Mesenchymal stromal/stem cells (MSCs) are increasingly employed for tissue regeneration, largely mediated through paracrine actions. Currently, extracellular vesicles (EVs) released by MSCs are major mediators of these paracrine effects. We evaluated whether rat-bonemarrow-MSC-derived EVs (rBMSCs-EVs) can ameliorate tendon injury in an in vivo rat model. Pro-collagen1A2 and MMP14 protein are expressed in rBMSC-EVs, and are important factors for extracellular-matrix tendon-remodeling. In addition, we found pro-col-lagen1A2 in rBMSC-EV surface-membranes by dot blot. In vitro on cells isolated from Achilles tendons, utilized as rBMSC-EVs recipient cells, EVs at both low and high doses induce migration of tenocytes; at higher concentration, they induce proliferation and increase expression of Collagen type I in tenocytes. Pretreatment with trypsin abrogate the effect of EVs on cell proliferation and migration, and the expression of collagen I. When either low-or high-dose rBMSCs-EVs were injected into a rat-Achilles tendon injury-model (immediately after damage), at 30 days, rBMSC-EVs were found to have accelerated the remodeling stage of tendon repair in a dose-dependent manner. At histology and histomorphology evaluation, high doses of rBMSCs-EVs produced better restoration of tendon architecture, with optimal tendon-fiber alignment and lower vascularity. Higher EV-concentrations demonstrated greater expression of collagen type I and lower expression of

ABSTRACT

Background This pilot study aimed to ascertain whether the local application of ascorbic acid (AA), of T 3 , and of rat (r) bone marrow mesenchymal stem cells (BMSCs), alone or in all possible combinations, promoted healing after an Achilles tendon injury in a rat model. Methods An Achilles tendon defect was produced in 24 6–8-week-old male inbred Lewis rats. The animals were then randomly divided into eight groups of three rats each. The tendon defect was filled with 50 μL of phosphate-buffered saline (PBS) containing (1) 50 μg/mL AA (AA group), (2) 10 −7 M T 3 (T 3 group), (3) 4 × 10 6 rBMSCs (rBMSC group), (4) 50 μg/mL AA + 10 −7 M T 3 (AA + T 3 group), (5) 4 × 10 6 rBMSCs + 50 μg/mL AA (rBMSC + AA group), (6) 4 × 10 6 rBMSCs + 10 −7 M T 3 (rBMSC + T 3 group), (7) 4 × 10 6 rBMSCS + 50 μg/mL AA + 10 −7 M T 3 (rBMSC + AA + T 3 group), and (8) PBS only (control group: CTRL). All treatments were administered by local injection immediately after the tendons had been damaged; additionally, AA was injected also on the second and fourth day from the first injection (for groups 1, 4, 5, and 7), and T 3 was injected again every day for 4 days (for groups 2, 4, 6, and 7). At 30 days from initial treatment, tendon samples were harvested, and the quality of tendon repair was evaluated using histological and histomorphological analysis. The structure and morphology of the injured Achilles tendons were evaluated using the modified Svensson, Soslowsky, and Cook score, and the collagen type I and III ratio was calculated. Results The group treated with AA combined with T 3 displayed the lowest Svensson, Soslowsky, and Cook total score value of all tissue sections at histopathological examination, with fiber structure close to regular orientation, normal-like tendon vasculature, and no cartilage formation. AA + T 3 also showed the highest collagen I and the lowest collagen III values compared to all other treatments including the CTRL. Conclusion There are potential benefits using a combination of AA and T 3 to accelerate tendon healing.

Non-traumatic rotator cuff tears (RCTs) are a frequent and potentially disabling injury. There is growing evidence that hyaluronic acid is effective for pain relief and to counteract inflammation in RCTs, however, its effective role in tendinopathies remains poorly studied. The present study aims to disclose a possible molecular mechanism underlying the cytoprotective effects of four different hyaluronic acid preparations (Artrosulfur HA®, Synolis-VA ®, Hyalgan® and Hyalubrix®) under H 2 O 2 -induced oxidative stress. Expression-levels of Lactate dehydrogenase (LDH) released were quantified in cell supernatants, CD44 expression levels were analysed by fluorescence microscopy, the mitochondrial membrane depolarization (TMRE assay) was measured by flow cytometry and the role of the transcription factor Nrf2 was investigated as a potential therapeutic target for RCT treatment. The modulation of extracellular matrix-(ECM) related protein expression (Integrin β1, Pro-collagen 1A2 and Collagen 1A1) and autophagy occurrence (Erk 1/2 and phosphoErk 1/2 and LC3B), were all investigated by Western Blot. Results demonstrate that Artrosulfur HA, Hyalubrix and Hyalgan improve cell escape from H 2 O 2 -induced oxidative stress, decreasing cytotoxicity, reducing Nrf2 expression and enhancing catalase recovery. The present study lays the grounds for further investigations insight novel pharmaceutical strategies targeting key effectors involved in the molecular cascade triggered by hyaluronic acid.

Background: Hyaluronic Acid (HA) has been already approved by Food and Drug Administration (FDA) for osteoarthritis (OA), while its use in the treatment of tendinopathy is still debated. The aim of this study was to evaluate the effects of two different HA on human rotator cuff tendon derived cells in terms of cell viability, proliferation and apoptosis. Methods: An in vitro model was developed on human tendon derived cells from rotator cuff tears to study the effects of two different HA preparations: Sinovial HL® (High-Low molecular weight) (MW: 80-100 kDa) and KDa Sinovial Forte SF (MW: 800-1200), at various concentrations. Tendon de-rived cells morphology was evaluated after 0, 7 and 14 d of culture. Viability and proliferation were analyzed after 0, 24, and 48 h of culture and apoptosis occurrence was assessed after 24 h of culture.Results: All the HAPs tested here increased viability and proliferation, in a dose-dependent manner and they reduced apoptosis at early stages (24 h) compared to control cells (without HAPs). Conclusions: HAPs enhanced viability and proliferation and counteracted apoptosis in tendon derived cells.