Characterization of two rat models of cystic fibrosis—KO and F508del CFTR—Generated by Crispr-Cas9

Background: Genetically engineered animals are essential for gaining a proper understanding of the disease mechanisms of cystic fibrosis(CF). The rat is a relevant laboratory model for CF because of its zootechnical capacity, size, and airway characteristics, including the presence of submucosal glands.Methods: We describe the generation of a CF rat model(F508 del) homozygous for the p.Phe508 del mutation in the transmembrane conductance regulator(Cftr) gene. This model was compared to new Cftr-/-rats(CFTR KO). Target organs in CF were examined by histological staining of tissue sections and tooth enamel was quantified by micro-computed tomography. The activity of CFTR was evaluated by nasal potential difference(NPD) and short-circuit current measurements. The effect of VX-809 and VX-770 was analyzed on nasal epithelial primary cell cultures from F508 del rats.Results: Both newborn F508 del and Knock out(KO) animals developed intestinal obstruction that could be partly compensated by special diet combined with an osmotic laxative. The two rat models exhibited CF phenotypic anomalies such as vas deferens agenesis and tooth enamel defects. Histology of the intestine, pancreas, liver, and lungs was normal. Absence of CFTR function in KO rats was confirmed ex vivo by short-circuit current measurements on colon mucosae and in vivo by NPD, whereas residual CFTR activity was observed in F508 del rats. Exposure of F508 del CFTR nasal primary cultures to a combination of VX-809 and VX-770 improved CFTR-mediated Cl-transport.Conclusions: The F508 del rats reproduce the phenotypes observed in CFTR KO animals and represent a novel resource to advance the development of CF therapeutics.

Targeted therapy for capillary-venous malformations

Sporadic venous malformations are genetic conditions primarily caused by somatic gain-of-function mutation of PIK3CA or TEK,an endothelial transmembrane receptor signaling through PIK3CA.Venous malformations are associated with pain,bleedings,thrombosis,pulmonary embolism,esthetic deformities and,in severe cases,life-threatening situations.No authorized medical treatment exists for patients with venous malformations.Here,we created a genetic mouse model of PIK3CA-related capillary venous malformations that replicates patient phenotypes.We showed that these malformations only partially signal through AKT proteins.We compared the efficacy of different drugs,including rapamycin,a mTORC1 inhibitor,miransertib,an AKT inhibitor and alpelisib,a PI3Kαinhibitor at improving the lesions seen in the mouse model.We demonstrated the effectiveness of alpelisib in preventing vascular malformations’occurrence,improving the already established ones,and prolonging survival.Considering these findings,we were authorized to treat 25 patients with alpelisib,including 7 children displaying PIK3CA(n=16)or TEK(n=9)-related capillary venous malformations resistant to usual therapies including sirolimus,debulking surgical procedures or percutaneous sclerotherapies.We assessed the volume of vascular malformations using magnetic resonance imaging(MRI)for each patient.Alpelisib demonstrated improvement in all 25 patients.Vascular malformations previously considered intractable were reduced and clinical symptoms were attenuated.MRI showed a decrease of 33.4%and 27.8%in the median volume of PIK3CA and TEK malformations respectively,over 6 months on alpelisib.In conclusion,this study supports PI3Kαinhibition as a promising therapeutic strategy in patients with PIK3CA or TEK-related capillary venous malformations.