Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.

Murine IgM monoclonal antibody STRO-1 identifies a cell surface antigen expressed by stromal elements in human bone marrow (BM). STRO-1 binds to approximately 10% of BM mononuclear cells, greater than 95% of which are nucleated erythroid precursors, but does not react with committed progenitor cells (colony-forming unit granulocyte-macrophage [CFU-GM], erythroid bursts [BFU-E], and mixed colonies [CFU-Mix]). Fibroblast colony-forming cells (CFU-F) are present exclusively in the STRO-1+ population. Dual-color cell sorting using STRO-1 in combination with antibody to glycophorin A yields a population approximately 100-fold enriched in CFU-F in the STRO-1+/glycophorin A+ population. When plated under long-term BM culture (LTBMC) conditions, STRO-1+ cells generate adherent cell layers containing multiple stromal cell types, including adipocytes, smooth muscle cells, and fibroblastic elements. STRO-1+ cells isolated from LTBMC at later times retain the capacity to generate adherent layers with a cellular composition identical to that of the parent cultures. The STRO-1-selected adherent layers are able to support the generation of clonogenic cells and mature hematopoietic cells from a population of CD34+ cells highly enriched in so-called long-term culture-initiating cells. We conclude that antibody STRO-1 binds to BM stromal elements with the capacity to transfer the hematopoietic microenvironment in vitro.

Abstract. Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSC). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 90 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graftversus-host-disease (GVHD), grades II-IV occurred in 47% of patients and grades III-IV in 17%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. There have also been successful reports of using G-CSF mobilized allogeneic PBSC following second transplants for graft rejection or relapse. Allogeneic PBSC have been infused without reconditioning for correction of graft failure and unmodified or CD34 selected PBSC have also been given with marrow to augment the dose of hematopoietic cells. Further studies are needed to define the role of allogeneic PBSC for transplantation, refine PBSC mobilization and collection techniques and to evaluate the long-term effects of cytokines in normal donors.