D spheroids of GPCs and BMSCs were formed via self-assembly and cultured in HPL. Expression of stemness- (SOX2, OCT4, NANOG) and osteogenesis-related markers (BMP2, RUNX2, OPN, OCN) was assessed at gene and protein levels in 3D and 2D cultures. The cytokine profile of 3D and 2D GPCs and BMSCs was assessed via a multiplex immunoassay. Monolayer GPCs in both HPL and FBS demonstrated a characteristic MSC-like immunophenotype and multi-lineage differentiation; osteogenic differentiation of GPCs was enhanced in HPL vs. FBS. CD271⁺ GPCs in HPL spontaneously acquired a neuronal phenotype and strongly expressed neuronal/glial markers. 3D spheroids of GPCs and BMSCs with high cell viability were formed in HPL media. Expression of stemness- and osteogenesis-related genes was significantly upregulated in 3D vs. 2D GPCs/BMSCs; the latter was independent of osteogenic induction. Synthesis of SOX2, BMP2 and OCN was confirmed via immunostaining, and in vitro mineralization via Alizarin red staining. Finally, secretion of several growth factors and chemokines was enhanced in GPC/BMSC spheroids, while that of pro-inflammatory cytokines was reduced, compared to monolayers. In summary, monolayer GPCs expanded in HPL demonstrate enhanced osteogenic differentiation potential, comparable to that of BMSCs. Xeno-free spheroid culture further enhances stemness- and osteogenesis-related gene expression, and cytokine secretion in GPCs, comparable to that of BMSCs.

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

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

Autologous plasma rich in growth factors technology for isolation and ex vivo expansion of human dental pulp stem cells for clinical translation

AIM

This study investigated the use of the autologous technology of plasma rich in growth factors (PRGF) as a human-based substitute to fetal bovine serum (FBS) in the culture of human dental pulp stem cells.

MATERIALS & METHODS

Stem cell characterization was performed. Analysis of isolation, proliferation, migration, trilineage differentiation, senescence and cryopreservation were compared between FBS and PRGF.

RESULTS

Human dental pulp stem cell cultures isolated and maintained with PRGF showed a significantly higher number of cells per explant than FBS cultures. Cell proliferation, migration, osteogenic mineralization and adipogenic differentiation were found to be significantly higher in PRGF than FBS.

CONCLUSION

The autologous PRGF technology could be a suitable and safer substitute for FBS as a culture medium supplement for clinical translation of cell therapy.

Comparative effect of platelet-rich plasma, platelet-poor plasma, and fetal bovine serum on the proliferative response of periodontal ligament cell subpopulations

OBJECTIVES

Cell-based therapies involve the need to expand cell cultures ex vivo for their subsequent implantation in an autologous manner. An important limitation regarding this technology is the use of fetal bovine serum (FBS) that has critical safety limitations. Platelet-derived fractions represent an autologous source of growth factors that may be used for the expansion of these cell cultures. Periodontal ligament (PDL) cells comprise a heterogeneous cell population that may not necessarily respond in a uniform manner to proliferative stimuli. The aim of this study was to evaluate the ability of two platelet-derived fractions, platelet-rich plasma (PRP) and platelet-poor plasma (PPP) and FBS on the proliferative response of different subpopulations of PDL cell cultures.

MATERIALS AND METHODS

PDL cells were characterized and then exposed to PRP, PPP, or FBS during 2, 5, or 14 days to analyze cell proliferation and clonogenic capability. Cell proliferation was evaluated through immunofluorescence for Ki67 and by tracing carboxyfluorescein diacetate succinimidyl ester (CFSE) dye in combination with mesenchymal stem cell markers using flow cytometry.

RESULTS

Both PRP and PPP stimulated PDL cell proliferation and their clonogenic ability. We found a significant increase of CD73- and CD90-positive cells after PRP or PPP treatment, compared to FBS. Otherwise, no differences were found regarding the response of CD146-or CD105-positive cells when stimulated with PRP, PPP, or FBS.

CONCLUSION

PRP and PPP can stimulate the proliferation and clonogenicity of PDL cell populations including cells positive for CD90 and CD73 markers.

CLINICAL RELEVANCE

These findings may have implications for future therapies aiming to stimulate periodontal regeneration using autologous growth factors.

Hyaluronic acid hydrogels incorporating platelet lysate enhance human pulp cell proliferation and differentiation

The restoration of dentine-pulp complex remains a challenge for dentists; nonetheless, it has been poorly addressed. An ideal system should modulate the host response, as well as enable the recruitment, proliferation and differentiation of relevant progenitor cells. Herein was proposed a photocrosslinkable hydrogel system based on hyaluronic acid (HA) and platelet lysate (PL). PL is a cocktail of growth factors (GFs) and cytokines involved in wound healing orchestration, obtained by the cryogenic processing of platelet concentrates, and was expected to provide the HA hydrogels specific biochemical cues to enhance pulp cells' recruitment, proliferation and differentiation. Stable HA hydrogels incorporating PL (HAPL) were prepared after photocrosslinking of methacrylated HA (Met-HA) previously dissolved in PL, triggered by the Ultra Violet activated photoinitiator Irgacure 2959. Both the HAPL and plain HA hydrogels were shown to be able to recruit cells from a cell monolayer of human dental pulp stem cells (hDPSCs) isolated from permanent teeth. The hDPCs were also seeded directly over the hydrogels (5 × 10⁴ cells/hydrogel) and cultured in osteogenic conditions. Cell metabolism and DNA quantification were higher, in all time-points, for PL supplemented hydrogels (p < 0,05). Alkaline phosphatase (ALPL) activity and calcium quantification peaks were observed for the HAPL group at 21 days (p < 0,05). The gene expression for ALPL and COLIA1 was up-regulated at 21 days to HAPL, compared with HA group (p < 0,05). Within the same time point, the gene expression for RUNX2 did not differ between the groups. Overall, data demonstrated that the HA hydrogels incorporating PL increased the cellular metabolism and stimulate the mineralized matrix deposition by hDPSCs, providing clear evidence of the potential of the proposed system for the repair of damaged pulp/dentin tissue and endodontics regeneration.

Macrophage involvement affects matrix stiffness-related influences on cell osteogenesis under three-dimensional culture conditions

Accumulating evidence indicates that the physicochemical properties of biomaterials exert profound influences on stem cell fate decisions. However, matrix-based regulation selected through in vitro analyses based on a given cell population do not genuinely reflect the in vivo conditions, in which multiple cell types are involved and interact dynamically. This study constitutes the first investigation of how macrophages (Mφs) in stiffness-tunable transglutaminase cross-linked gelatin (TG-gel) affect the osteogenesis of bone marrow-derived mesenchymal stem cells (BMMSCs). When a single cell type was cultured, low-stiffness TG-gels promoted BMMSC proliferation, whereas high-stiffness TG-gels supported cell osteogenic differentiation. However, Mφs in high-stiffness TG-gels were more likely to polarize toward the pro-inflammatory M1 phenotype. Using either conditioned medium (CM)-based incubation or Transwell-based co-culture, we found that Mφs encapsulated in the low-stiffness matrix exerted a positive effect on the osteogenesis of co-cultured BMMSCs. Conversely, Mφs in high-stiffness TG-gels negatively affected cell osteogenic differentiation. When both cell types were cultured in the same TG-gel type and placed into the Transwell system, the stiffness-related influences of Mφs on BMMSCs were significantly altered; both the low- and high-stiffness matrix induced similar levels of BMMSC osteogenesis. Although the best material parameter for synergistically affecting Mφs and BMMSCs remains unknown, our data suggest that Mφ involvement in the co-culture system alters previously identified material-related influences on BMMSCs, such as matrix stiffness-related effects, which were identified based on a culture system involving a single cell type. Such Mφ-stem cell interactions should be considered when establishing proper matrix parameter-associated cell regulation in the development of biomimetic biomaterials for regenerative applications.

STATEMENT OF SIGNIFICANCE

The substrate stiffness of a scaffold plays critical roles in modulating both reparative cells, such as mesenchymal stem cells (MSCs), and immune cells, such as macrophages (Mφs). Although the influences of material stiffness on either Mφs or MSCs, have been extensively described, how the two cell types respond to matrix cues to dynamically affect each other in a three-dimensional (3D) biosystem remains largely unknown. Here, we report our findings that, in a platform wherein Mφs and bone marrow-derived MSCs coexist, matrix stiffness can influence stem cell fate through both direct matrix-associated regulation and indirect Mφ-based modulation. Our data support future studies of the MSC-Mφ-matrix interplay in the 3D context to optimize matrix parameters for the development of the next biomaterial.

Plasma Rich in Growth Factors Induces Cell Proliferation, Migration, Differentiation, and Cell Survival of Adipose-Derived Stem Cells

Adipose-derived stem cells (ASCs) are a promising therapeutic alternative for tissue repair in various clinical applications. However, restrictive cell survival, differential tissue integration, and undirected cell differentiation after transplantation in a hostile microenvironment are complications that require refinement. Plasma rich in growth factors (PRGF) from platelet-rich plasma favors human and canine ASC survival, proliferation, and delaying human ASC senescence and autophagocytosis in comparison with serum-containing cultures. In addition, canine and human-derived ASCs efficiently differentiate into osteocytes, adipocytes, or chondrocytes in the presence of PRGF. PRGF treatment induces phosphorylation of AKT preventing ASC death induced by lethal concentrations of hydrogen peroxide. Indeed, AKT inhibition abolished the PRGF apoptosis prevention in ASC exposed to 100 μM of hydrogen peroxide. Here, we show that canine ASCs respond to PRGF stimulus similarly to the human cells regarding cell survival and differentiation postulating the use of dogs as a suitable translational model. Overall, PRGF would be employed as a serum substitute for mesenchymal stem cell amplification to improve cell differentiation and as a preconditioning agent to prevent oxidative cell death.

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.

The Alpha 7 Nicotinic Acetylcholine Receptor of Deciduous Dental Pulp Stem Cells Regulates Osteoclastogenesis During Physiological Root Resorption

The physiological root resorption of deciduous teeth is a normal phenomenon, but the mechanisms underlying this process are still unclear. In this study, deciduous dental pulp stem cells (DDPSCs) and permanent dental pulp stem cells (DPSCs) were derived from deciduous teeth and normal permanent teeth at different stages of resorption. In the middle stage of root resorption, DDPSCs exhibited an increase in the ability to induce osteoclast differentiation. Activation of the alpha 7 nicotinic acetylcholine receptor (α7 nAChR) by secretory mammalian Ly-6 urokinase-type plasminogen activator receptor-associated protein 1 (SLURP-1) caused a significant increase in the expression levels of NF-κB, receptor activator of nuclear factor-kappa B ligand (RANKL), and the ratio of RANKL/osteoprotegerin (OPG). These effects were inhibited by alpha-bungarotoxin (α-BTX). Furthermore, the expression levels of RANKL/OPG were significantly reduced following inhibition of NF-κB. High-strength, dynamic positive pressure increased the expression of SLURP-1 and α7 nAChR in DDPSCs in the stable stage. These data indicated that mechanical stress stimulated the expression of SLURP-1 and α7 nAChR in DDPSCs. Additionally, SLURP-1 activated α7 nAChR, thereby upregulating the expression of NF-κB and enhancing its activity, thus regulating RANKL/OPG expression and affecting the ability of DDPSCs to influence osteoclastogenesis, which likely enhances root resorption and leads to the physiological loss of deciduous teeth.

Efficacy of Human Platelet Rich Fibrin Exudate vs Fetal Bovine Serum on Proliferation and Differentiation of Dental Pulp Stem Cells

Background and Objectives

The imperative role of dental pulp stem cells (DPSCs) in regenerative therapy demands an in-vitro expansion which must deal with the safety and ethical problems associated with fetal bovine serum (FBS). The primary aim of this study was to compare the effects of human platelet rich fibrin (hPRF) exudate Vs FBS on proliferation and osteodifferentiation of human dental pulp stem cells (hDPSCs). The secondary one was to determine the optimum concentration of hPRF exudate inducing hDPSCs proliferation and osteodifferentiation.

Methods

The direct method was used to prepare hPRF exudate. hDPSCs were isolated from impacted mandibular third molars of twelve donors by the outgrowth method. For cell viability and proliferation rate testing, 96 well plates were used and the assay was done in duplicate and the trial repeated four times under the same conditions. Six wells were used to contain 10% FBS, serum free media, 1%, 5%, 10% and 20% concentrations of hPRF exudates, respectively. The proliferation assay was carried out by MTS tetrazolium cell proliferation assay kit and Elisa reader. The study design for osteodifferentiation protocol was exactly as the proliferation one and instead the assay was carried out by alizarin red with Elisa reader.

Results

Compared to 10% FBS, 10% hPRF exudate was the optimum concentration for hDPSCs proliferation, while 1% hPRF exudate was the optimum concentration for osteodifferentiation of hDPSCs.

Conclusions

Avoiding the risk of zoonosis which may be occurred with FBS, it is recommended to use 10% hPRF exudate for proliferation and 1% for osteodifferentiation.

Periodontal tissue engineering: current strategies and the role of platelet rich hemoderivatives

Periodontal tissue engineering procures to regenerate the periodontal tissue assuring the right combination of scaffolds, biochemical cues and cells. The platelet rich hemoderivatives might provide the adequate growth factors and structural proteins for the predictable regeneration of periodontium.

Effects of short-term inflammatory and/or hypoxic pretreatments on periodontal ligament stem cells: in vitro and in vivo studies

In this study, we extensively screened the in vitro and in vivo effects of PDLSCs following short-term inflammatory and/or hypoxic pretreatments. We found that the 24-h hypoxic pretreatment of PDLSCs significantly enhanced cell migration and improved cell surface CXCR4 expression. In addition, hypoxia-pretreated PDLSCs exhibited improved cell colony formation and proliferation. Cells that were dually stimulated also formed more colonies compared to untreated cells but their proliferation did not increase. Importantly, the hypoxic pretreatment of PDLSCs enhanced cell differentiation as determined by elevated RUNX-2 and ALP protein expression. In this context, the inflammatory stimulus impaired cell OCN protein expression, while dual stimuli led to decreased RUNX-2 and OCN mRNA levels. Although preconditioning PDLSCs with inflammatory and/or hypoxic pretreatments resulted in no differences in the production of matrix proteins, hypoxic pretreatment led to the generation of thicker cell sheets; the inflammatory stimulus weakened the ability of cells to form sheets. All the resultant cell sheets exhibited clear bone regeneration following ectopic transplantation as well as in periodontal defect models; the amount of new bone formed by hypoxia-preconditioned cells was significantly greater than that formed by inflammatory stimulus- or dual-stimuli-treated cells or by nonpreconditioned cells. The regeneration of new cementum and periodontal ligaments was only identified in the hypoxia-stimulus and no-stimulus cell groups. Our findings suggest that PDLSCs that undergo short-term hypoxic pretreatment show improved cellular behavior in vitro and enhanced regenerative potential in vivo. The preconditioning of PDLSCs via combined treatments or an inflammatory stimulus requires further investigation.