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p21-senescent cells drive pancreatic islet dysfunction through targetable paracrine signaling in type 2 diabetes.

Cellular senescence is an irreversible stress response, which leads to loss of cellular function and remodeling of the cellular secretory profile. In humans, pancreatic β cells undergo cellular senescence during the progression to type 2 diabetes (T2D). However, the mechanism linking β cell senescence to islet dysfunction remains unknown, and thus the therapeutic potential of targeting senescent cells in T2D is not established. Herein, we identified a subpopulation of senescent β cells expressing p21, which emerged early in the progression of T2D in humans and mice. Spatial transcriptomics and proteomics analyses confirmed senescence and loss of cellular identity in this subpopulation in humans. Functional analysis revealed lack of glucose responsiveness, high basal insulin secretion, and transcription of senescence-associated secretory phenotype (SASP) factors. SASP factors from p21+ β cells induced secondary senescence in neighboring cells, characterized by dysfunction and loss of identity. JAK inhibitors counteracted the induction of secondary senescence and restored β cell function in islets from humans with T2D and in mice fed a high-fat diet. These findings reveal the critical role of p21+ β cells in T2D pathogenesis and the therapeutic potential of targeting this pathophysiological process.

Animals

Prolonged In Vitro Expansion Shapes the Neuro-Supportive Potential of Jaw Periosteum Secretomes: Implications for Secretome Product Quality.

Nerve injuries are frequent complications of complex oral and maxillofacial surgical procedures, particularly following extensive tumor resections. Secretome-based, cell-free therapies derived from mesenchymal stromal cells have emerged as promising regenerative approaches; however, robust manufacturing requires the identification of critical quality attributes (CQAs) that ensure product potency and consistency. The influence of replicative senescence during in vitro expansion on the quality of jaw periosteum-derived mesenchymal stromal cell (JPC) secretomes has not yet been established. This study investigated whether the expansion state of JPCs affects the composition and neuro-supportive potency of their secretomes. Secretomes from four independent JPC donors were collected separately at early and late passages, pooled within each passage-specific preparation, and applied to human induced pluripotent stem cell-derived neurons. Neuronal survival, neurite outgrowth, and neuronal marker expression were assessed as functional readouts. Secretome composition was characterized by quantitative proteomics and enzyme-linked immunosorbent assay (ELISA) of selected senescence-associated secretory phenotype (SASP) factors. Secretomes derived from early-passage JPCs significantly enhanced neuronal survival and neurite outgrowth, whereas late-passage secretomes displayed reduced neuro-supportive activity. Proteomic profiling identified a pronounced shift toward inflammatory and stress-associated signaling, whereas performed ELISAs confirmed senescence-associated remodeling of the secretome, including increased abundance of SASP-associated factors in late-passage preparations. These findings demonstrate that prolonged in vitro expansion profoundly influences both the composition and biological potency of JPC-derived secretomes. Collectively, this study identifies the passage-associated senescence-like phenotype of JPCs as a key determinant of secretome quality and supports its consideration as a critical quality attribute for the manufacturing and standardization of JPC-derived secretome products. Monitoring and controlling the expansion state of JPCs may therefore be essential to ensure the consistency, potency, and clinical translation of secretome-based regenerative therapies.

Humans

Interfollicular communication among preovulatory follicles after luteinizing hormone signaling.

Luteinizing hormone (LH) triggers the resumption of oocyte meiosis and ovulation in preovulatory ovarian follicles. These events have generally been viewed as autonomous responses occurring independently within each follicle. Here, however, we show that mouse preovulatory follicles can communicate with one another through an LH-induced paracrine signaling network. Isolated preovulatory follicles lacking LH receptors (Lhr-KO) resumed oocyte meiosis when co-cultured with LH-stimulated wildtype follicles, despite being unable to respond directly to LH. Oocytes within Lhr-KO follicles also resumed meiosis when exposed to conditioned medium from LH-treated wildtype follicles, demonstrating that diffusible factors mediate this interfollicular communication. Neutralizing antibodies against the epidermal growth factor receptor ligands epiregulin and amphiregulin inhibited the LH-induced interfollicular communication, identifying these LH-induced factors as key signaling molecules. Although epiregulin and amphiregulin are known to transmit LH signals within individual follicles, our findings indicate that they can also coordinate responses among neighboring follicles. Together, these results demonstrate that LH regulates a communication network between preovulatory follicles rather than acting solely at the level of individual follicles.

epidermal growth factor receptor

Multiplexed microfluidic chip for cell co-culture.

Paracrine signaling is challenging to study in vitro, as conventional culture tools dilute soluble factors and offer little to no spatiotemporal control over signaling. Microfluidic chips offer potential to address both of these issues. However, few solutions offer both control over onset and duration of cell-cell communication, and high throughput. We have developed a microfluidic chip designed to culture cells in adjacent chambers, separated by valves to selectively allow or prevent exchange of paracrine signals. The chip features 16 fluidic inputs and 128 individually-addressable chambers arranged in 32 sets of 4 chambers. Media can be continuously perfused or delivered by diffusion, which we model under different culture conditions to ensure normal cell viability. Immunocytochemistry assays can be performed in the chip, which we modeled and fine-tuned to reduce total assay time to 1 h. Finally, we validate the use of the chip for co-culture studies by showing that HEK293Ta cells respond to signals secreted by RAW 264.7 immune cells in adjacent chambers, only when the valve between the chambers is opened.

Microfluidics