Bone marrow connexin-43 expression is critical for hematopoietic regeneration after chemotherapy.
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/beta -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.
Hoxworth Blood Center, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA.
Cynthia A
CA
Presley
Andrew W
AW
Lee
Bryan
B
Kastl
Irogue
I
Igbinosa
Yoshiyuki
Y
Yamada
Glenn I
GI
Fishman
David E
DE
Gutstein
Jose A
JA
Cancelas
D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000009:adverse effects / Q000627:therapeutic use*; D001772:Blood Cell Count; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018031:Connexin 43 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D005472:Fluorouracil / Q000009:adverse effects / Q000627:therapeutic use*; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010641:Phenotype; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D013154:Spleen / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013997:Time Factors
D000950:Antigens, Ly; D000964:Antimetabolites, Antineoplastic; D018031:Connexin 43; C074650:Ly6a protein, mouse; D008565:Membrane Proteins; D019009:Proto-Oncogene Proteins c-kit; D005472:Fluorouracil