Role of VLA-4 and VLA-5 in ex vivo maintenance of human and pig hematopoiesis in human stroma-supported long-term cultures

Exp Hematol. 2005 Mar;33(3):363-70. doi: 10.1016/j.exphem.2004.11.011.

Abstract

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.

Conclusion: 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies / immunology
  • Antibodies / pharmacology
  • Cells, Cultured
  • Hematopoiesis / drug effects
  • Hematopoiesis / physiology*
  • Hematopoietic Stem Cell Transplantation
  • Hematopoietic Stem Cells / physiology*
  • Humans
  • Immune Tolerance / drug effects
  • Immune Tolerance / physiology
  • Integrin alpha4beta1 / immunology
  • Integrin alpha4beta1 / metabolism*
  • Integrin alpha5beta1 / immunology
  • Integrin alpha5beta1 / metabolism*
  • Proto-Oncogene Proteins c-kit / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Species Specificity
  • Stromal Cells / physiology
  • Swine
  • Transplantation, Heterologous

Substances

  • Antibodies
  • Integrin alpha4beta1
  • Integrin alpha5beta1
  • Proto-Oncogene Proteins c-kit