Bone Marrow-derived Endothelial Progenitor Cells Are Associated with Bone Mass and Strength

Area of Science:

• Bone biology and vascularization
• Osteoporosis research
• Endothelial progenitor cell function

Background:

• Bone vascularity is hypothesized to influence bone formation (osteogenesis).
• Clinical data linking angiogenesis to bone mass and growth factor gene expression are limited.
• Endothelial progenitor cells (EPCs) are key regulators of bone angiogenesis.

Purpose of the Study:

• To investigate the relationship between bone marrow EPCs, bone mineral density (BMD), and gene expression in postmenopausal women with osteoporosis.
• To compare EPC levels and related gene expression in women with osteoporosis versus controls with normal bone mass.

Main Methods:

• Bone specimens and serum were collected from women with osteoporosis (OP) and controls (COM).
• Mononuclear cells were isolated to detect EPCs via flow cytometry.
• Gene expression of growth factors and osteoblast markers was measured; BMD and bone turnover markers were assessed.

Main Results:

• Osteoporosis patients exhibited lower serum osteocalcin, procollagen type-1 N-terminal propeptide, 25-hydroxy vitamin D, BMD, and bone marrow EPCs compared to controls.
• Expression of vascular endothelial growth factor, Angiopoietin-1 (Ang-1), Angiopoietin-2 (Ang-2), RUNX2, and osterix was significantly lower in OP.
• Mature EPCs positively correlated with BMD, Ang-1, RUNX2, CD31 gene expression and negatively with RANKL and Ang-2.

Conclusions:

• Bone marrow EPCs show significant correlations with bone mass and growth factor gene expression.
• These findings support a crosstalk mechanism between angiogenesis and osteogenesis in maintaining bone health.