We previously reported the purification, culture-expansion, and osteogenic differentiation potential of mesenchymal progenitor cells (MPCs) derived from human bone marrow. As a first step to establishing the phenotypic characteristics of MPCs, we reported on the identification of unique cell surface proteins which were detected with monoclonal antibodies. In this study, the phenotypic characterization of human marrow-derived MPCs is further established through the identification of a cytokine expression profile under standardized growth medium conditions and in the presence of regulators of the osteogenic and stromal cell lineages, dexamethasone and interleukin-1 alpha (IL-1 alpha), respectively. Constitutively expressed cytokines in this growth phase include G-CSF, SCF, LIF, M-CSF, IL-6, and IL-11, while GM-CSF, IL-3, TGF-beta 2 and OSM were not detected in the growth medium. Exposure of cells in growth medium to dexamethasone resulted in a decrease in the expression of LIF, IL-6, and IL-11. These cytokines have been reported to exert influence on the differentiation of cells derived from the bone marrow stroma through target cell receptors that utilize gp130-associated signal transduction pathways. Dexamethasone had no effect on the other cytokines expressed under growth medium conditions and was not observed to increase the expression of any of the cytokines measured in this study. In contrast, IL-1 alpha increased the expression of G-CSF, M-CSF, LIF, IL-6 and IL-11 and induced the expression of GM-CSF. IL-1 alpha had no effect on SCF expression and was not observed to decrease the production of any of the cytokines assayed. These data indicate that MPCs exhibit a distinct cytokine expression profile. We interpret this cytokine profile to suggest that MPCs serve specific supportive functions in the microenvironment of bone marrow. MPCs provide inductive and regulatory information which are consistent with the ability to support hematopoiesis, and also supply autocrine, paracrine, and juxtacrine factors that influence the cells of the marrow microenvironment itself. In addition, the cytokine profiles expressed by MPCs, in response to dexamethasone and IL-1 alpha, identify specific cytokines whose levels of expression change as MPCs differentiate or modulate their phenotype during osteogenic or stromagenic lineage entrance/progression.

The effective delivery of bioactive molecules to wound sites hasten repair. Cellular therapies provide a means for the targeted delivery of a complex, multiple arrays of bioactive factors to wound sites. Thus, the identification of ideal therapeutic populations is an essential aspect of this approach. In vitro assays can provide an important first step toward this goal by selecting populations that are likely suitable for more expensive and time-consuming in vivo assays. In this study, bone marrow-derived mesenchymal stem cells (BM-MSCs) were integrated into a three-dimensional coculture system that supports the development and stabilization of vascular tube-like structures. The presence of a limited number of BM-MSCs resulted in their coalignment with vascular structures, and it further resulted in increased tubule numbers and complexity. Thus, these studies suggest that BM-MSCs functionally interacted with and were attracted to in vitro formed vascular structures. Further, these cells also provided sufficient bioactive factors and matrix molecules to support the formation of tubular arrays and the stabilization of these arrays. This in vitro system provides a means for assessing the function of BM-MSCs in aspects of the angiogenic component of wound repair.

The interfollicular dermis of adult human skin is partitioned into histologically and physiologically distinct papillary and reticular zones. Each of these zones contains a unique population of fibroblasts that differ in respect to their proliferation kinetics, rates at which they contract type I collagen gels, and in their relative production of decorin and versican. Here, site-matched papillary and reticular dermal fibroblasts couples were compared to determine whether each population interacted with keratinocytes in an equivalent or different manner. Papillary and reticular fibroblasts grown in monolayer culture differed significantly from each other in their release of keratinocyte growth factor (KGF) and granulocyte-macrophage colony stimulating factor (GM-CSF) into culture medium. Some matched fibroblast couples also differed in their constitutive release of interleukin-6 (IL-6). Papillary fibroblasts produced a higher ratio of GM-CSF to KGF than did corresponding reticular fibroblasts. Interactions between site-matched papillary and reticular couples were also assayed in a three-dimensional culture system where fibroblasts and keratinocytes were randomly mixed, incorporated into type I collagen gels, and allowed to sort. Keratinocytes formed distinctive cellular masses in which the keratinocytes were organized such that the exterior most layer of cells exhibited characteristics of basal keratinocytes and the interior most cells exhibited characteristics of terminally differentiated keratinocytes. In the presence of papillary dermal fibroblasts, keratinocyte masses were highly symmetrical and cells expressed all levels of differentiation markers. In contrast, keratinocyte masses that formed in the presence of reticular fibroblasts tended to have irregular shapes, and terminal differentiation was suppressed. Furthermore, basement membrane formation was retarded in the presence of reticular cells. These studies indicate that site-matched papillary and reticular dermal fibroblasts qualitatively differ in their support of epidermal cells, with papillary cells interacting more effectively than corresponding reticular cells.

No abstract

We previously reported the purification, culture-expansion, and osteogenic differentiation potential of mesenchymal progenitor cells (MPCs) derived from human bone marrow. As a first step to establishing the phenotypic characteristics of MPCs, we reported on the identification of unique cell surface proteins which were detected with monoclonal antibodies. In this study, the phenotypic characterization of human marrow-derived MPCs is further established through the identification of a cytokine expression profile under standardized growth medium conditions and in the presence of regulators of the osteogenic and stromal cell lineages, dexamethasone and interleukin-1 alpha (IL-1 alpha), respectively. Constitutively expressed cytokines in this growth phase include G-CSF, SCF, LIF, M-CSF, IL-6, and IL-11, while GM-CSF, IL-3, TGF-beta 2 and OSM were not detected in the growth medium. Exposure of cells in growth medium to dexamethasone resulted in a decrease in the expression of LIF, IL-6, and IL-11. These cytokines have been reported to exert influence on the differentiation of cells derived from the bone marrow stroma through target cell receptors that utilize gp130-associated signal transduction pathways. Dexamethasone had no effect on the other cytokines expressed under growth medium conditions and was not observed to increase the expression of any of the cytokines measured in this study. In contrast, IL-1 alpha increased the expression of G-CSF, M-CSF, LIF, IL-6 and IL-11 and induced the expression of GM-CSF. IL-1 alpha had no effect on SCF expression and was not observed to decrease the production of any of the cytokines assayed. These data indicate that MPCs exhibit a distinct cytokine expression profile. We interpret this cytokine profile to suggest that MPCs serve specific supportive functions in the microenvironment of bone marrow. MPCs provide inductive and regulatory information which are consistent with the ability to support hematopoiesis, and also supply autocrine, paracrine, and juxtacrine factors that influence the cells of the marrow microenvironment itself. In addition, the cytokine profiles expressed by MPCs, in response to dexamethasone and IL-1 alpha, identify specific cytokines whose levels of expression change as MPCs differentiate or modulate their phenotype during osteogenic or stromagenic lineage entrance/progression.