DEVELOPMENT OF CULTURE METHODS FOR EXOCRINE GLAND STEM CELLS USING GENE-TRANSDUCED FEEDER CELLS AND THEIR APPLICATION FOR TREATMENT

干细胞为基础的治疗被认为是一种很有前途的策略，用于再生因无法治愈的疾病而失去的组织。虽然纯化干细胞的技术很大程度上依赖于特定的表面标记物，但侧群体（SP）细胞在没有干细胞标记物的情况下也适用。然而，SP细胞的功能仍存在争议。为了探索SP细胞的确切功能，我们评估了它们在小鼠外分泌腺（即唾液腺）中的功能，因为这些腺体作为方便的模型，其能力可以通过分别测量泪液和唾液分泌物来轻松评估。在这里，我们表明SP细胞移植恢复了两个因辐射而功能低下的腺体的功能，并阐明了一种假定的保护细胞免受氧化应激损伤的底物。我们从泪腺和唾液腺中分离SP细胞，并将其移植到辐射诱导的各腺体功能减退的小鼠体内。结果显示，移植后2个月内，受体小鼠的两个腺体的分泌物都得到了恢复，但移植的细胞只是稀疏分布且没有生长，这表明SP细胞分泌的可溶性因子，而不是重组细胞，可能恢复了残留腺体的功能。Clusterin是一种分泌性糖蛋白，被认为是SP细胞特异性基因之一，具有抑制氧化应激诱导的细胞死亡和活性氧（ROS）积累的作用。我们的研究结果表明，SP细胞移植的益处不是归因于细胞移植介导的腺体重建，而是归因于SP细胞衍生的可溶性因子（包括簇蛋白）的功能。

Stem cell-based therapy has been proposed as a promising strategy for regenerating tissues lost through incurable diseases. Although the technology to purify stem cells largely depends on specific surface markers, side population (SP) cells are applicable without stem cell markers. However, the functions of SP cells still remain controversial. To explore the precise functions of SP cells, we assessed their functions in mouse exocrine glands, namely, salivary glands, because these glands serve as convenient models whose ability can be easily evaluated by measurement of their tear and saliva secretions, respectively. Here we show that SP cell transplantation restores the functions of both the glands rendered hypofunctional by irradiation, and clarify a putative substrate that protects the cells from damage by oxidative stress. We isolated SP cells from the lachrymal and salivary glands and transplanted them into mice with irradiation-induced hypofunction in each gland. The results revealed that the secretions from both glands in the recipient mice were restored within two months after the transplantation, although transplanted cells were only sparsely distributed and produced no outgrowths, indicating that soluble factors secreted by SP cells, and not reconstituted cells, possibly restored the functions of the residual glands. Clusterin, which has been identified as one of the SP cell-specific genes, is a secretory glycoprotein, and been shown to inhibit cell death and reactive oxygen species (ROS) accumulation induced by oxidative stress. Our results indicate that the benefits of SP cell transplantation are attributable to not cell transplantation-mediated reconstitution of the glands but the functions of SP cell-derived soluble factors including clusterin.