The interweaved signatures of common-gamma-chain cytokines across immunologic lineages

"γc" cytokines are a family whose receptors share a "common-gamma-chain" signaling moiety, and play central roles in differentiation, homeostasis, and communications of all immunocyte lineages. As a resource to better understand their range and specificity of action, we profiled by RNAseq the immediate-early responses to the main γc cytokines across all immunocyte lineages. The results reveal an unprecedented landscape: broader, with extensive overlap between cytokines (one cytokine doing in one cell what another does elsewhere) and essentially no effects unique to any one cytokine. Responses include a major downregulation component and a broad Myc-controlled resetting of biosynthetic and metabolic pathways. Various mechanisms appear involved: fast transcriptional activation, chromatin remodeling, and mRNA destabilization. Other surprises were uncovered: IL2 effects in mast cells, shifts between follicular and marginal zone B cells, paradoxical and cell-specific cross-talk between interferon and γc signatures, or an NKT-like program induced by IL21 in CD8+ T cells.

Osteoclasts and Macrophages-Their Role in Bone Marrow Cavity Formation During Mouse Embryonic Development

The formation of the bone marrow cavity is a prerequisite for endochondral ossification. In reviews and textbooks, it is occasionally reported that osteoclasts are essential for bone marrow cavity formation removing hypertrophic chondrocytes. Mice lacking osteoclasts or having functionally defective osteoclasts have osteopetrotic bones, yet they still form a bone marrow cavity. Here, we investigated the role of osteoclasts and macrophages in bone marrow cavity formation during embryogenesis. Macrophages can assist osteoclasts in matrix removal by phagocytosing resorption byproducts. Rank-deficient mice, lacking osteoclasts, and Pu.1-deficient mice, lacking monocytes, macrophages, and osteoclasts, displayed a delay in bone marrow cavity formation and a lengthening of the zone of hypertrophic chondrocytes. F4/80-positive monocyte/macrophage numbers increased by about fourfold in the bone marrow cavity of E18.5 Rank-deficient mice. Based on lineage-tracing experiments, the majority of the excess F4/80 cells were derived from definitive hematopoietic precursors of the fetal liver. In long bones of both Rank^-/- and Pu.1^-/- specimens, Mmp9-positive cells were still present. In addition to monocytes, macrophages, and osteoclasts, Ctsb-positive septoclasts were lost in Pu.1^-/- specimens. The mineralization pattern was altered in Rank^-/- and Pu.1^-/- specimens, revealing a significant rise in transverse-oriented mineralized structures. Taken together, our findings imply that early on during bone marrow cavity formation, osteoclasts facilitate the entry of blood vessels and later the turnover of hypertrophic chondrocytes, whereas macrophages appear to play no major role. Furthermore, the absence of septoclasts in Pu.1^-/- specimens suggests that septoclasts are either derived from Pu.1-dependent precursors or require PU.1 activity for their differentiation. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Therapeutic inhibition of the SRC-kinase HCK facilitates T cell tumor infiltration and improves response to immunotherapy

Although immunotherapy has revolutionized cancer treatment, many immunogenic tumors remain refractory to treatment. This can be largely attributed to an immunologically "cold" tumor microenvironment characterized by an accumulation of immunosuppressive myeloid cells and exclusion of activated T cells. Here, we demonstrate that genetic ablation or therapeutic inhibition of the myeloid-specific hematopoietic cell kinase (HCK) enables activity of antagonistic anti-programmed cell death protein 1 (anti-PD1), anti-CTLA4, or agonistic anti-CD40 immunotherapies in otherwise refractory tumors and augments response in treatment-susceptible tumors. Mechanistically, HCK ablation reprograms tumor-associated macrophages and dendritic cells toward an inflammatory endotype and enhances CD8⁺ T cell recruitment and activation when combined with immunotherapy in mice. Meanwhile, therapeutic inhibition of HCK in humanized mice engrafted with patient-derived xenografts counteracts tumor immunosuppression, improves T cell recruitment, and impairs tumor growth. Collectively, our results suggest that therapeutic targeting of HCK activity enhances response to immunotherapy by simultaneously stimulating immune cell activation and inhibiting the immunosuppressive tumor microenvironment.

The Presence of MMP-20 Reinforces Biomimetic Enamel Regrowth

Biomimetic synthesis of artificial enamel is a promising strategy for the prevention and restoration of defective enamel. We have recently reported that a hydrogel system composed of chitosan-amelogenin (CS-AMEL) and calcium phosphate is effective in forming an enamel-like layer that has a seamless interface with natural tooth surfaces. Here, to improve the mechanical system function and to facilitate the biomimetic enamel regrowth, matrix metalloproteinase-20 (MMP-20) was introduced into the CS-AMEL hydrogel. Inspired by our recent finding that MMP-20 prevents protein occlusion inside enamel crystals, we hypothesized that addition of MMP-20 to CS-AMEL hydrogel could reinforce the newly grown layer. Recombinant human MMP-20 was added to the CS-AMEL hydrogel to cleave full-length amelogenin during the growth of enamel-like crystals on an etched enamel surface. The MMP-20 proteolysis of amelogenin was studied, and the morphology, composition, and mechanical properties of the newly grown layer were characterized. We found that amelogenin was gradually degraded by MMP-20 in the presence of chitosan. The newly grown crystals in the sample treated with MMP-20-CS-AMEL hydrogel showed more uniform orientation and greater crystallinity than the samples treated with CS-AMEL hydrogel without MMP-20. Stepwise processing of amelogenin by MMP-20 in the CS-AMEL hydrogel prevented undesirable protein occlusion within the newly formed crystals. As a result, both the modulus and hardness of the repaired enamel were significantly increased (1.8- and 2.4-fold, respectively) by the MMP-20-CS-AMEL hydrogel. Although future work is needed to further incorporate other enamel matrix proteins into the system, this study brings us one step closer to biomimetic enamel regrowth.

Proximity-Based Differential Single-Cell Analysis of the Niche to Identify Stem/Progenitor Cell Regulators

Physiological stem cell function is regulated by secreted factors produced by niche cells. In this study, we describe an unbiased approach based on the differential single-cell gene expression analysis of mesenchymal osteolineage cells close to, and further removed from, hematopoietic stem/progenitor cells (HSPCs) to identify candidate niche factors. Mesenchymal cells displayed distinct molecular profiles based on their relative location. We functionally examined, among the genes that were preferentially expressed in proximal cells, three secreted or cell-surface molecules not previously connected to HSPC biology-the secreted RNase angiogenin, the cytokine IL18, and the adhesion molecule Embigin-and discovered that all of these factors are HSPC quiescence regulators. Therefore, our proximity-based differential single-cell approach reveals molecular heterogeneity within niche cells and can be used to identify novel extrinsic stem/progenitor cell regulators. Similar approaches could also be applied to other stem cell/niche pairs to advance the understanding of microenvironmental regulation of stem cell function.

A critical role of dendritic cells in CD8 T cell IL-10 expression during inflammatory response triggered by CD40-activated B cells (159.16)

CD40LBTg mice, expressing a CD40 ligand (CD40L) transgene on B cells, represent a model for human diseases where B cells aberrantly express CD40L or receive excess CD40/CD40L signaling under inflammatory conditions. Here, we show that B cells expressing transgenic CD40L are capable of priming CD8 T cells and generate strong antigen-specific cytotoxicity. Adoptively transferred SIINFEKL peptide-loaded B cells from CD40LBTg but not wild type mice were able to activate self-reactive OT-I CD8 T cells upon immunization with OVA plus alum and trigger diabetes in RIP-OVA mice by enhancing the help of endogenous self-reactive CD4 T cells. CD40L expressing B cells also trigger spontaneous activation of splenic CD8 T cells, which rapidly up-regulate PD-1, Blimp-1 and LAG-3 and lose cytotoxicity along with IL-10 expression via interaction with PDL-1hi CD11c+ dendritic cells in T cell zones. Thus, CD11c+ dendritic cells from CD40LBTg mice exhibit regulatory phenotype, which block granzyme B expression and preferentially induce IL-10 expression in activated CD8 T cells. These results demonstrate that constitutive CD40 signaling on B cells under inflammation increases the risk of breaking peripheral CD8 T cell tolerance. However, the presence of CD40-activated B cells results in PDL-1hi CD11c+ dendritic cells, which exhibit a regulatory role to dampen harmful self-reactive cytotoxicity by promoting IL-10 expression in CD8 T cells.

Expanded γδ T cell populations in absence of transcription factor PU.1 (36.49)

T cell development is characterized by a succession of developmental stages that lead to the generation of mature αβ and γδ T cells. γδ T cells are considered innate cells that critically contribute to host defense. PU.1, an Ets family transcription factor, also identified as the spleen focus forming virus proviral integration site-1 (Sfpi-1) is essential for early stages of T cell development and is down regulated during the pro T-cell stage. PU.1 is expressed in Th2 cells but not Th1 cells. Expression of PU.1 in other T cell subsets has not been studied extensively. In this study, we show that PU.1 is expressed in γδ T cells, and in mice that specifically lack PU.1 in T cells using an lck-Cre transgene with a conditional Sfpi1 allele (Sfpilck-/-) there are increased numbers of γδ T cells in spleen, thymus and in the intestine when compared to wild type mice. The increase in γδ T cell numbers in PU.1 deficient mice is reflected in several subsets examined (Vγ2T, Vγ3T and Vδ4T). In mice where PU.1 was deleted using a CD4-Cre transgene, the expansion of γδ T cell numbers was restricted to the intestinal population. PU.1-deficient γδ T cells secrete higher levels of IL-17 than wild type cells, but similar levels of IFN-γ. Thus, our data show that PU.1 is expressed in γδ T cells and that deletion of PU.1 results in γδ T cell expansion. This suggests that PU.1 has a negative influence on γδ T cell development or expansion.

PU.1 expression in T cells is required for the development of IL-9 producing T cells in allergic inflammation (141.14)

The well documented Ets family transcription factor, PU.1 is an important regulator of mast cell, granulocyte and B cell development. Previous studies from our laboratory have identified a novel role for PU.1 in regulating Th2 cell cytokine expression. To further define a role for PU.1 in the development of allergic inflammation in vivo, we studied the development of allergic airway inflammation in mice with a conditional deletion of PU.1 in T cells. Despite the development of normal Th2-responses in the periphery, PU.1 deficient T cells have attenuated allergic inflammation in the lung as compared to wild type mice. To elucidate the mechanism for decreased inflammation in the lung, analysis of cytokines and chemokines from mice that had T cells lacking PU.1, demonstrated significantly decreased levels of IL-9 in the bronchoalveolar lavage fluid concomitant with a significant reduction in the pro-allergic chemokines, CCL17 & CCL22 in lung tissue. We identified PU.1 as a factor that promotes the Th9 phenotype by both repressing Th2 cytokine production and increasing IL-9 production. PU.1 was required for normal generation of IL-9 secreting T cells in vitro and ectopic expression of PU.1 increased IL-9 and chemokine production from Th9 cultures. Together, these data suggest a critical role for PU.1 in generating the Th9 phenotype and in the development of allergic inflammation.

Inactivation of PU.1 in adult mice leads to the development of myeloid leukemia

Genetically primed adult C57BL mice were deleted of exon 5 of the gene encoding the transcription factor PU.1 by IFN activation of Cre recombinase. After a 13-week delay, conditionally deleted (PU.1(-/-)) mice began dying of myeloid leukemia, and 95% of the mice surviving from early postinduction death developed transplantable myeloid leukemia whose cells were deleted of PU.1 and uniformly Gr-1 positive. The leukemic cells formed autonomous colonies in semisolid culture with varying clonal efficiency, but colony formation was enhanced by IL-3 and sometimes by granulocyte-macrophage colony-stimulating factor. Nine of 13 tumors analyzed had developed a capacity for autocrine IL-3 or granulocyte-macrophage colony-stimulating factor production, and there was evidence of rearrangement of the IL-3 gene. Acquisition of autocrine growth-factor production and autonomous growth appeared to be major events in the transformation of conditionally deleted PU.1(-/-) cells to fully developed myeloid leukemic populations.

Molecular cloning, expression, and pharmacological characterization of humEAA1, a human kainate receptor subunit

Kainate is a potent neuroexcitatory agent; its neurotoxicity is thought to be mediated by an ionotropic receptor with a nanomolar affinity for kainate. In this report, we describe the cloning of a cDNA encoding a human glutamate ionotropic receptor subunit protein from a human hippocampal library. This cDNA, termed humEAA1, is most closely related to rat and human cDNAs for kainate receptor proteins and, when expressed in COS or Chinese hamster ovary cells, is associated with high-affinity kainate receptor binding. We have successfully established cell lines stably expressing humEAA1. This is the first report of establishment of stable cell lines expressing a glutamate receptor subunit. The relative potency of compounds for displacing [3H]kainate binding of humEAA1 receptors expressed in these stable cell lines was kainate > quisqualate > domoate > L-glutamate >> (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid > dihydrokainate > 6,7-dinitroquinoxaline-2,3-dione > 6-cyano-7-nitroquinoxaline-2,3-dione. Homooligomeric expression of humEAA1 does not appear to elicit ligand-gated ion channel activity. Nevertheless, the molecular structure and pharmacological characterization of high-affinity kainate binding of the humEAA1 expressed in the stable cell line (ppEAA1-16) suggest that the humEAA1 is a subunit protein of a human kainate receptor complex.

Molecular structure and pharmacological characterization of humEAA2, a novel human kainate receptor subunit

A cDNA encoding a novel human glutamate receptor subunit protein was isolated from a human hippocampal library. This cDNA, termed humEAA2, is most closely related to rat cDNAs for kainate receptor proteins and, when expressed in COS cells, is associated with high affinity kainate receptor binding. The relative potency of compounds in displacing [3H]kainate binding was kainate greater than quisqualate greater than domoate greater than L-glutamate much greater than 6,7-dinitroquinoxaline-2,3-dione greater than dihydrokainate greater than 6-cyano-7-nitroquinoxaline-2,3-dione greater than (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid. Homomeric expression of humEAA2 does not appear to elicit ligand-gated channel activity. Nevertheless, the molecular structure and pharmacology of high affinity kainate binding suggest that humEAA2 is a novel subunit protein of a human kainate receptor complex.

Housing the homeless mentally ill: a longitudinal study of a treatment approach

In a one-year study of 49 homeless chronic mentally ill patients, the subjects, selected at admission for inpatient treatment, were randomly assigned to one of two groups. One group was placed in an experimental residential treatment program following discharge, and the other group received standard postdischarge care. Subjects were interviewed every four months during the year as well as at index hospitalization and discharge. Although the study remains exploratory due to the small sample size and case attrition, the authors found that compared with the control group, the subjects in the residential treatment program spent significantly more nights in adequate shelter, spent fewer nights in hospitals or undomiciled, and were more satisfied with and committed to their living arrangements.