As classical transplantation repopulation assays for studying the radiobiology of rat mammary stem/progenitor cells are extremely time-consuming, this study aimed to characterize the radiobiological properties of mammospheres, spherical clumps of mammary cells formed under non-adherent culture conditions, which are a simple and widely used technique for assessing progenitor cell activity. Rat mammary cells were dissociated and used in transplantation repopulation assays and for the formation of mammospheres. Immunofluorescence for cytokeratin 14 and 18 was used to identify basal and luminal mammary epithelial cells, respectively. Incorporation of 5-bromo-2′-deoxyuridine was used to evaluate cell proliferation. The repopulating activity of the transplanted primary rat mammary cells demonstrated their radiosensitivity, reproducing previous data, with a significant reduction in repopulating activity at ≥ 2 Gy. Cells constituting rat mammospheres were positive for either cytokeratin 14 or 18, with occasional double-positive cells. Both proliferation and aggregation contributed to sphere formation. Cells obtained from the spheres showed lower repopulating activity after transplantation than primary cells. When primary cells were irradiated and then used for sphere formation, the efficiency of sphere formation was significantly decreased at 8 Gy but not at ≤ 6 Gy, indicating radioresistance of the formation process. Irradiation at 8 Gy reduced the proliferation of cells during sphere formation, whereas the cellular composition of the resulting spheres was unaffectes. Thus, mammosphere formation assays may measure a property of putative mammary progenitors that is different from what is measured in the classic transplantation repopulation assay in radiobiology.

由于用于研究大鼠乳腺干细胞/祖细胞放射生物学的经典移植再填充测定非常耗时，因此本研究旨在表征乳球的放射生物学特性，这是在非贴壁培养条件下形成的乳细胞的球形团块，这很简单。广泛用于评估祖细胞活性的技术。将大鼠乳腺细胞解离，并用于移植再种群测定和乳球形成。细胞角蛋白14和18的免疫荧光分别用于鉴定基底和腔乳腺上皮细胞。5-溴-2'-脱氧尿苷的掺入用于评估细胞增殖。移植的原代大鼠乳腺细胞的再增殖活性证明了它们的放射敏感性，再现了以前的数据，≥2 Gy时，种群繁殖活动显着降低。构成大鼠小球的细胞对细胞角蛋白14或18呈阳性，偶有双阳性细胞。增殖和聚集都有助于球的形成。移植后，从球体获得的细胞显示出比原代细胞更低的繁殖活性。当照射原代细胞然后用于形成球体时，在8 Gy时球体形成效率显着降低，而在≤6 Gy时不降低，这表明形成过程的耐辐射性。8 Gy辐照减少了球形成过程中细胞的增殖，而所得球的细胞组成未受影响。从而，