Alba Arco

Costameric proteins in human skeletal muscle during muscular inactivity.

Costameres are regions that are associated with the sarcolemma of skeletal muscle fibres and comprise proteins of the dystrophin–glycoprotein complex and vinculin–talin–integrin system. Costameres play both a mechanical and a signalling role, transmitting force from the contractile apparatus to the extracellular matrix in order to stabilize skeletal muscle fibres during contraction and relaxation. Recently, it was shown that bidirectional signalling occurs between sarcoglycans and integrins, with muscle agrin potentially interacting with both types of protein to enable signal transmission. Although numerous studies have been carried out on skeletal muscle diseases, such as Duchenne muscular dystrophy, recessive autosomal muscular dystrophies and other skeletal myopathies, insufficient data exist on the relationship between costameres and the pathology of the second motor nerve and between costameric proteins and muscle agrin in other conditions in which skeletal muscle atrophy occurs. Previously, we carried out a preliminary study on skeletal muscle from patients with sensitive‐motor polyneuropathy, in which we analysed the distribution of sarcoglycans, integrins and agrin by immunostaining only. In the present study, we have examined the skeletal muscle fibres of ten patients with sensitive‐motor polyneuropathy. We used immunofluorescence and reverse transcriptase PCR to examine the distribution of vinculin, talin and dystrophin, in addition to that of those proteins previously studied. Our aim was to characterize in greater detail the distribution and expression of costameric proteins and muscle agrin during this disease. In addition, we used transmission electron microscopy to evaluate the structural damage of the muscle fibres. The results showed that immunostaining of α7B‐integrin, β1D‐integrin and muscle agrin appeared to be severely reduced, or almost absent, in the muscle fibres of the diseased patients, whereas staining of α7A‐integrin appeared normal, or slightly increased, compared with that in normal skeletal muscle fibres. We also observed a lower level of α7B‐ and β1D‐integrin mRNA and a normal, or slightly higher than normal, level of α7A‐integrin mRNA in the skeletal muscle fibres of the patients with sensitive‐motor polyneuropathy, compared with those in the skeletal muscle of normal patients. Additionally, transmission electron microscopy of transverse sections of skeletal muscle fibres indicated that the normal muscle fibre architecture was disrupted, with no myosin present inside the actin hexagons. Based on our results, we hypothesize that skeletal muscle inactivity, such as that found after denervation, could result in a reorganization of the costameres, with α7B‐integrin being replaced by α7A‐integrin. In this way, the viability of the skeletal muscle fibre is maintained. It will be interesting to clarify, by future experimentation, the mechanisms that lead to the down‐regulation of integrins and agrin in muscular dystrophies.

Immunohistochemical study of epidermal nerve fibres in involved and uninvolved psoriatic skin using confocal laser scanning microscopy.

Abstract Psoriasis is a typical hyperproliferative epidermal disease whose aetiopathogenesis is still to be defined. One of the most likely hypotheses is that it has a neurogenic origin correlated with an altered release of some neuropeptides by sensitive cutaneous nerves via antidromic pathways. As there are conflicting reports about the existence of cutaneous nerve alterations in psoriasis, we carried out an immunolocalization study using the protein gene product 9.5 as a marker for neuronal structures observed by confocal laser scanning microscopy in order to determine the pattern of sensory nerves in psoriatic skin. The investigation was carried out on cutaneous biopsies taken from involved (mature and long-established lesions) and uninvolved skin of ten patients with extensive chronic plaque psoriasis. In uninvolved psoriatic skin a significant decrease in epidermal nerve fibres was found, a further decrease was observed in mature lesions and almost a complete lack of epidermal nerve fibres in long-established psoriatic lesions. The reduction in epidermal nerve fibres and the consequent loss of relationship between these nerve structures and the skin immunocompetent cells (antigen-presenting cells, Langerhans cells, keratinocytes) might be a factor of fundamental importance in the self-maintenance of the disease.

Sarcoglycan and integrin localization in normal human skeletal muscle: a confocal laser scanning microscope study

Many studies have been performed on the sarcoglycan sub-complex and a7B and b1D integrins, but their distribution and localization patterns along the non-junctional sarcolemma are still not clear. We have carried out an indirect immunofluorescence study on surgical biopsies of normal human skeletal muscle, performing double localization reactions with antibodies to sarcoglycans, integrins and sarcomeric actin. Our results indicate that the tested proteins colocalize with each other. In a few cases, a-sarcoglycan does not colocalize with the other sarcoglycans and integrins. We also demonstrated, by employing antibodies to all the tested proteins, that these proteins can be localized to regions of the sarcolemma corresponding either to the I-band or A-band. Our results seem to confirm the hypothesis of a correlation between the region of the sarcolemma occupied by costameric proteins and the metabolic type (fast or slow) of muscle fibers. On this basis, we suggest that slow fibers are characterized by localization of costameric proteins to I-bands, while fast fibers are characterized by localization of costameric proteins to A-bands. The results open a new line of research in understanding interactions between the components of the DGC and vinculin-talin-integrin complexes in the context of different fiber types. Moreover, the same results may be extended to skeletal muscle fibers affected by neuromuscular diseases to detect possible structural alterations.

Integrins, muscle agrin and sarcoglycans during muscular inactivity conditions: an immunohistochemical study

Sarcoglycans are transmembrane proteins that seem to be functionally and pathologically as important as dystrophin. Sarcoglycans cluster together to form a complex, which is localized in the cell membrane of skeletal, cardiac, and smooth muscle. It has been proposed that the dystrophin-glycoprotein complex (DGC) links the actin cytoskeleton with the extracellular matrix and the proper maintenance of this connection is thought to be crucial to the mechanical stability of the sarcolemma. The integrins are a family of heterodimeric cell surface receptors which play a crucial role in cell adhesion including cell-matrix and intracellular interactions and therefore are involved in various biological phenomena, including cell migration, and differentiation tissue repair. Sarcoglycans and integrins play a mechanical and signaling role stabilizing the systems during cycles of contraction and relaxation. Several studies suggested the possibility that integrins might play a role in muscle agrin signalling. On these basis, we performed an immunohistochemical analyzing sarcoglycans, integrins and agrin, on human skeletal muscle affected by sensitive-motor polyneuropathy, in order to better define the correlation between these proteins and neurogenic atrophy due to peripheral neuropathy. Our results showed the existence of a cascade mechanism which provoke a loss of regulatory effects of muscle activity on costameres, due to loss of muscle and neural agrin. This cascade mechanism could determine a quantitative modification of transmembrane receptors and loss of alpha7B could be replaced and reinforced by enhanced expression of the alpha7A integrin to restore muscle fiber viability. Second, it is possible that the reduced cycles of contraction and relaxation of muscle fibers, during muscular atrophy, provoke a loss of mechanical stresses transmitted over cell surface receptors that physically couple the cytoskeleton to extracellular matrix. Consequently, these mechanical changes could determine modifications of chemical signals through variations of pathway structural integrins, and alpha7A could replace alpha7B.

Ultrastructural Study of the Conjunctival Epithelium in the Mongolian Gerbil (Meriones unguiculatus)

The conjunctival epithelium of the Mongolian gerbil (Meriones unguiculatus) was studied using the transmission and scanning electron microscopy. The superficial cells of the conjunctival epithelium were isoprismatic in shape and were covered, on their luminal surface, with microplicae. They were connected with the adjacent cells by junctional complexes and desmosomes. Some of the superficial cells were partially or completely detached from the underlying intermediate cells: this morphological pattern was interpreted as an expression of cellular renewal of the conjunctival surface. Goblet cells were either isolated or gathered in clusters: in any case, they were firmly connected with the adjacent epithelial cells. The apical part of the goblet cells was covered with a great number of long microvilli: they showed a variety of morphological aspects, which were interpreted as occurring in a sequential pattern during the secretory process. The Mongolian gerbil can be considered among the laboratory animals used for ophthalmic research.

Sarcoglycans in the Normal and Pathological Breast Tissue of Humans: An Immunohistochemical and Molecular Study

The sarcoglycan complex, consisting of α-, β-, γ-, δ- and ε-sarcoglycans, is a multimember transmembrane system providing a mechanosignaling connection from the cytoskeleton to the extracellular matrix. Whereas the expression of α- and γ-sarcoglycan is restricted to striated muscle, other sarcoglycans are widely expressed. Although many studies have investigated sarcoglycans in all muscle types, insufficient data are available on the distribution of the sarcoglycan complex in nonmuscle tissue. On this basis, we used immunohistochemical and RT-PCR techniques to study preliminarily the sarcoglycans in normal glandular breast tissue (which has never been studied in the literature on these proteins) to verify the effective wider distribution of this complex. Moreover, to understand the role of sarcoglycans, we also tested samples obtained from patients affected by fibrocystic mastopathy and breast fibroadenoma. Our data showed, for the first time, that all sarcoglycans are always detectable in all normal samples both in epithelial and myoepithelial cells; in pathological breast tissue, all sarcoglycans appeared severely reduced. These data demonstrated that all sarcoglycans, not only β-, δ-, and ε-sarcoglycans, have a wider distribution, implying a new unknown role for these proteins. Moreover, in breast diseases, sarcoglycans containing cadherin domain homologs could provoke a loss of strong adhesion between epithelial cells, permitting and facilitating the degeneration of these benign breast tumors into malignant tumors. Consequently, sarcoglycans could play an important and intriguing role in many breast diseases and in particular in tumor progression from benign to malignant.

Morphological differentiation of the conjunctival goblet cells in the chick (Gallus domesticus)

Abstract• Background: These is no consensus in the literature regarding the differentiation of conjunctival goblet cells in vertebrates. • Method: The conjunctival epithelium of the chick was studied before and after hatching in order to demonstrate the morphological evolution of the goblet cells. The entire conjunctiva was processed for light microscopy either on semithin sections stained with toluidine blue-pironine or on traditional sections stained with Alcian blue pH 2.5-PAS. • Results: It was possible to demonstrate that goblet cells underwent remarkable changes in their secretory activity. At 12 h after hatching, isolated Alcian blue-positive cells were present in the fornix. At 24 h after hatching, cells positive for both Alcian blue and PAS were scattered among epithelial cells. Two days after hatching, cells which reacted positively only to PAS were also present. • Conclusion: It is suggested that the differentiation of conjunctival goblet cells occurs first in the fornix, probably due to the particular vascular environment of this region, and then spreads all over the conjunctiva.

Morphofunctional compensation of masseter muscles in unilateral posterior crossbite patients

Unilateral posterior crossbite is a widespread, asymmetric malocclusion characterized by an inverse relationship of the upper and lower buccal dental cusps, in the molar and premolar regions, on one side only of the dental arch. Patients with unilateral posterior crossbite exhibit an altered chewing cycles and the crossbite side masseter results to be less active with respect to the contralateral one. Few studies about morphological features of masticatory muscle in malocclusion disorders exist and most of these have been performed on animal models. The aim of the present study was to evaluate morphological and protein expression characteristics of masseter muscles in patients affected by unilateral posterior crossbite, by histological and immunofluorescence techniques. We have used antibody against PAX-7, marker of satellite cells, and against α-, β-, γ-, δ-, ε- and ζ-sarcoglycans which are transmembrane glycoproteins involved in sarcolemma stabilization. By statistical analysis we have evaluated differences in amount of myonucley between contralateral and ipsilateral side. Results have shown: i) altered fibers morphology and atrophy of ipsilateral muscle if compared to the contralateral one; ii) higher number of myonuclei and PAX-7 positive cells in contralateral side than ipsilateral one; iii) higher pattern of fluorescence for all tested sarcoglycans in contralateral side than ipsilateral one. Results show that in unilateral posterior crossbite hypertrophic response of contralateral masseter and atrophic events in ipsilateral masseter take place; by that, in unilateral posterior crossbite malocclusion masticatory muscles modify their morphology depending on the function. That could be relevant in understanding and healing of malocclusion disorders; in fact, the altered balance about structure and function between ipsilateral and contralateral muscles could, long-term, lead and/ or worsen skeletal asymmetries.

Flavocoxid mitigates cadmium-induced toxicity: structural, immunohistochemical and molecular analysis in mice kidney

Background: Cadmium (Cd), a diffused environmental pollutant, has adverse effects on urinary apparatus [1]. The role of flavocoxid, a flavonoid with antioxidant activity [2], on the morphological and biochemical changes induced in vivo by Cd in mice kidneys was evaluated. Methods: C57 BL/6J mice received 0.9% NaCl alone, flavocoxid (20 mg/kg/day i.p.) alone, Cd chloride (CdCl2) (2 mg/kg i.p.) alone, or CdCl2 plus Flavocoxid (2 mg/kg i.p. plus 20 mg/kg/day i.p.) for 14 days. At the end of experiment, the mice were killed with an overdose of ketamine and xylazine and the kidneys were collected and processed for structural, immunohistochemical and biochemical analysis. Results: Cd treatment alone significantly increased iNOS, TNF-α and MMP-9 expression, induced structural damages in the glomeruli and in the proximal tubule epithelium, and reduced claudin-11, occludin and N-cadherin immunoreactivity. Flavocoxid administration reduced iNOS, TNF-α and MMP-9 expression, ameliorated glomerular and tubular changes and enhanced claudin-11, occludin and N-cadherin immunoreactivity. Conclusions: We demonstrated for the first time that flavocoxid has a protective role against Cd-induced damages in mice kidney. Therefore, flavocoxid may have a promising role against environmental Cd, in particular against its harmful effects on glomerular and tubular lesions.

Polydeoxyribonucleotide, an adenosine-A2A receptor agonist, preserves blood testis barrier from cadmium-induced injury

Cadmium (Cd) impairs the blood-testis barrier (BTB) with changes of its junctional complexes [1]. Polydeoxyribonucleotide (PDRN), an adenosine A2A agonist, has positive effects on male reproductive system [2]. We investigated the effects of PDRN on the morphological and functional Cd-induced changes in mice testes. Swiss mice were divided into four groups: control animals treated with 0.9% NaCl (1 ml/kg, i.p., daily); control animals treated with PDRN (8 mg/kg, i.p. daily), animals challenged with Cd chloride (CdCl2) (2 mg/kg i.p, daily) and animals challenged with CdCl2 and treated with PDRN. The experiments lasted 14 days. At the end of experiment, the testes were processed for biochemical, structural and ultrastructural evaluation. CdCl2 increased pERK 1/2 expression and Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) levels, decreased testosterone (TE) and inhibin-B levels and induced structural damages in the extratubular compartment and in the seminiferous epithelium, with ultrastructural features of BTB disruption. Many TUNEL-positive germ cells were present in the peripheral parts of the tubules. CdCl2 increased also tubular TGF-β3 immunoreactivity and reduced claudin-11, occludin and N-cadherin immunoreactivity. PDRN administration reduced pERK 1/2 expression, FSH and LH levels, increased TE and inhibin-B levels, ameliorated germinal epithelium changes and protected BTB ultrastructure. Only few TUNEL-positive germ cells were present and the extratubular compartment was preserved, showing only a mild edema. Furthermore PDRN decreased TGF-β3 immunoreactivity and enhanced claudin-11, occludin and N-cadherin immunoreactivity. We demonstrate, for the first time, a protective effect of PDRN on Cd-induced BTB damages in mice testes. We suggest that the A2A agonist may play an important role against environmental Cd, and in particular against its harmful effects on gametogenesis.