The effectiveness of bone mineral density as supplementary tool for evaluation of the osteogenic potential in patients with spinal fusion

Abstract

Study design: Retrospective study.

Purpose: This study was designed to determine the effectiveness of bone mineral density measurement as a supplementary tool for evaluation of osteogenic potential in patients with spinal fusion. To this end, we correlated bone mineral density (BMD) with osteogenic potential from cultured mesenchymal stem cells (MSCs).

Overview of literature: Many studies have correlated osteogenic potential of in vitro cultured MSCs with aging or osteoporosis.

Methods: We studied twenty-five individuals with harvested bone marrow from the ilium during lumbar spinal surgery. The BMD of the femoral neck was measured using dual energy X-ray absorptiometry prior to bone marrow aspiration, and the osteoporotic group was classified as those with T-scores below-2.5. After MSCs were isolated from bone marrow, in vitro induction of osteogenesis was performed. We analyzed the patient's osteogenic potential from cultured MSCs such as mineral deposition stain, bone alkaline phosphatase (ALP) activity and osteoblast-specific gene expression in RT-PCR.

Results: On mineral staining, the osteoporotic group had a scanty matrix mineral deposition in contrast to the non-osteoporotic group. The expression of osteocalcin in the osteoporotic group was 1.5 to 3 times less than in the non-osteoporotic group. At the 3(rd) week after the induction of osteogenesis, the activity of ALP of cultured MSCs in the osteoporotic group was lower than in the control group (mean, 45+/-19 u/L, in osteoporotic group vs 136+/-7 u/L in non-osteoporotic), and there was a statistically significant and positive correlation between BMD & ALP (r=0.487, p=0.013).

Conclusions: There is a positive correlation between BMD and osteogenic potential derived from MSCs. The measurement of BMD can provide supplementary data for evaluating osteogenic potential clinically.

Keywords: Bone mineral density; Mesenchymal stem cells; Osteogenic potential.

Fig. 1

Photomicroscopic findings of the induction of osteogenesis from bone marrow-derived MSCs (400×). Mesenchymal stem cells from bone marrow were cultured at the 2nd week (A). Other figures are for the 1st week (B), the 3rd week (C) and the 4th week (D) after the induction of osteogenesis. Bone formation increased prominently at the 3rd week.

Fig. 2

The von Kossa stain for matrix mineral deposition (400×). Matrix mineral deposition confirmed at the 3rd week after the induction of osteogenesis. The staining of the non-osteoporotic control group (A) was denser than the staining in the osteoporotic group (B).

Fig. 3

Osteoblast-specific gene expression in RT-PCR. Type I collagen, Osteocalcin and Osteopontin in RT-PCR increased by the 3rd & 4th weeks after the induction of osteogenesis.

Fig. 4

The expression of osteocalcin in [[the electrophoresis of RT-PCR]]. The expression of osteocalcin in the osteoporotic group (O) was 1.5 to 3 times less than in the non-osteoporotic control group (C). (n=3, O: Osteoporotic group, N: Non osteogenesis induced group, C: Control, non-osteoporotic group ^*p<0.05, ^**p<0.01)

Fig. 5

Quantitative assay of alkaline phosphatase activity (U/L) in bone marrow-derived MSCs. The non-osteoporotic control group (n=16) showed that alkaline phosphatase activity reached peak levels by the 3rd & 4th weeks after induction.

Fig. 6

Comparison of alkaline phosphatase activity (U/L) in bone marrow-derived MSCs between the osteoporotic group (n=9) and the non-osteoporotic group (n=16). The osteoporotic group showed lower alkaline phosphatase activities than the non-osteoporotic control group.

Fig. 7

Scatter plot for the relationship between the bone mineral density (BMD) and alkaline phosphatase activity. There was a statistically significant and positive correlation between BMD and alkaline phosphatase activity by the 3rd & 4th weeks after the induction of osteogenesis. R: correlation efficient.

Fig. 8

Scatter plot for the relationship between patient's age and alkaline phosphatase activity. There was a negative correlation between the patient's age and the alkaline phosphatase activity at the 3rd & 4th weeks after the induction of osteogenesis but it was not is no statistically significant. R: correlation efficient.