Impairment of two types of circulating endothelial progenitor cells in patients with glucocorticoid-induced avascular osteonecrosis of the femoral head.

OBJECTIVES

This study examined whether abnormalities of early EPCs and endothelial colony forming cells (ECFCs) are present and compared their functions in glucocorticoid (GC)-induced avascular osteonecrosis of the femoral head (ANFH).

METHODS

Early EPCs and endothelial colony forming cells (ECFCs) were obtained from 33 patients with glucocorticoid-induced ANFH and 33 age- and sex-matched control subjects. Cells were isolated, in vitro cultured and studied by Flow Cytometry and Immunofluorescence. Colony-forming unit counts were observed from 33 patients and 33 healthy controls. Growth kinetics, migratory capacity to multiple chemo-attractants, in vitro tube formation capacity and cytokine (vascular endothelial growth factor and stromal cell-derived factor-1) levels in supernatants of two types of EPCs were assayed in ANFH patients and matched controls (n=4).

RESULTS

Mean numbers of colonies formed by both types of EPCs were decreased in ANFH patients (Early EPCs: 2.42±1.46 versus 4.52±2.00, p<0.05; ECFCs: 0.62±0.55 versus 1.12±0.82, p<0.05). Early EPCs from ANFH patients showed impaired migratory capacity (63.8±11.7 versus 152.3±12.4, p<0.001) and VEGF secretion (50.8±7.2 pg/ml versus 62.8±10.1 pg/ml, p<0.05). ECFCs from ANFH patients showed decreased tube formation capacity (7.1±2.7 versus 23.8±4.3, p<0.001) and proliferation.

DISCUSSION

Early EPCs and ECFCs were impaired in number and function in GC-induced ANFH, and their distinct reduced capacity profiles might reflect different roles they played in endothelial dysfunction of GC-induced ANFH.