Vascular endothelial growth factor for the treatment of femoral head osteonecrosis: An experimental study in canines

Abstract

Aim: To evaluate the treatment of osteonecrosis of the femoral head (ONFH) with the use of vascular endothelial growth factor (VEGF).

Methods: In 30 mature beagles (6 groups of 5 beagles) ONFH was induced cryosurgically and one of the following solutions was administered locally in the femoral head (FH) in each group: Single injection of 500 μg VEGF (t-VEGFμ group); single injection of 500 ng VEGF (t-VEGFn group); continuous delivery of 500 μg VEGF through osmotic micropump (t-VEGFpump-μ group); continuous delivery of 500 ng VEGF through osmotic micropump (t-VEGFpump-n group); single injection of 0.9% sodium chloride (t-NS group), while one group that served as control group did not receive any local solution (No-t group). FHs were retrieved 12 wk postoperatively, underwent decalcification and hematoxylin/eosin and toluidine blue staining. In two canines per group, one half of FH was processed without decalcification and stained with modified Masson Trichrome. Histological sections were observed by light microscopy and measured with a semi-automatized bone histomorphometry system and Bone Volume/Total Volume (BV/TV), Marrow Volume/Total Volume (MaV/TV), and Trabecular Thickness (TbTh) were assessed. Standard and robust tests (Welch, Brown Forsythe) of analysis of variance along with multiple comparisons, were carried out among the categories.

Results: The untreated (No-t) group had signs of osteonecrosis, whereas the VEGF groups revealed reversal of the osteonecrosis. Statistical analysis of the decalcified specimens revealed a significantly better BV/TV ratio and a higher TbTh between the VEGF treatment groups (except the t-VEGFn group) and the No-t group or the control t-NS group. Single dose 500 μgVEGF group had significantly better BV/TV ratio and higher TbTh when compared to the No-t group (50.45 ± 6.18 vs 29.50 ± 12.27, P = 0.002 and 151.44 ± 19.07 vs 107.77 ± 35.15, P = 0.161 respectively) and the control t-NS group (50.45 ± 6.18 vs 30.9 ± 6.67, P = 0.004 and 151.44 ± 19.07 vs 107.14 ± 35.71, P = 0.151 respectively). Similar differences were found for the prolonged VEGF delivery/pump groups of 500 μg and 500 ng. Analysis of the totality of specimens (decalcified/non-decalcified) enhanced the aforementioned differences and additionally revealed significant differences in the comparison of the TbTh.

Conclusion: In an experimental model of ONFH in canines it was found that local treatment with VEGF leads to bone tissue remodeling and new bone formation.

Keywords: Animal model; Avascular necrosis; Femoral head; Osteogenesis; Osteonecrosis; Vascular endothelial growth factor.

Figure 1

Cryosurgically-induced osteonecrosis of the femoral head (No-t group). The specimen was retrieved 12 wk postoperatively. A: Cancellous lamellar bone (T) with empty bone lacunae (L) marked with arrows, and fibrotic/loose connective tissue marrow space (F), indicating osteonecrosis (Obj. × 10, H and E); B: Lamellar compact bone (Lm) of cortical type, in between spaces filled with adipose tissue (A). The absence of nuclei in osteocyte’s lacunae (L) (marked with arrows) indicates that the bone is necrotic (Obj. × 10, TB).

Figure 2

Osteonecrosis of the femoral head treated with a single injection of 500 μg vascular endothelial growth factor (t-VEGFμ group); specimen retrieved 12 wk postoperatively. A well-formed cancellous bone network with thickened lamellar trabeculae is visible, while the in between spaces are filled with normal marrow cells (M). A: Newly formed (vT) were noticed on the surface of the trabeculae (T) (Obj. × 10, H and E). B: Almost all trabeculae’s (T) surface is covered by newly (vT) formed bone (Obj. × 10, TB).

Figure 3

Osteonecrosis of the femoral head treated with prolonged delivery of 500 μg of vascular endothelial growth factor through a pump (t-VEGFpump-μ group). At 12 wk postoperatively, a well-formed trabecular network is visible, with slightly thickened lamellar trabeculae, and normal marrow cells and adipose tissue (A) in between. A: Few trabeculae are covered by newly formed bone (vT), the presence of nuclei in lacunae is noticed (Obj. × 10, H and E); B: New bone (vT) formation is observed on the surface of some trabeculae (Obj. × 10, TB).

Figure 4

Comparative boxplot of the bone volume/total volume values across the different groups for the decalcified specimens. BV/TV: Bone volume/total volume; VEGF: Vascular endothelial growth factor.

Figure 5

Comparative boxplot of the trabecular thickness values across the different groups for the decalcified specimens. Higher box and whiskers stand for higher TbTh values. TbTh: Trabecular thickness; VEGF: Vascular endothelial growth factor.

Figure 6

Comparative boxplot of the bone volume/total volume values across the different groups for the decalcified and non-decalcified specimens. BV/TV: Bone volume/total volume; VEGF: Vascular endothelial growth factor.

Figure 7

Comparative boxplot of the trabecular thickness values across the different groups for the decalcified and non-decalcified specimens. Higher box and whiskers stand for higher TbTh values. TbTh: Trabecular thickness; VEGF: Vascular endothelial growth factor.

Figure 8

Diagram summarizing potential interactions of vascular endothelial growth factor related to bone tissue healing in femoral head osteonecrosis. VEGF: Vascular endothelial growth factor; HIF: Hypoxia–inducible factor; EPO: Erythropoietin; TNF: Tumor necrosis factor; IL: Interleukin.