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.
Presley
Cynthia A
CA
Hoxworth Blood Center, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA.
Lee
Andrew W
AW
Kastl
Bryan
B
Igbinosa
Irogue
I
Yamada
Yoshiyuki
Y
Fishman
Glenn I
GI
Gutstein
David E
DE
Cancelas
Jose A
JA
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