Effects of plating density and culture time on bone marrow stromal cell characteristics

Identification of rare progenitor cells from human periosteal tissue using droplet microfluidics

The isolation and characterisation of single cells from a heterogeneous population are important processes in cell biology, immunology, stem cell research, and cancer research. In the development of novel cell-based therapies, there is a considerable need to target specific cell types to allow for further analysis and amplification ex vivo. We introduce, herein, the use of droplet-based microfluidics as a platform technology for the identification and quantification of distinct cell phenotypes. Using molecular labelling of specific cell populations by antibodies and fluorescent dyes, detection of single cells encapsulated within picolitre-sized aqueous droplets can be performed using high-sensitivity confocal fluorescence detection. Specifically, rare progenitor cells were immunodetected within a heterogeneous population of cells isolated from human periosteal tissue. Using this model human cell population, the accuracy and reproducibility of the droplet system were tested and the results were verified using conventional flow cytometry. It was found that the quantitation of phenotypic subpopulations measured using both techniques is directly comparable. Accordingly, this study demonstrates the biological capacity of droplet-based microfluidics for cellular analysis and provides a necessary first step towards the development of a novel cell sorting technology.

Comparative characterization of bone marrow-derived mesenchymal stromal cells from four different rat strains

BACKGROUND AIMS

Bone marrow (BM) multipotent mesenchymal stromal cells (MSC) hold great potential for cell-based regenerative medicine. Because of the growing use of autologous rat MSC transplantation in various rat models, there is a need to establish minimal criteria for rat MSC characterization independent of the specific strain employed in each study. We aimed to compare the phenotypic and functional traits of BM MSC from the four strains of rats commonly used in research: Fisher, Lewis, Sprague-Dawley and Wistar.

METHODS

Rat MSC were isolated from the BM of the four different rat strains in an identical fashion. Cells were characterized for their cell-surface phenotype in early and late passage. Functional mesenchymal differentiation capacities were examined following adipogenic and osteogenic inductions. Population doubling times were determined across the four strains throughout 10 passages. In vitro proliferation assays of immune cells were conducted following co-culture of spleen cells and MSC of the four different strains.

RESULTS

We found that rat MSC from different strains exhibited similar cell-surface phenotype. Expansion rates and differentiation capacities of the MSC were also similar across the different strains. Co-culture of rat MSC with spleen cells obtained from rats of a different strain did not induce proliferation of immune cells.

CONCLUSIONS

Our findings suggest that BM-derived MSC from different strains share similar characteristics, in contrast to the variations previously described in the characterization of mice MSC from different strains.

Osteogenic properties of late adherent subpopulations of human bone marrow stromal cells

The nonadherent (NA) population of bone-marrow-derived mononuclear cells (MNC) has been demonstrated to be a source of osteogenic precursors in addition to the plastic-adherent mesenchymal stromal cells (MSC). In the current study, two subpopulations of late adherent (LA) osteoprogenitors were obtained by subsequent replating of NA cells, and their phenotypic, functional, and molecular properties were compared with those of early adherent (EA) MSC. Approximately 35% of MNC were LA cells, and they acquired a homogeneous expression of MSC antigens later than EA cells. In EA-MSC, the alkaline phosphatase (ALP) activity increased significantly from time of seeding to the first confluence, whereas in LA cells it raised later, after the addition of mineralization medium. All subpopulations were able to produce type I collagen and to deposit extracellular matrix with organized collagen fibrils. The proportion of large colonies with more than 50% of ALP positive cells as well as the calcium content was higher in LA than in EA cells. Molecular analysis highlighted the upregulation of bone-related genes in LA-MSC, especially after the addition of mineralization medium. Our results confirm that bone marrow contains LA osteoprogenitors which exhibit a delay in the differentiation process, despite an osteogenic potential similar to or better than EA-MSC. LA cells represent a reservoir of osteoprogenitors to be recruited to gain an adequate bone tissue repair and regeneration when a depletion of the most differentiated component occurs. Bone tissue engineering and cell therapy strategies could take advantage of LA cells, since an adequate amount of osteogenic MSCs may be obtained while avoiding bone marrow manipulation and cell culture expansion.

Liquid storage of marrow stromal cells

BACKGROUND

Marrow stromal cells (MSCs) for clinical trials are inevitably stored before administration, but little is known about the effects of storage on MSCs. The effects of short-term liquid storage on the in vitro function of MSCs intended for a clinical trial were studied.

STUDY DESIGN AND METHODS

Early-passage human MSCs were suspended in 0.9% saline or culture medium and stored at 4 degrees C or room temperature for up to 72 hours followed by assessment of cell loss, viability, and growth in culture.

RESULTS

When stored in saline at 4 degrees C, MSC counts decreased by 5% to 20%, MSC viability decreased 17% to 37%, and MSC growth decreased 65% to 100% after 24-hour storage. Similar results were obtained by MSC storage at room temperature or in Dulbecco's modified Eagle's medium or by addition of 1% human serum albumin (HSA) from two manufacturers. Storage of MSCs in saline with HSA from a third manufacturer maintained MSC viability at prestorage levels and improved poststorage MSC growth versus saline (32 +/- 9% vs. 9 +/- 9%; p < 0.05) or saline with two other HSA preparations (4 +/- 4 and 8 +/- 11%; p < 0.05).

CONCLUSION

MSCs stored at 4 degrees C or room temperature, in saline or culture medium, rapidly become nonviable. HSA preparations vary significantly in their ability to maintain poststorage MSC viability and growth. These results provide insight regarding the effects of storage on MSCs and indicate the need to screen HSA preparations before their use as additives to preserve MSCs during short-term liquid storage.