IDENTIFICATION AND CHARACTERIZATION OF DISTINCT POPULATIONS OF CLONOGENIC BONE MARROW STROMAL CELLS CAPABLE OF TRANSFERRING THE HEMATOPOIETIC MICROENVIRONMENT IN VIVO AND SUPPORTING LT-HSCs IN VITRO

Bone marrow (BM) stromal cells are ascribed two key functions, 1) stem cells for non-hematopoietic tissues (MSC) and 2) as components of the hematopoietic stem cell niche. Current approaches studying the stromal cell system in the mouse are complicated by the low yield of clonogenic progenitors (CFU-F). Given the perivascular location of MSC in BM, we developed an alternative methodology to isolate MSC from mBM. An intact ‘plug’ of bone marrow is expelled from bones and enzymatically disaggregated to yield a single cell suspension. The recovery of CFU-F (1917.95+199) reproducibly exceeds that obtained using the standard BM flushing technique (14.32+1.9) by at least 2 orders of magnitude (P<0.001; N = 8) with an accompanying 196-fold enrichment of CFU-F frequency. Purified BM stromal and vascular endothelial cell populations are readily obtained by FACS. A detailed immunophenotypic analysis of lineage depleted BM identified PDGFRαβPOS stromal cell subpopulations distinguished by their expression of CD105. Both subpopulations retained their original phenotype of CD105 expression in culture and demonstrate MSC properties of multi-lineage differentiation and the ability to transfer the hematopoietic microenvironment in vivo. To determine the capacity of either subpopulation to support long-term multi-lineage reconstituting HSCs, we fractionated BM stromal cells into either the LinNEGPDGFRαβPOSCD105POS and LINNEGPDGFRαβPOSCD105LOW/- populations and tested their capacity to support LT-HSC by co-culturing each population with either 1 or 10 HSCs for 10 days. Following the 10 day co-culture period, both populations supported transplantable HSCs from 10 cells/well co-cultures demonstrating high levels of donor repopulation with an average of 65+23.6% chimerism from CD105POS co-cultures and 49.3+19.5% chimerism from the CD105NEG co-cultures. However, we observed a significant difference when mice were transplanted with the progeny of a single co-cultured HSC. In these experiments, CD105POS co-cultures (100%) demonstrated long-term multi- lineage reconstitution, while only 4 of 8 mice (50%) from CD105NEG -single HSC co-cultures demonstrated long-term reconstitution, suggesting a more limited expansion of functional stem cells. Taken together, these results demonstrate that the PDGFRαβCD105POS stromal cell subpopulation is distinguished by a unique capacity to support the expansion of long-term reconstituting HSCs in vitro.

AIDS talk

The observations of Michel Foucault, noted Twentieth Century French philosopher, regarding modern power relations and orders of discourse, form the framework utilized to analyze and interpret the power struggles of AIDS activists and their opponents--the religious and radical right, and the administrative agencies of the 'Liberal' welfare State. Supported by the tools of sociolinguistic inquiry, the analysis highlights the success of a safer sex campaign in Houston, Texas to illustrate the dynamics of cultural and political change by means of discursive transformations initiated by the gay micro-culture. The KS/AIDS Foundation, allied with both the biomedical community and gay entertainment spheres, was successful in conveying biomedical cautions that resulted in altered personal behavior and modified public attitudes by using linguistic conventions consonant with the discourse of the Houston gay micro-culture. The transformation of discursive practices transgressed not only the Houston gay micro-culture's boundaries, but the city boundaries of Houston as well. In addition to cultural and political change, moderate and confrontational gay activists also sought to change the cognitive boundaries surrounding 'the gold standard' for clinical research trials.^ From a Foucauldian perspective, the same-sex community evolved from the subordinated Other to a position of power in a period of five years. Transformations in discursive practices and power relations are exemplified by the changing definitions employed by AIDS policy-makers, the public validation of community-based research and the establishment of parallel track drug studies. Finally, transformations in discursive practices surrounding the issues of HIV antibody testing are interpreted using Foucault's six points of power relations. The Montrose Clinic provides the case study for this investigation. The clinic turned the technical rationalities of the State against itself to achieve its own ends and those of the gay micro-culture--anonymous testing with pre and post test counseling. AIDS Talk portrays a dramatic transformation in discursive practices and power relations that transcends the historical moment to provide a model for future activists. Volume 2 contains copies of fugitive primary source materials largely unavailable elsewhere. Original documents are archived in the Harris County Medical Archives in the Houston Academy of Medicine located in the Texas Medical Center Library, Houston, Texas. ^