Histologic and immunohistochemical evaluation of biocompatibility of castor oil polyurethane polymer with calcium carbonate in equine bone tissue.

In this study, scientists investigated the effectiveness of castor oil polyurethane polymer with calcium carbonate as a bone substitute in equine bone tissue. The substance was used in a small surgical procedure performed on the metacarpal bones of horses and then thoroughly evaluated for biocompatibility and osteoconductive properties.

Study Design

• The researchers first performed a unicortical ostectomy on the dorsal surface of both third metacarpal bones of each participating horse. An ostectomy is a surgical removal of bone and ‘unicortical’ implies a procedure affecting only one layer or section of the bone.
• Then, a polyurethane polymer derived from castor oil and calcium carbonate was implanted into the ostectomy site on one limb. The corresponding ostectomy site on the opposite limb was left unfilled and used as a control sample.

Study Conduct and Analysis

• All the ostectomy sites were evaluated after 120 days. This involved obtaining biopsy specimens from the interface of bone and either the polymer or the new tissue formation in the control sample.
• The obtained specimens were then subjected to histomorphometric evaluation, employing various microscopic techniques such as light microscopy, immunohistochemical analysis, histochemical analysis, and transmission electron microscopy.

Results and Conclusions

• The researchers found osteoblasts (cells responsible for new bone formation) in the biopsy samples, confirming the osteoconductive activity of the biomaterial.
• Furthermore, the absence of chronic inflammatory response or foreign body reaction indicated the biocompatibility of the substance. Biocompatibility refers to the ability of a substance to interact with a biological system without eliciting harmful effects.
• The expression of osteoblast markers was also detected in the newly formed tissue, further authenticating its role in new bone formation.
• Based on these results, the researchers concluded that castor oil polyurethane polymer with calcium carbonate may be an acceptable compound for use as a bone substitute in horses, especially in cases that require bone filling.