Mesenchymal stem cells (MSCs) are known to migrate to tissue injury sites to participate in immune modulation, tissue remodelling and wound healing, reducing tissue damage. Upon neutrophil activation, there is a release of myeloperoxidase (MPO), an oxidant enzyme. But little is known about the direct role of MSCs on MPO activity. The aim of this study was to investigate the effect of equine mesenchymal stem cells derived from muscle microinvasive biopsy (mdMSC) on the oxidant response of neutrophils and particularly on the activity of the myeloperoxidase released by stimulated equine neutrophils. After specific treatment (trypsin and washings in phosphate buffer saline), the mdMSCs were exposed to isolated neutrophils. The effect of the suspended mdMSCs was studied on the ROS production and the release of total and active MPO by stimulated neutrophils and specifically on the activity of MPO in a neutrophil-free model. Additionally, we developed a model combining adherent mdMSCs with neutrophils to study total and active MPO from the neutrophil extracellular trap (NET). Our results show that mdMSCs inhibited the ROS production, the activity of MPO released by stimulated neutrophils and the activity of MPO bound to the NET. Moreover, the co-incubation of mdMSCs directly with MPO results in a strong inhibition of the peroxidase activity of MPO, probably by affecting the active site of the enzyme. We confirm the strong potential of mdMSCs to lower the oxidant response of neutrophils. The novelty of our study is an evident inhibition of the activity of MPO by MSCs. The results indicated a new potential therapeutic approach of mdMSCs in the inhibition of MPO, which is considered as a pro-oxidant actor in numerous chronic and acute inflammatory pathologies.

There is a growing interest in the use of natural compounds to tackle inflammatory diseases and cancers. However, most of them face the bioavailability and solubility challenges to reaching cellular compartments and exert their potential biological effects. Polyphenols belong to that class of molecules, and numerous efforts have been made to improve and overcome these problems. Curcumin is widely studied for its antioxidant and anti-inflammatory properties as well as its use as an anticancer agent. However, its poor solubility and bioavailability are often a source of concern with disappointing or unexpected results in cellular models or in vivo, which limits the clinical use of curcumin as such. Beside nanoparticles and liposomes, cyclodextrins are one of the best candidates to improve the solubility of these molecules. We have used lysine and cyclodextrin to form a water-soluble curcumin complex, named NDS27, in which potential anti-inflammatory effects were demonstrated in cellular and in vivo models. Herein, we investigated for the first time its direct free radicals scavenging activity on DPPH/ABTS assays as well as on hydroxyl, superoxide anion, and peroxyl radical species. The ability of NDS27 to quench singlet oxygen, produced by rose bengal photosensitization, was studied, as was the inhibiting effect on the enzyme-catalyzed oxidation of the co-substrate, luminol analog (L012), using horseradish peroxidase (HRP)/hydrogen peroxide (H₂O₂) system. Finally, docking was performed to study the behavior of NDS27 in the active site of the peroxidase enzyme.

Laminitis in horses is a crippling condition marked by the deterioration of the dermal–epidermal interface, leading to intense lameness and discomfort, often necessitating euthanasia. This study aimed to establish an in vitro model of laminitis using a continuous keratinocyte cell line exposed to anoxia–reoxygenation and an activated neutrophil supernatant. A significant decrease in the keratinocytes’ metabolism was noted during the reoxygenation period, indicative of cellular stress. Adding muscle-derived mesenchymal stem/stromal cells during the reoxygenation demonstrated a protective effect, restoring the keratinocytes’ metabolic activity. Moreover, the incubation of the keratinocytes with either an activated neutrophil supernatant or myeloperoxidase alone induced increased keratinocyte myeloperoxidase activity, which was modulated by stem cells. These findings underscore the potential of muscle-derived mesenchymal stem/stromal cells in mitigating inflammation and restoring keratinocyte metabolism, offering insights for future cell therapy research in laminitis treatment.

We investigated the antioxidant potential of equine mesenchymal stem cells derived from muscle microbiopsies (mdMSCs), loaded by a water-soluble curcumin lysinate incorporated into hydroxypropyl-β-cyclodextrin (NDS27). The cell loading was rapid and dependent on NDS27 dosage (14, 7, 3.5 and 1 µM). The immunomodulatory capacity of loaded mdMSCs was evaluated by ROS production, on active and total myeloperoxidase (MPO) degranulation and neutrophil extracellular trap (NET) formation after neutrophil stimulation. The intracellular protection of loaded cells was tested by an oxidative stress induced by cumene hydroperoxide. Results showed that 10 min of mdMSC loading with NDS27 did not affect their viability while reducing their metabolism. NDS27 loaded cells in presence of 14, 7 µM NDS27 inhibited more intensively the ROS production, the activity of the MPO released and bound to the NET after neutrophil stimulation. Furthermore, loaded cells powerfully inhibited intracellular ROS production induced by cumene as compared to control cells or cyclodextrin-loaded cells. Our results showed that the loading of mdMSCs with NDS27 significantly improved their antioxidant potential against the oxidative burst of neutrophil and protected them against intracellular ROS production. The improved antioxidant protective capacity of loaded mdMSCs could be applied to target inflammatory foci involving neutrophils.

Tendon and ligament injuries are frequent in sport horses and are prone to recurrence due to incomplete healing. Platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) are increasingly used, but data controlled on the early effects of autologous MSCs remain limited. A prospective randomized, double-blind, placebo-controlled trial was conducted in horses with naturally occurring tendinopathies. After standardized PRP pretreatment, non-responders were randomized to receive intralesional autologous muscle-derived MSCs (mdMSCs, n = 17) or placebo (n = 6). Clinical and ultrasonographic parameters were evaluated at the recruitment period (T0) before the administration of the local treatment (T1), 4 (T2) and 8 weeks later (T3). Eighteen horses from both groups received at T2 a second intralesional injection of mdMSCs at the investigator’s discretion; this phase was not randomized. Horses treated with mdMSCs showed significant improvements from T1 to T2 across both clinical and ultrasonographic parameters, whereas no significant changes were observed in the placebo group. Between-group comparison at T2 confirmed the significant superiority of mdMSCs. Further improvements were observed between T2 and T3 in the 18 horses that received a second injection. No systemic adverse events were recorded, and local reactions were mild and transient. This randomized controlled trial demonstrates early clinical and ultrasonographic efficacy of autologous mdMSCs in equine tendinopathy, with additional benefit from a second injection. The autologous approach combines efficacy and safety while avoiding the immunological and logistical constraints of allogeneic strategies.

Equine laminitis is a debilitating condition characterized by the breakdown of the dermal–epidermal junction, resulting in severe lameness and pain, often requiring euthanasia. This study aimed to establish an in vitro model of laminitis using a continuous keratinocyte cell line exposed to anoxia-reoxygenation and activated neutrophil supernatant. A significant decrease in keratinocytes metabolism was noted during the reoxygenation period, indicative of cellular stress. Adding muscle-derived mesenchymal stem/stroma cells during reoxygenation demonstrated a protective effect, restoring keratinocytes metabolic activity. Moreover, incubation of keratinocytes with activated neutrophil supernatant or myeloperoxidase alone induced increased keratinocyte myeloperoxidase activity, which was modulated by stem cells. These findings underscore the potential of muscle-derived mesenchymal stem/stroma cells in mitigating inflammation and restoring keratinocyte metabolism, offering insights for future cell therapy research in laminitis treatment.