A Novel Therapy for Radiation-Induced Xerostomia Using Human Salivary Stem Cells

项目描述（由申请人提供）：该项目旨在从人唾液腺中分离干细胞，并确定最佳的药物和生长因子组合，以增加干细胞的富集，并促进其在照射小鼠下颌下腺（SMG）中的植入和分化。我们的最终目标是利用人类唾液干细胞来恢复放射头颈癌（HNC）患者的唾液功能。大多数HNC患者需要放射治疗（RT）来控制疾病。在70%的患者中，放疗导致慢性口干（口干），这可能对他们的生活质量产生不利影响，并导致严重的后续并发症，如下颌骨放射性坏死和/或吞咽困难。目前与rt相关的口干的药物治疗是昂贵和无效的。强度调节放疗（IMRT），旨在节省一个腮腺，已导致一些改善刺激唾液功能，如进食。然而，由于SMG腺体位于引流淋巴结附近，因此IMRT不能放过SMG腺体，SMG腺体对全天的静息唾液功能至关重要。出于这个原因，人们对挽救SMG功能非常感兴趣。目前使用诱导多能干细胞或组织工程的努力看起来很有希望，但仍处于非常早期的阶段。最近发表的数据表明，干细胞可以从成年小鼠SMG腺中分离出来，并可以在移植到受辐照受体小鼠体内时形成功能亚基。初步数据还表明，干细胞可以改善这些小鼠的唾液分泌。因此，需要测试分离人SMG干细胞的可行性及其重建腺体功能亚单位的能力。然而，这些成体SMG干细胞非常罕见，仅占整个SMG细胞群的0.3%。需要努力提高它们的分离性、培养存活率和体内植入。醛脱氢酶同工酶（ALDH）是众所周知的干细胞标志物，其活性水平与祖细胞向靶组织分化的能力有关。最近，我们发现与非干细胞相比，某些ALDH酶在成人SMG干细胞中表达水平较高。我们已经使用高通量筛选确定了几种不同ALDH同工酶的小分子激活剂。我们假设选择性ALDH同工酶的激活，结合生长因子，将增强唾液干细胞的分离和存活，并促进其在体内的植入。我们建议：(1)鉴定在人和小鼠SMG干细胞中优先表达和活跃的ALDH同工酶，(2)确定最佳的ALDH激活剂，以增强干细胞的分离、存活和增殖，(3)评估这些细胞在裸鼠SMG中形成功能亚基和拯救功能的功效，(4)确定功能拯救所需的最小数量的干细胞。(5)确定ALDH激活剂的最佳给药途径和时间表，以促进干细胞的植入。这些研究将支持SMG干细胞用于放射HNC患者唾液功能恢复的未来应用。

DESCRIPTION (provided by applicant): The project aims to isolate stem cells from human salivary glands and to determine the optimal drug and growth factor combination to increase stem cell enrichment and facilitate their engraftment and differentiation in irradiated mouse submandibular (SMG) glands. Our ultimate goal is to employ human salivary stem cells to rescue salivary function in irradiated head and neck cancer (HNC) patients. Most patients with HNC require radiation therapy (RT) to manage their disease. In >70% of these patients, RT results in chronic xerostomia (dry mouth), which can adversely impact their quality of life and lead to severe subsequent complications, such as mandibular osteoradionecrosis and/or dysphagia. Current pharmacologic management of RT-related xerostomia is costly and ineffective. Intensity modulated radiotherapy (IMRT), which aims to spare one parotid gland, has resulted in some improvement of stimulatory salivary function, such as with eating. However, IMRT cannot spare the SMG glands, which are crucial for resting salivary function throughout the day, because of their locations adjacent to the draining lymph nodes. For this reason, there is strong interest in rescuing SMG function. Present efforts using induced pluripotent stem (IPS) cells or tissue engineering appear promising but are still at a very early stage. Recently published data indicate that stem cells can be isolated from adult mouse SMG glands and can form functional subunits when transplanted into irradiated recipient mice. Preliminary data also suggest that stem cells could improve saliva production in these mice. Therefore, it is desirable to test the feasibility of isolating human SMG stem cells and their ability to reconstitute functional subunits of the gland. However, these adult SMG stem cells are rare, making up only 0.3% of the entire SMG cell population. Efforts are needed to improve their isolation, survival in culture and engraftment in vivo. Aldehyde dehydrogenase isozymes (ALDH) are well-known stem cell markers whose activity levels correlate with the ability of progenitor cells to differentiate into target tissues. Recently, we found certain ALDH enzymes are expressed at high level in adult SMG stem cells compared to non-stem cells. We have identified several small molecular activators of different ALDH isozymes using a high-throughput screen. We hypothesize that activation of selective ALDH isozymes, in combination with growth factors, will enhance isolation and survival of salivary stem cells and facilitate their engraftment in vivo. We propose to (1) identify ALDH isozymes that are preferentially expressed and active in human and mouse SMG stem cells, (2) determine the optimal ALDH activator(s) to enhance stem cell isolation, survival and proliferation, (3) evaluate the efficacy of these cells to form functional subunits & rescue function in SMG of nude mice, (4) identify the minimal number of stem cells required for functional rescue, and (5) determine the optimal route and schedule of administration of ALDH activators to facilitate stem cell engraftment. These studies will support future use of SMG stem cells for salivary function restoration in irradiated HNC patients.