Deficiency of the Metalloproteinase-Disintegrin ADAM8 Is Associated with Thymic Hyper-Cellularity

Thymopoiesis requires thymocyte-stroma interactions and proteases that promote cell migration by degrading extracellular matrix and releasing essential cytokines and chemokines. A role for several members of the A Disintegrin and Metalloprotease (ADAM) family in T cell development has been reported in the past

Trim28 Haploinsufficiency Triggers Bi-stable Epigenetic Obesity.

This is the final version of the article. It first appeared from Cell Press via http://dx.doi.org/10.1016/j.cell.2015.12.025More than one-half billion people are obese, and despite progress in genetic research, much of the heritability of obesity remains enigmatic. Here, we identify a Trim28-dependent network capable of triggering obesity in a non-Mendelian, "on/off" manner. Trim28(+/D9) mutant mice exhibit a bi-modal body-weight distribution, with isogenic animals randomly emerging as either normal or obese and few intermediates. We find that the obese-"on" state is characterized by reduced expression of an imprinted gene network including Nnat, Peg3, Cdkn1c, and Plagl1 and that independent targeting of these alleles recapitulates the stochastic bi-stable disease phenotype. Adipose tissue transcriptome analyses in children indicate that humans too cluster into distinct sub-populations, stratifying according to Trim28 expression, transcriptome organization, and obesity-associated imprinted gene dysregulation. These data provide evidence of discrete polyphenism in mouse and man and thus carry important implications for complex trait genetics, evolution, and medicine.This work was supported by funding from the Max-Planck Society, ERC (ERC-StG-281641), DFG (SFB992 “MedEp”; SFB 1052 “ObesityMechanisms”), EU_FP7 (NoE ”Epigenesys”; “Beta-JUDO” n° 279153), BMBF (DEEP), MRC (Metabolic Disease Unit - APC, SOR, GSHY, MRC_MC_UU_12012/1), Wellcome Trust (SOR, 095515/Z/11/Z) and the German Research Council (DFG) for the Clinical Research Center "Obesity Mechanisms" CRC1052/1 C05 and the Federal Ministry of Education and Research, Germany, FKZ, 01EO1001 (Integrated Research and Treatment Center (IFB) Adiposity Diseases

Thymic progenitor homing and lymphocyte homeostasis are linked via S1P-controlled expression of thymic P-selectin/CCL25

Thymic T cell progenitor (TCP) importation is a periodic, gated event that is dependent on the expression of functional P-selectin ligands on TCPs. Occupancy of intrathymic TCP niches is believed to negatively regulate TCP importation, but the nature of this feedback mechanism is not yet resolved. We show that P-selectin and CCL25 are periodically expressed in the thymus and are essential parts of the thymic gate-keeping mechanism. Periodicity of thymic TCP receptivity and the size of the earliest intrathymic TCP pool were dependent on the presence of functional P-selectin ligand on TCPs. Furthermore, we show that the numbers of peripheral blood lymphocytes directly affected thymic P-selectin expression and TCP receptivity. We identified sphingosine-1-phosphate (S1P) as one feedback signal that could mediate influence of the peripheral lymphocyte pool on thymic TCP receptivity. Our findings suggest a model whereby thymic TCP importation is controlled by both early thymic niche occupancy and the peripheral lymphocyte pool via S1P

Regulation of thymic T cell progenitor importation

The thymus does not contain self-renewing T cell progenitors (TCP) and therefore requires continuous importation of progenitors from the blood to sustain T cell production. Recruitment of TCP to the thymus is facilitated by a multistep adhesion cascade initiated by the interaction of PSGL-1 expressed on TCP with P-selectin expressed on thymic endothelium. Thymic TCP importation is not a steady state process but is a periodic, gated event thought to be regulated by a negative feedback signal dependent on the occupation status of intrathymic TCP niches. However the nature of this feedback mechanism remains enigmatic. The aim of this study is to analyze the underlying mechanism that control thymic TCP importation in a temporal and quantitative manner. The study is based on the hypothesis that ingress of TCP into the thymus is controlled by the regulated expression of key molecules within the thymic adhesion cascade. Indeed, the first set of data shows that Pselectin and CCL25 expression correlate with thymic receptivity. Furthermore, this study finds that P-selectin and CCL25 are periodically expressed in thymic tissues indicating that they are essential parts of the thymic gate-keeping-mechanism. Absence of the P-selectin on thymic endothelial cells or functional P-selectin ligands on TCP significantly reduces the numbers of the earliest intrathymic TCP population and abolishes periodic expression of Pselectin and CCL25 suggesting that niche occupancy plays a role in regulating the periodicity of thymic TCP importation. The study further shows that the size of the peripheral lymphocyte pool directly affects thymic P-selectin expression and TCP receptivity indicating that extrathymic factors also control thymic receptivity. As a feedback signal that could mediate changes in the peripheral lymphocyte pool into altered thymic TCP receptivity sphingosine-1-phosphate (S1P) was identified. These findings suggest a model whereby thymic TCP importation is controlled by both early thymic niche occupancy and the peripheral lymphocyte pool via S1P.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat

Comparison of the differentiation potential of cell populations isolated from human lipoaspirate, trabecular bone tissue and periosteal tissue

Recent studies indicate that a variety of cells derived from adult human tissues show the capacity to change their tissue specific differentiation program. In this study we harvested cells from lipoaspirated adipose tissue, trabecular bone and pericranium tissue in order to evaluate and compare the differentiation potential of these populations by exposing them to adipogenic, chondrogenic, osteogenic and neurogenic induction media. Histological and immunochemistry analysis after adipogenic induction revealed adipocyte-like characteristic for all populations. Under osteogenic induction, all populations expressed the bone matrix proteins osteocalcin, osteopontin, osteonectin and secreted alkaline phosphatase, an early bone marker, into the culture medium. The chondrogenic potential was evaluated after staining of acidic glycoconjugates within the extracellular matrix. All induced cell populations were stained positive, indicating the presence of de novo cartilage. After neuronal induction, responsive cells exhibited neuron-like morphology with refractile cell bodies, extended long processes terminating in typical growth cones and long axon-like filopodia. Immunocytochemistry revealed the expression of neurofilament M and neuron specific enolase. Due to the use of heterogeneous cell populations each cell population preferentially expressed the phenotype of the tissue it was isolated from. In comparison; under the respective experimental conditions the periosteal and adipose derived cell populations demonstrated equal versatile developmental potentials according to cell morphology, immunocytochemistry and histology. In contrast the trabecular derived cells displayed a lower differentiation potential. These findings indicate that there are subpopulations within the isolated cell populations allowing all these cell preparations to express adipocyte-, osteoblast-, chondrocyte-, and neuron-like phenotypes.</p

ADAM8^−/− thymocytes have increased proliferation and reduced apoptosis rates.

<p>(A) Frequencies of Ki-67^hi cells in DN, DP^lo and DP^hi subsets of wt and ADAM8^−/− thymi. (B) Frequency of Caspase-3⁺ thymocytes in wt and ADAM8^−/− thymi. Data are representative of two independent experiments with n≥4 age- and gender-matched mice per group in each experiment. Data are presented as mean values and error bars as SEM. *, p<0.05, **, p<0.01.</p

ADAM8^−/− thymi have an increased mass and a reduced cortex/medulla ratio associated with a relative increase in mTEC.

<p>(A) Weight and (B) total numbers of thymocytes thymi from age- and gender-matched wt and ADAM^−/− mice (n = 8). (C) Cortex/medulla ratios examined on Hematoxylin/Eosin stained 20 µm sections of wt and ADAM8^−/− thymi (each 6 sections of 6 wt or ADAM^−/− thymi). Frequencies of (D) cTEC (Ly51^hi, UEA-1^lo) and (E) mTEC (Ly51^lo, UEA-1^hi) in CD45⁻, EpCAM⁺ thymic epithelial fraction of thymic suspensions obtained by collagenase/dispase treatment. Data are representative of two independent experiments with at least four mice per group. Data are presented as mean values and error bars as SEM. *, p<0.05, **, p<0.01, *** p<0.001.</p