Fetal Liver Cells CD34+ Cells

GH Supplementation Hastens Human Lymphohematopoietic Cell Recovery in the Blood

Humanized mice generated through human hematopoietic stem cell (HSC) transplantation play a critical role in biomedical research. One of the factors hindering the efficacy of their construction is the lack or insufficiency of interactions between human cells and murine cytokines and growth hormones (GH). GH is a pluripotent cytokine that can regulate the proliferation, apoptosis, and differentiation of various cells. In this study, Zhang's team investigated the effects of recombinant human growth hormone (rhGH) on humanized mice transplanted with CD34+ cells.

Humanized mice were generated by transplanting human CD34 fetal liver cells from immunodeficient mice pretreated with total body irradiation. Subsequently, peripheral blood, spleen and bone marrow were harvested, and levels of human lymphohematopoietic cells were determined by flow cytometry. The low amino acid identity between mouse GH (mGH) and human GH (hGH) suggests that mGH may not provide survival or proliferation signals to the human GH receptor (hGHR) on the human cells engrafted in mice. Therefore, they investigated whether supplementation with a hGHR agonist could optimize the establishment of a human lymphohematopoietic system. They treated NCG mice with transplanted human CD34 fetal liver cells with hGH. Human lymphohematopoietic chimerism in the hGH-treated mice was significantly higher (Fig. 1). Human B cells and myeloid cells are the major human lymphohematopoietic cell populations in NCG mice having undergone human CD34 cell transplantation at adult stages. Therefore, they also analyzed the recovery of human CD19 B cells and CD33 myeloid cells in the blood of these mice. Similarly, the recovery of both human B cells and myeloid cells was significantly enhanced by hGH treatment (Fig. 1).

Fig. 1. Growth hormone supplement hastens human lymphohematopoietic cell reconstitution in the blood of NCG mice (Zhang, S., Wang, G., et al., 2022).

SRSF2 P95H Mutation Reduces Colony Formation and Skews Towards Monocytic Lineage in Human CD34+ Fetal Liver Cells

SRSF2 is a splicing factor that normally plays a critical role in the precursor RNA splicing process. However, mutations in SRSF2 disrupt this process, leading to aberrant alternative splicing events. These abnormal splicing events can activate a global gene expression program, which drives the abnormal proliferation and transformation of hematopoietic cells into malignant cells. Using high-throughput sequencing of RNA isolated by UV crosslinking and immunoprecipitation (HITS-CLIP), Liang's team found SRSF2 P95H mutations impact RNA binding and splicing, especially in RNA processing and splicing genes, suggesting a "splicing-cascade" effect. This cascade may lead to widespread gene alterations and impaired hematopoietic differentiation, ultimately driving cancer.

To characterize the in vivo effects of SRSF2 P95H mutation in the hematopoietic context, Liang's team generated stable, isogenic Human Erythroid Leukemia (HEL) cell lines with lentivirally conferred inducible expression of Flag-tagged wild-type (WT) and mutant (P95H) SRSF2 (Fig. 2a). And then, Liang's team tested their lentiviral construct in primary human CD34+ fetal liver cells, and performed Colony Forming Unit (CFU) assays to monitor the impact of SRSF2 mutations on hematopoiesis. The total number of colonies was significantly reduced upon SRSF2P95H expression compared to WT SRSF2, with a relative increase of monocytic lineage colonies (CFU-M) in colony composition (Fig. 2c), consistent with the monocytic lineage skewing observed in previous studies and the preferential occurrence of SRSF2 mutations in chronic myelomonocytic leukemia (CMML).

Fig. 2. The SRSF2 P95H mutation alters SRSF2 in vivo RNA interactome (Liang, Y., Tebaldi, T., et al., 2018).