Neurokinin A in the parotid and submandibular glands of the rat: immunohistochemical localization and effect on protein and peroxidase secretion

An indirect immunofluorescence technique was used to study the distribution of neurokinin A immunoreactive (NKA-IR) nerve fibres in submandibular and parotid glands of the rat. The functional role of neurokinin A on protein and peroxidase secretion in these glands was evaluated by using in vitro methods. In the parotid gland neurokinin A immunoreactive fibres were mainly distributed around the secretory acini, but some were also in evidence around the stromal blood vessels and ducts. The number of the neurokinin A immunoreactive nerve fibres was lower in the submandibular gland than in the parotid gland. They were mainly distributed around the secretory acini and stromal blood vessels and ducts. In vitro, neurokinin A significantly stimulated the release of total amount of released proteins and peroxidase from parotid gland fragments, while in the submandibular gland only the release of peroxidase was increased. By using SDS polyacrylamide gel electrophoresis (SDS-PAGE) specific changes were found in the release of proteins after neurokinin A stimulation. The results of the present study demonstrate that neurokinin A immunoreactive nerve fibres are present in the rat parotid and submandibular glands. Their localization around the secretory elements of the glands and the effect of neurokinin A in vitro experiments indicates that neurokinin A might have a significant role in the regulation of salivary secretion.     

Epidermal growth factor and insulin-like growth factor I are localized in different compartments of salivary gland duct cells. lmmunohistochemical evidence

Immunohistochemical methods were used to map EGF (epidermal growth factor) and IGF-I (insulin-like growth factor I; somatomedin C) immunoreactivities in salivary glands of adult rodents. Epidermal growth factor is, as is NGF (nerve growth factor), limited in distribution to the granules in granular duct cells in the submandibular gland. Insulin-like growth factor I is, in contrast, cytoplasmic and has a much more widespread distribution. It is seen in intercalated, striated and granulated duct cells as well as in apical parts of excretory duct cells. The parotid and the palatine salivary glands, lacking EGF immunoreactivity, have their IGF-I immunoreactivity similarly distributed as the submandibular gland. Isoproterenol treatment of adult male rats results in rapid and extensive growth of the submandibular and the parotid glands, which double their weights in just a few days. Isoproterenol causes release of granules from the submandibular granular duct cells and decrease in frequency of EGF immunoreactive cells. However, there is no or only minor concomitant changes in the distribution and intensity of the IGF-I immunoreactivity in these duct cells. Our results indicate that the trophic peptides EGF (and NGF) and IGF-I are localized in different compartments in salivary gland duct cells and that divergent pathways control their release.     

Epidermal growth factor and insulin-like growth factor I are localized in different compartments of salivary gland duct cells. Immunohistochemical evidence

Immunohistochemical methods were used to map EGF (epidermal growth factor) and IGF-I (insulin-like growth factor I; somatomedin C) immunoreactivities in salivary glands of adult rodents. Epidermal growth factor is, as is NGF (nerve growth factor), limited in distribution to the granules in granular duct cells in the submandibular gland. Insulin-like growth factor I is, in contrast, cytoplasmic and has a much more widespread distribution. It is seen in intercalated, striated and granulated duct cells as well as in apical parts of excretory duct cells. The parotid and the palatine salivary glands, lacking EGF immunoreactivity, have their IGF-I immunoreactivity similarly distributed as the submandibular gland. Isoproterenol treatment of adult male rats results in rapid and extensive growth of the submandibular and the parotid glands, which double their weights in just a few days. Isoproterenol causes release of granules from the submandibular granular duct cells and decrease in frequency of EGF immunoreactive cells. However, there is no or only minor concomitant changes in the distribution and intensity of the IGF-I immunoreactivity in these duct cells. Our results indicate that the trophic peptides EGF (and NGF) and IGF-I are localized in different compartments in salivary gland duct cells and that divergent pathways control their release.     

鼻咽癌IMRT前后唾液腺功能变化及与受照剂量的关系

目的:探讨鼻咽癌患者调强放射治疗（IMRT）前后唾液腺的功能变化及与受照剂量的关系。方法:选取广西医科大学第一附属医院接受IMRT初治鼻咽癌患者30例为研究对象,在放疗前、放疗后3个月采用99mTcO4-SPECT唾液腺动态显像测定腮腺、颌下腺的时间-放射性曲线（TAC）、最大浓聚率（MAR）和酸刺激最大分泌率（MSR）,研究唾液腺的功能变化及与受照剂量的关系。结果:放疗后3个月出现1~2级口干症状,腮腺、颌下腺TAC曲线主要表现为轻中度受损,口干程度、TAC曲线与唾液腺受照剂量正相关。放疗后3个月较放疗前腮腺MAR、MSR和颌下腺MSR明显减低（P<0.05）,而颌下腺的MAR无减低（P>0.05）,但两组唾液腺的MAR、MSR对比差异无统计学意义（P>0.05）,两组唾液腺照射剂量均合理。结论:鼻咽癌患者IMRT后出现唾液腺摄取和排泄功能轻中度受损,引起1~2级口干,IMRT能够将唾液腺的受照射剂量控制在合理范围内。     

Long‐term dexamethasone treatment alters the histomorphology of acinar cells in rat parotid and submandibular glands

Glucocorticoids (GCs) induce insulin resistance (IR), a condition known to alter oral homeostasis. This study investigated the effects of long‐term dexamethasone administration on morphofunctional aspects of salivary glands. Male Wistar rats received daily injections of dexamethasone [0.1 mg/kg body weight (b.w.), intraperitoneally] for 10 days (DEX), whereas control rats received saline. Subsequently, glycaemia, insulinaemia, insulin secretion and salivary flow were analysed. The parotid and submandibular glands were collected for histomorphometric evaluation and Western blot experiments. The DEX rats were found to be normoglycaemic, hyperinsulinaemic, insulin resistant and glucose intolerant (P < 0.05). DEX rat islets secreted more insulin in response to glucose (P < 0.05). DEX rats had significant reductions in the masses of the parotid (29%) and submandibular (16%) glands (P < 0.05) that was associated with reduced salivary flux rate. The hypotrophy in both glands observed in the DEX group was associated with marked reduction in the volume of the acinar cells in these glands of 50% and 26% respectively (P < 0.05). The total number of acinar cells was increased in the submandibular glands of the DEX rats (P < 0.05) but not in the parotid glands. The levels of proteins related to insulin and survival signalling in both glands did not differ between the groups. In conclusion, the long‐term administration of dexamethasone caused IR, which was associated with significant reductions in both mass and flux rate of the salivary glands. The parotid and submandibular glands exhibited reduced acinar cell volume; however, the submandibular glands displayed acinar hyperplasia, indicating a gland‐specific response to GCs. Our data emphasize that GC‐based therapies and insulin‐resistant states have a negative impact on salivary gland homeostasis.     

Fractionated irradiation and early changes in salivary glands. Different effects on potassium efflux, exocytotic amylase release and gland morphology.

Irradiation is a potent treatment modality of head and neck cancer. However, the irradiation is usually associated with an influence on salivary glands with ensuing dryness and discomfort for the patients. In the present study we used different in vitro secretory models and morphologic characterization of rat parotid gland. Radiation was given to one gland on a 5-day schedule with 6 MV photons (total dose 20, 30, 35, 40, 45 Gy). The contralateral gland served as control, and the analysis of glands were performed 10 days after the last irradiation treatment. The noradrenaline stimulated electrolyte secretion (86rubidium tracer for potassium) was decreased in relation to the irradiation dose and in comparison to contralateral control glands. Noradrenaline stimulated exocytotic amylase release was not affected by irradiation and, there were no signs of obvious quantitative morphologic alterations after irradiation compared with controls. The results suggest that there are differences in the sensitivity to radiation for the two different secretory processes in salivary glands, and, thus, the structures regulating electrolyte and fluid secretion seem to be more vulnerable to irradiation than the process of exocytosis. The results, however, do not allow discrimination between temporary cellular impairment and irreversible damage leading to cell death.     

Characterization of the myoepithelial cells in the major salivary glands of the fruit bat Artibeus jamaicensis

Bats constitute one of the most numerous mammalian species. Bats have a wide range of dietary habits and include carnivorous, haematophagous, insectivorous, frugivorous and nectivorous species. The salivary glands of these species have been of particular research interest due to their structural variability among chiropterans with different types of diets. Myoepithelial cells (MECs), which support and facilitate the expulsion of saliva from the secretory portions of salivary glands, are very important for their function; however, this cell type has not been extensively studied in the salivary glands of bats. In this study, we characterized the MECs in the major salivary glands of the fruit bat Artibeus jamaicensis. Herein, we describe the morphology of the parotid, submandibular and sublingual glands of A. jamaicensis at the light‐ and electro‐microscopic level and the distribution of MECs in these glands, as defined by their expression of smooth‐muscle markers such as α‐smooth muscle actin (SMAα) and desmin, and of epithelial cell markers, such as KRT14. We found that the anatomical locations of the major salivary glands in this bat species are similar to those of humans, except that the bat sublingual gland appears to be unique, extending to join the contralateral homologous gland. Morphologically, the parotid gland has the characteristics of a mixed‐secretory gland, whereas the submandibular and sublingual glands were identified as mucous‐secretory glands. MECs positive for SMAα, KRT14 and desmin were found in all of the structural components of the three glands, except in their excretory ducts. Desmin is expressed at a lower level in the parotid gland than in the other glands. Our results suggest that the major salivary glands of A. jamaicensis, although anatomically and structurally similar to those of humans, play different physiological roles that can be attributed to the dietary habits of this species.     

Biophysical and morphological properties of parasympathetic neurons controlling the parotid and von Ebner salivary glands in rats

The inferior salivatory nucleus (ISN) contains parasympathetic neurons controlling the parotid and von Ebner salivary glands. To characterize the neurophysiological and morphological properties of these neurons, intracellular recordings were made from anatomically identified ISN neurons in rat brain slices. Neurons were also filled with Lucifer yellow and morphometrically analyzed. Based on responses to membrane hyperpolarization followed by depolarization, three types of repetitive discharge patterns were defined for neurons innervating the parotid gland. The regular, repetitive discharge response to membrane depolarization was changed by hyperpolarization resulting either in a delay in the occurrence of the first spike or to an increase in the length of the first interspike interval in the action potential train. Membrane hyperpolarization had little effect on the discharge pattern of some neurons. Similar response discharge patterns were found for neurons innervating the von Ebner salivary gland, which also included a further group of neurons that responded with a short burst of action potentials. Neurons innervating the parotid salivary glands differed morphologically from the von Ebner salivary glands having significantly larger soma and more and longer dendrites than von Ebner gland neurons. In addition, the mean membrane input resistance, time constant, and spike half-width of parotid gland neurons was significantly lower than in von Ebner gland neurons. These differences in intrinsic membrane properties and morphology may relate to the functions of the von Ebner and parotid glands. von Ebner glands are involved in taste stimulus delivery and removal from posterior tongue papillae while the parotid glands contribute saliva to the entire mouth.     

The distribution and secretion of kallikrein in some exocrine organs of the rat

ørstavik , T. B. The distribution and secretion of kallikrein in some exocrine organs of the rat. Acta physiol. scand. 1978. 104. 431–442. Extractable kallikrein was quantitated in the submandibular, sublingual, and parotid glands and in the pancreas. No kallikrein was detected in the exorbital lacrimal glands and tears. The highest kallikrein concentrations (EU/ml) were in all major salivary gland secretions seen after α-adrenergic stimulation, less after β-adrenergic and least after parasympathetic stimulation. When taking into account the large variations in salivary flow rate, α-adrenergic stimulation was in the parotid and particularly in the submandibular gland found to result in the highest kallikrein secretory activity measured by the kallikrein secretory rate (EU/ min). This shows that the kallikrein-rich granular tubular cells are selectively activated through α-adrenergic sympathetic receptors. The differences observed in the parotid saliva were small and not always statistically significant. However, when cervical nerve stimulation was superimposed upon parasympathetic stimulation, kallikrein secretory rate as well as kallikrein concentration increased. The large individual variations in salivary gland kallikrein content and secretion and the rather small differences observed in kallikrein secretory rate after nervous stimulation of the parotid and sublingual glands, may indicate that the kalli-krein-containing striated ducts are also influenced by factors other than the secretory nerves. The kallikrein concentration and secretory rate in urine was studied. A strong positive correlation between kallikrein secretory rate and fluid volume was found in urine but not in saliva.     

Proliferative activity by cell type in the developing rat parotid gland

Background: In contrast to the considerable amount of research that has been done on the proliferative activity of the several types of parenchymal cells in the developing submandibular glands of rodents, systematic studies of cellular proliferation in the developing parotid gland have been confined to the acinar cells. The purpose of the present study was to attempt to fill this knowledge gap. Methods: Tritiated thymidine was parenterally administered to Sprague-Dawley rats at ages representative of the pre- and postnatal development of the parotid gland, and glands were harvested for autoradiography 90 min after injection. Mitotic activity among all cell types was verified by electron microscopy. Results: At all ages, the % labeled cells was much greater among the acini than any other cell type, including well-differentiated cells at 25 and 40 days. However, there were only small alterations in the proportions of cells comprised by the major cell types. Conclusions: Current theories on the histogenesis of salivary glands and their neoplasms are based on the renewing population model, in which both normal differentiated cells and neoplastic cells arise from undifferentiated stem cells in the ducts. However, these results suggest that most of the migration and redifferentiation in the developing rat parotid gland must be in the opposite direction, i.e., the acinar cells redifferentiate into ductal cells. They also indicate that until there are precise data on the rates of cell death among the several cell types, it remains more appropriate for salivary glands to be categorized as an expanding, rather than renewing, population. © 1995 Wiley-Liss, Inc.     

Secretory protein expression patterns during rat parotid gland development

The rat parotid gland produces a number of well-characterized secretory proteins. Relatively little is known, however, about the onset of their synthesis and cellular localization during gland development. Secretory protein expression was studied in parotid glands of fetal and postnatal rats using light and electron microscopic immunocytochemistry and Northern blotting. Amylase, parotid secretory protein (PSP), common salivary protein-1 (CSP-1), and SMGB were first detected by immunofluorescence in parotid glands of 18 day fetuses. By 5 days after birth, light and electron microscopic immunolabeling localized all of these proteins to the secretory granules of developing acinar cells. Labeling of acinar cells for DNAse I, however, was not observed until 18 days after birth. Between 9 and 25 days, CSP-1 and SMGB reactivity of acinar cells declined, but increased in intercalated duct cells. After 25 days, CSP-1 and SMGB were found only in intercalated ducts, and amylase, PSP, and DNAse I were restricted to acinar cells. Levels of CSP-1 and SMGB mRNA were relatively constant through 21 postnatal days, but declined significantly after that. Amylase and PSP mRNA increased rapidly and continuously from five days after birth to the adult stage. In contrast, DNAse I mRNA was not detectable until 18 days after birth. The immunocytochemical and molecular analyses define three basic patterns of protein expression in the rat parotid gland: proteins whose synthesis is initiated early in development and is maintained in the acinar cells, such as amylase and PSP; proteins that are initially synthesized by immature acinar cells but are restricted to intercalated ducts in the adult gland, such as CSP-1 and SMGB; and proteins that are synthesized only by mature acinar cells and first appear during the third postnatal week, such as DNAse I. The parotid gland exhibits four distinct developmental stages: prenatal, from initiation of the gland rudiment until birth; neonatal, from 1 day up to about 9 days postnatal; transitional, from 9 days to 25 days of age; and adult, from 25 days on. Although differences exist in timing and in the specific proteins expressed, these developmental stages are similar to those seen in the rat submandibular gland. Additionally, the results support the suggestion that intercalated ducts may differentiate from the neonatal acini. Anat. Rec. 252:485–497, 1998. © 1998 Wiley-Liss, Inc.     

Lack of effects of viral sialoadenitis and depletion of epidermal growth factor on initiation of hepatic carcinogenesis in the rat.

Sialodacryoadenitis (SDA) is a commonly-encountered coronaviral infection in laboratory rats that causes acute destruction of submandibular salivary glands. SDA results in depletion of salivary epidermal growth factor (EGF) and may thereby affect EGF-dependent cell growth processes. The purpose of this study was to determine the effects of SDA virus (SDAV) infection on the growth factor-dependent stages of experimental liver carcinogenesis. Rats were injected ip with the carcinogen diethylnitrosamine (DENA) at 1, 2, or 3 weeks following inoculation with SDAV. Uninfected control rats were treated only with DENA. The salivary glands of SDAV-inoculated and control rats were stained using the immunoperoxidase method for the detection of EGF. Residual submandibular salivary gland lesions and focal depletion of EGF were still evident in affected submandibular glands for up to 42 days after SDAV infection. Serum EGF concentrations measured at 9, 28, and 42 days following SDAV inoculation were reduced, but were not significantly different in comparison with non-inoculated, DENA-treated control rats. Initiated hepatocytes were detected 21 days after DENA treatment in formalin-fixed sections by an immunoperoxidase stain for the P isoenzyme of the enzyme glutathione S-transferase (GST-P). There was no significant difference in the number of foci of GST-P positive cells in a comparison of initiated cells in SDAV-inoculated and non-inoculated rats. Based on this model, concurrent infection with SDAV does not appear to have any significant effects on the initial stages of chemical hepatocarcinogenesis in the rat.     

An optimized growth factor cocktail for ovine mesenchymal stem cells

Growth factors that regulate proliferation, migration, and invasion of ovine mesenchymal stem cells (oMSCs) are not well defined. In this study, we have evaluated five growth factors for their ability to initiate and support in vitro proliferation, migration, and invasion of oMSCs. oMSCs were exposed to different doses and combinations of the growth factors: basic fibroblast growth factor (bFGF), transforming growth factor-β (TGF-β), epidermal growth factor (EGF), insulin growth factor-I (IGF-I), connective tissue growth factor, and platelet-derived growth factor-AB (PDGF-AB). Cellular proliferation, motility, and invasiveness were assayed. The most proliferative stimulating growth factors are PDGF-AB+TGF-β and PDGF-AB+IGF-I. Combinations EGF+bFGF and EGF+bFGF+PDGF-AB demonstrated the greatest ability to stimulate migration. Moreover, the triple cocktail EGF+bFGF+TGF-β has the most significant effect on invasion. Different growth factor cocktails are required to enhance proliferation, migration, and invasion. These results may be useful for the development of a tissue-engineered heart valve by stimulating cellular repopulation.     

Acute and late radiation injury in rhesus monkey parotid glands. Evidence of interphase cell death.

Acute and chronic salivary gland dysfunction are common sequelae of radiotherapy for head and neck cancer; but the associated morphologic changes, especially of the acute damage, have received relatively little study. For investigation of the morphologic characteristics of acute radiation injury to parotid glands, rhesus monkeys were studied 1-72 hours after parotid irradiation with single doses of 2.5-15.0 Gy. The acute damage from all doses was clearly expressed by 24 hours. Histologically, parotid glands irradiated with 2.5 or 5.0 Gy had random degeneration and necrosis of the serous acinar cells. Doses of 7.5-15.0 Gy produced widespread degeneration along with necrosis of whole acini. Serous cell damage was accompanied by neutrophilic inflammation that subsided after 24 hours to become replaced by plasma cell and lymphocytic infiltrates. Parotid glands receiving 7.5-15.0 Gy were atrophic at 16-22 weeks after irradiation and showed no recovery by 40 weeks. Although parotid acinar cells are well-differentiated nondividing cells, these observations show that they express lethal radiation injury in interphase within hours of receiving a radiation dose as low as 2.5 Gy. This is unlike most mammalian cells that express radiation injury during mitosis. Chronic atrophy is a consequence of this direct, irreversible, and early injury, rather than the result of radiation-induced changes in the vasculature.     

Gene expression profiles of the three major salivary glands in rats

The protein components of saliva reflect the condition of the whole body as well as the salivary glands. The aim of this study is to characterize the gene expression profiles in each of the rat major salivary glands-the parotid, submandibular, and sublingual glands. Gene expression was analyzed using DNA microarrays, and observed differences in expression of representative genes were confirmed by quantitative, real-time polymerase chain reaction. Among the glands, the contribution to the high expression of genes encoding various proteins, specifically mucin 10, proline-rich glycoproteins, proline-rich protein 2, proline-rich proteoglycans, cystatin 10, amylase, deoxyribonuclease I, and von Ebner's gland protein, was significantly greater in the parotid gland than the other glands. The submandibular and sublingual glands had similar gene expression profiles that differed from profile of the parotid gland. For example, the genes encoding mucin 19 and ovomacroglobulin were highly expressed only in the submandibular and sublingual glands. In summary, we characterized gene expression in the rat major salivary glands and provided basic information on salivary gland marker proteins.     

The role of cyclic 3',5'-adenosine monophosphate (cyclic AMP) in the ability of sympathetic nerve stimulation to enhance growth and secretion in rat salivary glands in vivo.

1. The cyclic AMP content of the rat salivary glands was measured after sympathetic and parasympathetic nerve stimulation, and after the administration of isoprenaline and phenylephrine. 2. Stimulation of the sympathetic nerves (20 Hz, 1 msec supramaximal voltage for 30 sec of every min) initially raised the cyclic AMP level in both the parotid and submaxillary glands. The rise, which was blocked by propranolol, was not maintained and declined during stimulation from the maximum (reached after 3 min stimulation) to control levels after approximately 15 min. Stimulation of the parasympathetic nerves for 5 min did not raise the cyclic AMP levels. 3. Isoprenaline and phenylephrine raised the cyclic AMP level in both glands. 4. Theophylline enhanced the growth of the parotid and submaxillary glands as measured either by an increase in the wet and dry weights or in acinar axes lengths. N6O2-dibutyryl cyclic monophosphoric acid (dibutyryl cyclic AMP), did not enhance the growth of the glands. 5. It is concluded that cyclic AMP does not directly control cell growth in the rat salivary glands but may be a 'trigger' for events leading eventually to increased growth.     

Rat salivary gland ligation causes reversible secretory hypofunction

Aim: To determine the influence of inflammation on salivary secretion. Secretion by salivary glands involves interactions between nerves, blood vessels and salivary cells. The present study investigated the effects of inflammation on rat submandibular gland function following acute ductal obstruction. Methods: Under recovery anaesthesia a metal clip was placed on the main duct of the submandibular gland. After 24 h salivary secretion was evoked by nerve and methacholine stimulation. For recovery experiments the clip was removed after 24 h and the animal left to recover for 3 days when salivary function was again assessed. Results: By 24 h of obstruction an inflammatory infiltrate had developed within the obstructed gland and stimulated salivary flows were just 20% of the normal secretion, whilst protein secretion and ion reabsorption were also severely impaired. If ductal obstruction was removed after 24 h the salivary function returned to normal after 3 days of recovery. In vitro analysis of cells from 24‐h ligated glands revealed normal changes in intracellular calcium (the main secondary messenger involved in fluid secretion) in response to methacholine stimulation. Protein secretion from isolated cells indicated some changes in particular to methacholine‐induced protein secretion although a significant protein secretion was still seen in response to isoprenaline – the main stimulus for protein secretion. Conclusion: This report demonstrates reversible salivary inhibition associated with an inflammatory infiltrate within the salivary gland.     

Chronology of peroxidase activity in the developing rat parotid gland

The course of development of salivary peroxidase, an enzyme that has an important role in oral defense mechanisms, has been well documented in rat submandibular glands. However, the only report on salivary peroxidase activity in the other major salivary glands of the rat has been a cytochemical study of the adult parotid gland. In the present investigation, the accumulation of salivary peroxidase activity in developing parotid glands of rats was followed both biochemically and cytochemically. Specific activity (units per mg protein) attributable to salivary peroxidase began at 1 day after birth, then rose rapidly but unevenly, with peaks at 21 and 70 days, and no difference between the sexes at any age. Activity per gland increased progressively to 42 days in both sexes and was significantly higher in males at 70 days. The cytochemical observations on peroxidase activity localized to the rough endoplasmic reticulum and secretory granules of the developing acini were well correlated with the biochemical findings. Peroxidase-negative cells occurred in immature acini at 1 and 7 days, but only in the intercalated ducts thereafter. This observation suggests that the acini are a source of some of the ductal cells, at least during early postnatal development. The developmental pattern of specific activity differed from those of other rat parotid secretory enzymes, indicating that control of their synthesis during development is noncoordinate. The patterns of specific activity of the parotid and submandibular glands were complementary, suggesting that their combined secretions may supply biologically significant peroxidase activity to the oral cavities of rats throughout postnatal development. © 1993 Wiley-Liss, Inc.     

Keratinocyte growth factor prevents radiation damage to salivary glands by expansion of the stem/progenitor pool

Irradiation of salivary glands during radiotherapy treatment of patients with head and neck cancer evokes persistent hyposalivation. This results from depletion of stem cells, which renders the gland incapable of replenishing saliva to produce acinar cells. The aim of this study was to investigate whether it is possible to expand the salivary gland stem/progenitor cell population, thereby preventing acinar cell depletion and subsequent gland dysfunction after irradiation. To induce cell proliferation, keratinocyte growth factor (DeltaN23-KGF, palifermin) was administered to C57BL/6 mice for 4 days before and/or after local irradiation of salivary glands. Salivary gland vitality was quantified by in vivo saliva flow rates, morphological measurements, and a newly developed in vitro salisphere progenitor/stem cell assay. Irradiation of salivary glands led to a pronounced reduction in the stem cells of the tissues, resulting in severe hyposalivation and a reduced number of acinar cells. DeltaN23-KGF treatment for 4 days before irradiation indeed induced salivary gland stem/progenitor cell proliferation, increasing the stem and progenitor cell pool. This did not change the relative radiation sensitivity of the stem/progenitor cells, but, as a consequence, an absolute higher number of stem/progenitor cells and acinar cells survived after radiation. Postirradiation treatment with DeltaN23-KGF also improved gland function, and this effect was much more pronounced in DeltaN23-KGF pretreated animals. Post-treatment with DeltaN23-KGF seemed to act through accelerated expansion of the pool of progenitor/stem cells that survived the irradiation treatment. Overall, our data indicate that DeltaN23-KGF is a promising drug to enhance the number of salivary gland progenitor/stem cells and consequently prevent radiation-induced hyposalivation. Disclosure of potential conflicts of interest is found at the end of this article.