Immunohistochemical profile of cytokines and growth factors expressed in vestibular schwannoma and in normal vestibular nerve tissue.

Vestibular schwannomas, also known as acoustic neuromas, are benign tumors, which originate from myelin-forming Schwann cells. They develop in the vestibular branch of the eighth cranial nerve in the internal auditory canal or cerebellopontine angle. The clinical progression of the condition involves slow and progressive growth, eventually resulting in brainstem compression. The objective of the present study was to investigate the expression level and the localization of the pro-inflammatory cytokines, transforming growth factor-ß1 (TGF-ß1) interleukin (IL)-1ß, IL-6 and tumor necrosis factor-α (TNF-α), as well as the adhesion molecules, intracellular adhesion molecule-1 and vascular endothelial growth factor (VEGF), in order to determine whether these factors are involved in the transformation and development of human vestibular schwannoma. The present study investigated whether changes in inflammation are involved in tumor growth and if so, the mechanisms underlying this process. The results of the current study demonstrated that pro-inflammatory cytokines, including TGF-ß1, IL-1ß and IL-6 exhibited increased expression in human vestibular schwannoma tissue compared with normal vestibular nerve samples. TNF-α was weakly expressed in Schwann cells, confirming that a lower level of this cytokine is involved in the proliferation of Schwann cells. Neoplastic Schwann cells produce pro-inflammatory cytokines that may act in an autocrine manner, stimulating cellular proliferation. In addition, the increased expression of VEGF in vestibular schwannoma compared with that in normal vestibular nerve tissue, suggests that this factor may induce neoplastic growth via the promotion of angiogenesis. The present findings suggest that inflammation may promote angiogenesis and consequently contribute to tumor progression. In conclusion, the results of the present study indicated that VEGF and pro-inflammatory cytokines may be potential therapeutic targets in vestibular schwannoma. Further studies are necessary to confirm the involvement of these factors in the growth of neoplasms and to develop inhibitors of pro-inflammatory cytokines as a potential treatment option in the future.

Cardiomyopathies due to homoplasmic mitochondrial tRNA mutations: morphologic and molecular features.

Isolated hypertrophic cardiomyopathy may represent the sole clinical feature of a mitochondrial disorder in adult patients. The clinical outcome is characterized by a rapid progression to dilation and failure. A mitochondrial etiology in these cases is not obvious at clinical investigation and may represent an unexpected finding at autopsy or after cardiac transplant. We describe the morphologic, biochemical, and molecular features of hearts from 3 transplanted patients with isolated mitochondrial cardiomyopathy caused by homoplasmic mutations in the MTTI gene, coding for mitochondrial isoleucine tRNA (mt-tRNA(Ile)). On gross examination, the 3 hearts showed a symmetric pattern of hypertrophy. At histology, cardiomyocytes were hypertrophic and showed sarcoplasmic vacuoles filled with granules that stain with antimitochondrial antibodies. On frozen sections, the combined cytochrome c oxidase (COX)/succinate dehydrogenase stain showed a large prevalence of COX-deficient cardiomyocytes. Mitochondrially encoded COX subunit I was almost absent on immunohistochemistry, whereas the nuclear-encoded COX subunit IV was normally expressed. Ultrastructural analysis confirmed the marked mitochondrial proliferation. Biochemical studies of cardiac homogenates revealed a combined respiratory chain defect. Quantitative restriction fragment length polymorphism analysis of DNA from cardiac homogenate confirmed that the mt-tRNA mutations were also detected in the patient's blood. High-resolution Northern blot analysis showed a marked decrease in the steady-state level of mt-tRNA(Ile), confirming pathogenicity. In conclusion, pathologists play a major role in unraveling the mitochondrial etiology of isolated hypertrophic cardiomyopathies, provided that a detailed diagnostic flowchart is followed. Once the mitochondrial etiology is clearly defined, molecular analyses on the heart are an invaluable tool to assign mutation pathogenicity.