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ImmunoPET imaging applications One of the most promising areas of ImmunoPET imaging application is in oncology, where it has shown potential in tumor detection, monitoring, and treatment response assessment. Novel strategies, such as the use of nanobodies or engineered antibody fragments, are being explored to overcome these limitations and further enhance the performance of ImmunoPET imaging. [...]the development of novel targeting agents, such as immune checkpoint inhibitors and CAR T-cell therapies, has opened new avenues for ImmunoPET imaging applications. By combining these innovative treatments with ImmunoPET imaging, researchers and clinicians can obtain a wealth of information on disease processes and treatment response, ultimately leading to more effective and personalized therapeutic strategies for patients. First and foremost, I would like to thank Jorge Luis Martinez Torrecuadrada for his guidance feedback and constructive criticism have significantly improved the quality of this editorial.

Mucopolysaccharidosis type IVA (MPSIVA) or Morquio A disease, a lysosomal storage disorder, is caused by N -acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency, resulting in keratan sulfate (KS) and chondroitin-6-sulfate accumulation. Patients develop severe skeletal dysplasia, early cartilage deterioration and life-threatening heart and tracheal complications. There is no cure and enzyme replacement therapy cannot correct skeletal abnormalities. Here, using CRISPR/Cas9 technology, we generate the first MPSIVA rat model recapitulating all skeletal and non-skeletal alterations experienced by patients. Treatment of MPSIVA rats with adeno-associated viral vector serotype 9 encoding Galns (AAV9- Galns ) results in widespread transduction of bones, cartilage and peripheral tissues. This led to long-term (1 year) increase of GALNS activity and whole-body correction of KS levels, thus preventing body size reduction and severe alterations of bones, teeth, joints, trachea and heart. This study demonstrates the potential of AAV9- Galns gene therapy to correct the disabling MPSIVA pathology, providing strong rationale for future clinical translation to MPSIVA patients. Mucopolysaccharidosis type IVA (MPSIVA) is a lysosomal storage disorder causing severe skeletal and non-skeletal alterations in patients. Here, the authors generate a MPSIVA rat model that mimics the disabling human pathology and develop an AAV9-Galns gene therapy to treat the disease.

Prevalence of type 2 diabetes (T2D) and obesity is increasing worldwide. Currently available therapies are not suited for all patients in the heterogeneous obese/T2D population, hence the need for novel treatments. Fibroblast growth factor 21 (FGF21) is considered a promising therapeutic agent for T2D/obesity. Native FGF21 has, however, poor pharmacokinetic properties, making gene therapy an attractive strategy to achieve sustained circulating levels of this protein. Here, adeno‐associated viral vectors (AAV) were used to genetically engineer liver, adipose tissue, or skeletal muscle to secrete FGF21. Treatment of animals under long‐term high‐fat diet feeding or of ob/ob mice resulted in marked reductions in body weight, adipose tissue hypertrophy and inflammation, hepatic steatosis, inflammation and fibrosis, and insulin resistance for > 1 year. This therapeutic effect was achieved in the absence of side effects despite continuously elevated serum FGF21. Furthermore, FGF21 overproduction in healthy animals fed a standard diet prevented the increase in weight and insulin resistance associated with aging. Our study underscores the potential of FGF21 gene therapy to treat obesity, insulin resistance, and T2D. Synopsis This study describes the use of adeno‐associated viral (AAV) vectors to achieve long‐term production of fibroblast growth factor 21 (FGF21) to treat obesity and insulin resistance. AAV‐FGF21 gene transfer to healthy animals also prevented age‐associated weight gain and insulin resistance. A one‐time administration of an AAV vector encoding FGF21 counteract obesity and insulin resistance for more than a year. The approach works in two different animal models of obesity, induced either by diet or genetic mutations. Administration of AAV‐FGF21 to healthy animals promotes healthy aging. AAV‐FGF21 pharmacological effects are demonstrated after genetic engineering of 3 different tissues (liver, adipose tissue and skeletal muscle). FGF21 gene therapy holds great translational potential in the fight against insulin resistance, T2D, obesity and related comorbidities. Graphical Abstract This study describes the use of adeno‐associated viral (AAV) vectors to achieve long‐term production of fibroblast growth factor 21 (FGF21) to treat obesity and insulin resistance. AAV‐FGF21 gene transfer to healthy animals also prevented age‐associated weight gain and insulin resistance.

Nanotechnology changed the concept of treatment for a variety of diseases, producing a huge impact regarding drug and gene delivery. Among the different targeted diseases, osteoporosis has devastating clinical and economic consequences. Since current osteoporosis treatments present several side effects, new treatment approaches are needed. Recently, the application of small interfering RNA (siRNA) has become a promising alternative. Wnt/β‐catenin signaling pathway controls bone development and formation. This pathway is negatively regulated by sclerostin, which knock‐down through siRNA application would potentially promote bone formation. However, the major bottleneck for siRNA‐based treatments is the necessity of a delivery vector, bringing nanotechnology as a potential solution. Among the available nanocarriers, mesoporous silica nanoparticles (MSNs) have attracted great attention for intracellular delivery of siRNAs. The mesoporous structure of MSNs permits the delivery of siRNAs together with another biomolecule, achieving a combination therapy. Here, the effectiveness of a new potential osteoporosis treatment based on MSNs is evaluated. The proposed system is effective in delivering SOST siRNA and osteostatin through systemic injection to bone tissue. The nanoparticle administration produced an increase expression of osteogenic related genes improving the bone microarchitecture. The treated osteoporotic mice recovered values of a healthy situation approaching to osteoporosis remission. A mesoporous silica nanoparticles‐based system is designed for co‐delivering small interfering RNAs and an osteogenic peptide (osteostatin). The system is able to protect and deliver both biomolecules in the target tissue with promising results. It modifies gene expression and improves bone microarchitecture recovering healthy values. The application of nanoparticles can be considered a new potential alternative for osteoporosis remission.

Senescent cells accumulate in multiple aging‐associated diseases, and eliminating these cells has recently emerged as a promising therapeutic approach. Here, we take advantage of the high lysosomal β‐galactosidase activity of senescent cells to design a drug delivery system based on the encapsulation of drugs with galacto‐oligosaccharides. We show that gal‐encapsulated fluorophores are preferentially released within senescent cells in mice. In a model of chemotherapy‐induced senescence, gal‐encapsulated cytotoxic drugs target senescent tumor cells and improve tumor xenograft regression in combination with palbociclib. Moreover, in a model of pulmonary fibrosis in mice, gal‐encapsulated cytotoxics target senescent cells, reducing collagen deposition and restoring pulmonary function. Finally, gal‐encapsulation reduces the toxic side effects of the cytotoxic drugs. Drug delivery into senescent cells opens new diagnostic and therapeutic applications for senescence‐associated disorders. Synopsis Senescent cells are present in many diseases where they play an active pathological role. A common feature of senescent cells is their high content of lysosomes. Here, it is reported a pharmacological vehicle with lysosomal tropism that preferentially releases drugs into senescent cells. Drugs encapsulated with galacto‐oligosaccharides (gal‐encapsulation) are released into cells after digestion with lysosomal β‐galactosidase and this happens more efficiently in senescent cells. After intravenous injection, gal‐encapsulated drugs preferentially deliver their cargo into pathological tissues with high content of senescent cells. Gal‐encapsulated doxorubicin ameliorates lung fibrosis in mice, reducing collagen and recovering normal breathing, and this is in contrast to free doxorubicin. When xenograft tumors in mice are treated with chemotherapy, a fraction of tumor cells undergo senescence, and concomitant treatment with gal‐encapsulated doxorubicin results in full tumor regression. Gal‐encapsulation prevents the exposure of non‐pathological tissues to drugs and therefore reduces their associated toxicities, as it is shown for doxorubicin cardiotoxicity and for navitoclax‐induced thrombocytopenia. Graphical Abstract Senescent cells are present in many diseases where they play an active pathological role. A common feature of senescent cells is their high content of lysosomes. Here, it is reported a pharmacological vehicle with lysosomal tropism that preferentially releases drugs into senescent cells.

The mechanistic target of rapamycin complex 1 (mTORC1) integrates cellular nutrient signaling and hormonal cues to control metabolism. We have previously shown that constitutive nutrient signaling to mTORC1 by means of genetic activation of RagA (expression of GTP-locked RagA, or RagA GTP ) in mice resulted in a fatal energetic crisis at birth. Herein, we rescue neonatal lethality in RagA GTP mice and find morphometric and metabolic alterations that span glucose, lipid, ketone, bile acid and amino acid homeostasis in adults, and a median lifespan of nine months. Proteomic and metabolomic analyses of livers from RagA GTP mice reveal a failed metabolic adaptation to fasting due to a global impairment in PPARα transcriptional program. These metabolic defects are partially recapitulated by restricting activation of RagA to hepatocytes, and revert by pharmacological inhibition of mTORC1. Constitutive hepatic nutrient signaling does not cause hepatocellular damage and carcinomas, unlike genetic activation of growth factor signaling upstream of mTORC1. In summary, RagA signaling dictates dynamic responses to feeding-fasting cycles to tune metabolism so as to match the nutritional state. The mechanistic target of rapamycin complex 1 (mTORC1) integrates nutrient and hormonal signals to control metabolism. Here the authors investigate the effects of constitutive nutrient signaling through genetic activation of RagA in adult mice and show that constitutive nutrient signaling regulates the response to feeding-fasting cycles and does not drive liver cancer.

KRASG12C inhibitors have revolutionized the clinical management of patients with KRASG12C-mutant lung adenocarcinoma. However, patient exposure to these inhibitors leads to the rapid onset of resistance. In this study, we have used genetically engineered mice to compare the therapeutic efficacy and the emergence of tumor resistance between genetic ablation of mutant Kras expression and pharmacological inhibition of oncogenic KRAS activity. Whereas Kras ablation induces massive tumor regression and prevents the appearance of resistant cells in vivo, treatment of KrasG12C/Trp53-driven lung adenocarcinomas with sotorasib, a selective KRASG12C inhibitor, caused a limited antitumor response similar to that observed in the clinic, including the rapid onset of resistance. Unlike in human tumors, we did not observe mutations in components of the RAS-signaling pathways. Instead, sotorasib-resistant tumors displayed amplification of the mutant Kras allele and activation of xenobiotic metabolism pathways, suggesting that reduction of the on-target activity of KRASG12C inhibitors is the main mechanism responsible for the onset of resistance. In sum, our results suggest that resistance to KRAS inhibitors could be prevented by achieving a more robust inhibition of KRAS signaling mimicking the results obtained upon Kras ablation.

Oscar Fernandez-Capetillo and colleagues report a mouse model of the human Seckel syndrome characterized by a deficiency in ATR. The Seckel mice show high levels of replicative stress during embryogenesis, and the adults show premature aging. Although DNA damage is considered a driving force for aging, the nature of the damage that arises endogenously remains unclear. Replicative stress, a source of endogenous DNA damage, is prevented primarily by the ATR kinase. We have developed a mouse model of Seckel syndrome characterized by a severe deficiency in ATR. Seckel mice show high levels of replicative stress during embryogenesis, when proliferation is widespread, but this is reduced to marginal amounts in postnatal life. In spite of this decrease, adult Seckel mice show accelerated aging, which is further aggravated in the absence of p53. Together, these results support a model whereby replicative stress, particularly in utero , contributes to the onset of aging in postnatal life, and this is balanced by the replicative stress–limiting role of the checkpoint proteins ATR and p53.

The use of flow cytometry in mice is constrained by several factors, including the limited availability of mouse-specific antibodies and the need to work with small volumes of peripheral blood. This is particularly challenging for longitudinal studies, as serial blood samples should not exceed 10% of the total blood volume in mice. To address this, we have developed two novel flow cytometry panels designed to extensively analyze immune cell populations in mice during longitudinal studies, using only 50 µL of peripheral blood per panel. Additionally, a third panel has been designed to conduct a more detailed analysis of cytotoxic and inhibitory markers at the end point. These panels have been validated on a lipopolysaccharide (LPS)-induced lung inflammation model. Two experiments were conducted to 1) validate the panels’ sensitivity to immune challenges ( n =12) and 2) to assess intrinsic variability of measurements ( n =5). In both experiments, we collected 50 µL of peripheral blood for each cytometry panel from the maxillary venous sinus. All antibodies were titrated to identify the optimal concentration that maximized the signal from the positive population while minimizing the signal from the negative population. Samples were processed within 1 hour of collection using a MACSQuant Analyzer 16 cytometer. Our results demonstrate that these immunological panels are sensitive enough to detect changes in peripheral blood after LPS induction. Moreover, our findings help determine the sample size needed based on the immune population variability. In conclusion, the panels we have designed enable a comprehensive analysis of the murine immune system with a low blood volume requirement, enabling the measure of both absolute values and relative percentages effectively. This approach provides a robust platform for longitudinal studies in mice and can be used to uncover significant insights into immune responses.

Significance Noonan syndrome (NS) is a developmental disorder caused by germ-line mutations in various components of the RAS signaling pathway. The pathophysiological mechanisms underlying the clinical manifestations in NS patients and the basis for the observed phenotypic variability are poorly understood. To date, mouse models carrying mutations in Protein Tyrosine Phosphatase Non-Receptor type 11 ( Ptpn11 ), Son of Sevenless homolog 1 ( Sos1 ), and Raf1 loci have been described. The new model described here, induced by K- Ras ⱽ¹⁴ᴵ expression, recapitulates most of the NS features including small size, craniofacial dysmorphism, cardiac defects, and myeloproliferative disorders, highly reminiscent of juvenile myelomonocytic leukemia. These mice should help us understand better the phenotypic variations of NS and serve as a preclinical tool to test forthcoming therapies based on the design of novel inhibitors of the RAS pathway. Noonan syndrome (NS) is an autosomal dominant genetic disorder characterized by short stature, craniofacial dysmorphism, and congenital heart defects. NS also is associated with a risk for developing myeloproliferative disorders (MPD), including juvenile myelomonocytic leukemia (JMML). Mutations responsible for NS occur in at least 11 different loci including KRAS . Here we describe a mouse model for NS induced by K -Ras ⱽ¹⁴ᴵ, a recurrent KRAS mutation in NS patients. K -Ras ⱽ¹⁴ᴵ–mutant mice displayed multiple NS-associated developmental defects such as growth delay, craniofacial dysmorphia, cardiac defects, and hematologic abnormalities including a severe form of MPD that resembles human JMML. Homozygous animals had perinatal lethality whose penetrance varied with genetic background. Exposure of pregnant mothers to a MEK inhibitor rescued perinatal lethality and prevented craniofacial dysmorphia and cardiac defects. However, Mek inhibition was not sufficient to correct these defects when mice were treated after weaning. Interestingly, Mek inhibition did not correct the neoplastic MPD characteristic of these mutant mice, regardless of the timing at which the mice were treated, thus suggesting that MPD is driven by additional signaling pathways. These genetically engineered K -Ras ⱽ¹⁴ᴵ–mutant mice offer an experimental tool for studying the molecular mechanisms underlying the clinical manifestations of NS. Perhaps more importantly, they should be useful as a preclinical model to test new therapies aimed at preventing or ameliorating those deficits associated with this syndrome.