Anti-Müllerian Hormone Regulation of Synaptic Transmission in the Hippocampus Requires MAPK Signaling and Kv4.2 Potassium Channel Activity

Anti-Müllerian hormone (AMH) is a paracrine factor generated peripherally by the gonads to regulate gonadal function in adult mammals. We recently reported that AMH and AMH-specific receptor Anti-Müllerian hormone receptor 2 (AMHR2) are expressed in the hippocampus, and exogenous AMH protein rapidly increased synaptic transmission and long-term synaptic plasticity at the CA3-CA1 synapses. Here we examined the cell-specific expression of AMHR2 and the cellular mechanism of rapid boosting effect of AMH on synaptic transmission in mouse hippocampus. Immunofluorescence staining showed that AMHR2 was specifically expressed in the soma and dendrites of hippocampal pyramidal neurons, but not glial cells. Electrophysiological recordings on acute hippocampal slices showed that AMH did not affect AMPAR-mediated or N-Methyl-D-aspartic acid receptor (NMDAR)-mediated excitatory postsynaptic currents at the CA3-CA1 synapses. The small-conductance Ca2+-activated K+ channel (SK2) and A-type K+ channel (Kv4.2) contribute to shaping excitatory postsynaptic potentials (EPSPs) at the CA3-CA1 synapses. Bath application of apamin to block SK2 did not alter AMH effect on increasing EPSPs, whereas blocking Kv4.2 channel with 4-aminopyridine, or chelating internal Ca2+ with BAPTA occluded the action of AMH on boosting EPSPs. Kv4.2 activity is regulated by p38 mitogen-activated kinase (MAPK). Blocking p38 MAPK with SB203580 occluded the effect of AMH on increasing EPSPs. These results show that Kv4.2 channel contributes to the rapid action of AMH on boosting synaptic transmission in a Ca2+- and p38 MAPK-dependent manner. Our findings provide functional evidence that AMH enhances synaptic transmission through Kv4.2 channel in the hippocampus, suggesting a possible role of Kv4.2 channel in AMH-regulated neuronal process underlying learning and memory.

Anti-senescence ion-delivering nanocarrier for recovering therapeutic properties of long-term-cultured human adipose-derived stem cells

Background Human adipose-derived stem cells (hADSCs) have been used in various fields of tissue engineering because of their promising therapeutic efficacy. However, the stemness of hADSCs cannot be maintained for long durations, and their therapeutic cellular functions, such as paracrine factor secretion decrease during long-term cell culture. To facilitate the use of long-term-cultured hADSCs (L-ADSCs), we designed a novel therapeutic anti-senescence ion-delivering nanocarrier (AIN) that is capable of recovering the therapeutic properties of L-ADSCs. In the present study, we introduced a low-pH-responsive ion nanocarrier capable of delivering transition metal ions that can enhance angiogenic paracrine factor secretion from L-ADSCs. The AINs were delivered to L-ADSCs in an intracellular manner through endocytosis. Results Low pH conditions within the endosomes induced the release of transition metal ions (Fe) into the L-ADSCs that in turn caused a mild elevation in the levels of reactive oxygen species (ROS). This mild elevation in ROS levels induced a downregulation of senescence-related gene expression and an upregulation of stemness-related gene expression. The angiogenic paracrine factor secretion from L-ADSCs was significantly enhanced, and this was evidenced by the observed therapeutic efficacy in response to treatment of a wound-closing mouse model with conditioned medium obtained from AIN-treated L-ADSCs that was similar to that observed in response to treatment with short-term-cultured adipose-derived stem cells. Conclusions This study suggests a novel method and strategy for cell-based tissue regeneration that can overcome the limitations of the low stemness and therapeutic efficacy of stem cells that occurs during long-term cell culture. Graphical Abstract

Collagen Fibers-based Self-assembled 3D Spheroids Alleviate Thioacetamide-induced Liver Cirrhosis in Rats

Cirrhosis refers to irreversible liver damage where healthy tissue is replaced by scar tissue which impairs liver function. There is no cure and current treatments only prevent further liver damage; thus novel therapeutic options are urgently needed. Here, we report a new approach that enables the formation of the self-assembled 3D spheroids of adipose-derived stem cells (ADSCs) and murine hepatocytes (AML12) via reconstituted collagen fibers. Compared with the spheroids formed in the commercially available EZSHERE dish, the collagen fiber-based ADSC/hepatocyte spheroids offer a notable benefit in structure formation and paracrine factor secretion. To test regenerative capability of the collagen fiber-based 3D ADSC/hepatocyte spheroids, a rat model of thioacetamide (TAA)-induced liver cirrhosis was employed. The transplantation of the collagen fiber-based 3D ADSC/hepatocyte spheroids show an improvement in liver function and ameliorates pathological liver cirrhosis in TAA-treated rats. In summary, our data show collagen fiber-based self-assembled 3D ADSC/hepatocyte spheroids to possess excellent regenerative capacity in response to TAA-induced liver injury, promising an alternative therapeutic strategy for liver cirrhosis.

From Mesenchymal Stromal Cells to Engineered Extracellular Vesicles: A New Therapeutic Paradigm

Mesenchymal stromal cells (MSCs) are multipotent cells obtained from many tissues including bone marrow, adipose tissue, umbilical cord, amniotic fluid, and placenta. MSCs are the leading cell source for stem cell therapy due to their regenerative and immunomodulatory properties, their low risk of tumorigenesis and lack of ethical constraints. However, clinical applications of MSCs remain limited. MSC therapeutic development continues to pose challenges in terms of preparation, purity, consistency, efficiency, reproducibility, processing time and scalability. Additionally, there are issues with their poor engraftment and survival in sites of disease or damage that limit their capacity to directly replace damaged cells. A key recent development in MSC research, however, is the now widely accepted view that MSCs primarily exert therapeutic effects via paracrine factor secretion. One of the major paracrine effectors are extracellular vesicles (EVs). EVs represent a potential cell-free alternative to stem cell therapy but are also rapidly emerging as a novel therapeutic platform in their own right, particularly in the form of engineered EVs (EEVs) tailored to target a broad range of clinical indications. However, the development of EVs and EEVs for therapeutic application still faces a number of hurdles, including the establishment of a consistent, scalable cell source, and the development of robust GMP-compliant upstream and downstream manufacturing processes. In this review we will highlight the clinical challenges of MSC therapeutic development and discuss how EVs and EEVs can overcome the challenges faced in the clinical application of MSCs.

Myeloid-derived growth factor regulates neutrophil motility in interstitial tissue damage

Neutrophil recruitment to tissue damage is essential for host defense but can also impede tissue repair. The cues that differentially regulate neutrophil responses to tissue damage and infection remain unclear. Here, we report that the paracrine factor myeloid-derived growth factor (MYDGF) is induced by tissue damage and regulates neutrophil motility to damaged, but not infected, tissues in zebrafish larvae. Depletion of MYDGF impairs wound healing, and this phenotype is rescued by depleting neutrophils. Live imaging and photoconversion reveal impaired neutrophil reverse migration and inflammation resolution in mydgf mutants. We found that persistent neutrophil inflammation in tissues of mydgf mutants was dependent on the HIF-1α pathway. Taken together, our data suggest that MYDGF is a damage signal that regulates neutrophil interstitial motility and inflammation through a HIF-1α pathway in response to tissue damage.

Neuregulin-1 Compensates for Endothelial Nitric Oxide Synthase Deficiency

Endothelial cells (ECs) secrete different paracrine signals that modulate the function of adjacent cells; two examples of these paracrine signals are nitric oxide (NO) and neuregulin-1 (NRG1), a cardioprotective growth factor. Currently, it is undetermined whether one paracrine factor can compensate for the loss of another. Herein, we hypothesized that NRG1 can compensate for endothelial NO synthase (eNOS) deficiency. Methods. We characterized eNOS null and wild type (WT) mice by cardiac ultrasound and histology and we determined circulating NRG1 levels. In a separate experiment, 8 groups of mice were divided into 4 groups of eNOS null mice and wild type (WT) mice; half of the mice received angiotensin II (Ang II) to induce a more severe phenotype. Mice were randomized to daily injections with NRG1 or vehicle for 28 days. Results. eNOS deficiency increased NRG1 plasma levels, indicating that ECs increase their NRG1 expression when NO production is deleted. eNOS deficiency also increased blood pressure, lowered heart rate, induced cardiac fibrosis, and affected diastolic function. In eNOS null mice, Ang II administration increased cardiac fibrosis, but also induced cardiac hypertrophy and renal fibrosis. NRG1 administration prevented the cardiac and renal hypertrophy and fibrosis caused by Ang II infusion and eNOS deficiency. Moreover, Nrg1 expression in the myocardium is shown to be regulated by miR-134. Conclusion. This study indicates that administration of endothelium-derived NRG1 can compensate for eNOS deficiency in the heart and kidneys.

Interaction of thyroid hormones and gonadotropin inhibitory hormone in the multifactorial control of zebrafish (Danio rerio) spermatogenesis

ABSTRACTReproduction is under multifactorial control of neurohormones, pituitary gonadotropins, as well as a number of gonadal hormones including sex steroids and growth factors. Gonadotropin-inhibitory hormone (Gnih), a novel RFamide neuropeptide, was shown to be involved in the control of pituitary gonadotropin production, as well as being involved as a paracrine factor in the regulation of gonadal function. In this context, recent studies have demonstrated that Gnih inhibited gonadotropin-induced spermatogenesis in the zebrafish testicular explants. Thyroid hormones are known to interact with the reproductive axis, and are, in particular, involved in the regulation of testicular function. Based on this background, we investigated the interaction between Gnih and thyroid hormones in the control of zebrafish spermatogenesis. To this end, zebrafish adult males were treated with the goitrogen methimazole (1mM for 21 days) in order to generate a hypothyroid model organism. Subsequently, a factorial design using an ex vivo testis culture system in combination with histomorphometrical and FACScan cell cycle analyses were adopted. Our results showed that methimazole treatment affected both basal and gonadotropin-induced spermatogenesis, in particular, meiosis and spermiogenesis. Moreover, the goitrogen treatment nullified the inhibitory actions of Gnih on the gonadotropin-induced spermatogenesis, specifically in the haploid cell population. We have demonstrated that thyroid hormones interaction with gonadotropin and Gnih are important components for the regulation of zebrafish spermatogenesis. The results provide a support for the hypothesis that thyroid hormones are important contributors in multifactorial control of spermatogenesis in zebrafish.

Physiological and Pharmacological Roles of PTH and PTHrP in Bone Using Their Shared Receptor, PTH1R

Parathyroid hormone (PTH) and the paracrine factor, PTH-related protein (PTHrP), have preserved in evolution sufficient identities in their amino-terminal domains to share equivalent actions upon a common G protein-coupled receptor, PTH1R, that predominantly uses the cyclic adenosine monophosphate-protein kinase A signaling pathway. Such a relationship between a hormone and local factor poses questions about how their common receptor mediates pharmacological and physiological actions of the two. Mouse genetic studies show that PTHrP is essential for endochondral bone lengthening in the fetus and is essential for bone remodeling. In contrast, the main postnatal function of PTH is hormonal control of calcium homeostasis, with no evidence that PTHrP contributes. Pharmacologically, amino-terminal PTH and PTHrP peptides (teriparatide and abaloparatide) promote bone formation when administered by intermittent (daily) injection. This anabolic effect is remodeling-based with a lesser contribution from modeling. The apparent lesser potency of PTHrP than PTH peptides as skeletal anabolic agents could be explained by lesser bioavailability to PTH1R. By contrast, prolongation of PTH1R stimulation by excessive dosing or infusion, converts the response to a predominantly resorptive one by stimulating osteoclast formation. Physiologically, locally generated PTHrP is better equipped than the circulating hormone to regulate bone remodeling, which occurs asynchronously at widely distributed sites throughout the skeleton where it is needed to replace old or damaged bone. While it remains possible that PTH, circulating within a narrow concentration range, could contribute in some way to remodeling and modeling, its main physiological role is in regulating calcium homeostasis.

Human Induced Pluripotent Stem Cell-Derived Exosomes as a New Therapeutic Strategy for Various Diseases

Recently, an increasing number of studies have demonstrated that induced pluripotent stem cells (iPSCs) and iPSC-derived cells display therapeutic effects, mainly via the paracrine mechanism in addition to their transdifferentiation ability. Exosomes have emerged as an important paracrine factor for iPSCs to repair injured cells through the delivery of bioactive components. Animal reports of iPSC-derived exosomes on various disease models are increasing, such as in heart, limb, liver, skin, bone, eye and neurological disease and so forth. This review aims to summarize the therapeutic effects of iPSC-derived exosomes on various disease models and their properties, such as angiogenesis, cell proliferation and anti-apoptosis, with the hopes of improving their potential role in clinical applications and functional restoration.