Lucia Tarantino

Satellite cell characterization from aging human muscle

Abstract Objectives: Satellite cells (SCs) are skeletal muscle progenitor cells located between the basal lamina and the sarcolemma of muscle fibers. They are responsible for muscle growth and repair. In humans, aging results in the depletion of the SC population and in its proliferative activity, but not in its function. It has not yet been determined whether under conditions of massive muscle fiber death in vivo, the regenerative potential of SCs is totally or partially compromised in old muscle. No studies have yet tested whether advanced age is a factor that restrains the response of SCs to muscle denervation in humans; this is also due to difficulties in the isolation and in the culture of SCs from a small human surgery fragment. The aim of this study was to study in depth muscle regeneration analysing the SC ability of SCs to proliferate and differentiate in aging human patients. Methods: In order to study in more detail the molecular mechanism, the proliferative and differentiative ability of aging SCs, we isolated SCs from aging human muscle biopsies and analysed their morphology by transmission electron microscopy and immunocytochemical analysis (antibodies against desmin, N-CAM and M-cadherin) and their capacity to grow and to expand in vitro. Moreover, in order to evaluate gene expression of myogenic regulatory factors Myf5, MyoD and myogenin (Myf4), RT-PCR was performed. Results and discussion: SCs isolated from aging human muscle biopsies and plated into favorable proliferation and differentiation conditions were able to proceed through the myogenic program and actively form myotubes, although taking longer than the young control sample. The RT-PCR analysis together with the ultrastructural SC features showed that the myogenic potential seemed to be compromised during the aging human muscle proliferation in vitro.

Validity of internal expression of the major histocompatibility complex class I in the diagnosis of inflammatory myopathies

Objective The inflammatory myopathies (IMs) are a group of disorders characterised by weakness and inflammation of the skeletal muscles. Muscle biopsy is the most crucial test to confirm the clinical diagnosis, but also the most common cause of misdiagnosis. There are currently no markers specific or sensitive enough to distinguish IMs from other diseases with similar clinical and morphological features, and an international multidisciplinary effort is under way to develop new classification criteria for IMs. Methods Standards for Reporting of Diagnostic Accuracy recommendations to validate a diagnostic test based on the quantification of internal major histocompatibility complex class I (MHC-I) positive fibres were adopted. MHC-I immunostained specimens from 64 patients were scored by two independent blinded investigators, and the percentage of positive fibres was determined. Agreement between investigators was evaluated with the k-weighted statistic. The receiver operating characteristic curve, area under the curve, sensitivity, specificity, and positive and negative predictive values of each percentage range of positive fibres versus the diagnosis of IM were calculated. Results The main difference between IM and non-inflammatory samples was the number of internal MHC-I positive fibres. The k-weighted value was 0.89 for a percentage of MHC-I positive fibres above 50%; the positive predictive value was 100%, and the negative predictive value was 94%. Conclusions This is the first study on the validity of a quantitative analysis of internal MHC-I positive fibres for an IM diagnosis performed according to Standards for Reporting of Diagnostic Accuracy recommendations. The interobserver agreement was almost perfect, thus making the method reproducible. Applying an MHC-I cut-off above 50% is an optimal marker for polymyositis (PM) and dermatomyositis (DM) diagnosis.

Secretory meningioma of the middle ear: A light microscopic, immunohistochemical and ultrastructural study of one case

A 66‐year‐old woman was referred with left hearing loss. A probable diagnosis of left secretory otitis media with effusion was formulated. A left myringotomy was performed to remove hyperplastic hard tissue from the tympanic cavity. A high resolution CT scan of the temporal bone disclosed a soft‐tissue mass completely involving the mastoid and tympanic cavity, surrounding the ossicular chain which appeared spared with no signs of infiltration. The histopathologic, immunohistochemical and ultrastructural response was secretory meningioma, a rare variant of conventional meningothelial meningioma in atypical sites.

The Role of Ultrastructural Examination in Storage Diseases

Storage diseases (SDs) are rare metabolic disorders characterized by the intra- or extralysosomal accumulation of unmetabolized compounds. Different causes determine the buildup of undigested material, resulting in typical histochemical and ultrastructural changes. Ultrastructural examination of tissue from patients with clinically suspected SDs may disclose pathognomonic alterations or suggest a differential diagnosis even in the absence of clinically evident involvement of the biopsied tissue. Accurate diagnosis of SDs requires a continuous integration of clinical, biochemical, ultrastructural, and, when available, molecular data. It is also important for the pathologist to be familiar with the morphological variability characterizing each SD, because some morphologies are often the early stages of undeveloped forms and morphologically similar diseases are easily confused. The major advantages of transmission electron microscopy (TEM) techniques are discussed, emphasizing the current role of TEM as a rapid, cost-effective, and efficient diagnostic tool.