Bone marrow-derived mesenchymal stem cells migrate to healthy and damaged salivary glands following stem cell infusion

Abstract

Xerostomia is a severe side effect of radiation therapy in head and neck cancer patients. To date, no satisfactory treatment option has been established. Because mesenchymal stem cells (MSCs) have been identified as a potential treatment modality, we aimed to evaluate stem cell distribution following intravenous and intraglandular injections using a surgical model of salivary gland damage and to analyse the effects of MSC injections on the recruitment of immune cells. The submandibular gland ducts of rats were surgically ligated. Syngeneic adult MSCs were isolated, immortalised by simian virus 40 (SV40) large T antigen and characterized by flow cytometry. MSCs were injected intravenously and intraglandularly. After 1, 3 and 7 days, the organs of interest were analysed for stem cell recruitment. Inflammation was analysed by immunohistochemical staining. We were able to demonstrate that, after intravenous injection, MSCs were recruited to normal and damaged submandibular glands on days 1, 3 and 7. Unexpectedly, stem cells were recruited to ligated and non-ligated glands in a comparable manner. After intraglandular injection of MSCs into ligated glands, the presence of MSCs, leucocytes and macrophages was enhanced, compared to intravenous injection of stem cells. Our data suggest that injected MSCs were retained within the inflamed glands, could become activated and subsequently recruited leucocytes to the sites of tissue damage.

Figure 1

Salivary duct ligation induced an inflammatory response and necrosis. HE staining of a non-ligated submandibular gland (a) with the typical physiological appearance of a normal submandibular gland and (b) a ligated salivary gland showing histological changes following surgical duct ligation for 7 days. Cell nuclei are decentralized, inflammatory cell infiltrate is visible and thickening of the basal lamina can be observed. Magnification ×40. HE, haematoxylin–eosin.

Figure 2

Stem cells were found in lymphatic organs after intravenous injections. Original magnification ×40. Anti-SV40 immunohistochemistry. (a) Lymph node 3 days; (b) spleen 3 days; (c) Peyer's patch of the small intestine 3 days; (d) thymus 3 days. SV40, simian virus 40.

Figure 3

Stem cells migrated to normal salivary glands after intravenous injections. Distribution of stem cells in salivary glands (a) 1, (b) 3 and (c) 7 days after intravenous injections. In these animals, no further manipulation (surgery) took place. Magnification ×10.

Figure 4

Stem cells migrated to normal and damaged salivary glands after intravenous injections. Distribution of stem cells in ligated (a, c, e) and non-ligated (b, d, f) glands 1 (a and b), 3 (c and d) and 7 (e and f) days after intravenous injections. Magnification ×10.

Figure 5

Stem cells were present in normal and ligated salivary glands after intraglandular injections. Distribution of stem cells in ligated (a, c, e) and non-ligated (b, d, f) glands 1 (a and b), 3 (c and d) and 7 (e and f) days after intraglandular injections. Magnification ×10.

Figure 6

Leucocytes and macrophages preferentially migrated to ligated salivary glands. Enhanced accumulation of leukocytes (a and b) and macrophages (c and d) in ligated (a and c) and non-ligated (b and d) salivary glands 3 days after intraglandular stem cell injections. Magnification ×10.