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Osteogenesis and expression of the bone marrow niche in endothelial cell-depleted HipOPs

Kristen P McKenzie1, Dana C Mayer, Jane E Aubin

  • 1Department of Dentistry, University of Toronto, 1 King's College Circle, Medical Sciences Building, Room 4245, Toronto, Ontario, Canada M5S 1A8.

Journal of Cellular Biochemistry
|November 20, 2012
PubMed

Insights

Researchers isolated highly purified osteoprogenitor cells (HipOPs) from mouse bone marrow. Depleting vascular endothelial cells (VECs) did not affect osteogenesis, suggesting VECs do not regulate this process in HipOPs.

Area of Science:

  • Stem cell biology
  • Hematopoietic stem cell niche research
  • Osteogenesis and vascular biology

Background:

  • Murine multipotent mesenchymal stem cells (MSCs) are challenging to isolate due to low frequency and lack of specific markers.
  • Previous work identified a highly purified osteoprogenitor (HipOP) population from mouse bone marrow stromal cells (BMSCs) using magnetic microbead negative selection.
  • HipOPs were found to be enriched in vascular endothelial cells (VECs).

Purpose of the Study:

  • To investigate the role of VECs in osteogenesis within the HipOP population.
  • To determine if VECs are essential accessory cells regulating osteogenesis in HipOPs.
  • To analyze the characteristics of HipOPs and VEC-depleted HipOPs in relation to the hematopoietic stem cell (HSC) niche.

Main Methods:

  • Isolation of HipOPs from mouse BMSCs using magnetic microbead negative selection to remove hematopoietic cells.
  • Immunodepletion of VECs from HipOPs using anti-CD31 antibodies.
  • Assessment of osteogenic capacity of HipOPs and CD31(-) HipOPs in vitro and in vivo.
  • Gene expression analysis of key markers related to osteogenesis and HSC niche.

Main Results:

  • Depletion of VECs from HipOPs (resulting in CD31(-) HipOPs) did not alter their osteogenic capacity in vitro or in vivo.
  • Gene expression analysis suggested that both HipOPs and CD31(-) HipOPs represent hematopoietic stem cell (HSC) niche populations.
  • Osteoblast differentiation and VEC depletion appear to modulate the HSC niche.

Conclusions:

  • Vascular endothelial cells (VECs) are not essential accessory cells regulating osteogenesis in the purified osteoprogenitor (HipOP) population.
  • HipOPs, even after VEC depletion, maintain characteristics of hematopoietic stem cell (HSC) niche populations.
  • The study provides insights into the interplay between osteogenesis and the HSC niche, highlighting the modulatory role of osteoblast differentiation and VEC presence.

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