title: Osteogenic potential of rat spleen stromal cells.
abstract: Evidence is mounting that an increasing number of cell populations in the adult organism already committed and/or differentiated retain the ability to reprogram themselves and give rise to a different phenotype. Bone marrow stromal cells have long been recognized as early progenitor cells for osteoblasts, chondrocytes, hematopoietic-supportive fibroblasts and adipocytes. Recent reports though have demonstrated a potential of cell populations outside the bone marrow environment to sustain bone formation under specific circumstances. The formation of bone nodules in the spleen of IL-5 transgenic mice has been recently reported (Macias et al. (2001): J. Clin. Invest. 107, 949 - 959). We thus postulated that a cell population exists in the spleen that under particular microenvironmental conditions is able to reprogram itself and pursue a fate other than the tissue-specific one. Therefore we isolated and expanded in vitro spleen-derived stromal cells. After expansion, these cells were challenged with culture conditions designed to induce osteogenic differentiation. We hypothesized that the combination of a proliferating factor (fibroblast growth factor 2) and a differentiating hormone (dexamethasone) would allow us to induce spleen-derived stromal cells to proliferate and at the same time to express osteoblast-specific genes. Thus, spleen-derived stromal cells were isolated from rat spleen and expanded in the presence of fibroblast growth factor 2 and dexamethasone. Once primary cultures reached confluence they were either switched to an osteo-inductive medium or implanted in immunodeficient mice. Although no bone formation was observed in in vivo experiments, in vitro spleen-derived stromal cells were able to deposit a mineralized matrix. Gene expression, as revealed by RT-PCR analysis, evidenced that the deposition of a mineralized matrix was concomitant with the expression of CBFA1 and osteocalcin, along with alkaline phosphatase and bone sialoprotein. Our data suggest that rat spleen-derived stromal cells can undergo osteogenic differentiation in a permissive microenvironment.
authors.affiliation: Istituto Nazionale per la Ricerca sul Cancro, Centro di Biotecnologie Avanzate and Dipartimento di Oncologia, Biologia e Genetica, Universitá di Genova, Genova Italy.
authors.forename: Anna R
authors.initials: AR
authors.lastname: Derubeis
authors.forename: Maddalena
authors.initials: M
authors.lastname: Mastrogiacomo
authors.forename: Ranieri
authors.initials: R
authors.lastname: Cancedda
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Quarto
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D020869:Gene Expression Profiling; D018380:Hematopoietic Stem Cell Transplantation; D058574:Integrin-Binding Sialoprotein; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins; D015675:Osteocalcin / Q000235:genetics; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012795:Sialoglycoproteins / Q000235:genetics; D013154:Spleen / Q000166:cytology*; D017154:Stromal Cells / Q000166:cytology* / Q000378:metabolism / Q000637:transplantation; D014157:Transcription Factors / Q000235:genetics
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C546872:Ibsp protein, mouse; C546873:Ibsp protein, rat; D058574:Integrin-Binding Sialoprotein; D009363:Neoplasm Proteins; D012795:Sialoglycoproteins; D014157:Transcription Factors; D016222:Fibroblast Growth Factor 2; D015675:Osteocalcin; D003907:Dexamethasone; D000469:Alkaline Phosphatase