Enhancement of human osteoblast proliferation and phenotypic expression when cultured in human serum

The dark side of foetal bovine serum in extracellular vesicle studies

Extracellular vesicles (EVs) have been shown to be involved in cell-cell communication and to take part in both physiological and pathological processes. Thanks to their exclusive cargo, which includes proteins, lipids, and nucleic acids from the originating cells, they are gaining interest as potential biomarkers of disease. In recent years, their appealing features have been fascinating researchers from all over the world, thus increasing the number of in vitro studies focused on EV release, content, and biological activities. Cultured cell lines are the most-used source of EVs; however, the EVs released in cell cultures are influenced by the cell culture conditions, such as the use of foetal bovine serum (FBS). FBS is the most common supplement for cell culture media, but it is also a source of contaminants, such as exogenous bovine EVs, RNA, and protein aggregates, that can contaminate the cell-derived EVs and influence their cargo composition. The presence of FBS contaminants in cell-derived EV samples is a well-known issue that limits the clinical applications of EVs, thus increasing the need for standardization. In this review, we will discuss the pros and cons of using FBS in cell cultures as a source of EVs, as well as the protocols used to remove contaminants from FBS.

The Impact of Various Culture Conditions on Human Mesenchymal Stromal Cells Metabolism

In vitro and in vivo analyses are closely connected, and the reciprocal relationship between the two comprises a key assumption with concern to the conducting of meaningful research. The primary purpose of in vitro analysis is to provide a solid background for in vivo and clinical study purposes. The fields of cell therapy, tissue engineering, and regenerative medicine depend upon the high quality and appropriate degree of the expansion of mesenchymal stromal cells (MSCs) under low-risk and well-defined conditions. Hence, it is necessary to determine suitable alternatives to fetal bovine serum (FBS—the laboratory gold standard) that comply with all the relevant clinical requirements and that provide the appropriate quantity of high-quality cells while preserving the required properties. Human serum (autologous and allogeneic) and blood platelet lysates and releasates are currently considered to offer promising and relatively well-accessible MSC cultivation alternatives. Our study compared the effect of heat-inactivated FBS on MSC metabolism as compared to its native form (both are used as the standard in laboratory practice) and to potential alternatives with concern to clinical application—human serum (allogeneic and autologous) or platelet releasate (PR-SRGF). The influence of the origin of the serum (fetal versus adult) was also determined. The results revealed the key impact of the heat inactivation of FBS on MSCs and the effectiveness of human sera and platelet releasates with respect to MSC behaviour (metabolic activity, proliferation, morphology, and cytokine production).

Human Serum for Culture of Articular Chondrocytes

In the field of cell and tissue engineering, culture expansion of human cells in monolayer plays an important part. Traditionally, cell cultures have been supplemented with serum to support attachment and proliferation, but serum is a potential source of foreign protein contamination and viral protein transmission. In this study, we evaluated the use of human serum for experimental human articular chondrocyte expansion and to develop a method for preparation of large volumes of high-quality human serum from healthy blood donors. Human autologous serum contained high levels of epidermal-derived growth factor and platelet-derived growth factor-AB and supported proliferation up to 7 times higher than FCS in primary chondrocyte cultures. By letting the coagulation take place in a commercially available transfusion bag overnight, up to 250 ml of growth factor-rich human serum could be obtained from one donor. The allogenic human serum supported high proliferation rate without loosing expression of cartilage-specific genes. The expanded chondrocytes were able to redifferentiate and form cartilage matrix in comparable amounts to autologous serums. In conclusion, the transfusion bags allow preparation of large volumes of growth factor-rich human serum with the capacity to support in vitro cell expansion. The data further indicate that by controlling the coagulation process there are possibilities of optimizing the release of growth factors for other emerging cell therapies.

A consensus introduction to serum replacements and serum-free media for cellular therapies

The cell therapy industry is a fast-growing industry targeted toward a myriad of clinical indications. As the cell therapy industry matures and clinical trials hit their pivotal Phase 3 studies, there will be a significant need for scale-up, process validation, and critical raw material quality assurance. Part of the well discussed challenges of upscaling manufacturing processes there is a less discussed issue relating to the availability of raw materials in the needed quality and quantities. The FDA recently noted that over 80% of the 66 investigational new drug (IND) applications for mesenchymal stem cell (MSC) products analyzed described the use of FBS during manufacturing. Accumulated data from the past years show an acceleration in serum consumption by at least 10%-15% annually, which suggests that the global demand for serum may soon exceed the supply. Ongoing concerns of safety issues due to risks of various pathogen contaminations, as well as issues related to the aforementioned serum variability that can affect final product reproducibility, are strong motivators to search for serum substitutes or serum-free media. it is important to note that there are no accepted definitions for most of these terms which leads to misleading's and misunderstandings, where the same term might be defined differently by different vendors, manufacturer, and users. It is the drug developer's responsibility to clarify what the supplied labels mean and to identify the correct questions and audits to ensure quality. The paper reviews the available serum replacements, main components, basic strategies for replacement of serum and suggests definitions.

Culture of human cell lines by a pathogen-inactivated human platelet lysate

Alternatives to the use of fetal bovine serum (FBS) have been investigated to ensure xeno-free growth condition. In this study we evaluated the efficacy of human platelet lysate (PL) as a substitute of FBS for the in vitro culture of some human cell lines. PL was obtained by pools of pathogen inactivated human donor platelet (PLT) concentrates. Human leukemia cell lines (KG-1, K562, JURKAT, HL-60) and epithelial tumor cell lines (HeLa and MCF-7) were cultured with either FBS or PL. Changes in cell proliferation, viability, morphology, surface markers and cell cycle were evaluated for each cell line. Functional characteristics were analysed by drug sensitivity test and cytotoxicity assay. Our results demonstrated that PL can support growth and expansion of all cell lines, although the cells cultured in presence of PL experienced a less massive proliferation compared to those grown with FBS. We found a comparable percentage of viable specific marker-expressing cells in both conditions, confirming lineage fidelity in all cultures. Functionality assays showed that cells in both FBS- and PL-supported cultures maintained their normal responsiveness to adriamycin and NK cell-mediated lysis. Our findings indicate that PL is a feasible serum substitute for supporting growth and propagation of haematopoietic and epithelial cell lines with many advantages from a perspective of process standardization, ethicality and product safety.

Analysis of human synovial and bone marrow mesenchymal stem cells in relation to heat-inactivation of autologous and fetal bovine serums

Background

Though sera are essential for Mesenchymal stem cells (MSCs), the effect of heat-inactivation remains unknown. Autologous human serum is recommended for clinical use; however, it is unclear whether differentiation potentials are maintained. To examine whether heat-inactivation of serum affected the proliferation and whether autologous human serum influenced their multipotentiality.

Methods

After whole blood collection, human synovium and bone marrow were harvested. Nucleated cells were expanded with autologous human serum and FBS.

Results

Heat-inactivation of autologous human serum enhanced proliferation of synovial MSCs. Heat-inactivation of each types of serum didn't affect calcification of synovial MSCs. The induction of calcification increased ALP activity, with the exception of bone marrow MSCs with autologous human serum. For adipogenesis of synovial MSCs, the Oil Red-O positive colony forming efficiency with autologous human serum was similar to or less than that with FBS.

Conclusion

These clarified the processing of human autologous serum and the influence of different sera for differentiation of synovial and bone marrow MSCs.

Ectopic Bone Formation from Mandibular Osteoblasts Cultured in a Novel Human Serum-derived Albumin Scaffold

The aim of this study was to evaluate the ectopic bone formation using a novel serum-derived albumin scaffold and cultured human mandibular osteoblasts in nude mice. Osteoblasts were cultured with 10% human serum and plated in a novel spongy noncalcified protein scaffold prepared with plasmatic albumin crossed with a glutaraldehyde type agent. Hematoxylin-eosin staining revealed a bone-like extracellular matrix and in vitro mineralization was confirmed by von Kossa staining. Histological and immunohistochemical evaluation showed progression of mineralization in vivo. These results suggest the clinical feasibility of alveolar cells and albumin scaffold as a good alternative for bone regeneration.

The cultivation of human multipotent mesenchymal stromal cells in clinical grade medium for bone tissue engineering

Clinical application of human multipotent mesenchymal stromal cells (hMSCs) requires their expansion to be safe and rapid. We aimed to develop an expansion protocol which would avoid xenogeneic proteins, including fetal calf serum (FCS), and which would shorten the cultivation time and avoid multiple passaging. First, we have compared research-grade alpha-MEM medium with clinical grade CellGro for Hematopoietic Cells' Medium. When FCS was used for supplementation and non-adherent cells were discarded, both media were comparable. Both media were comparable also when pooled human serum (hS) was used instead of FCS, but the numbers of hMSCs were lower when non-adherent cells were discarded. However, significantly more hMSCs were obtained both in alpha-MEM and in CellGro supplemented with hS when the non-adherent cells were left in the culture. Furthermore, addition of recombinant cytokines and other supplements (EGF, PDGF-BB, M-CSF, FGF-2, dexamethasone, insulin and ascorbic acid) to the CellGro co-culture system with hS led to 40-fold increase of hMSCs' yield after two weeks of cultivation compared to alpha-MEM with FCS. The hMSCs expanded in the described co-culture system retain their osteogenic, adipogenic and chondrogenic differentiation potential in vitro and produce bone-like mineralized tissue when propagated on 3D polylactide scaffolds in immunodeficient mice. Our protocol thus allows for very effective one-step, xenogeneic protein-free expansion of hMSCs, which can be easily transferred into good manufacturing practice (GMP) conditions for large-scale, clinical-grade production of hMSCs for purposes of tissue engineering.

Human plasma accelerates immortalization of B lymphocytes by Epstein-Barr virus

OBJECTIVE

Serum and plasma contain species-specific factors that modulate cell population growth and function, and that are required for proliferation of most cell cultures. Foetal calf serum (FCS) is the most common source of these growth factors. We studied the effect of human plasma (HP) on the immortalization process of B lymphocytes by Epstein-Barr virus (EBV) was studied.

MATERIALS AND METHODS

The effect of HP as compared to FCS was done through assessment of cell proliferation.

RESULTS

It was found that HP (autologous and non-autologous plasma) is more effective than FCS in generating lymphoblastoid cell lines, regardless of EBV status of the donors: 65% of HP-supplemented cultures developed into lymphoblastoid cell lines by 7-14 culture days, as compared to 16% of cultures with FCS. In addition, 6% of HP-supplemented cultures did not achieve becoming lymphoblastoid cell lines by day 35 in comparison to 94% of cultures with FCS. The higher proliferative effect of HP was not altered by heat inactivation or filtration. HP maintained its proliferative activity at 4 degrees C over 8 months, thus indicating that HP contains a stable growth factor(s), which accelerates B-lymphocyte immortalization.

CONCLUSION

The results support other studies that recommend the use of autologous plasma for tissue culture, mainly in the case of autologous transplantation. Furthermore, the use of HP allows preparation of lymphoblastoid cell lines from a small amount of peripheral blood in a shorter period of time and with a higher rate of success.

Homologous activated platelets stimulate differentiation and proliferation of primary human bone cells

In bone tissue engineering approaches the expansion of bone cells is an essential part. In recent years the search for an appropriate alternative to fetal bovine serum (FBS) in the ex vivo expansion process has increased. This study demonstrates that platelet-rich clot releasate (PRCR) could be an appropriate alternative. The effects of PRCR on bone cell cultures derived from 5 different human donors were analyzed with respect to morphology, proliferation, apoptosis and gene expression. Five different PRCR concentrations were used: 1, 5, 10, 20 and 40%. The population doubling (PD) values were calculated for each concentration. Light microscopy analysis was done after 3 and 9 days. Flow cytometry was used to analyze cell cycle effects. The gene expression of alkaline phosphatase, collagen type 1, osteocalcin, bone sialoprotein and osteopontin was analyzed with RT-PCR. 10% FBS cultures were used as controls. With 10% PRCR the cell morphology resembled the control cultures; however, the PD values were significantly higher (p < 0.01). Concentrations of 20 and 40% had a clear cytotoxic effect, observed with light microscopy analysis and flow cytometry. PRCR had a potent effect on the expression of osteogenic markers and resulted in a concentration-dependent upregulation. We demonstrate that human bone cells derived from the maxillary alveolar ridge can be cultured in medium containing PRCR instead of FBS. The addition of PRCR results in higher proliferative capacity and upregulation of osteogenic markers. These results indicate that FBS could be avoided in future tissue engineering approaches using bone cells from this anatomic site.

Mesenchymal stem cell tissue engineering: techniques for isolation, expansion and application

Mesenchymal stem cells (MSCs) are undifferentiated multipotent cells which reside in various human tissues and have the potential to differentiate into osteoblasts, chondrocytes, adipocytes, fibroblasts and other tissues of mesenchymal origin. In the human body they could be regarded as readily available reservoirs of reparative cells capable to mobilize, proliferate and differentiate to the appropriate cell type in response to certain signals. These properties have triggered a variety of MSC-based therapies for pathologies including nonunions, osteogenesis imperfecta, cartilage damage and myocardial infarction. The outcome of these approaches is influenced by the methodologies and materials used during the cycle from the isolation of MSCs to their re-implantation. This review article focuses on the pathways that are followed from the isolation of MSCs, expansion and implantation.

Cryopreservation of osteoblast-like cells: viability and differentiation with replacement of fetal bovine serum in vitro

In reconstructive medicine, the clinical use of cryopreservation techniques depends on the absence of infectious agents such as prions. Therefore, we investigated the viability and differentiation of human osteoblast-like cells during replacement of fetal bovine serum in vitro. The aim of the present study is to replace the potentially infectious supplement fetal bovine serum during the cryopreservation procedure in order to perform future clinical trials. We used a cryopreservation technique with Me(2)SO for human osteoblast-like cells of iliac cancellous bone. In the cell culture of cryopreserved and fresh osteoblast-like cells, we substituted Dulbecco's modification of Eagle's medium (DMEM)/Ham's F12 plus 1% penicillin/streptomycin with autologous serum, human serum albumin and Biseko for fetal bovine serum. For the fourth treatment group, we removed fetal bovine serum without replacing it. DMEM/Ham's F12 plus 1% penicillin/streptomycin with fetal bovine serum served as the control group. After 4, 7, 14 and 21 days of culture for the cryopreserved and noncryopreserved cells, we performed cell counting, a WST-1 test, ELISA for collagen type I, and osteocalcin. The activity of alkaline phosphatase was also measured. The best results were obtained for the group with autologous serum as a supplement after thawing, exceeding the other groups with regard to proliferation rate. Most viable cells were observed with no replacement before freezing and after thawing of the cells. With regard to differentiation, the cultures with autologous serum after thawing of the cells showed little concentration of the differentiation markers, probably due to early contact inhibition of the cells in vitro. With regard to effort and outcome, the most promising group for cryopreservation was the one with DMEM/Ham's F12 plus 1% penicillin/streptomycin alone before freezing, especially when osteoblast-like cells were cultured in medium with autologous serum after thawing. This is important, as this in vitro setting resembles the in vivo situation when cryopreserved bone is transplanted. These findings indicate that, for clinical purposes, fetal bovine serum can be removed for cryopreservation of iliac cancellous bone with minor loss of viability.

Use of CFDA-SE for evaluating the in vitro proliferation pattern of human mesenchymal stem cells

BACKGROUND

Mesenchymal stem cells (MSC) are multipotent progenitors retaining the capability to undergo multilineage differentiation, mostly towards all the mesodermal cellular lineages. MSC growing under standard conditions are composed of two main subpopulations with a characteristic distribution in the morphologic flow cytometric scatter: RS (recycling stem) cells (small, agranular) and m (mature) MSC (large, moderately granular cells).

METHODS

MSC obtained from BM of healthy donors and expanded in culture were characterized by evaluating both the expression of conventional markers and differentiation potential. We used CFSE, a lipophilic dye that is taken up by cell membranes, to investigate separately the proliferative activity of RS cells and mMSC subsets.

RESULTS

With flow cytometric analysis, RS cells and mMSC showed nearly the same immunophenotypic pattern, even if a significantly smaller percentage of RS cells expressed some of the classic mesenchymal Ag. The RS cell fraction was confirmed to have a higher proliferative potential and such a feature was particularly evident under certain culture conditions.

DISCUSSION

CFSE has been shown as a reliable method for studying the proliferative activity of MSC subpopulations identified by flow cytometric analysis. The acquisition parameter strategy is crucial for the accuracy of the analysis.

Optimization of the differentiation of human preadipocytes in vitro

This study aimed at developing an optimal protocol for proliferation and differentiation of preadipocytes that is a prerequisite for constructing an ideal biohybrid composed of viable adipose precursor cells in a three-dimensional matrix. Such an implant could represent an adequate solution for correcting soft tissue defects, e.g., extensive deep burns or tumor resections. Preadipocytes were isolated from human subcutaneous adipose tissue samples and cultured in Dulbecco's modified eagle medium (DMEM)/Ham's F12 medium (F12) or OPTIMEM medium with or without the addition of human serum (hS) or fetal calf serum (FCS). The advantages of fibronectin-coated culture dishes for preadipocyte yield after isolation and differentiation were evaluated. After culture expansion, differentiation was induced by insulin, isobutylmethylxanthine, pioglitazone, dexamethasone, and transferrin in the absence of serum. The extent of differentiation was assayed by measuring the activity of glycerophosphate dehydrogenase as well as counting of differentiated versus undifferentiated cells. Our results show that fibronectin coating does not only strongly increase the yield of preadipocytes after isolation from adipose tissue but also significantly enhances differentiation of precursor cells to mature adipocytes. For optimal cell expansion, DMEM/F12 is more promoting than OPTIMEM and culturing with FCS shows a slightly better proliferation compared with hS supplementation. Differentiation, in contrast, is significantly improved when hS is used instead of FCS during proliferation. Our results smooth the way for autologous preadipocyte culturing and show that hS for preadipocyte culturing opens new and promising perspectives for adipose tissue engineering by optimizing in vitro expansion in cell culture and inducing substantial differentiation.

Evaluation of 45S5 Bioactive Glass Combined as a Bone Substitute in the Reconstruction of Critical Size Calvarial Defects in Rabbits

Biomaterial research and tissue engineering have guided new developments in bone replacement. In this study, the osteoconductive and osteoinductive properties of 45S5 Bioglass (Novabone-C/M, Porex Surg., Newnan, GA), granules as a bone replacement material for large calvarial defects were evaluated. Rabbit periosteal cells were expanded in culture and used in vivo. Alkaline-phosphatase assay, collagen type I, and calcium expression were applied to confirm osteoblast phenotype. In the in vivo phase, a 15-mm diameter critical size calvarial defect was created in rabbits (n = 14). The defect was reconstructed according to four treatment groups: autogenous bone (n = 2), Bioglass alone (n = 2), Bioglass + bone (n = 5), Bioglass + periosteal cells (n = 5). The animals were killed 12 weeks after surgery, and the samples were analyzed. Periosteal cells grew successfully in vitro. Because of their fast proliferation and potential to differentiate into osteoblasts, they were an excellent source of cells for bone tissue engineering. The best ossification was seen when autogenous bone was used (79.4% ossified), whereas only 8.2% of the defect in the Bioglass group showed ossification. Addition of bone or cells to the Bioglass increased the area of ossification to 42.7% and 30.2%, respectively. Defects replaced with Bioglass showed varying degrees of inflammatory reaction because of the intense cell-mediated biodegradation process. Based on these findings, the use of Bioglass granules to repair large craniofacial defects cannot be advised.

Long-term effects of neridronate on human osteoblastic cell cultures

Bisphosphonates (BPs) are widely used in the treatment of a variety of bone-related diseases, particularly where the bone turnover is skewed in favor of osteolysis. The mechanisms by which BPs reduce bone resorption directly acting on osteoclasts are now largely clarified even at molecular level. Researches concerning the BP's effects on osteoblast have instead shown variable results. Many in vitro studies have reported positive effects on osteoblasts proliferation and mineralization for several BPs; however, the observed effects differ, depending on the variety of different model system that has been used.

OBJECTIVES

We have investigated if neridronate, an aminobisphosphonate suitable for pulsatory parenteral administration, could have an effect on human osteoblastic proliferation and differentiation in vitro.

METHODS

We have investigated whether prolonged addition of neridronate (from 10(-3) to 10(-11) M) to different human osteoblasts cultures, obtained from 14 different bone specimens, could affect the cells number, the endogenous cellular alkaline phosphatase (ALKP) activity, and the formation of mineralized nodules.

RESULTS

Our results show that neridronate does not negatively affect in vitro the viability, proliferation, and cellular activity of normal human osteoblasts even after a long period addition of the drug (20 days) at concentrations equal or lower than 10(-5) mol/l (therapeutic dose). In addition, neridronate seems to enhance the differentiation of cultured osteoblasts in mature bone-forming cells. A maximum increase of alkaline phosphatase activity (+50% after 10 days; P < 0.01) and mineralized nodules (+48% after 20 days; P < 0.05) was observed in cultures treated with neridronate 10(-8) M.

CONCLUSIONS

These results encourage the use of neridronate in long-term therapy of demineralizing metabolic bone disorders.

In vitro growth and osteoblastic differentiation of human bone marrow stromal cells supported by autologous plasma

Autologous bone marrow stromal cells have been proposed as an adjuvant in the treatment of bone nonunion. This cell therapy requires the establishment of culture conditions that permit the rapid expansion of these cells ex vivo while retaining their potential for further differentiation. Several culture models have been proposed, all of them using fetal calf serum (FCS) as a source of growth factors. This is problematic for subsequent autologous implantation because of possible disease transmission. Here we report the establishment and characterization of a cell culture system in which standard FCS has been replaced by autologous plasma recovered from bone marrow (APM). Short-term cultures of human bone marrow stromal (HBMS) cells grown in mineralizing conditions with APM exhibited a significantly higher number of ALP-positive colonies than those grown with FCS, indicating an enhanced ability of APM to recruit osteoprogenitor cells for culture. Analyses of long-term cultures showed that the use of APM did not affect cell proliferation as cell number at confluence and proliferation rate were similar whether primary cultures had been maintained with APM or FCS. In first-passage cultures, an osteoblastic differentiation was observed in both cases as the cells expressed ALP and formed mineralized bone-like nodules. We noted that the age of donor had a negative effect on the number of osteoprogenitor cells recruited for culture. This effect had an impact on proliferation rate in primary cultures performed with APM, although the cell number obtained after expansion remained independent of age. Our study shows that proliferative capacity and osteoblastic differentiation potential of HBMS cells are maintained when cultured with APM. Thus, this cell culture system could provide a new and safer tool to elaborate an autologous cell therapy designed to enhance osteogenesis.