Calcium Signaling in Interstitial Cells: Focus on Telocytes

In this review, we describe the current knowledge on calcium signaling pathways in interstitial cells with a special focus on interstitial cells of Cajal (ICCs), interstitial Cajal-like cells (ICLCs), and telocytes. In detail, we present the generation of Ca²⁺ oscillations, the inositol triphosphate (IP₃)/Ca²⁺ signaling pathway and modulation exerted by cytokines and vasoactive agents on calcium signaling in interstitial cells. We discuss the physiology and alterations of calcium signaling in interstitial cells, and in particular in telocytes. We describe the physiological contribution of calcium signaling in interstitial cells to the pacemaking activity (e.g., intestinal, urinary, uterine or vascular pacemaking activity) and to the reproductive function. We also present the pathological contribution of calcium signaling in interstitial cells to the aortic valve calcification or intestinal inflammation. Moreover, we summarize the current knowledge of the role played by calcium signaling in telocytes in the uterine, cardiac and urinary physiology, and also in various pathologies, including immune response, uterine and cardiac pathologies.

Dynamic morphometric characterization of local connective tissue network structure in humans using ultrasound

Background

In humans, connective tissue forms a complex, interconnected network throughout the body that may have mechanosensory, regulatory and signaling functions. Understanding these potentially important phenomena requires non-invasive measurements of collagen network structure that can be performed in live animals or humans. The goal of this study was to show that ultrasound can be used to quantify dynamic changes in local connective tissue structure in vivo. We first performed combined ultrasound and histology examinations of the same tissue in two subjects undergoing surgery: in one subject, we examined the relationship of ultrasound to histological images in three dimensions; in the other, we examined the effect of a localized tissue perturbation using a previously developed robotic acupuncture needling technique. In ten additional non-surgical subjects, we quantified changes in tissue spatial organization over time during needle rotation vs. no rotation using ultrasound and semi-variogram analyses.

Results

3-D renditions of ultrasound images showed longitudinal echogenic sheets that matched with collagenous sheets seen in histological preparations. Rank correlations between serial 2-D ultrasound and corresponding histology images resulted in high positive correlations for semi-variogram ranges computed parallel (r = 0.79, p < 0.001) and perpendicular (r = 0.63, p < 0.001) to the surface of the skin, indicating concordance in spatial structure between the two data sets. Needle rotation caused tissue displacement in the area surrounding the needle that was mapped spatially with ultrasound elastography and corresponded to collagen bundles winding around the needle on histological sections. In semi-variograms computed for each ultrasound frame, there was a greater change in the area under the semi-variogram curve across successive frames during needle rotation compared with no rotation. The direction of this change was heterogeneous across subjects. The frame-to-frame variability was 10-fold (p < 0.001) greater with rotation than with no rotation indicating changes in tissue structure during rotation.

Conclusion

The combination of ultrasound and semi-variogram analyses allows quantitative assessment of dynamic changes in the structure of human connective tissue in vivo.

Synergistic effects of combined cytotoxic and apoptosis-inducing drugs on Tenon's capsule fibroblasts in vitro and in vivo

BACKGROUND

Highly toxic antimetabolites have gained access to routine clinical use to modulate and reduce the amount of postoperative scarring following glaucomatous filtering procedures. It could be speculated that by combining two different antiproliferative substances with different mechanisms of action total amounts of the substances could be decreased and side effects reduced.

METHODS

Twenty-two substances were tested that had antiproliferative effects by acting cytotoxically, inhibiting growth factors, or inducing apoptosis. With combinations of each two substances, cell culture experiments using 3T3 and human Tenon's capsule fibroblasts were performed evaluating cell toxicity, proliferation and migration, the extent of free radicals, and the amount of apoptosis (TUNEL, electron microscopy). The five most potent combinations were used in an animal experiment with rabbits performing filtering procedures. The extent of episcleral scarring was evaluated by histopathology.

RESULTS

The results of the various assays revealed consistently strong effects in 5 of the 462 combinations. Of these five combinations, two were highly effective in the rabbit model. Substances with strong effects when applied in combination included staurosporine, mitomycin, and CD95L.

CONCLUSIONS

We found synergistic effects in assays that evaluated different aspects of cell function. The amount of scarring in an animal experiment was inhibited to a level comparable with a high single dose of mitomycin. Combination therapy of two antiproliferative acting substances may be a promising concept.

Beyond the epithelium: Cadherin function in fibrous connective tissues

In fibrous connective tissues, fibroblasts are organized into syncytia, cellular networks that enable matrix remodeling and that are interconnected by intercellular adherens junctions (AJs). The AJs of fibroblasts are mediated by N-cadherin, a broadly expressed classical cadherin that is critically involved in developmental processes, wound healing and several diseases of mesenchymal tissues. In contrast to E-cadherin-dependent junctions of epithelia, the formation of AJs in fibrous connective tissues is relatively uncharacterized. Work over the last several years has documented an expanding list of molecules which function to regulate N-cadherin mediated junctions such as: Fer, PTP1B, cortactin, calcium, gelsolin, PIP5KIgamma, PIP2, and the Rho family of GTPases. We present an overview on the regulation of N-cadherin-mediated junction formation that highlights recent molecular advances in the field and rationalizes the roles of N-cadherin in connective tissue function.

Derivation of muscles of the Aristotle’s lantern from coelomic epithelia

Transmission electron microscopy was employed to study structural changes in the lantern muscles occurring during the transition from young to adult in the sea urchin Strongylocentrotus nudus. A comparative examination of four major lantern muscles (compass depressors, compass elevators, protractors and retractors) suggests that myogenesis involves four consecutive stages. At the initial stage, the muscles show the organization of a mesentery delimited by pseudostratified coelomic epithelia, which are composed of peritoneal cells spanning the whole height of each epithelium, and myoepithelial cells, which are clustered together to fill the interstices between the basal processes of the peritoneal cells. During the next stage, the clusters of myoepithelial cells partly "sink" into the underlying connective tissue. At the third stage of muscularization, the myoepithelial cells increase in size and further invade the underlying connective tissue so that the myoepithelium splits into an apical peritoneal layer and a deeper mass of myoepithelial cells immersed in the connective tissue. However, these two layers are connected by a continuous basal lamina. This is thus the first description of an intermediate developmental stage between pseudostratified myoepithelim and genuine echinoderm muscles. For such a myoepithelium, we propose the term "immersed myoepithelium". At the most advanced stage of myogenesis, the myocytes detach completely from the epithelium to form subepithelial muscle bundles. Myogenesis in the sea urchin takes a long time during which continuous myogenic differentiation occurs in the coelomic epithelium and the newly formed myocytes and associated neurons penetrate into the underlying connective tissue.

Interstitial Cajal-like cells (ICLC) in human resting mammary gland stroma. Transmission electron microscope (TEM) identification

We have previously shown the existence of ICLC in human resting mammary gland stroma by means of methylene blue (vital) staining and c-kit immunopositivity (immunofluorescence and immunohistochemistry). In addition, we reported the phenotype characteristics of these ICLC in vitro (primary cell cultures). Since the identification of ICLC outside the gut requires, at this moment, the obligatory use of TEM, we used this technique and provide unequivocal evidence for the presence of ICLC in the intralobular stroma of human resting mammary gland. According to the 'platinum standard' (10 TEM criteria for the certitude diagnosis of ICLC), we found interstitial cells with the following characteristics: 1. location: among the tubulo-alveolar structures, in the non-epithelial space; 2. caveolae: approximately 2.5% of cell volume; 3. mitochondria: approximately 10% of cell volume; 4. endoplasmic reticulum: either smooth or rough, approximately 2-3% of cell volume; 5. cytoskeleton: intermediate and thin filaments, as well as microtubules are present; 6. myosin thick filaments: undetectable; 7. basal lamina: occasionally found; 8. gap junctions: occasionally found; 9. close contacts with targets: nerve fibers, capillaries, immunoreactive cells by 'stromal synapses'; 10. characteristic cytoplasmic processes: i) number: frequently 2-3; ii) length: several tens of mum; iii) thickness: uneven caliber, 0.1-0.5 microm, with dilations, but very thin from the emerging point; iv) aspect: moniliform, usually with mitochondria located in dilations; v) branching: dichotomous pattern; vi) Ca(2+) release units: are present; vii) network labyrinthic system: overlapping cytoplasmic processes. It remains to be established which of the possible roles that we previously suggested for ICLC (e.g. juxta- and/or paracrine secretion, uncommited progenitor cells, immunological surveillance, intercellular signaling, etc.) are essential for the epithelium/stroma equilibrium in the mammary gland under normal or pathological conditions.

C-kit immunopositive interstitial cells (Cajal-type) in human myometrium

Previous reports describing Cajal-like interstitial cells in human uterus are contradictory in terms of c-kit immunoreactivity: either negative (but vimentin-positive) in pregnant myometrium, or positive, presumably in the endometrium. The aim of this study was to verify the existence of human myometrial Cajal-like interstitial cells (m-CLIC). Six different, complementary approaches were used: 1) methylene-blue supravital staining of tissue samples (cryosections), 2) methylene blue and Janus green B vital staining (m-CLIC and mitochondrial markers, respectively), and 3) extracellular single-unit electrophysiological recordings in cell cultures, 4) non-conventional light microscopy on glutaraldehyde/osmium fixed, Epon-embedded semi-thin sections (less than 1 microm) stained with toluidine blue (TSM), 5) transmission electron microscopy (TEM), and 6) immunofluorescence (IF). We found m-CLIC in myometrial cryosections and in cell cultures. In vitro, m-CLIC represented approximately 7% of the total cell number. m-CLIC had 2-3 characteristic processes which were very long (approximately 60 microm), very thin (< or =0.5 microm) and moniliform. The dilated portions of processes usually accommodated mitochondria. In vitro, m-CLIC exhibited spontaneous electrical activity (62.4+/-7.22 mV membrane potentials, short duration: 1.197+/-0.04 ms). Moreover, m-CLIC fulfilled the usual TEM criteria, the so-called 'gold' or 'platinum' standards (e.g. the presence of discontinuous basal lamina, caveolae, endoplasmic reticulum, and close contacts between each other, with myocytes, nerve fibers and/or capillaries etc.). IF showed that m-CLIC express CD117/c-kit, sometimes associated with CD34, with vimentin along their processes. In conclusion, we describe myometrial Cajal-like interstitial cells that have affinity for methylene blue and Janus green B vital dyes, fulfill (all) TEM criteria, express CD117/c-kit and have spontaneous electric activity.

Interstitial cells in the vasculature

Interstitial cells of Cajal are believed to play an important role in gastrointestinal tissues by generating and propagating electrical slow waves to gastrointestinal muscles and/or mediating signals from the enteric nervous system. Recently cells with similar morphological characteristics have been found in the wall of blood vessels such as rabbit portal vein and guinea pig mesenteric artery. These non-contractile cells are characterised by the presence of numerous processes and were easily detected in the wall of the rabbit portal vein by staining with methylene blue or by antibodies to the marker of Interstitial Cells of Cajal c-kit. These vascular cells have been termed "interstitial cells" by analogy with interstitial cells found in the gastrointestinal tract. Freshly dispersed interstitial cells from rabbit portal vein and guinea pig mesenteric artery displayed various Ca2+-release events from endo/sarcoplasmic reticulum including fast localised Ca2+ transients (Ca2+ sparks) and longer and slower Ca2+ events. Single interstitial cells from the rabbit portal vein, which is a spontaneously active vessel, also demonstrated rhythmical Ca2+ oscillations associated with membrane depolarisations, which suggests that in this vessel interstitial cells may act as pacemakers for smooth muscle cells. The function of interstitial cells from the mesenteric arteries is yet unknown. This article reviews some of the recent findings regarding interstitial cells from blood vessels obtained by our laboratory using electron microscopy, immunohistochemistry, tight-seal patch-clamp recording, and fluorescence confocal imaging techniques.

About the presence of interstitial cells of Cajal outside the musculature of the gastrointestinal tract

Santiago Ramon y Cajal observed a special cell type that appeared to function as endstructures of the intrinsic nervous system in several organs. These cells were structurally and functionally further characterized in the gut musculature and named interstitial cells of Cajal (ICC). In recent years, interstitial cells have been identified in the vasculature, urinary tract, glands and other organs. Their morphologies and functions are just beginning to be clarified. It is likely that amongst them, subtypes will be discovered that warrant the classification of interstitial cells of Cajal. This "point of view" continues the discussion on the criteria that should be used to identify ICC outside the musculature of the gut.

Novel type of interstitial cell (Cajal-like) in human fallopian tube

We describe here--presumably for the first time--a Cajal-like type of tubal interstitial cells (t-ICC), resembling the archetypal enteric ICC. t-ICC were demonstrated in situ and in vitro on fresh preparations (tissue cryosections and primary cell cultures) using methylene-blue, crystal-violet, Janus-Green B or MitoTracker-Green FM Probe vital stainings. Also, t-ICC were identified in fixed specimens by light microscopy (methylene-blue, Giemsa, trichrome stainings, Gomori silver-impregnation) or transmission electron microscopy (TEM). The positive diagnosis of t-ICC was strengthened by immunohistochemistry (IHC; CD117/c-kit+ and other 14 antigens) and immunofluorescence (IF; CD117/c-kit+ and other 7 antigens). The spatial density of t-ICC (ampullar-segment cryosections) was 100-150 cells/mm2. Non-conventional light microscopy (NCLM) of Epon semithin-sections revealed a network-like distribution of t-ICC in lamina propria and smooth muscle meshwork. t-ICC appeared located beneath of epithelium, in a 10-15 microm thick 'belt', where 18+/-2% of cells were t-ICC. In the whole lamina propria, t-ICC were about 9%, and in muscularis approximately 7%. In toto, t-ICC represent ~8% of subepithelial cells, as counted by NCLM. In vitro, t-ICC were 9.9+/-0.9% of total cell population. TEM showed that the diagnostic 'gold standard' (Huizinga et al., 1997) is fulfilled by 'our' t-ICC. However, we suggest a 'platinum standard', adding a new defining criterion- characteristic cytoplasmic processes (number: 1-5; length: tens of microm; thickness: < or =0.5 microm; aspect: moniliform; branching: dichotomous; organization: network, labyrinthic-system). Quantitatively, the ultrastructural architecture of t-ICC is: nucleus, 23.6+/-3.2% of cell volume, with heterochromatin 49.1+/-3.8%; mitochondria, 4.8+/-1.7%; rough and smooth endoplasmic-reticulum (1.1+/-0.6%, 1.0+/-0.2%, respectively); caveolae, 3.4+/-0.5%. We found more caveolae on the surface of cell processes versus cell body, as confirmed by IF for caveolins. Occasionally, the so-called 'Ca2+-release units' (subplasmalemmal close associations of caveolae+endoplasmic reticulum+mitochondria) were detected in the dilations of cell processes. Electrophysiological single unit recordings of t-ICC in primary cultures indicated sustained spontaneous electrical activity (amplitude of membrane potentials: 57.26+/-6.56 mV). Besides the CD117/c-kit marker, t-ICC expressed variously CD34, caveolins 1&2, alpha-SMA, S-100, vimentin, nestin, desmin, NK-1. t-ICC were negative for: CD68, CD1a, CD62P, NSE, GFAP, chromogranin-A, PGP9.5, but IHC showed the possible existence of (neuro)endocrine cells in tubal interstitium. We call them 'JF cells'. In conclusion, the identification of t-ICC might open the door for understanding some tubal functions, e.g. pace-making/peristaltism, secretion (auto-, juxta- and/or paracrine), regulation of neurotransmission (nitrergic/purinergic) and intercellular signaling, via the very long processes. Furthermore, t-ICC might even be uncommitted bipotential progenitor cells.

Network organization of interstitial connective tissue cells in the human endolymphatic duct

The human endolymphatic duct (ED) and sac of the inner ear have been suggested to control endolymph volume and pressure. However, the physiological mechanisms for these processes remain obscure. We investigated the organization of the periductal interstitial connective tissue cells and extracellular matrix (ECM) in four freshly fixed human EDs by transmission electron microscopy and by immunohistochemistry. The unique surgical material allowed a greatly improved structural and epitopic preservation of tissue. Periductal connective tissue cells formed frequent intercellular contacts and focally occurring electron-dense contacts to ECM structures, creating a complex tissue network. The connective tissue cells also formed contacts with the basal lamina of the ED epithelium and the bone matrix, connecting the ED with the surrounding bone of the vestibular aqueduct. The interstitial connective tissue cells were non-endothelial and non-smooth muscle fibroblastoid cells. We suggest that the ED tissue network forms a functional mechanical entity that takes part in the control of inner ear fluid pressure and endolymph resorption.

Cell-based quantitative evaluation of the MTT assay

OBJECTIVE

To analyze the bioreduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) on a per cell basis and evaluate its modulation as a function of different stages of cell metabolism.

STUDY DESIGN

Following MTT bioreduction, total optical density (TOD), cell area and specific activity (TOD/area) of V79 cells and cultured macrophages were recorded for individual cells by means of digital image analysis. The effect of different serum (0-10% vol/vol) or genistein (0-100 microM) concentrations was used to modulate the MTT-specific activity response.

RESULTS

As cells in culture are heterogeneous in cell size, the contribution of each cell to the total amount of formazan formed per dish is variable. The production of formazan per cell as a result of MTT bioreduction was found to be proportional to cell size.

CONCLUSION

Specific MTT-reducing activity was analyzed in phagocytes and nonphagocyte cells, revealing the utility of this variable in evaluating the MTT assay at the single-cell level.

Extra-cellular matrix changes in Schistosoma mansoni-infected Biomphalaria glabrata

Reactivity of snails against parasites exhibits a primitive focal reaction, with encapsulation, phagocytosis and destruction of parasite larvae by macrophage-like cells - the hemocytes. This reaction mimics granulomatous inflammation seen in higher animals. However, different from the latter, little is known about the participation of extra-cellular matrix in such snail defense reactions. Normal and Schistosoma mansoni-infected Biomphalaria glabrata of different strains were submitted to cytological, histological, ultrastructural and biochemical methods in order to investigate the behavior of extra-cellular tissues at the site of anti-parasite reactions. In spite of the presence of two cell-types in peripheral hemolymph, only one cell-type was present at the sites of tissue reactions. Although pre-existent collagen and elastic fibers and microfibrils sometimes appeared slightly compressed around focal reactions, no evidences of duplication, synthesis or deposition of connective-tissue extra-cellular components were observed within or around the zones of reactive cell accumulations. Thus, tissue reactions against S. mansoni in the snail B. glabrata appeared exclusively dependent on one specific population of hemocytes.

Microscopic, immunocytochemical, and ultrastructural properties of peri-implant mucosa in humans

BACKGROUND

Microscopic and immunocytochemical studies have demonstrated both similarities and differences between the gingival mucosa and the peri-implant mucosa restored around dental implants.

METHODS

This study was performed on 10 samples of peri-implant mucosa from 10 patients who had undergone implant treatment 16 to 18 months before. Microscopic, ultrastructural, and immunocytochemical investigations were performed to characterize the epithelial and connective layers of the peri-implant mucosa.

RESULTS

All specimens showed the morphologic characteristics of well restored tissues. The immunocytochemical reactions used to detect cytokeratins demonstrated that the restored peri-implant mucosa had a non-keratinized epithelium. The apical part of the inner epithelium was a few cell layers thick, like the corresponding junctional epithelium, but it stained positively with the markers for the cytokeratins expressed by the stratified epithelia. Ultrastructurally the keratinocytes adjacent to the implant displayed nuclei containing a rich cytoplasm with filaments and specialized intercellular junctions right up to the more superficial strata. Immunocytochemical reactions and ultrastructural observations demonstrated the presence of non-keratinocyte cells; i.e., Langerhans cells, melanocytes, and Merkel cells. Several cells were found to be proliferating by immunoreaction with mAb anti-PCNA, while immunoreactions with mAbs to detect von Willebrand factor, CD34, and vascular endothelial growth factor marked the well-developed networks of blood and lymphatic vessels in the connective tissue. S-100 and protein gene product 9.5 positive nerve fibers were marked. Immunocytochemical reactions with mAbs anti-vimentin, anti-laminin were also performed.

CONCLUSIONS

Our results demonstrated that all the epithelial and connective components of the mucosa are involved in the substantial regrowth of the peri-implant tissue and subsequently in the success of the implant.

Alterations of neurokinin receptors and interstitial cells of Cajal during and after jejunal inflammation induced by Nippostrongylus brasiliensis in the rat

Substance P (SP) and its receptors NK1 and NK2 are widely expressed in the intestinal wall by neurones, interstitial cells of Cajal (ICC) and smooth muscle cells. Changes in SP and/or its NK receptors have been documented during experimental inflammation in animals or inflammatory bowel diseases in humans, but the data concern the acute phase of the inflammatory process. We determined immunohistochemically whether NK receptors and SP were altered in the muscle coat during jejunal inflammation induced by the nematode Nippostrongylus brasiliensis and whether these alterations persisted when inflammation had spontaneously resolved 30 days postinfection. An ultrastructural analysis was also conducted on ICC, nerves and muscle. At day 14, when inflammation peaked, there was a reduction in NK1 receptors in myenteric neurones and in SP-immunoreactive nerve endings. There were also ultrastructural anomalies in synaptic vesicles and NK2 receptor loss in the circular muscle layer. The SP decrease persisted at day 30, whereas neurones and circular muscle cells re-expressed NK1 and NK2 receptors, respectively. The ICC at the deep muscular plexus, located near to the inflammatory site, underwent alterations leading to their complete loss at day 30. These morphological changes are probably associated with impairment in tachykinergic control of jejunal functions leading to the alterations of motility and sensitivity to distension already described in these animals.

Ultrastructure and functional versatility of hirudinean botryoidal tissue

In leeches, the botryoidal tissue is composed of two different cell types--granular botryoidal cells and flattened endothelial-like cells--localized in the loose connective tissue between the gut and the body wall sac. We have observed that the botryoidal tissue undergoes functional and structural modifications in response to the different needs arising during the life-cycle of the animal. In healthy, untreated leeches, botryoidal cells are organized in cords or clusters, sometimes surrounding few, small lacunae. Conversely, in wounded animals we have observed the transition of the botryoidal tissue from cluster/cord-like structures to a hollow/tubular architecture, typical of pre-vascular structures. We have documented in botryoidal cell cytoplasm the presence of large calcium storage. Moreover, the cytoplasm of botryoidal cells was filled with granules of different form and size, containing iron or melanin, as tested by classic histochemical methods. The presence of elements like iron and calcium was confirmed by the well-established EDS analysis. In response to a surgical wound, botryoidal tissue cells changed their shape and formed new capillary vessels. Concurrently, botryoidal cells secreted iron from cytoplasmic granules into the new cavity: this secretory activity appeared to be related to intracellular calcium fluctuations. At the end of the angiogenic process, botryoidal cells lost their contact with the basal lamina and moved freely in the circulating fluid towards the lesioned area. Interestingly, circulating botryoidal cells were found to carry melanin in the wounded area. This function is probably involved in defense processes. Thus, we have shown that stimulated botryoidal tissue displays a variety of striking structural, secretory and defensive activities.

Human gingival fibroblast cytoskeleton is a target for volatile smoke components

BACKGROUND

Several in vitro investigations have indicated that the particulate phase of cigarette smoke as nicotine affects many cell types including gingival fibroblasts, but few studies have examined the effect of volatile fraction on cellular structures involved in cell functions such as adhesion and proliferation. Since gingival fibroblast survival and reproduction are fundamental to maintaining the oral connective tissue as well as to wound healing, the effects of acrolein and acetaldehyde, volatile fractions of cigarette smoke, on cytoskeleton were examined in human gingival fibroblasts (HGFs) in vitro.

METHODS

Human gingival fibroblast (HGF) strains from healthy subjects with non-inflamed gingiva were utilized. The cells were incubated in different concentrations of acrolein and acetaldehyde. Cell adhesion was evaluated after 3 hours. The influence of both substances on cytoskeletal structures, tubulin and vimentin intermediate filaments (VIF), was investigated using indirect immunofluorescence technique.

RESULTS

The results show that both substances produced similar effects, resulting in a dose-dependent inhibition of HGF adhesion. Disturbance of HGF cytoskeleton consisted of a disruption of microtubules and vimentin microfilaments with alterations in cell shape.

CONCLUSIONS

Our experimental findings suggest that volatile fractions of cigarette smoke such as acrolein and acetaldehyde, because their ability to bind and interact with the cytoskeleton, prevent HGF adhesion. Consequently the maintenance of the oral connective tissue and integrity and remodeling could be impaired. According to our morphological evidence, these findings confirm other clinical and epidemiological investigations reporting that volatile components of cigarette smoke could lead to the initiation and progression of periodontal disease.

The dento-epithelial junction: cell adhesion by type I hemidesmosomes in the absence of a true basal lamina

BACKGROUND

The junctional epithelium (JE) is a unique structure that makes contact with both a non-renewable hard tooth surface and with a basement membrane (BM) facing the connective tissue. Ultrastructurally, this attachment occurs through hemidesmosomes (HD) and a basal lamina-like extracellular matrix which, on the tooth side, is termed the internal basal lamina. In this study we investigated the expression of basal cell markers in the tooth-facing (TF) cells of JE.

METHODS

Samples of healthy marginal gingiva were removed by careful dissection. The expression of laminin-5 was used to indicate TF cell preservation in double immunofluorescence labeling and confocal laser scanning microscopy.

RESULTS

The results show that integrin alpha6beta4 and laminin-5 colocalize unequivocally in the TF cells. The results also show the specific expression of the basal cytokeratin 14 and the alpha(v) integrin subunit in the TF cells. All 3 major hemidesmosomal components BP180, BP230, and HD1 antigen are likewise present. On the other hand, type IV collagen, laminin-1/10, type VII collagen, and the BM proteoglycan perlecan are all absent from the dento-epithelial junction.

CONCLUSIONS

The results indicate that the epithelium-tooth interface is a unique structure wherein epithelial cells adhere by means of bona fide hemidesmosomes to an epithelium-derived extracellular matrix lacking most of the common BM components. Moreover, TF cells differ from connective tissue facing (CTF) cells, not only by their cell surface molecules and their production of extracellular matrix, but also by their cytoskeletal architecture.

Histological and histochemical observations in the stomach of the Senegal sole, Solea senegalensis

An histological and histochemical study was conducted on the stomach of adult Senegal sole, Solea senegalensis specimens. The stomach was made up of four distinct layers: mucosa, lamina propria-submucosa-, muscularis and serosa. Surface epithelial, glandular and rodlet cells were present in the mucosa. Cells of the columnar epithelium contained a basal nucleus. Numerous mitochondria, granular endoplasmic reticulum and Golgi apparatus consisting of several parallel cisternae and vesicles were observed in the cytoplasm of these cells. The lysosomes were small, round and dense. The gastric glands were numerous in the pyloric and fundic regions but absent in the cardiac stomach. These glands were formed by two cell-types: light and dark cells. The light cells were characterised by numerous mitochondria, while dark cells had slightly fewer mitochondria and a tubulo-vesicular system. Rodlet cells similar to those observed in other teleostean fish were present among the epithelial cells. Although the epithelial cells of the mucosa contained a weak presence of neutral and acid mucopolysaccharides/mucosubstances, these substances were abundant in the lamina propria-submucosa. Proteins rich in arginine, lysine, cysteine and cystine were rarely present in the mucosa and lamina propria-submucosa of stomach, while proteins rich in tyrosine were abundant in these layers. Acid phosphatase, and ATP-ase (pH 7.2 and 9.4) activities were detected in the mucosa and lamina propria-submucosa. Alkaline phosphatase activity was not detected.

Dynamics of nuclei of muscle fibers and connective tissue cells in normal and denervated rat muscles

The mitotic activity in muscles of growing rats and the effect of denervation were studied by means of continuous infusion of 5-bromo-2-deoxyuridine (BRDU). Denervated muscles after 10 weeks contained 20 to 60% fewer muscle nuclei than normal; BRDU labeled about 25% of the nuclei of normal soleus and extensor digitorum longus (EDL) and of denervated EDL muscles but only 5% in the denervated soleus muscle. Labeled nuclei persisted in denervated but not in normal muscles. After the main growth period, the turnover of myonuclei was at most 1 to 2% per week. The behavior of connective tissue nuclei was similar to that in muscle fibers. Infusion of BRDU had no effect on contractile properties. It is suggested that the exceptionally rapid atrophy of the denervated rat soleus associated with loss of satellite cells was due to loss of myonuclei and differentiation and fusion of satellite cells. The cause may possibly be that the phase of postdenervation fibrillation is shorter than in other muscles.

The glio-pial system in cortical ischemic lesions

The ultrastructural features of the glio-pial system have been analyzed in an animal model of brain focal ischemic lesion. Aim of the work was to describe the relationship between glial and pial cells in a condition of ischemic neurodegeneration and the eventual involvement of these cells in removal of debris and reconstruction of the glial-limiting lamina. The study was performed in rats in which the right middle cerebral artery was occluded. The development of a lesion and its extension was controlled in vivo 24 h after the middle cerebral artery occlusion by magnetic resonance imaging. The rats were sacrificed 10 or 15 days after the occlusion and their brain was processed for transmission and scanning electron microscopy. The ultrastructural examination of the lesion revealed that the nervous parenchyma was replaced by cicatricial tissue composed by glial and pial areas. The pial areas were composed mainly by leaf-like cells forming a network. Their main cytoplasmic feature was the presence of large lysosomes in which ferritine-like particles were often enclosed. The glial areas were composed by strictly packed cells which displayed at scanning electron microscopy a spider-like shape with a central body and elongated cell processes. These results suggest a role for the glio-pial system in acute ischemia. In particular, the pial cells seem to be directly involved in removal of cell debris while glial cells seem mainly devoted to the reconstruction of the glial limiting lamina.

Preparation and in vivo testing of porous alumina ceramics for cell carrier applications

Microporous alumina was used to develop implantable cell carriers shaped as a hollow-sphere with a central opening to allow ingrowth of vascularised tissues. The carriers were produced by suspending the ceramic raw materials in water, homogenising and dropping the resulting slurry onto a heated plate (hot plate moulding, HPM). Morphological characteristics of the cell carriers were investigated by SEM and optical microscopy. Produced carriers had an average diameter of 4.9 mm. The material was highly porous (56 +/- 8%). For in vivo testing the cell carriers were implanted into abdominal wall of Zur: SIV rats for up to 50 weeks and investigated by light microscopy, SEM and TEM. The surface of the hollow carriers was in close contact with unirritated muscle tissue; no inflammation or capsule formation was observed. Loose connective tissue had grown into the hollow cell carrier, and after prolonged implantation >20 weeks adipocytes were observed. The absence of scar tissue formation around the implant and the vitality within the cavity of the hollow carriers indicate that porous alumina may be used for cell transplantation devices.

Appearance of adipose cells in connective tissue at the implantation site of bone matrix gelatin and bupivacaine injection

Two types of adipose cells were found in the connective tissue on day 7 after bone matrix gelatin (BMG) implantation and an injection of bupivacaine: mature adipose cells with a large lipid droplet (2-140 microns) and immature adipose cells with many small lipid droplets (0.1-2 microns). On day 10 after BMG implantation, typical adipose tissue was observed near the implant. The immature adipose cells had small, spherical mitochondria, glycogen granules and cytoplasmic microvesicles, and they might differentiate from undifferentiated mesenchymal cells in the connective tissue or the peripheral cells around the vessels as a white adipose tissue. These findings suggest that the differentiation of adipose cells in the connective tissue near heterotopic bone formation might be induced not only by mechanical and/or bupivacaine injury, but also by some factor or factors of the BMG.

Fibrous structure of connective tissue in the vocal fold of the Japanese monkey (Macaca fuscata)

Fibrous structures in the vocal fold were studied in 8 adult Japanese monkeys. Their vocal folds were fixed with formalin and longitudinal and cross-sections were prepared. Some of the samples were treated with 10% NaOH to digest cellular components and elastic fibers, and some of them were treated with 90% formic acid to digest cellular components and collagen fibers. Each sample was then fixed with OsO4, dehydrated, dried at the critical point, ion-coated, and studied under a scanning electron microscope. The lamina propria mucosae in Japanese monkeys was thinner than that in humans and consisted of a superficial layer rich in connective tissue and a deep layer poor in this tissue. Both collagen fibers and elastic fibers mostly ran straight, and the fiber distribution and morphology slightly differed according to the depth of the layer. Their density was higher in upper layers. In the muscle layer, connective tissue surrounding muscle fibers was scarce. The fibrous structure of the monkey vocal fold is simpler than that of human vocal fold, and these findings reflect the short and monotonous phonation of monkeys.

Scanning electron microscopy study including maceration techniques of an absorbable alloplastic implant designed for the reconstruction of ventral abdominal wall defects

The interposition of synthetic material represents the most generally acknowledged method for achieving a tension-free surgical repair of major abdominal wall defects. As permanent materials are frequently associated with severe complications (rejection, peritonitis, enterocutaneous fistula, erosive invasion into the intestine), a newly designed absorbable prosthetic (polydioxanone, PDS) has been developed. The ellipsoid implant is composed of a knitted envelope and a filling of loosely arranged filaments. Interpositioning of the implant into an artificial circular abdominal wall defect was carried out on 30 Wistar rats. Explantation was performed 21 days post implantationem (p.i.), 42 days p.i. and 180 days p.i. The aim of the study was to evaluate the use of scanning electron microscopy (SEM) combined with maceration techniques (2 N NaOH for 1, 3 and 5 days) for a spatial assessment of the interactions between the implanted material and the ingrowing tissue components. Application of 2 N NaOH caused the complete dissolution of the PDS-material and a concomitant gradual disappearance of cellular and amorphous tissue components, thereby unmasking the remaining collageneous network. SEM of non-macerated specimens demonstrated that 21 days p.i. the entire implant has been filled with connective tissue components. Additionally, the ventral and dorsal surfaces of the implant were covered by a collageneous layer (neo-fascia). 21 days p.i. the PDS-filaments had developed minor clefts, which increased in number and depth 42 days p.i., and were transformed into small remnants 180 days p.i. Alkali treatment revealed the three-dimensional arrangement of collagen fibers, which ensheathed the PDS-filaments and formed interconnecting networks between them. At the ventral portion of the implant the fibrous network was more elaborate and densely distributed. 180 days p.i. the implant has been transformed into a membranous structure (neo-membrane) composed of the ventral and dorsal neofascia, remnants of PDS-filaments and a continuous connective tissue layer containing wave-like collagenous structures. Whereas 21 and 42 days p.i. no herniation was observed, 130 days p.i. the implant began to bulge out of the ventral abdominal wall. It is therefore concluded that inspite of the advantages of absorbable materials, longer resorption times may be required to allow a sufficient consolidation of the ingrowing connective tissue to resist the tensile forces of the abdominal muscle coat. SEM combined with 2N NaOH maceration proved to be a usefull tool in addition to conventional histological techniques for a three-dimensional assessment of fibrous connective tissue components ingrowing into alloplastic implants.

Histochemical localization of hyaluronan and versican in the rat molar dental pulp

The distribution of hyaluronan and versican in the dental pulp of the young rat was mapped histochemically. The pattern of staining showed considerable variation between different teeth and different specimens. The most common pattern was a strong reaction for hyaluronan and a weak reaction for versican in the subodontoblastic region, with the reverse deeper in the pulp. This was not an entirely consistent pattern and there was considerable regional variation in the staining intensity for both molecules. The localization of these molecules at similar sites could thus indicate related roles in the connective tissue matrix rather than any chemical bonding between them.

Centrilobular and perisinusoidal fibrosis in experimental congestive liver in the rat

BACKGROUND/AIMS

The pathogenesis of congestive hepatic fibrosis is known to be a reaction of hepatic stromal cells following prolonged congestive heart failure or hepatic outflow obstruction. However, little is known about the fibrotic process itself. This study documents the hepatic morphology and ultrastructure of the fibrotic processes in an experimental model of congestive hepatic fibrosis in rats.

METHODS

In this model we ligated the abdominal portion of the inferior vena cava in the space between the diaphragm and liver, and observed liver morphology 24 h, 1 week and 6 weeks after the operation. The cytoskeletal components of the hepatic stellate cells and myofibroblasts were identified by immunohistochemistry for glial fibrillary acidic protein (GFAP) and a-smooth muscle actin (a-SM actin). Extracellular matrices of reticulin fibers and fibronectin were localized using silver impregnation and immunohistochemical staining.

RESULTS

Soon after ligation of the vena cava, foci of cells at variable stages of necrosis appeared in the centrilobular areas, the topographical localization of which was highly variable within the liver. The fibrotic processes were subclassified into three stages. In the first stage (24 h after ligation), abundant neutrophils, macrophages and GFAP-positive stellate cells appeared, but a-SM actin-positive cells were not detected in the necrotic areas. In the second stage (1 week after ligation), the GFAP-positive cells disappeared, but a-SM actin-positive myofibroblasts appeared. In the third stage (6 weeks after ligation), a large number of a-SM actin-positive myofibroblasts were observed, and there was heavy deposition of connective tissue proteins, such as reticulin fibers and fibronectin, in centrilobular areas. Two interesting observations were that: (1) the distribution of centrilobular necrosis was highly variable within the liver, and (2) the fibrosis was confined to focal centrilobular areas involving the perivenular sinusoidal area without periportal fibrosis.

CONCLUSIONS

These findings suggest that GFAP-positive stellate cells are transformed into a-SM actin-positive myofibroblasts, and these myofibroblasts produce extracellular matrix proteins in centrilobular sinusoidal areas under congestive conditions.

Localisation of connective tissue and inhibition of autofluorescence in the human optic nerve and nerve head using a modified picrosirius red technique and confocal microscopy

The use of picrosirius red to localise connective tissue in thin tissue sections viewed by bright-field microscopy is well documented. Its use on thin tissue sections imaged by fluorescence confocal microscopy has also been reported. Here we describe modifications to published procedures that allow picrosirius red staining of thick 60-microm sections and their subsequent analysis by confocal microscopy. The use of phosphomolybdic acid pre-treatment was found to be essential for confocal analysis; in addition to preventing non-specific staining, it also quenched tissue autofluorescence. By incubating sections free-floating, pre-treating them with phosphomolybdic acid for 30 min and imaging them using an argon ion laser we were able to use confocal microscopy to image the entire depth of 60-microm human optic nerve and nerve head sections stained with picrosirius red. The application of this modified picrosirius red and confocal microscopy technique should be useful for analysing the three-dimensional structure of the optic nerve and other tissues with a similarly complex arrangement of connective tissue.

The ultrastructure of the intra-articular disc of the temporomandibular joint, with special reference to fibrocartilage

Cells in the intra-articular disc of the temporomandibular joint of the rat, guinea pig, rabbit, ferret, marmoset and sheep were studied at the ultrastructural level. The cells were generally rounded in outline and possessed moderate amounts of roughened endoplasmic reticulum and other organelles associated with protein synthesis and secretion. No intracellular collagen profiles were observed. Many of the cells possessed conspicuous amounts of microfilamentous material. Cell membranes in the rat, guinea pig, rabbit, ferret and sheep were closely applied to the collagen fibrils of the extracellular matrix. Occasionally in these animals, a narrow, irregular space containing microfilamentous material surrounded the cell membrane. Many cells in the marmoset differed from this description in being completely surrounded by an obvious pericellular matrix devoid of collagen fibrils and being comprised of microfilamentous material embedded in an amorphous ground substance. These chondrocyte-like cells in the intra-articular disc of the marmoset differed from chondrocytes in hyaline cartilage by lacking a pericellular capsule.

Relationship between epithelial and connective tissues in the stomach of the frog Rana temporaria during metamorphosis: an ultrastructural study

In the course of metamorphosis of the stomach of Rana temporaria tadpoles there is a marked increase in the amount of active mesenchymal fibroblasts and extracellular matrix underlying the regenerating gastric epithelium. At the onset of metamorphosis, a thick PAS-positive basement membrane is developed around the epithelial component of the mucosa, formed by the apical, degenerating larval epithelium and the basal, regenerative epithelial cords. Under the electron microscope, a folded basement membrane is usually revealed under the apical degenerating epithelium while a compact basement membrane (up to 1-2 microns thick), forming both patches and more extensive areas, is frequently seen around the regenerative glandular cords. Cytoplasmic processes, extending from both the epithelial and mesenchymal fibroblastic cells, cross the basement membrane and make physical contact between the two cellular types. At mid-metamorphosis areas of thick PAS-positive basement membrane are still observed around the differentiating glandular outlines, before disappearing completely at late metamorphosis. The probable involvement of intertissue interactions between epithelium and connective elements in the morphogenesis, proliferation and differentiation of secondary, definitive frog stomach is discussed. Early contacts between epithelium and phagocytes, probably related to the invasion of epithelium by the phagocytic cells, have also been observed.

Morphological organization of neuropile glial cells in the central nervous system of the medicinal leech (Hirudo medicinalis)

Neuropile glial (NPG) cells in the central nervous system of the medicinal leech, Hirudo medicinalis, were studied by histological, histochemical and immunocytochemical techniques. The NPG cells are often surrounded by electron-dense microglial cells. The central cytoplasm of NPG cells shows a significant zonation. The zone around the nucleus contains mitochondria, glycogen and vesicles. The cytoplasm also contains many ribosomes, a few dictyosomes and distinct inclusions up to 2 microns in diameter. A second zone around the perinuclear region is marked by the occurrence of bundles of intermediate filaments that correspond in thickness to glial filaments of vertebrates. We found a positive reaction with polyclonal antibodies against human glial fibrillary acidic protein (GFAP), and the areas of intense fluorescence correspond to the regions where intermediate filaments were found to be abundant. The peripheral zone contains numerous membrane stacks that could not be contrasted by lanthane nitrate or tannic acid. Therefore, the membrane stacks could be part of an extensive smooth endoplasmic reticulum, which is characteristic of cells with active lipid metabolism.

In situ characterization of mast cells in the frog Rana esculenta

The number, distribution, and ultrastructural characteristics of mast cells were assessed in the tongue, heart, and kidney of the frog Rana esculenta. The density of tongue mast cells (253+/-45 mast cells/mm2) was significantly higher than that of the heart (5.3+/-0. 4/mm2) and kidney (15.3+/-1.4 /mm2). A striking feature of this study was the remarkable association of frog mast cells to nerves. The ultrastructural study of the mast cell/nerve association demonstrated that mast cells were closely apposed to or even embedded in nerves. Mast cells were also physically associated with melanocytes even in the heart. Mast cells were Alcian blue+/safranin+ in the tongue and in the peritoneum, whereas in the heart and in the kidney they were Alcian blue-/safranin+. The mast cells in the lamina propria of the gastrointestinal tract were Alcian blue+/safranin-. The cytoplasm of frog mast cells was packed with numerous heterogeneous, membrane-bound granules. The ultrastructure of these cytoplasmic granules was unique, being totally unlike any other previously described granules in other animal species as well as in man. The histamine content/frog mast cell ( approximately 0.1 pg/cell) was approximately 30 times lower than that of human mast cells isolated from different tissues ( approximately 3 pg/cell). A monoclonal anti-histamine antibody was used to confirm the ultrastructural localization of histamine in secretory granules in frog mast cells.