Bone Marrow Connexin-43 Expression Is Critical for Hematopoietic Regeneration After Chemotherapy

• Published in: Cell communication & adhesion 2005-01, Vol.12 (5-6), p.307-317
• Main Authors: Presley, Cynthia A., Lee, Andrew W., Kastl, Bryan, Igbinosa, Irogue, Yamada, Yoshiyuki, Fishman, Glenn I., Gutstein, David E., Cancelas, Jose A.
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Ly - metabolism; Antimetabolites, Antineoplastic - adverse effects; Antimetabolites, Antineoplastic - therapeutic use; Blood Cell Count; Bone Marrow - drug effects; Bone Marrow - metabolism; Bone Marrow - pathology; Bone Marrow Cells - drug effects; Bone Marrow Cells - metabolism; Bone Marrow Cells - pathology; Chemotherapy; Connexin 43 - deficiency; Connexin 43 - genetics; Connexin 43 - metabolism; Connexin-43; Fluorouracil - adverse effects; Fluorouracil - therapeutic use; Hematopoiesis; Hematopoietic Stem Cells - drug effects; Hematopoietic Stem Cells - metabolism; Hematopoietic Stem Cells - pathology; Membrane Proteins - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Phenotype; Proto-Oncogene Proteins c-kit - metabolism; Spleen - drug effects; Spleen - metabolism; Spleen - pathology; stem cells; stress hematopoisis; Time Factors
• ISSN: 1541-9061; 1543-5180
• DOI: 10.1080/15419060500514200

Contact between bone marrow (BM) hematopoietic stem cells (HSC) and osteoblast/stromal (OS) cells has been shown to be crucial in the regulation of hematopoiesis. However, very little is known about the regulatory mechanisms of direct cell-to-cell communication in the hematopoietic microenvironment. Gap junction channels (connexons) are formed by polypeptides (connexins) arranged in hexamers and represent the best described intercellular communication system. Connexin-43 (Cx43) is expressed by BM OS cells and has been associated with the cadherin/β -catenin signaling pathway, recently reported as relevant in the OS/HSC interaction at the stem cell niche. Here, we employed an inducible gene-targeted murine approach to study the role of Cx43 in HSC proliferation and differentiation in vivo. Mx-Cre/Cx43+/+ and Mx-Cre/Cx43flox/flox littermates have been analyzed after gene deletion induced in vivo by the interferon-inducer poly (I)-poly (C), generating control (Cx43+) and Cx43-deficient (Cx43−/−) mice. After one week, Cx43+ and Cx43−/− mice were treated with 5-fluorouracil (5-FU). Cx43 expression in Cx43−/− BM was markedly reduced (>90%) as analyzed on day +14 post-5-FU treatment. Cx43 deficiency did not induce a significant change in peripheral blood counts before 5-FU treatment, but the hematopoiesis recovery after 5-FU treatment was severely impaired as demonstrated by absence of recovery of peripheral blood counts, including profound neutropenia, anemia with reticulocytopenia, thrombocytopenia and a 5- to 8-fold decrease of cellularity and hematopoietic progenitor content (granulomacrophagic colony-forming-units (CFU-GM-), erythroid burst forming units (BFU-E) and mixed colony forming units (CFU-mix-) in BM and spleen on day +14 post-5-FU treatment. However, the femoral content of Lin−/c-kit+/Sca1+ cells in Cx43−/− BM was maintained when compared to Cx43+ BM. Short-term competitive repopulation ability of Cx43−/− BM cells was diminished as compared to Cx43+ mice, specifically for myeloid and B lymphoid cells, but showed spared long-term competitive repopulation ability with roughly normal hematopoietic differentiation. These data suggest that hematopoietic regeneration after cycle-specific chemotherapy is blocked in Cx43-deficient mice at the long-term HSC repopulating level. Cx43 expression within the BM appears to be crucial in the development of an efficient response to hematopoietic stress.