Tracking of autologous adipose tissue-derived mesenchymal stromal cells with in vivo magnetic resonance imaging and histology after intralesional treatment of artificial equine tendon lesions - a pilot study

Abstract

BackgroundAdipose tissue-derived mesenchymal stromal cells (AT-MSCs) are frequently used to treat equine tendinopathies. Up to now, knowledge about the fate of autologous AT-MSCs after intralesional injection into equine superficial digital flexor tendons (SDFTs) is very limited. The purpose of this study was to monitor the presence of intralesionally injected autologous AT-MSCs labelled with superparamagnetic iron oxide (SPIO) nanoparticles and green fluorescent protein (GFP) over a staggered period of 3 to 9 weeks with standing magnetic resonance imaging (MRI) and histology.MethodsFour adult warmblood horses received a unilateral injection of 10 × 106 autologous AT-MSCs into surgically created front-limb SDFT lesions. Administered AT-MSCs expressed lentivirally transduced reporter genes for GFP and were co-labelled with SPIO particles in three horses. The presence of AT-MSCs in SDFTs was evaluated by repeated examinations with standing low-field MRI in two horses and post-mortem in all horses with Prussian blue staining, fluorescence microscopy and with immunofluorescence and immunohistochemistry using anti-GFP antibodies at 3, 5, 7 and 9 weeks after treatment.ResultsAT-MSCs labelled with SPIO particles were detectable in treated SDFTs during each MRI in T2*- and T1-weighted sequences until the end of the observation period. Post-mortem examinations revealed that all treated tendons contained high numbers of SPIO- and GFP-labelled cells.ConclusionsStanding low-field MRI has the potential to track SPIO-labelled AT-MSCs successfully. Histology, fluorescence microscopy, immunofluorescence and immunohistochemistry are efficient tools to detect labelled AT-MSCs after intralesional injection into surgically created equine SDFT lesions. Intralesional injection of 10 × 106 AT-MSCs leads to the presence of high numbers of AT-MSCs in and around surgically created tendon lesions for up to 9 weeks. Integration of injected AT-MSCs into healing tendon tissue is an essential pathway after intralesional administration. Injection techniques have to be chosen deliberately to avoid reflux of the cell substrate injected. In vivo low-field MRI may be used as a non-invasive tool to monitor homing and engraftment of AT-MSCs in horses with tendinopathy of the SDFT.

Mesenchymal stem cells in tendon repair and regeneration: basic understanding and translational challenges

“…For cell-based therapies, cells can be delivered in a suspension via injection at the site of injury, [83][84][85][86] implanted in the form of cell sheets, [87][88][89] or incorporated into a scaffold, [90][91][92] as done in preclinical studies for TSPCs (Table 1), in order to enable homogeneous cell distribution and localization to the site of injury. However, it is unclear at which time point or window cells should be implanted into the site of tendon injury after pretreatment with appropriate growth factors or mechanical stimulation.…”

Experimental bladder regeneration using a poly-L-lactide/silk fibroin scaffold seeded with nanoparticle-labeled allogenic bone marrow stromal cells

“…Similar data were obtained by other groups when SPION-labeled stem cells were applied. 41,43 In our study, we applied BMSCs, though combination with other methods might be beneficial in bladder repair. Another possible approach to stimulate bladder regeneration in vivo could be based on application of various agents (eg, cytokines, growth factors) that promote cellular ingrowth from the native bladder wall.…”

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.…”

“…62 Studies using SPIO labeling in naturally occurring tendinopathy were able to detect umbilical cord-derived MSCs within lesions in 5 of 7 horses for 8 weeks, 68 and adiposederived MSCs in 4 of 4 horses for 9 weeks. 63 Although these studies are focused on determining cell location and survival, it is still unclear exactly how long MSCs need to survive within a lesion or whether cells even need to remain at the site of injury to stimulate joint or tendon healing.…”