Dipeptidyl peptidase 4/CD26 expression in human idiopathic inflammatory myopathies reveals skeletal muscle injury and vascular inflammation.

OBJECTIVES: We performed a retrospective and prospective observational study to investigate whether the T lymphocyte activation antigen dipeptidyl peptidase 4 (DPP4)/CD26 is expressed in the skeletal muscle of patients with idiopathic inflammatory myopathies (IIM) and whether its expression offers clues to understand the events taking place in the tissue. METHODS: CD26 expression in the muscle, evaluated by immunofluorescence, was assessed in 32 patients with IIM and 5 healthy controls and compared among patients with dermatomyositis (DM), immune-mediated necrotising myopathy (IMNM), inclusion body myositis (IBM), and polymyositis (PM). The relationship of CD26 expression and localization with clinical, serological and histological features was determined. RESULTS: CD26 is selectively expressed in the skeletal muscle of patients with IIM. The highest levels of CD26 are found in the skeletal muscle from patients with DM and in particular in those characterized by tissue necrosis and vascular inflammation. CD26 expression is associated with decreased muscle performance and independently predicts the number of treatments before reaching disease stabilization or improvement (odds ratio, OR=1.2, p<0.05). CONCLUSIONS: CD26 is expressed in the IIM skeletal muscle and may represent a target of molecular intervention for patients with treatment-refractory myositis.

Rebalancing expression of HMGB1 redox isoforms to counteract muscular dystrophy.

Muscular dystrophies (MDs) are a group of genetic diseases characterized by progressive muscle wasting associated to oxidative stress and persistent inflammation. It is essential to deepen our knowledge on the mechanism connecting these two processes because current treatments for MDs have limited efficacy and/or are associated with side effects. Here, we identified the alarmin high-mobility group box 1 (HMGB1) as a functional link between oxidative stress and inflammation in MDs. The oxidation of HMGB1 cysteines switches its extracellular activities from the orchestration of tissue regeneration to the exacerbation of inflammation. Extracellular HMGB1 is present at high amount and undergoes oxidation in patients with MDs and in mouse models of Duchenne muscular dystrophy (DMD) and limb-girdle muscular dystrophy 3 (LGMDR3) compared to controls. Genetic ablation of HMGB1 in muscles of DMD mice leads to an amelioration of the dystrophic phenotype as evidenced by the reduced inflammation and muscle degeneration, indicating that HMGB1 oxidation is a detrimental process in MDs. Pharmacological treatment with an engineered nonoxidizable variant of HMGB1, called 3S, improves functional performance, muscle regeneration, and satellite cell engraftment in dystrophic mice while reducing inflammation and fibrosis. Overall, our data demonstrate that the balance between HMGB1 redox isoforms dictates whether skeletal muscle is in an inflamed or regenerating state, and that the nonoxidizable form of HMGB1 is a possible therapeutic approach to counteract the progression of the dystrophic phenotype. Rebalancing the HMGB1 redox isoforms may also be a therapeutic strategy for other disorders characterized by chronic oxidative stress and inflammation.

Intra-arterial transplantation of HLA-matched donor mesoangioblasts in Duchenne muscular dystrophy.

Intra-arterial transplantation of mesoangioblasts proved safe and partially efficacious in preclinical models of muscular dystrophy. We now report the first-in-human, exploratory, non-randomized open-label phase I-IIa clinical trial of intra-arterial HLA-matched donor cell transplantation in 5 Duchenne patients. We administered escalating doses of donor-derived mesoangioblasts in limb arteries under immunosuppressive therapy (tacrolimus). Four consecutive infusions were performed at 2-month intervals, preceded and followed by clinical, laboratory, and muscular MRI analyses. Two months after the last infusion, a muscle biopsy was performed. Safety was the primary endpoint. The study was relatively safe: One patient developed a thalamic stroke with no clinical consequences and whose correlation with mesoangioblast infusion remained unclear. MRI documented the progression of the disease in 4/5 patients. Functional measures were transiently stabilized in 2/3 ambulant patients, but no functional improvements were observed. Low level of donor DNA was detected in muscle biopsies of 4/5 patients and donor-derived dystrophin in 1. Intra-arterial transplantation of donor mesoangioblasts in human proved to be feasible and relatively safe. Future implementation of the protocol, together with a younger age of patients, will be needed to approach efficacy.

Supervised exercise training reduces oxidative stress and cardiometabolic risk in adults with type 2 diabetes: a randomized controlled trial.

To evaluate the effects of supervised exercise training (SET) on cardiometabolic risk, cardiorespiratory fitness and oxidative stress status in 2 diabetes mellitus (T2DM), twenty male subjects with T2DM were randomly assigned to an intervention group, which performed SET in a hospital-based setting, and to a control group. SET consisted of a 12-month supervised aerobic, resistance and flexibility training. A reference group of ten healthy male subjects was also recruited for baseline evaluation only. Participants underwent medical examination, biochemical analyses and cardiopulmonary exercise testing. Oxidative stress markers (1-palmitoyl-2-[5-oxovaleroyl]-sn-glycero-3-phosphorylcholine [POVPC]; 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine [PGPC]) were measured in plasma and in peripheral blood mononuclear cells. All investigations were carried out at baseline and after 12 months. SET yielded a significant modification (p < 0.05) in the following parameters: V'O2max (+14.4%), gas exchange threshold (+23.4%), waist circumference (-1.4%), total cholesterol (-14.6%), LDL cholesterol (-20.2%), fasting insulinemia (-48.5%), HOMA-IR (-52.5%), plasma POVPC (-27.9%) and PGPC (-31.6%). After 12 months, the control group presented a V'O2max and a gas exchange threshold significantly lower than the intervention group. Plasma POVC and PGPC were significantly different from healthy subjects before the intervention, but not after. In conclusion, SET was effective in improving cardiorespiratory fitness, cardiometabolic risk and oxidative stress status in T2DM.

Autocrine and immune cell-derived BDNF in human skeletal muscle: implications for myogenesis and tissue regeneration.

The neurotrophin system has a role in skeletal muscle biology. Conditional depletion of BDNF in mouse muscle precursor cells alters myogenesis and regeneration in vivo. However, the expression, localization and function of BDNF in human skeletal muscle tissue is not known, so the relevance of the rodent findings for human muscle are unknown. Here we address this by combining ex vivo histological investigations on human biopsies with in vitro analyses of human primary myocytes. We found that BDNF was expressed by precursor and differentiated cells both in vitro and in vivo. Differential analysis of BDNF receptors showed expression of p75NTR and not of TrkB in myocytes, suggesting that the BDNF-p75NTR axis is predominant in human skeletal muscle cells. Several in vitro functional experiments demonstrated that BDNF gene silencing or protein blockade in myoblast cultures hampered myogenesis. Finally, histological investigations of inflammatory myopathy biopsies revealed that infiltrating immune cells localized preferentially near p75NTR-positive regenerating fibres and that they produced BDNF. In conclusion, BDNF is an autocrine factor for skeletal muscle cells and may regulate human myogenesis. Furthermore, the preferential localization of BDNF-producing immune cells near p75NTR-positive regenerating myofibres suggests that immune cell-derived BDNF may sustain tissue repair in inflamed muscle.

Loss of glial fibrillary acidic protein (GFAP) impairs Schwann cell proliferation and delays nerve regeneration after damage.

Axonal loss causes disabling and permanent deficits in many peripheral neuropathies, and may result from inefficient nerve regeneration due to a defective relationship between Schwann cells, axons and the extracellular matrix. These interactions are mediated by surface receptors and transduced by cytoskeletal molecules. We investigated whether peripheral nerve regeneration is perturbed in mice that lack glial fibrillary acidic protein (GFAP), a Schwann-cell-specific cytoskeleton constituent upregulated after damage. Peripheral nerves develop and function normally in GFAP-null mice. However, axonal regeneration after damage was delayed. Mutant Schwann cells maintained the ability to dedifferentiate but showed defective proliferation, a key event for successful nerve regeneration. We also showed that GFAP and the other Schwann-cell-intermediate filament vimentin physically interact in two distinct signaling pathways involved in proliferation and nerve regeneration. GFAP binds integrin alphavbeta8, which initiates mitotic signals soon after damage by interacting with fibrin. Consistently, ERK phosphorylation was reduced in crushed GFAP-null nerves. Vimentin instead binds integrin alpha5beta1, which regulates proliferation and differentiation later in regeneration, and may compensate for the absence of GFAP in mutant mice. GFAP might contribute to form macro-complexes to initiate mitogenic and differentiating signaling for efficient nerve regeneration.