Acinar Basement Membrane Research Articles

Acinar-ductal cell rearrangement drives branching morphogenesis of the murine pancreas in an IGF/PI3K-dependent manner

During organ formation, progenitor cells need to acquire different cell identities and organize themselves into distinct structural units. How these processes are coordinated and how tissue architecture(s) is preserved despite the dramatic cell rearrangements occurring in developing organs remain unclear. Here, we identified cellular rearrangements between acinar and ductal progenitors as a mechanism to drive branching morphogenesis in the pancreas while preserving the integrity of the acinar-ductal functional unit. Using exvivo and invivo mouse models, we found that pancreatic ductal cells form clefts by protruding and pulling on the acinar basement membrane, which leads to acini splitting. Newly formed acini remain connected to the bifurcated branches generated by ductal cell rearrangement. Insulin growth factor (IGF)/phosphatidylinositol 3-kinase (PI3K) pathway finely regulates this process by controlling pancreatic ductal tissue fluidity, with a simultaneous impact on branching and cell fate acquisition. Together, our results explain how acinar structure multiplication and branch bifurcation are synchronized during pancreas organogenesis.

Immunosuppression via Tenascin-C.

Immunosuppression via Tenascin-C.

Sex steroids in Sjögren’s syndrome

The purpose of the review is to consider pathomechanisms of Sjögren’s syndrome (SS), which could explain the female dominance (9:1), the most common age of onset (40–50 years) and targeting of the exocrine glands. Estrogens seem to specifically protect secretory glandular acinar cells against apoptosis whereas lack of estrogens during menopause and climacterium specifically leads to increased apoptosis of the exocrine secretory cells. Male gonads produce testosterone and convert it in exocrine glands to dihydrotesterosterone (DHT), which is anti-apoptotic and protects against acinar cell apoptosis. Estrogen-deficient women need to produce dehydroepiandrosterone (DHEA) in the adrenal glands and convert it to DHT in exocrine glands in a complex and branching reaction network in which individual enzymatic reactions are catalyzed in forward and backward directions by a myriad of different isoforms of steroidogenic enzymes. Tailoring DHT in peripheral tissues is much more complex and vulnerable in women than in men. In SS the intracrine steroidogenic enzyme machinery is deranged. These endo-/intracrine changes impair acinar remodeling due to impaired integrin α1β1 and integrin α2β1 expression so that the intercalated duct progenitor cells are unable to migrate to the acinar space, to differentiate to secretory acinar cells upon contact with laminin-111 and laminin-211 specifically found in the acinar basement membrane. The disarranged endo-/intracrine estrogen/androgen balance induces acinar cells to release microparticles and apoptotic bodies and to undergo apoptotis and/or anoikis. Membrane particles contain potential autoantigens recognized by T- (TCRs) and B-cell receptors (BCRs) and danger-associated molecular patterns (DAMPs) recognized by Toll-like receptors (TLRs). In membrane particles (or carrier-complexes) antigen/adjuvant complexes could stimulate professional antigen capturing, processing and presenting cells, which can initiate auto-inflammatory and autoimmune cascades, break the self-tolerance and finally lead to SS.

Diabetes induces stromal remodelling and increase in chondroitin sulphate proteoglycans of the rat ventral prostate

Extracellular matrix (ECM) remodelling is an important process involved in prostate cancer progression. Alterations in ECM caused by diabetes in different tissues such as kidney is well described; however, it is poorly investigated in prostate. The aim of this study was to evaluate changes in ECM of rat prostate showing gland atrophy caused by diabetes and their implications in development of malignant lesions. Diabetes was induced in Wistar rats using alloxan (45 mg/kg bw). After 90 days of diabetes onset, animals were killed and ventral prostate was removed and prepared for light microscopy following immunoreaction for fibronectin, chondroitin sulphate and Picrossirius staining for collagen fibres. Proteoglycans (PG) were identified at transmission electron microscopy after fixation with Cuprolinic Blue. Diabetes led to a thickening of 25% in the acinar basement membrane accompanied by increase and disorganization of its proteoglycans (P1). Three additional populations of prostatic stromal PGs were identified: collagen fibril linked (P2) and interstitial (P3) and (P4) PGs. Diabetes increased P3 and mainly P4 which had higher dimension and accumulated around the smooth muscle cells. In addition, an increase in chondrotin sulphate (33%, mainly in sites where P4 were noted) and collagen (44%) was noted in diabetic rats, whereas fibronectin did not change. Atrophic changes observed in rat ventral prostate after diabetes are accompanied by stromal remodelation related to increase in collagen and chondroitin sulphate proteoglycans. Thus, diabetes can promote a stromal microenvironment rich in elements that could favour cell migration, proliferation and pathological process.

Detection of human and murine common idiotypes of DNA antibodies in tissues and sera of patients with autoimmune diseases

The expression in tissue and serum of a panel of murine and human common DNA antibody idiotypes (Ids) (BEG 2, PR 4, F-423, I-402, II-28, IV-228, V-88) has been investigated. The murine V-88 Id was detected in eight out of 10 and the human BEG 2 Id in five out of 10 labial biopsies from patients with Sjögren's syndrome. The murine F-423, I-402 and IV-228 Ids were identified in one out of 10 biopsies. In each case the pattern of staining was similar with staining of the acinar basement membrane and a cell population. Using double-labelling immunohistochemistry this cell population were identified as plasma cells. No staining was seen in four normal labial biopsies. The V-88 Id was detected on the epithelial aspect of the thickened basement membrane in three out of nine renal biopsies from patients with systemic lupus erythematosus (SLE). None of the other Ids (BEG 2, PR4, IV-228, F-423 or I-402) could be detected in renal tissue. None of the Ids were found in skin biopsies from SLE patients. Id V-88 may, like the 16/6 Id to which it is phenotypically related, play a role in the pathogenesis of renal lesions in SLE. The BEG 2 Id could be detected in the serum of patients with rheumatoid arthritis (RA) and active untreated tuberculosis. Ids II-28, V-88 and I-402 were elevated in serum from patients with Sjögren's syndrome and II-28 Id in serum from patients with myositis and RA. None of the Ids were elevated in serum from patients with SLE. Apart from the BEG 2 Id, none of the Ids were elevated in serum from patients with tuberculosis or Gram-negative infections. The presence of murine Ids in human tissue and serum suggests that they are cross-species idiotypes and have been conserved through evolution.

Segment‐specific but pathologic laminin isoform profiles in human labial salivary glands of patients with Sjögren's syndrome

To assess the laminins in basement membrane of the labial salivary glands of patients with Sjogren's syndrome (SS) and healthy controls. Labeling of laminin alpha1-alpha5, beta1, beta2, gamma1, and gamma2 chains was performed using immunohistochemistry with chain-specific monoclonal antibodies and pattern recognition analysis of the labeled specimens. Laminin alpha1, alpha2, and alpha4 chains were detected exclusively in the acinar basement membranes, whereas laminin alpha3, alpha5, beta1, gamma1, and gamma2 chains were also detected in ductal basement membranes. Laminin beta2 chain was not found. In patients with SS, laminin alpha1 and alpha2 chains were weakly labeled, but laminin alpha4 labeling was also intense in areas not infiltrated by lymphocytes. Pattern recognition analysis suggested that laminin alpha1, alpha2, and alpha4 chains were associated with acinar cells, myoepithelial cells, and tissue damage/repair, respectively. All salivary gland basement membranes signal through laminin 5, laminin 6, and laminin 10 trimers, but acinar basement membranes also signal through laminin 1, laminin 2, and laminin 8 trimers. Laminin alpha1 chain/laminin 1 may play a central role in the maintenance of acinar cells in healthy glands. This possibility was supported by the finding of variable expression of laminin alpha1 chain/laminin 1 in acinar basement membrane and its weak expression in SS with acinar cell atrophy. The impairment of myoepithelial laminin alpha2 chain/laminin 2 in patients with SS indicates a double defect in the acinar compartment and pathologic extracellular matrix-to-cell signaling, which may contribute to structural deterioration and functional abnormality of the exocrine glands.

Laminins alpha2 and alpha4 in pancreatic acinar basement membranes are required for basal receptor localization.

Basement membranes (BMs) are thin layers of extracellular matrix (ECM) found at the basal surface of many cell types, including epithelial cells. BMs present growth, differentiation, and anti-apoptotic signals and provide structural support to cells, compartmentalize tissues, and serve as filters. The structure and function of BMs depend on their complement of laminins, a family of alpha beta gamma heterotrimeric glycoproteins. We found that laminins containing the alpha2 and alpha4 chains are the major laminins in pancreatic acinar BMs. Importantly, these laminins were required for proper basal localization on acinar cells of two laminin receptors, dystroglycan and integrin alpha6beta4 .

Markers for the development of early prostate cancer.

Biochemical and genetic changes precede histologically identifiable changes accompanying cell transformation often by months or years. De-expression of the extracellular matrix adhesive glycoprotein tenascin and the cell-to-cell adherent protein E-cadherin have been suggested as markers of early neoplastic change in prostate epithelial cells. Previous studies have been inconclusive, probably due to epitope masking. This study examined 2,378 biopsy cores from 289 prostates using a heat antigen retrieval protocol at low pH to improve the accuracy of detection. Tenascin and E-cadherin de-expression was correlated with purinergic receptor and telomerase-associated protein labelling, as well as prostate-specific antigen (PSA) levels and Gleason scores. E-cadherin was a poor marker, as it was expressed in all lesions except carcinomas of the highest Gleason score. Tenascin was maximally expressed in the extracellular matrix and acinar basement membrane in normal and prostatic intraepithelial neoplasia tissue. In prostate cancer tissue, tenascin expression did not correlate with Gleason score but was significantly de-expressed as purinergic receptor and telomerase-associated protein expression increased. Marked changes in tenascin, telomerase-associated protein, and purinergic receptor expression were apparent before any histological abnormalities were visible by haematoxylin and eosin (H&E) stain, making these potential markers for early and developing prostate cancer. Moreover, the potential increased accuracy of diagnosis of underlying prostate cancer using purinergic receptor translocation (PRT) assessment suggests that PSA levels may be more accurate than has generally been supposed when apparent false negatives arising from H&E-based diagnoses are correctly categorized.

Differential expression of laminin chains in the human major salivary gland.

Laminin represents a macromolecule family. The heterotrimeric isoforms of laminin can be determined by immunohistochemical demonstration of the single chains. The laminin chain heterogeneity of the basement membrane in adult human major salivary glands was evaluated in relation to cellular differentiation of the epithelia and the stromal compartment. Monoclonal antibodies to the laminin alpha1, alpha3 (BM165) chains and epiligrin reacted with the basement membranes of serous and mucous acini and of intercalated, striated and excretory ducts. As evidenced by a double-labelling technique, the alpha2 chain showed a spatial association with the myoepithelium of the acini, whereas the ductal basement membranes containing no myoepithelial cells were negative. Almost exclusively, beta1 chain was detected in acinar basement membrane, beta2 chain whereas in ductal basement membrane. Gamma2 chain is a unique chain belonging to the laminin-5 isoform. It was restricted to the ductal basement membrane. Alpha1, alpha2, beta1, beta2 and gamma1 chains were detected in nerves of salivary tissue and alpha1, alpha3, beta1, beta2 and gamma1 chains and epiligrin in blood vessels. Our results indicate that the acinar ductal unit contains basement membranes with different isoforms, which relate to cell differentiation and cell function.

The Histopathology and the Mechanism of Entropion in Patients with Trachoma

Eyelids of patients with trachoma may be thickened. This thickening could be attributed to trachomatous changes in the conjunctiva and tarsus. Biopsies of tarsal plates and palpebral conjunctivae were obtained from 17 upper eyelids of 11 patients with inactive trachoma who underwent posterior tarsotomy procedures for entropion repair. Light microscopy studies showed a thick and compact subepithelial fibrous membrane adherent to the tarsal plate. This membrane caused apparent thickening of the tarsus when measured intraoperatively (range, 1.25-2.00 mm). Other histopathologic findings include atrophy of the meibomian glands with thickening of the acinar basement membrane, loss of goblet cells, retention cysts, and hyaline degeneration of the tarsal plate with focal replacement by adipose tissue. The contraction of the subepithelial fibrous membrane formed by vertically oriented parallel collagen fibers is one of the main factors contributing to the entropion formation.

Differential expression of α6 and α2 very late antigen integrins in the normal, hyperplastic, and neoplastic prostate: Simultaneous demonstration of cell surface receptors and their extracellular ligands

The very late antigens (VLAs) are αβ-heterodimeric transmembrane proteins that include surface cell receptors for laminin (VLA-6) and collagen (VLA-2), which mediate cell-matrix and cell-cell adhesion. We investigated the distribution of VLA-6 (α6, β1) and VLA-2 (α2, β1) proteins in normal, hyperplastic, and neoplastic human prostate tissue and lymph node metastases by the avidin-biotin complex method. In normal and hyperplastic glands we observed two staining patterns that differed according to the density of α6- and α2-receptors at the site of co-expression with their corresponding ligands (laminin, type IV collagen) in acinar basement membranes (BMs). Band-like deposits with high receptor density suggested strong anchorage of the prostate epithelium to acinar BMs, whereas the absence of this pattern most probably reflected reduced cellular attachment. Very late antigen-6 immunoreactivity showed the band-like pattern in approximately 70% of normal and hyperplastic glands compared with VLA-2, which showed the same pattern in only 5% of cases. In prostatic adenocarcinoma the band-like pattern significantly decreased with dedifferentiation and was consistently absent in grade III lesions. Compared with staining intensities in normal and hyperplastic conditions, grade I and II tumors maintained or overexpressed the VLA-6 receptor in 85% of cases, whereas the VLA-2 receptor was downregulated in approximately 70% of cases. Grade III tumors were characterized by a heterogenous expression of VLA-6 and VLA-2 proteins, but frequently upregulated their receptors in corresponding lymph node metastases. Regardless of the staining intensity, all primary and metastatic carcinomas investigated expressed VLA-6 and VLA-2 receptors whose extracellular domains were extensively co-expressed with their ligands in neoplastic BM formations. These findings suggest that VLA-6 and VLA-2 receptors mediate attachment of tumor cells to neoplastic BM material, which, in turn, may endow these cells with an increased ability to invade the extracellular matrix.

Heterogeneous distribution of a basement membrane heparan sulfate proteoglycan in rat tissues.

A heparan sulfate proteoglycan (HSPG) synthesized by murine parietal yolk sac (PYS-2) cells has been characterized and purified from culture supernatants. A monospecific polyclonal antiserum was raised against it which showed activity against the HSPG core protein and basement membrane specificity in immunohistochemical studies on frozen tissue sections from many rat organs. However, there was no reactivity with some basement membranes, notably those of several smooth muscle types and cardiac muscle. In addition, it was found that pancreatic acinar basement membranes also lacked the HSPG type recognized by this antiserum. Those basement membranes that lacked the HSPG strongly stained with antisera against laminin and type IV collagen. The striking distribution pattern is possibly indicative of multiple species of basement membrane HSPGs of which one type is recognized by this antiserum. Further evidence for multiple HSPGs was derived from the finding that skeletal neuromuscular junction and liver epithelia also did not contain this type of HSPG, though previous reports have indicated the presence of HSPGs at these sites. The PYS-2 HSPG was shown to be antigenically related to the large, low buoyant density HSPG from the murine Engelbreth-Holm swarm tumor. It was, however, confirmed that only a single population of antibodies was present in the serum. Despite the presence of similar epitopes on these two proteoglycans of different hydrodynamic properties, it was apparent that the PYS-2 HSPG represents a basement membrane proteoglycan of distinct properties reflected in its restricted distribution in vivo.

Observations on the pancreas of cattle deficient in copper

Lesions were found in the pancreas of clinically normal cattle of low copper status. In comparison with the pancreas of cattle with normal hepatic copper reserves, the abnormalities were an increase in the dry matter content and reduction in the concentrations of protein and copper in the wet tissue. Cytochrome oxidase activity and protein-to-RNA ratio were also reduced. Histologically, there were defects in acinar basement membranes, splitting and disorganization of acini, cellular atrophy and dissociation, and stromal proliferation. The pancreatic ductular system did not show atrophy or disorganization.

Parotid gland basement membrane variation in diabetes mellitus.

Post-mortem samples of parotid gland were obtained from 15 patients with a history of diabetes mellitus for a minimum of 5 years, and from 15 age- and sex-matched controls. The tissue was studied by direct immunofluorescence for abnormal binding of selected serum proteins, including IgG, IgM, IgA, C3, fibrinogen, polyvalent immunoglobulin and albumin, to acinar and ductal basement membranes of the gland. Thickness of these basement membranes was also assessed using a calibrated magnifier on uniformly enlarged photomicrographs of the tissue which had been stained by the chromotrope silver methenamine method to highlight basement membranes. Results of this investigation revealed parotid gland basement membrane abnormalities in all diabetic subjects as indicated by the binding of IgG, albumin and polyvalent immunoglobulins to ductal and acinar basement membranes. These basement membranes were uniformly negative in control subjects for the binding of all serum proteins tested. Binding of IgA was also noted in 7 of 15 experimental subjects, with 6 of these representing Type I diabetics. Basement membrane measurements revealed no difference in thickness between diabetic and non-diabetic subjects. Variations in parotid diabetic basement membranes evidenced in this study further substantiate the idea that membranopathy in this disease is systemic in nature.

Abnormal binding of negatively charged serum proteins to diabetic basement membranes is largely a systemic phenomenon.

Direct immunofluorescence employing goat anti-human IgG, IgA, IgM, C3 component of complement, fibrinogen, albumin, and polyvalent immunoglobulins was performed on postmortem samples of gingiva, parotid gland, thyroid, kidney, and pancreas tissue of 15 diabetic and 15 control patients. Basement membrane thickness quantification of kidney tubules, gingival capillaries, and parotid gland ducts and acini was also done utilizing a calibrated magnifier on uniformly enlarged photomicrographs which had been specially stained to highlight basement membranes. Results revealed binding of IgG, albumin, and polyvalent immunoglobulin to kidney glomerular and tubular basement membranes and parotid ductal and acinar basement membranes in all diabetic subjects. Thyroid follicular basement membranes were positive in 8 of 15 diabetic patients for the same antisera. All gingival and pancreatic tissue from diabetic and control patients was negative for binding of all serum proteins tested. Basement membrane thickening in kidney tubules and gingival capillaries was observed in diabetic subjects; however, there was no apparent difference between diabetic and control patients in thickness of ductal or acinar basement membranes of the parotid gland.

Amyloid P component in human thyroid.

The distribution of amyloid P component in the adult human thyroid was studied by direct immunofluorescence on frozen sections of surgically removed tissue. Amyloid P component shows a striking fibrillary and broken linear distribution in the interfollicular areas. This pattern corresponds to that of reticulin fibres. Amyloid P is also localised to the small amount of elastic tissue in blood vessels but is not demonstrable within cells or in acinar basement membranes.

Alkaline phosphatase reaction of canine mammary mixed tumours: a light and electron microscopic study

Alkaline phosphatase (ALK-P) reactions at the light and electron microscopic levels were performed on eight canine mammary mixed tumours. In the morphologically normal gland next to the tumours, the myoepithelial cells and the stromal tissues near the acinar basement membranes both showed a positive ALK-P reaction by light microscopy. At the electron microscopic level, those parts of the myoepithelial cell membrane that were in contact with other cells--myoepithelial or lumenal epithelial--showed an ALK-P-positive reaction, as did the adjacent stromal tissue. The characteristic tumour cells, at sites of early proliferation, were ALK-P-positive, while in the mucoid and chondroid areas of the mixed tumours they were largely ALK-P-negative by light microscopy. By electron microscopy, those neoplastic cells which were in contact with other cells typically showed a positive ALK-P reaction, while those cells which were in contact with mucoid or chondroid matrix were largely negative. Although the cytoplasmic filaments of the neoplastic cells were 10 nm thick, and those of normal myoepithelial cells were 6 to 8 nm thick, the observations reported provide further evidence for the view that the essential cells of the canine mammary mixed tumour are derived from myoepithelial cells.

Immunohistologic Studies of Human Lacrimal Gland: Localization of Immunoglobulins, Secretory Component and Lactoferrin

Abstract Studies of normal human lacrimal glands were performed by utilizing fluorescent antibody and ultrastructural techniques in order to examine immunoglobulin production and localization within the gland, and to investigate mechanisms of transport of these immunoglobulins from the gland. Throughout the interstitium of each gland, clusters of cells having the morphologic characteristics of plasma cells were evident. Fluorescent antibody staining showed these cells to contain predominantly IgA, with IgG or IgM occasionally present, and IgE only rarely demonstrable. Extracellular IgA staining was seen along basement membranes of acini, between acinar epithelial cells, and occasionally within acinar lumina. IgA was also occasionally seen intracellularly throughout acinar epithelial cells. IgG was diffusely evident throughout the interstitium but appeared particularly concentrated along the acinar basement membranes. Secretory component and lactoferrin were localized to the acinar epithelial cells, and secretory component could also be found in acinar intercellular spaces. The larger numbers of IgA-containing plasma cells relative to other immunoglobulin-specific plasma cells are consistent with the known proportions of immunoglobulins in tears, and suggest their local production within the lacrimal gland. A secretory mechanism involving intracellular transport of immunoglobulins by acinar epithelial cells is proposed.

The fine structure of the monkey submandibular gland with a special reference to intra-acinar nerve endings.

AbstractThe secretory terminations of monkey submandibular gland were studied by electron microscopy. The acini are composed of two types of secretory cells which are presumably serous and mucous in type. Myoepithelial cells are present also in the acini. The peri‐acinar connective tissue contains many unmyelinated nerve fibers. In some portions, the axons contain many synaptic vesicles of various types. These nerve endings partially lose their Schwann cell investment and reach the acinar basement membrane. In peri‐acinar connective tissue two types of nerve endings may be recognized. They are thought to be adrenergic and cholinergic in type. On the other hand, only one type of nerve ending (cholinergic) is observed within the acini. The intra‐acinar nerve endings are not surrounded by Schwann cell cytoplasm and make direct contact with plasma membranes of the myoepithelial and mucous cells, with a space about 200 Å wide intervening between the nerve and terminal cell. No nerve endings occur in the interspaces between the serous cells. Also, the ultrastructure of the secretory and myoepithelial cells is described.