Aortic valve stenosis and osteoporosis: insights from a mouse model

Abstract

Background: Aortic valve stenosis (AVS) is the most common heart valve disease requiring intervention. Osteoporosis, affecting ~ 10% of those over 50, is linked to aortic valve calcification and increased AVS risk. However, its direct role in AVS development or progression remains unclear. Using a mouse model, we examined whether estrogen-deficiency-induced osteoporosis modifies early hemodynamic and histological remodeling of the aortic valve after mechanical injury, and whether zoledronic acid (ZA) treatment alters these processes.

Methods: Osteoporosis was induced in mice via bilateral ovariectomy (OVX), with sham-operated controls. To prevent bone loss, ZA or vehicle were administered weekly via intraperitoneal injection. Two weeks post-OVX, AVS was induced by mechanically injuring the aortic valve under echocardiographic guidance, with control procedures (CTR) in separate groups. After model validation, C57BL/6J mice were assigned to six groups: WI Sham Vehicle, WI OVX Vehicle, WI OVX ZA, WI Sham ZA, CTR OVX Vehicle, and CTR OVX ZA. Echocardiography was performed at baseline and 2, 4, and 6 weeks post-injury. Bone density was assessed via micro-CT and histology, with peak aortic velocity as the primary endpoint. Mice were euthanized at 8 weeks for tissue analysis.

Results: OVX induced a significant reduction in trabecular bone mineral density (TBM, 50.6%, p = 0.0025). Treatment with ZA effectively reversed bone resorption in OVX mice (p < 0.0001) and even enhanced trabecular structures compared to sham-operated animals (increase of TBM by 130%, p < 0.0001). Mechanical injury to the aortic valve successfully induced AVS, as evidenced by increased peak velocity (1294 vs. 2157 mm/s, p < 0.0001) and mean pressure gradient 2 weeks post-procedure (1.58 vs. 4.19 mmHg, p < 0.0001). However, neither OVX nor ZA treatment influenced the severity of AVS. Histological analyses confirmed aortic valve thickening following injury. Picrosirius red and CD68 staining revealed no differences in collagen content or immune cell infiltration of the aortic valve between osteoporotic and non-osteoporotic animals.

Conclusion: OVX-induced osteoporosis did not affect AVS severity after mechanical injury in our study. This suggests osteoporosis may not directly influence AVS in the early, pre-calcific stage that was studied in this model. However, to overcome limitations of the study, further studies with longer durations or refined models are needed to confirm these findings.

Keywords: Animal model; Aortic valve stenosis; Heart valve disease; Osteoporosis.

Fig. 1

Experimental timeline and bone analysis after ovariectomy (OVX) and zoledronic acid (ZA) treatment. a Timeline of interventions: OVX or sham surgery, wire injury (WI), and weekly ZA/vehicle (VEH) injections. b µCT analysis shows OVX-induced reductions in trabecular and cortical bone parameters, which ZA treatment significantly preserved. c Representative µCT images of distal femurs highlight structural differences between groups. d Histological (H&E) images confirm ZA’s protective effects on trabecular bone

Fig. 2

Echocardiographic assessment of aortic valve and cardiac function over time. a, b Peak velocity and mean pressure gradient (MPG) increased significantly after wire injury (WI) compared to control (CTR) groups, with no substantial differences between groups based on osteoporosis status or zoledronic acid (ZA) treatment. c Ejection fraction velocity ratio was unaffected by osteoporosis or ZA treatment across all groups. d Ejection fraction showed a trend toward increase in ZA-treated groups compared to vehicle (VEH)-treated groups. e, f Cardiac output and left ventricular mass remained stable across all groups during the 8-week observation period, indicating no overt cardiac dysfunction regardless of treatment or osteoporosis status

Fig. 3

Histological and immunohistochemical analysis of aortic valves. a Hematoxylin and eosin (H&E) staining revealed increased cusp area in WI groups, with no significant differences based on ZA treatment or osteoporosis status. b Picrosirius red staining showed increased collagen deposition in WI groups, with higher levels observed in ZA-treated animals. c CD68 immunostaining indicated elevated immune cell infiltration in WI groups, independent of ZA treatment or osteoporosis status