Long-Term Cell Tracking following Local Injection of Mesenchymal Stromal Cells in the Equine Model of Induced Tendon Disease

Abstract

Tendon disease has been treated with multipotent mesenchymal stromal cells (MSCs) in the equine large-animal model with promising success. The aim of this study was to gain more insight into the fate and biodistribution of MSCs after local application into tendon lesions by long-term cell tracking in this large-animal model. Superficial digital flexor tendon lesions were induced in all limbs in six horses and injected with 10106 Molday ION Rhodamine B-labeled MSCs suspended in serum or serum alone. Follow-up was performed using low-field magnetic resonance imaging (MRI), flow cytometry, and histology. Cell tracking based on the hypointense artifacts induced by the superparamagnetic iron oxide (SPIO) labeling agent in MRI as well as based on Rhodamine B fluorescence was feasible. However, Prussian blue staining for assessment of histology was not entirely specific for SPIO. Labeled cells could be traced at their injection site by MRI as well as histology for the whole follow-up period of 24 weeks. Although the numbers of labeled cells within the injected tendon lesions decreased over time, part of the applied cells appeared to remain viable and integrated within the injured tissue. Furthermore, small numbers of labeled cells were identified in peripheral blood within the first 24 h after cell injection and could also be found until week 24 within the contralateral control tendon lesions that had been injected with serum. The present findings unveil details on MSC biodistribution and persistence after their local application, which are of clinical relevance with regard to MSC safety and mechanisms of action.

Persistence of fluorescent nanoparticle‐labeled bone marrow mesenchymal stem cells in vitro and after intra‐articular injection

“…To determine if injected MSCs participate in tissue repair, attempts have been made to label MSCs, so they may be tracked after injection. Methods for in vivo cell tracking in large animal models include labelling MSCs with compounds that can be imaged using nuclear scintigraphy or magnetic resonance imaging, such as technetium‐99 (Dudhia, Becerra, Valdés, et al, ; Spriet et al, ) and superparamagnetic iron‐oxide particles (Burk et al, ; Geburek et al, ), respectively. In a canine model, MSCs used for intra‐articular injection were labelled with iron oxide or with a fluorescent dye, and in vivo detection of the labelled MSCs was performed using magnetic resonance imaging and fluorescent imaging (Wood et al, ).…”

Equine Models for the Investigation of Mesenchymal Stem Cell Therapies in Orthopaedic Disease

“…62 To track MSCs, the cells can be labeled using technetium-99m and tracked using nuclear scintigraphy or labeled with superparamagnetic iron oxide (SPIO) nanoparticles for analysis by MRI. [63][64][65] In addition, Burk et al 66 has described labeling of cells with Molday ION Rhodamine B labeling, thereby allowing the cells to be tracked both with MRI and flow cytometry. Finally, cells may be marked with green flourescent protein (GFP) for histologic analysis.…”

Novel Application Method for Mesenchymal Stem Cell Therapy Utilizing Its Attractant-Responsive Accumulation Property

“…Therefore, we focused on the potential of MSCs to autonomously accumulate in damaged tissue [13][14][15]. Our hypothesis is that subcutaneous administration of a mixture of scaffold and MSCs into the body, such as under the easily accessible back skin, will result in MSCs autonomously migrating from the scaffold to the site where cytokines are produced and enhancing tissue repair [16].…”