Epidermal growth factor (EGF) is a polypeptide that stimulates cell division and differentiation, protecting gastric mucosa, as well as promoting substance transport and glucose metabolism (Kamentseva et al., 2023, Farooqi et al., 2022) and is widely used in clinical practice. EGF was first discovered in salivary glands by Stanley Cohen, who isolated and purified mouse EGF (mEGF) from mouse salivary glands and shared the 1986 Nobel Prize in physiology or medicine due to a series of research on EGF and nerve growth factor (NGF) (Cohen, 1960, Cohen, 1962). Later, urogastrone, which is structurally similar to EGF, was isolated from the urine of pregnant women (Gregory, 1975). It has been reported that various human body fluids such as saliva, gastric juice, urine, and milk contain EGF (Hirata and Orth, 1979, Gregory et al., 1979), and EGF is mainly produced in submandibular glands, Brunner's glands of the duodenum and Paneth cells of the small intestine (Elder et al., 1978, Heitz et al., 1978). It has been demonstrated that EGF is synthesized by salivary gland acinar cells, a portion of which is secreted into the oral cavity, and the rest enters the blood circulation (Koski, Konttinen, Hietanen, Tervo & Malmström, 1997). These studies also demonstrate that the submandibular gland is the main source of EGF in saliva. However, the results of saliva detection and immunofluorescent localization by Thesleff et al. (1988) indicated that the expression of EGF in the parotid gland is higher than in the submandibular gland. Similar results were reported by Ji et al. (1997) that the EGF concentration in the saliva secreted by parotid glands was 2.4 ng/ml, significantly higher than that in the saliva of submandibular glands (0.6 ng/ml). At present, the main source of EGF in saliva remains controversial, and EGF expression and tissue distribution in salivary glands are still unclear.

The purpose of the present study was 1) to determine the concentrations of EGF in the saliva and blood samples of a large group of healthy subjects; 2) to compare the expression of EGF in the normal submandibular gland, parotid gland, sublingual gland, and lower labial gland tissues collected from patients with mandibular ameloblastoma; and 3) to explore the influence of sex and age on EGF secretion.