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Stem cell biology is a promising, fast-growing field that aims to develop cell-based tools for the treatment of a wide range of diseases. Special attention is paid to bone marrow cells that play a role in the musculoskeletal system. Bone marrow contains hematopoietic stem cells (HSCs) and stromal cells that form the reticular network that supports HSCs formation. Stromal cells also contain mesenchymal stem cells (MSCs) that differentiate to various lineages. The major obstacles in utilizing stem cells are identifying these cells and following the signaling pathways that control the cells' fate. The interactions of stem cells with an extracellular matrix and other cells create a tissue-specific niche that is responsible for regulating cell differentiation. It is important to identify biomarkers that will enable the isolation, selection and expansion of stem cells in vitro to allow their use for cell therapy. The study of stem cells' differentiation is based on various techniques, including the generation of antibodies to specific cellular sub-populations and high throughput analysis at transcriptome and proteome levels. Advances in transcriptome and proteome profiling will establish the molecular signature and will allow the discovery of the cell type specific differentiation programming. Such analysis identified several proteins related to chromatin remodeling factors, cell adhesion molecules and extracellular matrix ligands that localize cells at the specific niche. Detailed interpretation of the transcriptional and translational expression patterns will provide understanding of key properties of MSCs and allow their future use in regenerative medicine.

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Design of tissue-engineered cell-loaded device involves cells seeding onto scaffolds in vitro, allowing them to settle and grow before in vivo transplantation. Interaction between scaffold and cells is important in the development of desired tissues. The present study aimed to investigate the effect of cell-polymer interactions on cell morphology and expression of surface markers of osteogenic MBA-15 cells cultured on various bioresorbable polymers. In this study, we used various polymers: poly(L-lactic acid) (PLLA), poly(DL-lactic acid) (PDLLA), poly(L-lactic-glycolic acid) (PLGA), and poly(DL-lactide-glycolide acid) PDLGA1 and PDLGA2. Expression of integrinalpha-M (CD11b), selectin-E (CD62E), and PECAM-1 (CD31), important in cell-cell and cell-matrix interactions, were quantified by flow-cytometry analysis. Cells grown on PDLGA1 films demonstrated fivefold increase in CD62E expression and two-folds increase in CD11b expression. None of the polymers affected the levels of CD31. Identified differential effect of polymers on the expression of cell-adhesion molecules by osteoprogenitors in vitro might help to choose optimal parameters for successful engraftment of cell-loaded constructs.

The present study describes a new three-dimensional (3-D) culture system that enables the maintenance and phenotypic expression of bone marrow stromal osteoblasts. This culture substratum is advantageous in that it provides suitable conditions for attachment, growth, and differentiation of cells forming 3-D layers. The MBA-15 cell line was grown in unlimited quantities on 3-D Fibro-Cel carriers. These cells mineralized when exposed to ascorbic acid and beta-glycerophosphate (beta GP). Under these mineralization conditions, mRNA expressions of procollagen alpha 2(I) and [3H]-proline-labeled protein were increased. The expression of mRNA for osteonectin and to a lesser extent, for osteopontin was increased, whereas alkaline phosphatase and biglycan remained unaffected under similar conditions. Exposure of mineralizing cultures to dexamethasone reduced mRNA of procollagen alpha 2 (I) and osteonectin to control level. Scanning electron microscopy revealed that cells were grown along the fabric's fibers and produced collagen fibrils. Under appropriate conditions, extensive mineralization had taken place. The mineralization process involves the formation of calcospherites, and correlates with an increase in calcium content. The Fibro-Cel carriers enable formation of 3-D architecture and mineralized tissue in vitro.