Mechanistic understanding of the inhibitory immunoreceptor PD-1 is largely based on mouse models, but human and mouse PD-1 share only 59.6% amino acid identity. Here, we found that human PD-1 is more inhibitory than mouse PD-1, owing to stronger interactions with the ligands PD-L1 and PD-L2 and more efficient recruitment of the effector phosphatase Shp2. In a mouse melanoma model with adoptively transferred T cells, humanization of a PD-1 intracellular domain disrupted the antitumor activity of CD8 ⁺ T cells and increased the magnitude of anti–PD-1 response. We identified a motif highly conserved across vertebrate PD-1 orthologs, absent in rodents, as a key determinant for differential Shp2 recruitment. Evolutionary analysis suggested that PD-1 underwent a rodent lineage–specific functional attenuation during evolution. Together, our study uncovers species-specific features of the PD-1 pathway, with implications for PD-1 evolution and differential anti–PD-(L)1 responses in mouse models and human patients.

Background: Chronic pain remains a major clinical challenge, which is often resistant to conventional treatments. Spinal cord stimulation has been used for decades to manage refractory pain, traditionally relying on open-loop systems with fixed-output stimulation. However, these systems fail to account for physiological variability, leading to inconsistent pain relief. Closed-loop spinal cord stimulation represents a significant advancement by utilizing evoked compound action potentials to continuously modulate stimulation intensity in real-time, ensuring more stable and effective pain management. Methods: A comprehensive literature review was conducted using PubMed and ClinicalTrials.gov to identify and synthesize relevant published and ongoing studies with a focus on open-loop spinal cord stimulation for managing lower back pain. Results: Clinical trials, including the Avalon and Evoke studies, have demonstrated that closed-loop spinal cord stimulation provides superior pain relief, functional improvement, and reduced opioid dependence compared to traditional open-loop systems. Patients receiving closed-loop stimulation reported significantly higher rates of sustained pain reduction, improved quality of life, and fewer complications related to overstimulation. Emerging studies suggest its potential for conditions beyond back pain, such as neuropathic pain, cancer-related pain, and Raynaud’s phenomenon. Furthermore, cost-effectiveness analyses indicate that closed-loop spinal cord stimulation is a more economically viable treatment option compared to conventional medical management and open-loop systems. Conclusions: Closed-loop spinal cord stimulation represents a transformative development in neuromodulation, offering personalized and adaptive pain management that is distinct from open-loop spinal cord stimulation. Further research is warranted to explore its long-term durability, broader applications, and integration with emerging technologies in pain management.

Background: Preterm birth is a leading cause of neonatal mortality and long-term disability worldwide. Injury in premature infants is demonstrated by disrupted organ development from inflammation, oxidative stress, hypoxia, and impaired vascular maturation. Current therapies largely provide supportive care and do not directly promote tissue regeneration. Mesenchymal stem cell (MSC)-based therapies have emerged as a potential strategy to enhance endogenous repair across organ systems commonly affected by prematurity. Results: Evidence indicates that MSCs exert therapeutic effects primarily through transient paracrine signaling rather than long-term engraftment. Following administration, MSCs release cytokines, growth factors, and extracellular vesicles that reduce inflammation, promote angiogenesis, and support tissue repair. In preclinical models of neonatal brain injury, MSC therapy has been associated with improved oligodendrocyte maturation and reduced white matter injury. Early clinical trials in neonatal encephalopathy demonstrate feasibility and short-term safety of both autologous and allogeneic cell products. However, studies remain limited by small sample sizes and short follow-up. Cell-free approaches using MSC-derived extracellular vesicles may offer similar biological benefits with potentially lower safety and regulatory concerns. Conclusions: MSC-based therapies represent a promising regenerative approach for complications of prematurity. Rigorous, large-scale trials with standardized protocols and long-term follow-up are necessary to clarify efficacy, optimize delivery strategies, and define safety in this vulnerable population.