Scintigraphic Tracking of Allogeneic Mesenchymal Stem Cells in the Distal Limb After Intra-Arterial Injection in Standing Horses.

This study looks into the feasibility of injecting allogeneic mesenchymal stem cells (MSC) into the median artery of standing horses and monitor their distribution and retention via scintigraphic imaging. The researchers found that the procedure could be carried out successfully and the MSC could be well-distributed in the distal limb of horses, despite some observed complications such as partial venous thrombosis and periarterial injection.

Methodology

• The experimental study involved six research horses.
• Technetium(99m) -HexaMethyl-Propylene-Amine Oxime-labeled MSC were injected into the median artery of 6 front limbs of 3 horses under ultrasound guidance. Technetium is a radioactive tracer that enables visualisation of the stem cells’ distribution through scintigraphic imaging.
• Scintigraphic images were obtained right at the injection time and at intervals post-injection: 1, 6, and 24 hours.
• Six additional limbs from 3 different horses were also injected with MSC but these cells did not contain any radiolabel, for comparison.
• Ultrasound scans were done the next day to assess potential vascular changes.

Results

• In 11 out of 12 limbs, the intra-arterial injection procedure was completed successfully.
• In one of the limbs, a partial periarterial injection was done mistakenly which hindered the success of the procedure.
• The distribution of radiolabeled MSC was seen throughout the entire distal limb, including within the hoof of the horse. The distribution indicates the ability of the stem cells to reach deep regions of the body.
• Thrombosis, or formation of blood clots, in the vein was observed in both groups of horse. However, it was less severe in the horses from the unlabeled MSC group.
• Nobody observed any instances of lameness in the horses and swelling was observed in just one limb, which was transient.

Conclusion

• Administering MSC intra-arterially is possible in standing horses under sedation, and it allows for successful distribution of the MSC to different parts of the distal limb.
• Complications such as periarterial injection were noticed which could be lessened with better sedation, local anesthesia, and more experience with the procedure.
• Partial venous thrombosis did occur as a side-effect, but it did not lead to significant clinical changes, other than rare instances of transient swelling.