SAHA Enhances Differentiation of CD34+CD45+ Hematopoietic Stem and Progenitor Cells from Pluripotent Stem Cells Concomitant with an Increase in Hemogenic Endothelium.

Epigenetic modification is an important process during hematopoietic cell differentiation. Histone deacetylase (HDAC) inhibitors have previously been shown to enhance expansion of umbilical cord blood-derived hematopoietic stem cells (HSCs). However, the effect of HDAC inhibitors on pluripotent stem cells (PSCs) in this context is less understood. For years, investigators have considered PSC-derived natural killer (NK) and T-cell therapies. These "off-the-shelf" cellular therapies are now entering the clinic. However, the in vitro commitment of PSCs to the hematopoietic lineage is inefficient and represents a major bottleneck. We investigated whether HDAC inhibitors (HDACi) influence human PSC differentiation into CD34+CD45+ hematopoietic stem and progenitor cells (HSPCs), focusing on hemogenic endothelium (HE). Pluripotent stem cells cultured in the presence of HDACi showed a 2-5 times increase in HSPCs. Concurrent with this, HDACi-treated PSCs increased expression of 7 transcription factors (HOXA5, HOXA9, HOXA10, RUNX1, ERG, SPI1, and LCOR) recently shown to convert HE to HSPCs. ChIP-qPCR showed that SAHA upregulated acetylated-H3 at the promoter region of the above key genes. SAHA-treated human PSC-derived CD34+CD45+ cells showed primary engraftment in immunodeficient mice, but not serial transplantation. We further demonstrate that SAHA-derived HSPCs could differentiate into functional NK cells in vitro. The addition of SAHA is an easy and effective approach to overcoming the bottleneck in the transition from PSC to HSPCs for "off-the-shelf" cellular immunotherapy.

Human innate lymphoid cell precursors express CD48 that modulates ILC differentiation through 2B4 signaling.

Innate lymphoid cells (ILCs) develop from common lymphoid progenitors (CLPs), which further differentiate into the common ILC progenitor (CILP) that can give rise to both ILCs and natural killer (NK) cells. Murine ILC intermediates have recently been characterized, but the human counterparts and their developmental trajectories have not yet been identified, largely due to the lack of homologous surface receptors in both organisms. Here, we show that human CILPs (CD34+CD117+α4ß7+Lin-) acquire CD48 and CD52, which define NK progenitors (NKPs) and ILC precursors (ILCPs). Two distinct NK cell subsets were generated in vitro from CD34+CD117+α4ß7+Lin-CD48-CD52+ and CD34+CD117+α4ß7+Lin-CD48+CD52+ NKPs, respectively. Independent of NKPs, ILCPs exist in the CD34+CD117+α4ß7+Lin-CD48+CD52+ subset and give rise to ILC1s, ILC2s, and NCR+ ILC3s, whereas CD34+CD117+α4ß7+Lin-CD48+CD52- ILCPs give rise to a distinct subset of ILC3s that have lymphoid tissue inducer (LTi)-like properties. In addition, CD48-expressing CD34+CD117+α4ß7+Lin- precursors give rise to tissue-associated ILCs in vivo. We also observed that the interaction of 2B4 with CD48 induced differentiation of ILC2s, and together, these findings show that expression of CD48 by human ILCPs modulates ILC differentiation.

Prolactin Acts on Myeloid Progenitors to Modulate SMAD7 Expression and Enhance Hematopoietic Stem Cell Differentiation into the NK Cell Lineage.

Numerous cell types modulate hematopoiesis through soluble and membrane bound molecules. Whether developing hematopoietic progenitors of a particular lineage modulate the differentiation of other hematopoietic lineages is largely unknown. Here we aimed to investigate the influence of myeloid progenitors on CD34+ cell differentiation into CD56+ innate lymphocytes. Sorted CD34+ cells cultured in the presence of stem cell factor (SCF) and FMS-like tyrosine kinase 3 ligand (FLT3L) give rise to numerous cell types, including progenitors that expressed the prolactin receptor (PRLR). These CD34+PRLR+ myeloid-lineage progenitors were derived from granulocyte monocyte precursors (GMPs) and could develop into granulocytes in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Moreover, CD34+PRLR+ myeloid progenitors lacked lymphoid developmental potential, but when stimulated with prolactin (PRL) they increased the differentiation of other CD34+ cell populations into the NK lineage in a non-contact dependent manner. Both mRNA and protein analyses show that PRL increased mothers against decapentaplegic homolog 7 (SMAD7) in CD34+PRLR+ myeloid cells, which reduced the production of transforming growth factor beta 1 (TGF-ß1), a cytokine known to inhibit CD56+ cell development. Thus, we uncover an axis whereby CD34+PRLR+ GMPs inhibit CD56+ lineage development through TGF-ß1 production and PRL stimulation leads to SMAD7 activation, repression of TGF-ß1, resulting in CD56+ cell development.

Transient Expression of GATA3 in Hematopoietic Stem Cells Facilitates Helper Innate Lymphoid Cell Differentiation.

Helper Innate lymphoid cells (ILCs) are tissue resident lymphocytes that play a critical role in a number of biological processes. Several transcription factors are required for the differentiation of hematopoietic stem cells (HSCs) into ILCs. Recent studies demonstrate GATA3 as a transcriptional regulator that plays an essential role in ILC development. We aimed to modulate the differentiation of human cord blood-derived CD34+ cells into ILCs by transient and ectopic expression of mRNA encoding transcription factors known to be important for ILC lineage differentiation, including GATA3, TOX, NFIL3, ID2, and RORγt. Using this experimental protocol, only GATA3 significantly modulated HSCs to differentiate into helper ILCs. Transient overexpression of GATA3 drove the emergence of CD34+α4ß7+ early ILC progenitors during the first few days of culture. These ILC progenitors further acquired IL-7Rα and CD117 to give rise to immediate ILC precursors. In support of these findings, analysis of the genes induced by GATA3 in HSCs showed an upregulation of those associated with ILC development. Moreover, we show GATA3 also acts on more committed progenitors and significantly shifts the differentiation of progenitors away from the ILC1/NK lineage to the ILC2 and ILC3 lineage. In summary, transient overexpression of GATA3 mRNA in CD34+ HSCs enhances the differentiation of HSCs into the helper ILC lineages, at the expense of NK cell development.

Atlantoaxial instability secondary to rheumatoid arthritis.

Multiple elements contribute to the stability of the anterior C1-C2 articulation, making this region subject to pathologies including trauma, inflammation, infection, and congenital deformities. C1-C2 instability places a patient at risk for significant neurologic compromise. Radiologic imaging plays a fundamental role in diagnosing atlantoaxial instability, indicating etiology, showing details of associated abnormalities, and providing information for planning treatment.