Distribution and persistence of technetium-99 hexamethyl propylene amine oxime-labelled bone marrow-derived mesenchymal stem cells in experimentally induced tendon lesions after intratendinous injection and regional perfusion of the equine distal limb.

This research article investigates the distribution and persistence of bone marrow-derived mesenchymal stem cells (MSCs) in tendon lesions in horses. The team compared different techniques for the injection of MSCs and hypothesized that vascular perfusion of the lower limb would lead to a higher concentration of MSCs in acute injuries. While the intralesional (i.l.) injection technique saw a higher initial uptake, its persistence decreased at similar rates across all methods. A time-dependent accumulation was found with intra-arterial regional limb perfusion (i.a. RLP).

Objective and Hypothesis

• The article’s objective is to study the efficiency of the different methods of injecting mesenchymal stem cells (MSCs) into tendon lesions, particularly comparing intratendinous injection and limb perfusion in horses.
• The hypothesis was that vascular perfusion of the distal limb in horses with MSCs would result in a more concentrated distribution of MSCs in acute tendon injuries.

Methodology

• An experimental study was conducted in vivo, meaning within the living body of the horse.
• Lesions were surgically induced in the superficial digital flexor tendons of the forelimbs of 8 horses. Three or 10 days after the lesion induction, MSCs labelled with technetium-99 hexamethyl propylene amine oxime were injected into the horses in three ways: intravenous or intra-arterial regional limb perfusion at the level of the distal antebrachium, and intratendinous injection.
• The persistence and distribution of MSCs within the forelimb and tendon lesions were assessed using scintigraphy, a diagnostic test that allows for imaging of the inside of the body, for 24 hours following the procedures.

Results

• Higher initial uptake was observed with direct injections into the lesion as compared to regional limb perfusion (RLP), however, the persistence of MSCs declined at similar rates across all three techniques.
• The intra-arterial RLP technique resulted in more evenly distributed MSCs and a higher uptake at the lesion site compared to intravenous RLP.
• When the limb was perfused intra-arterially on the tenth day, a greater accumulation of MSCs in the lesion was observed than when perfused on the third day.
• However, arterial thrombosis (blood clots) occurred with both intra-arterial and intravenous RLP, leading to clinical complications in one of the horses in the experiment.

Conclusion

• The article concludes that while RLP showed lower uptake than direct lesion injection, the two techniques exhibited similar persistence of MSCs at the lesion site.
• The scientists identified a time-dependent accumulation of MSCs with the use of intra-arterial RLP, although complications occurred such as arterial blood clots.
• It was concluded that the intra-arterial RLP method has advantages over the intravenous RLP method in terms of distribution and uptake, but due to the risk of arterial thrombosis, it cannot currently be suggested for clinical use.