ABSTRACT AND‐gating is a mechanism capable of generating nonlinear biological responses because a productive output requires the joint satisfaction of several necessary molecular events. AND gates are considered here in the context of gene expression. Three minimal architectures are discussed, parallel AND gates, kinetic AND gates, and a serial arrangement of AND gates. In a parallel AND gate, output depends on the simultaneous engagement of several modules. In a kinetic AND gate, output requires the completion of several events within a finite time window. In a serial arrangement, the output of one gate becomes the input of the next. These architectures can generate S‐shaped responses even when the elementary processes are non‐cooperative. Although transcription is our main focus, the same logic applies to other processes. The sigmoidal responses produced by these AND gates provide a phenomenological explanation for how a reduction in the abundance or activity of a dosage‐sensitive molecule can generate more‐than‐proportional downstream effects, a hallmark of haploinsufficiency (HI), a form of dominance. The same AND‐gate logic also sheds light on dominant‐negative effects, where a mutant protein interferes with its wild‐type counterpart. These models illustrate how AND gate architectures can contribute to biological threshold generation and to nonlinear genotype–phenotype relationships, which underlie dominance.
ABSTRACT Alveolar epithelial cell (AEC) inflammation is a key driver of infectious pneumonia pathology. Toll‐like receptor 4 (TLR4) is a central mediator in this response, but its specific regulatory mechanisms at the cellular level remain unclear. TLR4 was identified as a candidate target gene for childhood infectious pneumonia (CIP) using the GeneCards database, and analyzed in a lipopolysaccharide (LPS)‐induced A549 AEC injury model. Cell viability, apoptosis, and inflammatory cytokine levels were examined using the cell counting kit‐8 (CCK‐8) assay, flow cytometry, lactate dehydrogenase (LDH) assay, and inflammatory factor detection kits, respectively. Upstream miR‐21‐5p of TLR4 and its upstream lncRNA OTUD6B‐AS1 were predicted using bioinformatics databases, and binding interactions were confirmed by luciferase reporter assays. The functional role of the OTUD6B‐AS1‐miR‐21‐5p‐TLR4 axis was investigated by transfecting oe‐OTUD6B‐AS1 and miR‐21‐5p mimics. LPS upregulated TLR4 in A549 cells. TLR4 knockdown attenuated LPS‐induced reductions in viability, cytotoxicity, and apoptosis. Further studies revealed binding of miR‐21‐5p to both TLR4 and OTUD6B‐AS1. OTUD6B‐AS1 sponged miR‐21‐5p to reduce miR‐21‐5p‐mediated repression of TLR4, thereby promoting TLR4 expression and exacerbating the inflammatory response. The OTUD6B‐AS1/miR‐21‐5p/TLR4 axis plays a pivotal role in AEC inflammation and represents a promising therapeutic target for CIP.
ABSTRACT Skeletal muscle tissue is highly vascularized, and angiogenesis plays a key role in both muscle homeostasis and regeneration. Despite their importance in regulating various processes within skeletal muscle, little is known about the role of muscle‐resident fibro‐adipogenic progenitors (FAPs) in promoting microvascular angiogenesis. In order to better understand the effects of FAPs on angiogenesis, FAPs were co‐cultured with adipose‐derived microvascular fragments (MVFs) in three‐dimensional fibrin hydrogels. We further tested if pre‐culturing FAPs in brown adipogenic induction media (BAM) influences their ability to promote MVF angiogenesis. MVFs co‐cultured with control FAPs or BAM FAPs for 5 days exhibit robust microvascular network formation with significantly increased vessel percentage area and average vessel length compared to MVFs alone. FAPs cultured in BAM prior to co‐culture with MVFs alter vascular network development compared to MVFs co‐cultured with control FAPs by significantly increasing average vessel length. Collectively, these results indicate that FAPs are key regulators of microvascular angiogenesis and that BAM FAPs have an improved capacity to promote increases in average vessel length. The current findings support the transplantation of FAPs and MVFs and modulation of FAP pro‐angiogenic properties as potential therapeutic approaches for enhancing skeletal muscle angiogenesis in the context of injury and disease.
ABSTRACT The spike (S) protein plays a pivotal role in the invasion of host cells by SARS‐CoV‐2 (COVID‐19). However, the underlying mechanism of spike protein interaction with host cells remains elusive. Here, it was found that human amniotic epithelial stem cells (HuAECs)‐derived exosomes were able to mitigate the cell cycle arrest and lesions of human type II alveolar epithelial primary cells (hAEPC‐II) in vitro induced by SARS‐CoV‐2 S protein. Mechanistically, HuAECs transfered SENP mRNA to hAEPC‐II by releasing exosomes, induced FGF9 protein deSUMOylation and stimulated its expression in hAEPC‐II. Silencing endogenous SENP3 mRNA in HuAECs using siRNA weakens the protective effect of HuAECs‐derived exosomes on hAEPC‐II. Meanwhile, HuAEC‐derived exosomes significantly improved lung tissue damage, inflammatory and fibrosis symptoms of humanized hACE2 KI/KI transgenic mice treated to S protein in vivo. In conclusion, this study reveals a novel mechanism by which HuAECs transfered SENP mRNA to hAEPC‐II by releasing exosomes and attenuate the lesion of hAEPC‐II induced by SARS‐CoV‐2 spike protein.
Silk hydrogels have attracted increasing interest as biocompatible substrates for neural cell culture and regenerative research. Recent research has shown that activation of exchange protein directly activated by cAMP 2 (Epac2) promotes neurite outgrowth in several neuronal models. Here, we investigated the effects of Bombyx mori silk hydrogel, alone or in combination with S-220, a non-hydrolysable cAMP analogue that selectively activates Epac2, on neurite outgrowth. Epac2 activation significantly and dose-dependently enhanced both the total and longest neurite length. Neurons cultured on silk hydrogel alone exhibited neurite outgrowth comparable to control neurons, indicating good biocompatibility of the hydrogel. Addition of S-220 to the culture medium with silk hydrogel modestly improved neurite morphology; however, incorporation of S-220 directly into the hydrogel did not enhance neurite outgrowth but instead reduced neurite length. A subsequently established three-dimensional cortical neuron culture model using silk hydrogel supported neurite extension and increased branching complexity beyond that observed with two-dimensional cultures, despite a shorter overall neurite length. Collectively, these findings support silk hydrogel as a permissive biomaterial substrate for in vitro cortical neuron culture. The system provides a useful platform for investigating neurite outgrowth, neuron-biomaterial interactions and the delivery of bioactive compounds in two- and three-dimensional neural cultures.
