gms | German Medical Science

Objectives: Osteoporosis is one of the main diseases that burdens industrial societies in its socio-economic impact in both preventive and fracture healing stages. Therefore, a better understanding of cellular and extracellular mechanisms of osteoporotic fracture healing is the key to their treatment and management.

Methods: 31 female merino land sheep were randomly divided into 4 groups. 1) Untreated control-group (C, n=8) 2) bilateral ovariectomy (OVX, n=7) 3) OVX and calcium-deficient diet (OVXD, n=8) and 4) OVXD and additional biweekly corticosteroid injections (OVXDS, n=8). Drill-hole defects (7.5mm in diameter) were created in the iliac crest. Healing time points were 5 month (M) and 8M post fracture. Bone healing was histomorphometrically assessed using Movat pentachrom staining. Cellular changes were detected using TRAP and ALP staining, immunhistochemistry of Type I Collagen (Col I) was performed. Image J was used for image analysis and SPSS software was used to explore statically significant results.

Results and Conclusion: Qualitatively, trabecular bone thickness is lower especially in the OVXDS group during the timepoints, cortical bone thickness is higher in control and OVXD group, in OVX and OVXDS group it stays on the same level. Histomorphometry showed higher total ossified tissue (TOT) and lower total cartilage tissue (TCT) in control group from 5M to 8M marking the healing process. In contrast, OVXDS group showed the highest TCT and the lowest TOT at 8M. Osteoid formation was lower after 8M than 5M in control and OVX group, in OVXD and OVXDS group osteoid was higher than after 5M. The total number of osteoclasts was lower after 8M than after 5M in each group. Ratio of osteoclast resorption pits to bone surface was significant lower in control and OVX group throughout the time points compared to OVXD and OVXDS. ALP positive area was lower after 8M than 5M in experimental groups. Interestingly OVXDS group showed significantly higher levels of ALP than all other groups at both time points. Col I signal intensity and area was higher in C and surprisingly in OVXDS group after 8M compared to 5M, OVX and OVXD showed lower values after 8M compared to 5M.

The control group reflected normal healing pattern through the higher Col I, lower osteoclast number and lower ALP area after 8M of healing. However, experimental group pattern varied in respect to treatment indicating increased osteoid portions and cartilage remnant with treatment progression.

Currently Col X, RANKL and ASMA IHC are being explored for further cellular discrepancies in osteoporotic fractures.