Transient occurrence of 27 kDa heat‐shock protein in the terminal tubule cells during postnatal development of the rat submandibular gland

Abstract

It has been suggested that the 27 kDa heat-shock protein (Hsp27) plays a role at crucial cellular checkpoints for proliferation, apoptosis, and differentiation. We examined the immunolocalization of Hsp27 in the rat submandibular gland during postnatal development, wherein acinar cells proliferate and differentiate at earlier postnatal periods. At 2 weeks of age, weak Hsp27 immunoreactivity was distributed diffusely over all gland components. At 3 weeks, Hsp27 immunoreactivity disappeared in most parts of the acini and ducts, but was intensely accumulated in a small cell population located in the acinar center. This population was composed mostly of terminal tubule (TT) type I cells. At 4 weeks, the Hsp27-immunopositive cell population in the acinar center was composed primarily of immature (type II) acinar cells, partly of immature (granulated) intercalated duct (ID) cells, and occasionally of apoptotic cells. After 5 weeks, all acinar components became mature and were no longer immunoreactive for Hsp27. When acinar cell differentiation was accelerated by administration of isoproterenol to 3-week-old rats for 7 days, the number of Hsp27-positive cells was significantly lower than in the control gland at 4 weeks, confirming that Hsp27 expression is downregulated in mature acinar cells. These results suggest that at around 3-4 weeks in postnatal development, the centroacinar TT cells stop proliferating and begin to differentiate into acinar and ID cells, and occasionally undergo apoptosis. Hsp27 is transiently expressed in the centroacinar TT cells during this critical period, and thus may play a role in their differentiation into the immediate descendants. Anat Rec 264: 358 -366, 2001. Key words: small heat-shock protein; submandibular gland; terminal tubule cell; differentiation; immunohistochemistry; electron microscopy; rat (Wistar)The heat-shock proteins (HSPs) are highly conserved proteins in organisms ranging from prokaryotes to mammals which are induced by various physicochemical stresses and act in cellular protection (Lindquist and Craig, 1988). Moreover, HSPs are produced in significant amounts in a variety of nonstressed cells, implying a physiological role for these proteins in normal cell functions. HSPs have been classified into several families based on their molecular weights. The 27 kDa heat-shock protein (Hsp27) of rats and humans, and its mouse homolog Hsp25, belong to the family of small (20 -30 kDa) HSPs

Expression of Heat Shock Protein 27 with the Transition from Proliferation to Differentiation of Acinar Precursor Cell in Regenerating Submandibular Gland of Rats

“…Until P3-4w, a boundary period between the proliferation and differentiation stages of acinar cells of rat submandibular gland acinar cells, a small number of embryonic type secretory cells termed as terminal tubule (TT) cells remain in developing acini (Chang 1974). We have previously reported that Hsp27-immunoreactivity is temporarily detected in TT cells and its immunoreactivity quickly disappears with the progress of TT cell differentiation (Amano et al 2001). These results suggest that Hsp27 plays as a molecular switch that regulates the transition from the cell proliferation to differentiation.…”

An Immunohistochemical Study of the Localization of Inducible Nitric Oxide Synthase (iNOS) and Heat Shock Protein (HSP) in Pleomorphic Adenoma

“…Although the localization of iNOS and the HSPss and their roles in normal salivary gland are well documented [1,5,10,21,31], little information is available on their role in neoplasm of salivary gland [4,5]. The present study showed iNOS and the HSPs are widely localized at neoplastic epithelium in pleomorphic adenoma.…”

“…Both mesenchymal and neoplastic epithelial cells exist in the stromal tissues of pleomorphic adenoma [9]. The expression of iNOS and HSPs in normal salivary glands are observed in epithelial cells such as ductal and myoepithelial cells, but not in stromal cells [1,5,31]. The positive cells in stromal tissues may be neoplastic epithelial cells.…”

“…The expression of anti-apoptotic proteins such as Bcl-2 and Bcl-xL is closely involved with normal tissue and tumor development [7]. HSP27 is associated with tumorgenicity and normal tissues development [1,12,13,20,26,32]. HSP27 may contribute to the development and growth of pleomorphic adenoma.…”

“…E-mail: yoshi-ab@hoku-iryo-u.ac.jp gland have been well documented [1,5,10,21,31], little information is available on them in the pleomorphic adenoma. The present study investigates the localization of iNOS and HSPs in pleomorphic adenoma.…”