Transdifferentiation of bone marrow-derived mesenchymal stem cells into salivary gland-like cells using a novel culture method

Dental Pulp Stem Cells for Salivary Gland Regeneration-Where Are We Today?

Xerostomia is the phenomenon of dry mouth and is mostly caused by hypofunction of the salivary glands. This hypofunction can be caused by tumors, head and neck irradiation, hormonal changes, inflammation or autoimmune disease such as Sjögren's syndrome. It is associated with a tremendous decrease in health-related quality of life due to impairment of articulation, ingestion and oral immune defenses. Current treatment concepts mainly consist of saliva substitutes and parasympathomimetic drugs, but the outcome of these therapies is deficient. Regenerative medicine is a promising approach for the treatment of compromised tissue. For this purpose, stem cells can be utilized due to their ability to differentiate into various cell types. Dental pulp stem cells are adult stem cells that can be easily harvested from extracted teeth. They can form tissues of all three germ layers and are therefore becoming more and more popular for tissue engineering. Another potential benefit of these cells is their immunomodulatory effect. They suppress proinflammatory pathways of lymphocytes and could therefore probably be used for the treatment of chronic inflammation and autoimmune disease. These attributes make dental pulp stem cells an interesting tool for the regeneration of salivary glands and the treatment of xerostomia. Nevertheless, clinical studies are still missing. This review will highlight the current strategies for using dental pulp stem cells in the regeneration of salivary gland tissue.

Increased expression of ALDH-1 is associated with clinical parameters of salivary glands neoplasms

The enzyme aldehyde dehydrogenase-1 (ALDH-1) is a known putative tumour stem cells (TSC) marker, and these cells are implicated in carcinogenesis and progression of human neoplasms. We aimed to evaluate ALDH-1 expression in benign and malignant salivary gland neoplasms and its clinicopathological and prognostic significance. Expression of ALDH-1 was investigated by immunohistochemistry and confirmed by Western Blot analysis in 154 salivary gland neoplasms (103 malignant and 51 benign neoplasms). The expression was identified in the parenchyma of malignant (n = 88; 85.6%) and benign (100%) neoplasms. Overall, expression in the parenchyma varied considerably and was not associated with clinical parameters in most malignant neoplasms, however, a high expression in mucoepidermoid carcinomas (MEC) was associated with advanced pathological TNM stage (p = 0.047). The presence of ALDH-1 in stromal cells of malignant neoplasms (n = 67; 65.0%) was associated with lymph node metastasis (p = 0.032), tumour recurrence (p = 0.006) and death (p = 0.013). Overall and disease-free survival in 5 and 10 years was lower in patients with diagnosis of adenoid cystic carcinoma, tumour recurrence, advanced staging, and presence of ALDH-1 in the stroma. When adjusted by multivariate analysis, advanced staging and stromal expression were independent prognostic factors affecting disease-free survival. Our findings provide evidence that cells characterized as TSC in the parenchyma and stroma are differentially present among the different types of neoplasms studied and may be related to tumourigenesis, biological behaviour and persistence capacity of malignant tumours of the salivary gland.

First-in-man intraglandular implantation of stromal vascular fraction and adipose-derived stem cells plus platelet-rich plasma in irradiation-induced gland damage: a case study

BACKGROUND

Stromal vascular fraction (SVF) is a mixture of cells which can be isolated from a mini-lipoaspirate of fat tissue. Platelet-rich plasma (PRP) is a mixture of growth factors and other nutrients which can be obtained from peripheral blood. Adipose-derived stem/stromal cells (ADSCs) can be isolated from fat tissue and expanded in culture. The SVF includes a variety of different cells such as ADSCs, pericytes, endothelial/progenitor cells, and a mix of different growth factors. The adipocytes (fat cells) can be removed via centrifugation. Here, we describe the rationale and, to our knowledge, the first clinical implementation of SVF and PRP followed by repeat dosing of culture-expanded ADSCs into a patient with severe xerostomia postirradiation.

METHODS

Approximately 120 mLs of adipose tissue was removed via mini-lipoaspirate procedure under local anesthetic. The SVF was prepared from half of the fat and resuspended in PRP. The mixture was delivered via ultrasound directly into the submandibular and parotid glands on both the right and left sides. The remaining 60 mLs of fat was processed to culture-expand ADSCs. The patient received seven follow-up injections of the ADSCs plus PRP at 5, 8, 16, 18, 23, 28, and 31 months postliposuction. The subject was monitored over a period of 31 months for safety (adverse events), glandular size via ultrasound and saliva production.

RESULTS

Throughout the 31-month monitoring period, no safety events such as infection or severe adverse events were reported. The patient demonstrated an increase in gland size as measured by ultrasound which corresponded to increased saliva production.

CONCLUSION

Overall, the patient reported improved quality of life and willingness to continue treatments. The strong safety profile and preliminary efficacy results warrant larger studies to determine if this is a feasible treatment plan for patients postradiation.

Characteristics of Labial Gland Mesenchymal Stem Cells of Healthy Individuals and Patients with Sjögren's Syndrome: A Preliminary Study

Sjögren's syndrome (SS) is a systemic autoimmune disease that is characterized by focal lymphocytic infiltration into exocrine organs such as salivary and lacrimal glands, resulting in dry mouth and eyes, and other systemic injuries. There is no curative clinical therapy for SS, and stem cell therapy has shown great potential in this area. The mesenchymal stem cells (MSCs) in the salivary glands of healthy individuals and in patients with SS have not been extensively studied. The aim of this study was to elucidate the characteristics of MSCs from the labial glands of healthy controls and of those from patients with SS to elucidate the related pathogenesis and to uncover potential avenues for novel clinical interventions. Labial glands from patients with SS and healthy subjects were obtained, and MSCs were isolated and cultured by using the tissue adherent method. The MSC characteristics of the cultured cells were confirmed by using morphology, proliferation, colony forming-unit (CFU) efficiency, and multipotentiality, including osteogenic, adipogenic, and salivary gland differentiation. The MSCs from the healthy controls and SS patients expressed characteristic MSC markers, including CD29, CD44, CD73, CD90, and CD105; they were negative for CD34, CD45, and CD106, and also negative for the salivary gland epithelium markers (CD49f and CD117). Labial gland MSCs from both groups were capable of osteogenic and adipogenic differentiation. The CFU efficiency and adipogenic differentiation potential of MSCs were significantly lower in the SS group compared with the healthy controls. Cells from both groups could also be induced into salivary gland-like cells. Real-time polymerase chain reaction and immunofluorescence staining showed that the gene and protein expression of AMY1, AQP5, and ZO-1 in cells from the SS group was lower than that in cells from the healthy group. Thus, MSCs from the labial glands in patients with SS could lack certain characteristics and functions, especially related to salivary secretion. These preliminary data provided insights that could lead to the development of novel therapeutic strategies for the treatment of SS.

Primary Salivary Human Stem/Progenitor Cells Undergo Microenvironment-Driven Acinar-Like Differentiation in Hyaluronate Hydrogel Culture

Radiotherapy for head and neck cancer often has undesirable effects on salivary glands that lead to xerostomia or severe dry mouth, which can increase oral infections. Our goal is to engineer functional, three‐dimensional (3D) salivary gland neotissue for autologous implantation to provide permanent relief. An immediate need exists to obtain autologous adult progenitor cells as the use of embryonic and induced pluripotent stem cells potentially pose serious risks such as teratogenicity and immunogenic rejection. Here, we report an expandable population of primary salivary human stem/progenitor cells (hS/PCs) that can be reproducibly and scalably isolated and propagated from tissue biopsies. These cells have increased expression of progenitor markers (K5, K14, MYC, ETV4, ETV5) compared with differentiation markers of the parotid gland (acinar: MIST1/BHLHA15 and AMY1A; ductal: K19 and TFCP2L1). Isolated hS/PCs grown in suspension formed primary and secondary spheres and could be maintained in long‐term 3D hydrogel culture. When grown in a customized 3D modular hyaluronate‐based hydrogel system modified with bioactive basement membrane‐derived peptides, levels of progenitor markers, indices of proliferation, and viability of hS/PCs were enhanced. When appropriate microenvironmental cues were provided in a controlled manner in 3D, such as stimulation with β‐adrenergic and cholinergic agonists, hS/PCs differentiated into an acinar‐like lineage, needed for saliva production. We conclude that the stem/progenitor potential of adult hS/PCs isolated without antigenic sorting or clonal expansion in suspension, combined with their ability to differentiate into specialized salivary cell lineages in a human‐compatible culture system, makes them ideal for use in 3D bioengineered salivary gland applications. Stem Cells Translational Medicine2017;6:110–120