PURPOSE:The aim of this study was the establishment of a minimally invasive technique of mesenchymal stem cell (MSC) harvesting and a predictable isolation and cultivation method on 2 different bone substitutes used as potential scaffolds. MATERIALS AND METHODS:Human MSCs isolated from the posterior maxilla were characterized by flow cytometric analysis. After in vitro expansion, cells were cultured and differentiated toward osteogenic, adipogenic, and chondrogenic lineages in 2-dimensional cultures and on natural bone mineral of bovine origin and β-tricalcium phosphate scaffolds. Three-dimensional growth was analyzed using live cell staining and confocal laser scanning microscopy. RESULTS:MSCs from all patients demonstrated the same immunophenotype, with expression of CD73, CD90, and CD105 but no expression of CD45, CD34, CD14, CD11, and HLA-DR. The potential of MSCs for multilineage differentiation along osteogenic, adipogenic, and chondrogenic lines was shown. Based on knowledge of the characteristics of the cells, a method was established to increase MSC expansion efficiency and seeding conditions on each scaffold. Results of the in vitro characterization and laser scanning microscopy visualized the 3-dimensional growth of MSCs on the 2 scaffold types. CONCLUSIONS:The present data showed that intraoral MSCs can be cultured predictably under 2- and 3-dimensional conditions, have proved multiple potencies, and thus seem to be potential candidates for tissue engineering approaches in maxillofacial reconstructions.

Background Research on mesenchymal stromal cells has created high expectations for a variety of therapeutic applications. Extensive propagation to yield enough mesenchymal stromal cells for therapy may result in replicative senescence and thus hamper long-term functionality in vivo. Highly variable proliferation rates of mesenchymal stromal cells in the course of long-term expansions under varying culture conditions may already indicate different propensity for cellular senescence. We hypothesized that senescence-associated regulated genes differ in mesenchymal stromal cells propagated under different culture conditions.Design and Methods Human bone marrow-derived mesenchymal stromal cells were cultured either by serial passaging or by a two-step protocol in three different growth conditions. Culture media were supplemented with either fetal bovine serum in varying concentrations or pooled human platelet lysate.Results All mesenchymal stromal cell preparations revealed significant gene expression changes upon long-term culture. Especially genes involved in cell differentiation, apoptosis and cell death were up-regulated, whereas genes involved in mitosis and proliferation were down-regulated. Furthermore, overlapping senescence-associated gene expression changes were found in all mesenchymal stromal cell preparations.Conclusions Long-term cell growth induced similar gene expression changes in mesenchymal stromal cells independently of isolation and expansion conditions. In advance of therapeutic application, this panel of genes might offer a feasible approach to assessing mesenchymal stromal cell quality with regard to the state of replicative senescence.

Abstract U.S. regulations demand that tests for potency shall consist of either in vitro or in vivo tests, or both. These tests should be designed specifically for each product so as to indicate its potency in a manner adequate to satisfy the interpretation of potency given by the definition in 21 CFR 600.3(s). This article demonstrates that rapid and standardized expansion of human mesenchymal stromal cells (MSCs) to achieve a reasonable cell dose is feasible within less than four weeks and replacing fetal bovine serum (FBS) with human platelet lysate (HPL) provides one strategy toward a safer cell‐based medicinal product (CBMP).

Abstract Abstract 4775 Background: Based on promising experimental studies with mesenchymal stem and progenitor cells (MSPCs) multiple clinical trials have been initiated. In previous studies we have observed genomic stability of MSPCs after efficient short-term expansion in a humanized GMP compliant system with pooled human platelet lysate (pHPL) replacing fetal bovine serum (FBS) as the cell culture supplement (Schallmoser K. and Strunk D., Journal of Visualized Experiments (32) DOI: 10.3791/1523, 2009). Notably, depending on culture protocols, an extensive propagation with highly variable cell culture duration may be necessary to yield enough MSPCs for therapy. The decline in proliferation rates of MSPCs in the course of the different long-term expansion procedures may indicate a propensity for replicative senescence which may hamper long term functionality in vivo. We have therefore initiated a molecular profiling of senescence-associated regulated genes to determine the state of senescence before MSPC transplantation. Methods: Human bone marrow-derived MSPCs were cultured following a highly efficient two-passage protocol (primary culture of unseparated bone marrow and subsequent large scale expansion; Schallmoser K. et al., Tissue Engineering 14:185-196, 2008) compared to conventional serial passaging in three different growth conditions with regularly more then four passages to obtain comparable final cell numbers. Culture media were either supplemented with FBS in different concentrations or pHPL. Gene expression changes were tested by microarray analysis and selected targets were reanalyzed by quantitative real-time PCR. The genomic stability of MSPCs after long-term culture was determined by array comparative genomic hybridization (CGH). Results: Despite high proliferation rate large scale expanded MSPCs showed genomic stability in array CGH. Long-term MSPC growth induced similar gene expression changes in MSPCs irrespective of isolation and expansion conditions. In particular, genes involved in cell differentiation, apoptosis and cell death were up-regulated, whereas genes involved in mitosis and proliferation were down-regulated. Furthermore, overlapping senescence-associated gene expression changes were found in all MSPC preparations. The genomic copy number variations detected in MSPCs of early and late passages in all culture conditions did not coincide with differentially expressed genes. Conclusion: Our data indicate that MSPC expansion can induce gene expression changes independent of isolation and FBS-supplemented as well as FBS-free expansion conditions. A panel of genes will be presented that might offer a practicable approach to assess MSPC quality with regard to the state of replicative senescence in advance of therapeutic application. Determining the impact of senescence acquired during cell expansion on the therapeutic potential of MSCPs for both immune modulation and organ regeneration may help to develop more efficient treatment strategies. Disclosures: No relevant conflicts of interest to declare.

OBJECTIVES:The aim of this study was to test the applicability of multipotent maxillary cells (MMC) for cell therapy concepts and to evaluate their in vitro behaviour on two different bone substitutes.MATERIAL AND METHODS:Cells isolated from maxillary bone from 10 donors were expanded using media containing human platelet lysate (HPL) replacing foetal bovine serum and differentiated towards both the osteogenic and the adipogenic lineage. Surface markers were determined by fluorescence-activated cell sorting analysis. Calcium deposits, alkaline phosphatase (ALP) and osteocalcin (OC) were used as biomarkers of osteogenic differentiation. Oil Red O was used to verify adipogenic differentiation. The osteogenic lineage and undifferentiated controls were further cultured on natural bone mineral of bovine origin (BioOss) and beta-tricalcium phosphate (Vitoss) scaffolds. Scaffold efficacy and cell migration were evaluated with live cell imaging.RESULTS:Isolated cells presented characteristics of bone marrow (BM)-stromal cells and could easily be expanded to clinical scales. Cells expressed osteogenic and adipogenic markers when cultured with inductive media. There were no obvious differences in cell migration and growth behaviour between the two bone substitutes, but significantly higher OC expression was observed on BioOss scaffolds. Both osteogenically differentiated and undifferentiated cell lines expressed ALP activity on the scaffolds.CONCLUSION:Isolated maxillary cells demonstrate multipotent in vitro characteristics comparable with those of BM-stromal cells. HPL can predictably be used for clinical-scale expansion of MMCs. Both grafting materials provide potential carrier characteristics when loaded with MMCs.

Stem cell-based therapies are a promising prospect for regenerative medicine. Particularly, human multipotent mesenchymal stromal cells (MSCs) are currently in focus regarding their regenerative and immune modulating capacities. An increasing number of clinical trials investigating MSC efficiency and safety are ongoing. Ex vivo propagation of human MSCs is considered to be a prerequisite for MSC therapy. The to date standard use of fetal bovine serum in cell culture bears risks including xenoimmunization and transmission of pathogens. Alternatively, human platelet-derived growth factors have been efficiently implemented into routine MSC expansion protocols. In compliance with good manufacturing practice we established an effective time- and resource-saving procedure for MSC propagation in an animal serum-free system. Bone marrow was seeded without manipulation directly in pooled human platelet lysate (pHPL) and L-glutamine supplemented minimum essential medium without antibiotics. Clinical scale expanded MSCs were harvested already after primary culture. MSC quality, identity, purity and function were assessed according to a defined panel of release criteria and comparative genomic hybridization was used to determine genomic stability. Because various potential risks of MSCs have recently been reported, further research is required to prove efficiency and long-term safety of human MSCs for cell therapy.

Adult mesenchymal stem cells (MSCs) are considered as valuable mediators for tissue regeneration and cellular therapy. This study was performed to develop conditions for regularly propagating a clinical quantity of > 2 x 10(8) MSCs without animal serum from small bone marrow (BM) aspiration volumes within short time. We established optimized culture conditions with pooled human platelet lysate (pHPL) replacing fetal bovine serum (FBS) for MSC propagation. MSC quality, identity, purity, and function were assessed accordingly. Biologic safety was determined by bacterial/fungal/mycoplasma/endotoxin testing and genomic stability by array comparative genomic hybridization (CGH). We demonstrate that unmanipulated BM can be used to efficiently initiate MSC cultures without the need for cell separation. Just diluting 1.5-5 mL heparinized BM per 500 mL minimum essential medium supplemented with L-glutamine, heparin, and 10% pHPL sufficiently supported the safe propagation of 7.8 +/- 1.5 x 10(8) MSCs within a single 11- to 16-day primary culture under defined conditions. This procedure also resulted in sustained MSC colony recovery. MSC purity, immune phenotype, and in vitro differentiation potential fully matched current criteria. Despite high proliferation rate, MSCs showed genomic stability in array CGH. This easy single-phase culture procedure can build the basis for standardized manufacturing of MSC-based therapeutics under animal serum-free conditions for dose-escalated cellular therapy and tissue engineering.

Human multipotent mesenchymal stromal cells (MSCs) are currently tested in a growing number of clinical trials to determine their safety and efficiency as an immune modulating and organ regenerative therapy. Repeated observations of genomic instability in the commonly used fetal bovine serum (FBS)-driven MSC cultures and consecutive tumor formation by transformed MSCs in experimental animals have raised serious safety concerns. We and others have recently established alternative clinical scale MSC expansion protocols with pooled human platelet lysate (pHPL) as a substitute for fetal bovine serum. This study was performed to determine the genomic stability of MSCs expanded under humanized conditions ex vivo. Small volume (14–17mL) bone marrow aspirates of four donors (3 male: 30, 36 and 47 years; 1 female: 13 years) were seeded without manipulation directly in heparinized minimum essential medium just supplemented with pHPL and L-glutamine. Clinical scale propagation was done in a newly developed humanized cell expansion system. MSC quality, identity, purity and function were assessed according to a defined panel of release criteria. Array-comparative genomic hybridization (array-CGH) was carried out using a whole genome oligonucleotide microarray platform with female reference DNA. Samples were labeled and scanned images were analyzed using CGH Analytics software. Results confirmed that pHPL is highly efficient in stimulating MSC expansion resulting in the recovery of 780 ± 150 million MSCs (mean ± SEM) after one culture phase. Starting from 15 ± 0.6 mL bone marrow we were able to produce four application doses of MSCs (defined as 2 mio. MSCs/kg x 100kg) in a unique standardized single culture phase within 13.5 ± 1.0 days with a minimum of manipulation and without antibiotics in three of four expansions. MSC viability was ≥ 95%. Flow cytometry revealed virtually pure MSC products with >95% CD73/90/105 reactivity, <2% hematopoietic contamination with CD14/19/34/45-or HLA-DR-reactive cells and intact adipo-, osteo-and chondrigenic differentiation potential. Microbiologic safety measures included negative bacterial/ fungal/mycoplasma testing despite antibiotic/antimycotic-free culture and endotoxin levels <0.025 EU/mL. Array-CGH analysis revealed balanced profiles for all propagated MSC products. Five copy number variations (CNVs; >60kb) that were detected were not documented in the database of genomic variants. Several small (7kb–1.8Mb; n=33) autosomal CNVs were also observed previously in normal individuals and were not associated with phenotype changes. These data extend earlier results showing that MSCs expanded under humanized conditions did not form tumors in experimental animals in vivo. Our data show that despite high proliferation rate MSCs propagated in a human platelet-derived growth factor-driven system are genomically stable in array-CGH and do not form tumors in vivo. This indicates superior safety of the rapidly available humanized MSC transplants compared to currently used FBS-expanded MSCs.

Endothelial progenitor cells (EPC) are considered powerful biologic markers for vascular function and cardiovascular risk, predicting events and death from cardiovascular causes. Colony‐forming units of endothelial progenitor cells (CFU‐EC) are used to quantify EPC circulating in human peripheral blood. The mechanisms underlying colony formation and the nature of the contributing cells are not clear. We performed subtractive CFU‐EC analyses to determine the impact of various blood cell types and kinetics of protein and gene expression during colony formation. We found that CFU‐EC mainly comprise T cells and monocytes admixed with B cells and natural killer cells. The combination of purified T cells and monocytes formed CFU‐EC structures. The lack of colonies after depletion or functional ablation of T cells or monocytes was contrasted with effective CFU‐EC formation in the absence of CD34+ cells. Microarray analyses revealed activation of immune function‐related biological processes without changes in angiogenesis‐related processes during colony formation. In concordance with a regenerative function, soluble factors derived from CFU‐EC cultures supported vascular network formation in vitro. Recognizing CFU‐EC formation as the result of a functional cross between T cells and monocytes shifts expectations of vascular regenerative medicine. Our data support the move from a view of circulating EPC toward models that include a role for immune cells in vascular regeneration.

BACKGROUND: Human multipotent mesenchymal stromal cells (MSCs) are promising candidates for a growing spectrum of regenerative and immunomodulatory cellular therapies. Translation of auspicious experimental results into clinical applications has been limited by the dependence of MSC propagation from fetal bovine serum (FBS).STUDY DESIGN AND METHODS: The capacity of human platelet lysate (HPL) to replace FBS for clinicalscale MSC propagation was analyzed.RESULTS: HPL could be efficiently produced from buffy coats. Multiplex analyses allowed a distinct HPL growth factor profile to be delineated. With a previously established two-step clinical-scale procedure, HPL was reproducibly more efficient than FBS in supporting MSC outgrowth. With only 3 x 10(5) primary culture-derived MSCs, a mean of 4.36 x 10(8) HPL-MSCs (range, 3.01 x 10(8)-5.40 x 10(8)) was obtained within a single secondary 11- to 13-day culture step. Although morphologically distinct, HPL-MSCs and FBS-MSCs did not differ significantly in terms of immunophenotype, differentiation potential in vitro, and lack of tumorigenicity in nude mice in vivo.CONCLUSIONS: Replacing FBS with HPL prevents bovine prion, viral, and zoonose contamination of the stem cell product. This new efficient FBS-free two-step procedure for clinical-scale MSC propagation may represent a major step toward challenging new stem cell therapies.

BACKGROUND: Ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) is a prerequisite for evaluating their therapeutic potential in ongoing clinical trials. Even large volumes of starting material and extended culture periods, however, do not necessarily produce 2 × 106 MSCs per kg per adult patient. A new two‐step procedure has been devised to propagate more than 1 × 108 MSCs from small marrow volumes within fewer than 4 weeks.STUDY DESIGN AND METHODS: The influence of log fold decreased MSC seeding (2500, 250, 25, 2.5/cm2) on clinical‐scale expansion, MSC phenotype, and immunomodulatory function combined with multiplex cytokine display was analyzed. Maintenance of MSC characteristics was tested in fibroblast colony‐forming unit and differentiation assays.RESULTS: Reduced seeding density boosted MSC propagation. Low‐density expanded MSCs were CD29+, CD73+, CD90+, CD105+, CD14–, CD34–, CD45–, HLA‐DR–; retained their differentiation potential; and inhibited lymphocyte proliferation. This was accompanied by deregulated cytokine production. Seeding 0.7 × 106 to 1 × 106 MSCs derived from a 10‐ to 13‐day primary culture at a low density of 28 to 40 per cm2 permitted propagation of 1.5 × 108 to 3.7 × 108 functional MSCs within a 13‐ to 15‐day secondary expansion step.CONCLUSION: Primary seeding of only 10‐mL marrow aspirates on approximately 0.2‐m2 culture area (Step 1) followed by expansion on 2.5 m2 (Step 2) is sufficient to consistently generate at least 1.5 × 108 MSCs in fetal bovine serum–supplemented medium within less than 4 weeks. The efficiency of this two‐step procedure for clinical‐scale MSC propagation may facilitate rational clinical testing of MSC‐based therapies.

BACKGROUND:Umbilical cord blood (UCB) is an easily accessible alternative source for multipotent mesenchymal stromal cells (MSCs) and is generally believed to provide MSCs with a higher proliferative potential compared with adult bone marrow. Limitations in cell number and strict dependence of expansion procedures from selected lots of fetal bovine serum have hampered the progress of clinical applications with UCB-derived MSCs.METHODS:We analyzed the isolation and proliferative potential of human UCB MSCs compared with bone marrow MSCs under optimized ex vivo culture conditions. We further investigated human platelet lysate as an alternative to replace fetal bovine serum for clinical-scale MSC expansion. Clonogenicity was determined in colony-forming units-fibroblast assays. MSC functions were tested in hematopoiesis support, vascular-like network formation and immune modulation potency assays.RESULTS:MSCs could be propagated from UCB with and without fetal bovine serum. MSC propagation was effective in 46% of UCB samples. Once established, the proliferation kinetics of UCB MSCs did not differ significantly from that of bone marrow MSCs under optimized culture conditions, resulting in more than 50 population doublings after 15 weeks. A clinical quantity of 100 million MSCs with retained differentiation potential could be obtained from UCB MSCs within approximately 7 weeks. Ex vivo expansion of hematopoietic UCB-derived CD34+ cells as well as immune inhibition and vascular-like network formation could be shown for UCB MSCs propagated under both culture conditions.CONCLUSION:We demonstrate for the first time that human MSCs can be obtained and propagated to a clinical quantity from UCB in a completely bovine serum-free system. Surprisingly, our data argue against a generally superior proliferative potential of UCB MSCs. Functional data indicate the applicability of clinical-grade UCB MSCs propagated with human platelet lysate-conditioned medium for hematopoiesis support, immune regulation and vascular regeneration.