An evaluation of bone marrow-derived mesenchymal stem cells as a treatment for collagenase induced desmitis of the proximal suspensory ligament in horses

Chad Aaron Marsh

doi:10.7273/000004295

Objective – To evaluate the use of bone marrow derived mesenchymal stem cells (BMdMSC) to evaluate healing of the proximal suspensory ligament in horses with collagenase-induced desmitis and determine how evidence of healing on MRI and ultrasonographic examinations correlates to histologic and biochemical healing of the suspensory ligament. Animals – 6 horses Procedures – Clinical and MRI examinations were performed to confirm that the suspensory ligament was normal. Autologous bone marrow was collected from the tuber coxae, mesenchymal stem cells were cultured, expanded, and frozen at -80° C. Desmitis of the proximal suspensory ligament was induced with collagenase in both hindlimbs of each horse. One randomly assigned limb in each horse was treated with autogenous bone marrow derived mesenchymal stem cells (BMdMSC’s) at 2 weeks post collagenase injection, and the opposite limb was not treated. All horses were placed into a 6 months rest and rehabilitation program. Lameness examinations were performed throughout the study to determine clinical response to treatment. Healing was evaluated by MRI and ultrasound examinations 28, 90, and 200 days following induction of desmitis. Horses were euthanized at 228 days. Biochemical analysis of soluble collagen, DNA, proteoglycan and collagen type I and III were performed. Gross and histologic evaluation of ligament structure, fiber alignment, and collagen typing were used to define ligament architecture. Results – Immunohistochemical and histologic evaluation revealed improvements in ligament architectural organization, reduction in type III collagen, increases in type I collagen, and improvements in alignment of collagen fibers and fiber density in BMdMSC treated ligaments. There was no difference in biochemical indices between the two groups. MRI and ultrasound results revealed improvement in quality and rate of repair in BMdMSC treated and control ligaments over the course of the study. Ultrasonography underestimated ligament size and lesion size initially compared to MRI; however, at the conclusion of the study ultrasonographic examinations significantly overestimated lesion size. Low signal on Proton Density (PD) MRI at the previous site of desmitis correlated with histologic healing and collagen fiber reorganization at the conclusion of the study. Conclusions and Clinical Relevance – Intralesional injection of BMdMSC improves healing of the suspensory ligament. Rest alone has been a mainstay of treatment; however, ligaments treated with rest and intralesional injection of BMdMSC were more structurally normal than ligaments treated with rest alone. Ultrasound significantly underestimates the severity of ligament damage following an acute injury. MRI is recommended to determine an accurate estimate of the severity of damage to the proximal suspensory ligament in the rear limbs of horses.

An evaluation of bone marrow-derived mesenchymal stem cells as a treatment for collagenase induced desmitis of the proximal suspensory ligament in horses

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