The expression of adhesion molecules in muscle biopsies: the LFA-1/VLA-4 ratio in polymyositis

Anakinra treatment in patients with refractory inflammatory myopathies and possible predictive response biomarkers: a mechanistic study with 12 months follow-up

OBJECTIVE

To perform a mechanistic study on the effect of interleukin (IL)-1 blockade by anakinra in patients with refractory myositis and to explore possible predictive biomarkers.

METHODS

Fifteen patients with refractory myositis were treated with anakinra for 12 months. Clinical response was assessed by the six-item core set measures of disease activity International Myositis Assessment and Clinical Studies (IMACS) and functional index (FI). Repeated muscle biopsies were investigated for cellular infiltrates, IL-1α, IL-1β, IL-1Ra and major histocompatibility complex-class I by immunohistochemistry. Serum levels of IL-1Ra and granulocyte colony-stimulating factor (G-CSF) were measured by ELISA. T cell phenotype and functional assays were investigated by multicolour flow cytometry.

RESULTS

Seven patients had clinical response according to IMACS, four of them also showed improved FI. Responders had higher baseline extramuscular score compared with non-responders. In muscle biopsies, baseline CD163 macrophages and IL-1α expression were inversely correlated with muscle performance after 6 months treatment; all responders had IL-1Ra expression in the post-treatment biopsies but only 3/8 non-responders. In serum, IL-1Ra levels were increased and G-CSF was decreased after 6 months treatment, but their levels and changes were not related to clinical response. For T cells, an inverse correlation between baseline frequency of CD4 activated/memory T cells and decreased creatine kinase levels was observed. Five of six patients demonstrated less IL-17A and more IFN-γ secreting CD4 T cells after 6 months treatment. Moreover, anakinra reduced IL-17A secretion in vitro.

CONCLUSIONS

Patients with myositis may respond to anakinra. Extramuscular score, muscle CD163 macrophages and IL-1α expression, blood CD4 activated/memory T cells might associate with anakinra treatment response. Blocking the IL-1 receptor disfavoured Th17 cell differentiation both in vivo and in vitro.

Chemokine-like factor expression in the idiopathic inflammatory myopathies

OBJECTIVES

We evaluated the expression of chemokine-like factor (CKLF) in biopsied muscle fibers in inflammatory myopathies, non-inflammatory myopathies and neurologically diseased controls.

MATERIALS AND METHODS

We studied the expression of CKLF in 15 polymyositis (PM), five dermatomyositis (DM), 15 non-inflammatory myopathies and nine neurologically diseased patients by immunohistochemistry.

RESULTS

Chemokine-like factor was mostly expressed in small diameter muscle fibers surrounded by infiltrated lymphocytes of inflammatory myopathies patients. Parts of them were also positive for the staining of the developmental form of myosin heavy chain, a maker of regenerating muscle fibers. Thrombin immunoreactivity was observed in endomysium in PM and perimysium in DM. In vitro differentiation study showed a constitutive expression of CKLF in myoblasts that was abolished in myotubes during differentiation process and was induced again by thrombin. Thrombin regulates CKLF expression through protease-activated receptor-1 in myotubes. Treatment of a protein kinase C inhibitor partially blocked CKLF expression in myoblasts, while it remarkably inhibited that in myotubes.

CONCLUSION

Chemokine-like factor expression is differentially regulated in myoblasts and myotubes. Thrombin could be a strong regulator for its expression. As CKLF is immunohistochemically positive in regenerating muscle fibers, we postulate here that CKLF is a useful marker for regenerating muscle fibers in inflammatory myopathies.

Inflammatory disorders of muscle: progress in polymyositis, dermatomyositis and inclusion body myositis

PURPOSE OF REVIEW

To provide an update on the major advances in inflammatory myopathies.

RECENT FINDINGS

Polymyositis is an uncommon disorder that can be misdiagnosed when the old, and never validated, criteria of Bohan and Peter are used. New diagnostic criteria were recently introduced, in which the MHC/CD8 complex is considered a specific immunopathological marker because it distinguishes the antigen-driven inflammatory cells that characterize polymyositis and sporadic inclusion-body myositis from the non-specific, secondary inflammation seen in other disorders, such as dystrophies. In sporadic inclusion-body myositis the inflammatory cells invade non-vacuolated fibers, whereas the vacuolated fibers are not invaded by T cells, implying two independent processes, a primary immune process with antigen-driven T cells identical to polymyositis, and a degenerative process in which beta-amyloid and amyloid-related proteins participate in vacuolar degeneration. In polymyositis and sporadic inclusion-body myositis, antigen-specific and clonally expanded autoinvasive T cells persist for years, even in different muscles, as reconfirmed by proof-of-principle techniques involving CDR3 spectratyping combined with laser microdissected single-cell polymerase chain reaction of the T-cell receptor genes. The formation of immunological synapse between autoinvasive T cells and muscle fibers was recently strengthened by the upregulation of co-stimulatory molecules ICOS/ICOS-L and PD-L1. A new, distinct myopathy characterized by T-cell-triggered macrophage hyperactivation has now been recognized in patients with dermatomyositis-like disease.

SUMMARY

Despite recent progress, the antigen(s) responsible for T-cell activation in polymyositis and sporadic inclusion-body myositis and the cause of vacuolar degeneration in sporadic inclusion-body myositis remain unclear. Newer, more aggressive immunotherapies may be encouraging, but control trials are needed to prove efficacy.

Myositis: an update on pathogenesis

PURPOSE OF REVIEW

The etiology and much about the pathogenesis of the inflammatory myopathies remain a mystery. In this review, we investigate recent research efforts to understand the pathogenesis of the diverse entities of polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM), diseases that result from interactions between environmental risk factors and genetic susceptibility.

RECENT FINDINGS

Over the past year, there has been considerable progress toward better understanding of IBM, with relatively few developments toward understanding PM and DM. Although these diseases may share some common clinical phenotypic and serologic components, they differ on a molecular and cellular level.

SUMMARY

The need for definitive, safer therapies in these diseases makes vital the search for defining detailed pathogenesis of inflammation and muscle fiber damage at the molecular level.