Expression of beta-1 integrin in human developing salivary glands and its parallel relation with maturation markers: In situ hybridisation and immunofluorescence study

CD29 is highly expressed on epithelial, myoepithelial, and mesenchymal stromal cells of human salivary glands

OBJECTIVE

The phenotype of the cells present in the ductal region of salivary glands has been well characterized. However, it is imperative to identify novel biomarkers that can identify different cell types present in other glandular components for the development of therapeutic strategies and diagnostics of salivary gland disorders and malignancies. Our study aimed at the characterization of the expression and distribution of various cell surface markers, especially with a focus on CD29 in human fetal as well as adult glands.

MATERIALS AND METHODS

Paired human midgestation fetal and adult parotid, sublingual, and submandibular glands were collected. Phenotypic expression of various lineage-specific cell surface markers including CD29 was investigated in freshly collected glands. The findings were further corroborated by immunohistochemistry.

RESULTS

Enriched expression of CD29 was found on acinar and ductal epithelial, mesenchymal stromal, and myoepithelial cells; CD29⁺ cells co-expressed epithelial (CD324, CD326, NKCC1, and CD44), mesenchymal (CD73, CD90, vimentin, and CD34), and myoepithelial (α-SMA) cell-specific progenitor markers in both fetal as well as adult salivary glands.

CONCLUSION

CD29 is widely expressed in human salivary glands, and it could serve as a potential biomarker for devising novel cellular therapeutic and diagnostic strategies for salivary gland disorders and malignancies.

Glycomic profile of the human parotid gland between 18th and 26th week of fetal development

The formation of new and functional structural components of several organs, such as parotid glands, can be influenced by the glycocode. This study analyzed the glycobiology of parotid salivary gland tissue during fetal development using specific biochemical probes (lectins and antibodies). Eleven parotid gland samples from human fetuses were obtained from spontaneous abortions at 14-28 weeks of gestation, and tissue sections were analyzed for lectin histochemistry and immunohistochemistry. From the 18th to 26th week, Canavalia ensiformis agglutinin, wheat germ agglutinin, Ulex europaeus agglutinin-I, peanut agglutinin, Sambucus nigra agglutinin, and Vicia villosa agglutinin lectin staining were predominantly observed in the apical and/or basement membranes of the ducts and tubulo-acinar units. Moreover, the presence of galectin-1 was found in the membrane, cytoplasm, and nucleus of both structures. Conversely, Gal-3 and mucin-1 were restricted to the glandular ducts. The lectin staining pattern changed during the weeks evaluated. Nevertheless, the carbohydrate subcellular localization represented a key factor in the investigation of structural distribution profiles and possible roles of these glycans in initial parotid gland development. These findings are defined by their high biological value and provide an important base for the development of subsequent studies. (J Oral Sci 58, 353-360, 2016).

TGFβ signaling promotes matrix assembly during mechanosensitive embryonic salivary gland restoration

Mechanical properties of the microenvironment regulate cell morphology and differentiation within complex organs. However, methods to restore morphogenesis and differentiation in organs in which compliance is suboptimal are poorly understood. We used mechanosensitive mouse salivary gland organ explants grown at different compliance levels together with deoxycholate extraction and immunocytochemistry of the intact, assembled matrices to examine the compliance-dependent assembly and distribution of the extracellular matrix and basement membrane in explants grown at permissive or non-permissive compliance. Extracellular matrix and basement membrane assembly were disrupted in the glands grown at low compliance compared to those grown at high compliance, correlating with defective morphogenesis and decreased myoepithelial cell differentiation. Extracellular matrix and basement membrane assembly as well as myoepithelial differentiation were restored by addition of TGFβ1 and by mechanical rescue, and mechanical rescue was prevented by inhibition of TGFβ signaling during the rescue. We detected a basal accumulation of active integrin β1 in the differentiating myoepithelial cells that formed a continuous peripheral localization around the proacini and in clefts within active sites of morphogenesis in explants that were grown at high compliance. The pattern and levels of integrin β1 activation together with myoepithelial differentiation were interrupted in explants grown at low compliance but were restored upon mechanical rescue or with application of exogenous TGFβ1. These data suggest that therapeutic application of TGFβ1 to tissues disrupted by mechanical signaling should be examined as a method to promote organ remodeling and regeneration.

Heterogeneity of glandular cells in the human salivary glands: an immunohistochemical study using elderly adult and fetal specimens

Using immunohistochemical staining for alpha-smooth muscle actin (α-SMA), glial fibrillary acidic protein (GFAP), S100 protein (S100), p63, cytokeratin 14 (CK14), and cytokeratin 19 (CK19), we studied acinar and myoepithelial cells of major and minor salivary glands obtained from 14 donated cadavers (78-92 years old) and 5 donated fetuses (aborted at 15-16 weeks of gestation). CK and p63 expression was investigated only in the adult specimens. SMA was detected in all adult glands as well as in fetal sublingual and pharyngeal glands. GFAP expression was seen in a limited number of cells in adult glands, but was highly expressed in fetal pharyngeal glands. S100-positive myoepithelial-like cells were present in adult minor glands as well as in fetal sublingual and pharyngeal glands. Expression of p63 was evident in the ducts of adult glands. CK14 immunoreactivity was observed in a limited number of glandular cells in adults, in contrast to consistent expression of CK19. In both adults and fetuses, a mosaic expression pattern was usually evident for each of the examined proteins. A difference in immunoreactivity for the nerve markers GFAP and S100 was observed between the major and minor glands. Thus, in the present histologic study, we distinguished between the specific gland types on the basis of their immunohistochemical staining. A mosaic expression pattern suggested that the immunoreactivity against nerve protein markers in myoepithelial cells could not be due to the persistence of neural crest remnants or the physiological status of the gland, such as age-related degeneration.

Spatial relationship between expression of cytokeratin-19 and that of connexin-43 in human fetal kidney

Connexin-43, a major gap junction protein, and cytokeratin-19, one of the intermediate filament keratins, are known to be markers of well-differentiated epithelium. In this study, we investigated the expression of these markers in the head region, lungs, and abdominal organs of 10 human mid-term fetuses. The expression of connexin-43 was found to be restricted to the dura mater, kidney, and adrenal cortex. In the kidney, we found a clear site-dependent difference in the expression pattern of these markers: connexin-43 expression was observed in the tubules of the renal cortex whereas cytokeratin-19 was strongly expressed in the collecting ducts and renal pelvis. This difference remained unchanged throughout the fetal stages examined. Immunoreactivity was not observed for either of the markers in the intrarenal vessels, including the glomeruli, and mesangial cells. Connexin-43 expression seemed to be restricted to the metanephric vesicle-derived structures that differentiate in the urogenital ridge of the splanchnic mesoderm. The adrenal cortex also originates from the same para-aortic mesoderm. In contrast, in the urogenital organs, cytokeratin-19 seemed to be expressed in ducts derived from the urogenital sinus.

Comparison between human fetal and adult skin

Healing of early-gestation fetal wounds results in scarless healing. Since the capacity for regeneration is probably inherent to the fetal skin itself, knowledge of the fetal skin composition may contribute to the understanding of fetal wound healing. The aim of this study was to analyze the expression profiles of different epidermal and dermal components in the human fetal and adult skin. In the human fetal skin (ranging from 13 to 22 weeks' gestation) and adult skin biopsies, the expression patterns of several epidermal proteins (K10, K14, K16, K17, SKALP, involucrin), basement membrane proteins, Ki-67, blood vessels and extracellular matrix proteins (fibronectin, chondroitin sulfate, elastin) were determined using immunohistochemistry. The expression profiles of K17, involucrin, dermal Ki-67, fibronectin and chondroitin sulfate were higher in the fetal skin than in adult skin. In the fetal skin, elastin was not present in the dermis, but it was found in the adult skin. The expression patterns of basement membrane proteins, blood vessels, K10, K14, K16 and epidermal Ki-67 were similar in human fetal skin and adult skin. In this systematic overview, most of the differences between fetal and adult skin were found at the level of dermal extracellular matrix molecules expression. This study suggests that, especially, dermal components are important in fetal scarless healing.

Human salivary gland branching morphogenesis: morphological localization of claudins and its parallel relation with developmental stages revealed by expression of cytoskeleton and secretion markers

Development of salivary glands is a highly complex and dynamic process termed branching morphogenesis, where branched structures differentiate into mature glands. Tight junctions (TJ) are thought to play critical roles in physiological functions of tubular organs, contributing to cell polarity and preventing lateral movement of membrane proteins. Evidence demonstrated that claudins are directly involved in TJ formation and function. Using immunohistochemistry and immunofluorescence we have mapped the distribution of claudins-1, 2, 3, 4, 5, 7 and 11 and compared it with the expression of differentiation markers in human salivary glands obtained from foetuses ranging from weeks 4 to 24 of gestation. Expression of all claudins, except claudin-2 was detected in the various phases of human salivary gland development, up to fully mature salivary gland. The expression of all claudins increased according to the progression of salivary gland maturation evidenced by the classical markers-cytokeratin 14, cytokeratin low molecular weight, smooth muscle actin and human secretory component. Tight junction proteins-claudins appear to be important in the final shape and physiological functions of human salivary glands and are parallel related with markers of salivary gland differentiation.