Down J D, Ploemacher R E
Department of Radiobiology, University of Groningen, The Netherlands.
Exp Hematol. 1993 Jul;21(7):913-21.
Transplant of sorted donor (B6-Gpi-1a) hematopoietic stem cell subsets and host (B6-Gpi-1b) treatment with total body irradiation (TBI) or cytotoxic drugs were compared for induction of short- and long-term engraftment in a murine chimera model of congenic bone marrow transplantation (BMT). Parallel studies on donor and host marrow were performed in vitro in long-term bone marrow cultures to determine early and late cobblestone area forming cell (CAFC) frequencies in the grafts or in the transplant recipients 1 day after conditioning. Bone marrow cells (BMC) sorted for high wheat germ agglutinin affinity (WGA ) were enriched about 30-fold for early developing CAFC (colony-forming unit-spleen [CFU-S]) but not for primitive late CAFC (pre-CFU-S). This fraction showed only temporary engraftment when transplanted in irradiated recipients. In contrast, the low affinity (WGA+) fraction were preferentially enriched (200- to 300-fold) for late developing CAFC and were very effective for providing stable long-term engraftment following transplantation. Substituting radiation for chemotherapy in the host conditioning treatment also had diverse effects on the development of bone marrow engraftment. Pretreatment with 5-fluorouracil (5-FU, 200 mg/kg) allowed a discrete wave of donor engraftment that peaked at 2 to 4 weeks and then subsided to leave mostly host cells at 10 weeks and beyond. Busulfan preparation gave over 50% engraftment at 1 month after BMT but this continued to increase to reach stable donor chimerism of 80 to 90% beyond 10 weeks. The level of long-term engraftment given by 50 mg/kg busulfan appeared similar to that induced by doses of 6 to 8 Gy TBI. The changing patterns of erythroid chimerism for each preparative agent showed a remarkable correlation with depletion of defined hematopoietic stem cell subsets as quantified using the CAFC assay at 1 day after recipient treatment. These findings collectively show that the level of depletion of host CFU-S (CAFC-10) determines the extent of early and transient repopulation, whereas the degree of pre-CFU-S (CAFC-35) depletion determines the percentage of stable chimerism. Preliminary data on bone marrow CAFC content at 9 months after busulfan and BMT revealed a long-term reduction of the stem cell pool by about 50% but with relatively minor effects on supporting bone marrow stromas. The differential cytotoxic effects on stem cell subsets in relation to subsequent donor marrow engraftment offer a systematic and mechanistic approach toward identifying more effective chemotherapeutic compounds for use in clinical BMT conditioning regimens.
在同基因骨髓移植（BMT）的小鼠嵌合体模型中，比较了分选的供体（B6-Gpi-1a）造血干细胞亚群移植以及用全身照射（TBI）或细胞毒性药物处理宿主（B6-Gpi-1b）以诱导短期和长期植入的情况。在长期骨髓培养中对供体和宿主骨髓进行了平行研究，以确定预处理后1天移植物或移植受体中早期和晚期鹅卵石区域形成细胞（CAFC）的频率。分选具有高麦胚凝集素亲和力（WGA）的骨髓细胞（BMC），早期发育的CAFC（集落形成单位-脾[CFU-S]）富集了约30倍，但原始晚期CAFC（前CFU-S）没有富集。当移植到受照射受体中时，该部分仅显示出暂时植入。相比之下，低亲和力（WGA+）部分优先富集（200至300倍）晚期发育的CAFC，并且在移植后提供稳定的长期植入非常有效。在宿主预处理中用化疗代替放疗对骨髓植入的发展也有不同影响。用5-氟尿嘧啶（5-FU，200mg/kg）预处理可使供体植入出现离散波，在2至4周达到峰值，然后在10周及以后消退，留下的大多是宿主细胞。白消安预处理在BMT后1个月时植入率超过50%，但在10周后继续增加，达到80%至90%的稳定供体嵌合状态。50mg/kg白消安产生的长期植入水平似乎与6至8Gy TBI诱导的水平相似。每种预处理剂的红系嵌合变化模式与受体治疗后1天使用CAFC测定法量化的特定造血干细胞亚群的消耗有显著相关性。这些发现共同表明，宿主CFU-S（CAFC-10）的消耗水平决定了早期和短暂再填充的程度，而前CFU-S（CAFC-35）的消耗程度决定了稳定嵌合的百分比。白消安和BMT后9个月骨髓CAFC含量的初步数据显示，干细胞池长期减少约50%，但对支持骨髓基质的影响相对较小。与随后的供体骨髓植入相关的对干细胞亚群的不同细胞毒性作用为识别用于临床BMT预处理方案的更有效化疗化合物提供了一种系统的和机制性的方法。
