Role of VLA-4 and VLA-5 in ex vivo maintenance of human and pig hematopoiesis in human stroma-supported long-term cultures.
OBJECTIVE
The advantage of recipient hematopoiesis over that of xenogeneic donors poses a fundamental obstacle to the induction of xenograft tolerance through mixed hematopoietic chimerism. Here we explore the role of beta1 integrins in maintenance of human vs porcine hematopoiesis within a human hematopoietic environment.


METHODS
Porcine and human c-kit+ bone marrow cells were purified and cultured on human bone marrow stroma for 6 weeks. The role of VLA-4 and VLA-5 in the maintenance of porcine vs human hematopoiesis in this human stroma-supported long-term bone marrow culture (LTBMC) system was evaluated by using blocking mAbs that bind to both species.


RESULTS
Blocking VLA-4 with HP2/1 inhibited both human and porcine hematopoiesis, whereas anti-VLA-5 (SAM-1) suppressed the function of human, but not porcine, hematopoietic cells. In mixed LTBMC of porcine and human cells on a human stroma, porcine hematopoietic cells were at a competitive disadvantage, as seen by a rapid decline in cellularity, including clonogenic progenitors. This disadvantage was substantially overcome by the addition of SAM-1. Furthermore, human, but not porcine, cell adhesion to human fibronectin was inhibited by arginine-glycine-aspartic acid (RGD) peptides.


CONCLUSIONS
Taken together, these results indicate that VLA-4 plays critical role for porcine hematopoiesis in a human hematopoietic environment, and raise the possibility that porcine VLA-5 might be unable to bind the respective human ligand and/or to initiate adequate post-ligand-binding signaling. Thus, VLA-5 may provide a potential target for developing approaches to improve porcine hematopoiesis in human recipients.
Giovino
Maria A
MA
Immerge BioTherapeutics Inc., Cambridge, Mass., USA.
Wang
Hui
H
Sykes
Megan
M
Yang
Yong-Guang
YG
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D002478:Cells, Cultured; D006410:Hematopoiesis / Q000187:drug effects / Q000502:physiology*; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects / Q000502:physiology; D039041:Integrin alpha4beta1 / Q000276:immunology / Q000378:metabolism*; D039081:Integrin alpha5beta1 / Q000276:immunology / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013045:Species Specificity; D017154:Stromal Cells / Q000502:physiology; D013552:Swine; D014183:Transplantation, Heterologous
D000906:Antibodies; D039041:Integrin alpha4beta1; D039081:Integrin alpha5beta1; D019009:Proto-Oncogene Proteins c-kit