Characterization and functional analysis of laminin isoforms in human bone marrow.
Laminins are a family of disulfide-linked heterotrimeric proteins consisting of 3 different subunits termed alpha, beta, and gamma chains. Combinations of 11 characterized laminin subunits (alpha 1-alpha 5, beta 1-beta 3, and gamma 1-gamma 3) generate at least 12 laminin isoforms, which can serve different functions. Although expression of laminin in the hematopoietic microenvironment has been known for many years, the nature of the laminin isoforms present in the human bone marrow is poorly characterized. The present study attempts to clarify this issue. Reverse transcriptase-polymerase chain reaction analysis of human bone marrow stromal cells suggested the expression of many laminin isoforms in the marrow. Northern blot and immunoblot analysis, however, showed that laminin-8/9 and laminin-10/11 are the most abundant laminin isoforms synthesized by human bone marrow stromal cells. Other isoforms, if present, certainly play a minor role in the hematopoietic microenvironment. Functionally, laminin-10/11 preparations showed strong adhesive interactions with human CD34(+) cell lines. Antibodies against the beta 1 integrin subunit inhibited these interactions. Other laminin isoforms, especially laminin-1 and laminin-2/4, showed only weak or no adhesive interactions with the hematopoietic cell lines tested, explaining former negative results. In addition to its adhesion-mediating properties, laminin-10/11 preparations also showed a mitogenic activity for human hematopoietic progenitor cells. Taken together, these data suggest that laminin in the bone marrow plays a hitherto unexpected important function in the development of hematopoietic progenitor cells. (Blood. 2000;96:4194-4203)
Siler
U
U
University Medical Clinic, Section for Transplantation Immunology and Immunohematology, Tübingen, Germany.
Seiffert
M
M
Puch
S
S
Richards
A
A
Torok-Storb
B
B
Müller
C A
CA
Sorokin
L
L
Klein
G
G
D015153:Blotting, Western; D001853:Bone Marrow / Q000737:chemistry*; D001854:Bone Marrow Cells / Q000737:chemistry; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007106:Immune Sera; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism; D007797:Laminin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D005810:Multigene Family; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000494:pharmacology; D021122:Protein Subunits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000737:chemistry
D017077:Culture Media, Conditioned; D007106:Immune Sera; D019012:Integrin beta1; D007797:Laminin; D020033:Protein Isoforms; D021122:Protein Subunits