Ex vivo generation of red blood cells (RBCs) from hematopoietic stem cells (HSCs) used for blood transfusion represents one of the focuses in current regenerative medicine. However, massive production of HSCs-based RBCs requires a significant quantity of erythropoietic growth factors, making manufacturing at large scale cost prohibitive. Plant cell culture is proposed to be a promising bioproduction platform for functional human proteins in a safe and cost-efficient manner. This study exploited a proprietary technology, named HypGP engineering technology, for high-yield production of one of the key erythropoietic growth factors--stem cell factor (SCF)--in plant cell culture. Specifically, a designer hydroxyproline (Hyp)-O-glycosylated peptide (HypGP) comprised of 20 tandem repeats of the "Ser-Pro" motif, or (SP)20, was engineered at either the N-terminus or C-terminus of SCF in tobacco BY-2 cells. The (SP)20 tag dramatically increased the secreted yields of SCF up to 2.5 μg/ml. The (SP)20-tagged SCF showed bioactivity in promoting the proliferation of the TF-1 cell line, although the SCF-(SP)20 was 8.4-fold more potent than the (SP)20-SCF. Both the (SP)20-SCF and SCF-(SP)20 exhibited desired function in stimulating the expansion and differentiation of human umbilical cord blood CD34+ cells towards RBCs.

中文翻译：

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植物细胞分泌的干细胞因子刺激造血干细胞的扩增和分化

从用于输血的造血干细胞 (HSC) 体外生成红细胞 (RBC) 是当前再生医学的重点之一。然而，大量生产基于 HSC 的 RBC 需要大量的红细胞生成生长因子，这使得大规模制造成本高昂。植物细胞培养被认为是一种以安全且经济高效的方式生产功能性人类蛋白质的有前途的生物生产平台。本研究利用名为 HypGP 工程技术的专有技术，在植物细胞培养中高产地生产一种关键的红细胞生成生长因子——干细胞因子 (SCF)。具体而言，设计者羟脯氨酸 (Hyp)-O-糖基化肽 (HypGP) 由“Ser-Pro”基序或 (SP)20 的 20 个串联重复组成，在烟草 BY-2 细胞中 SCF 的 N 端或 C 端进行工程改造。(SP)20 标签显着增加了 SCF 的分泌产量，最高可达 2.5 μg/ml。(SP)20 标记的 SCF 在促进 TF-1 细胞系增殖方面显示出生物活性，尽管 SCF-(SP)20 比 (SP)20-SCF 强 8.4 倍。(SP)20-SCF 和 SCF-(SP)20 在刺激人脐带血 CD34+ 细胞向红细胞增殖和分化方面均表现出所需的功能。