BackgroundTwo coding renal risk variants (RRVs) of the APOL1 gene (G1 and G2) are associated with large increases in CKD rates among populations of recent African descent, but the underlying molecular mechanisms are unknown. Mammalian cell culture models are widely used to study cytotoxicity of RRVs, but results have been contradictory. It remains unclear whether cytotoxicity is RRV-dependent or driven solely by variant-independent overexpression. It is also unknown whether expression of the reference APOL1 allele, the wild-type G0, could prevent cytotoxicity of RRVs.MethodsWe generated tetracycline-inducible APOL1 expression in human embryonic kidney HEK293 cells and examined the effects of increased expression of APOL1 (G0, G1, G2, G0G0, G0G1, or G0G2) on known cytotoxicity phenotypes, including reduced viability, increased swelling, potassium loss, aberrant protein phosphorylation, and dysregulated energy metabolism. Furthermore, whole-genome transcriptome analysis examined deregulated canonical pathways.ResultsAt moderate expression, RRVs but not G0 caused cytotoxicity in a dose-dependent manner that coexpression of G0 did not reduce. RRVs also have dominant effects on canonical pathways relevant for the cellular stress response.ConclusionsIn HEK293 cells, RRVs exhibit a dominant toxic gain-of-function phenotype that worsens with increasing expression. These observations suggest that high steady-state levels of RRVs may underlie cellular injury in APOL1 nephropathy, and that interventions that reduce RRV expression in kidney compartments may mitigate APOL1 nephropathy.

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Purpose: The COVID-19 pandemic accelerated the need to develop remote monitoring of graft function in lung transplant (LT) recipients. While home spirometry has been used previously in LT, long-term engagement has been poor. We aimed to improve engagement and allow efficient data and symptom collection using Bluetooth enabled home spirometers coupled with a digital chatbot. Methods: We implemented an automated, chat-based mobile health intervention via text message or email paired with Bluetooth-enabled handheld spirometers. The chatbot engaged LT recipients weekly in a personalized, automated chat with symptom assessment, education modules, and spirometer data collection. Clinical team members received automatic notification of concerning symptoms or FEV1 declines of >10%. The correlation between home spirometry FEV1 values and lab-based values were assessed with Pearson's coefficient. Results: We mailed home spirometers to 424 patients. Between 5/4/2020 and 10/21/2020, 311 patients enrolled in the automated chat and, of these, 273 patients submitted ≥1 FEV1 measure, (median 13; IQR 6-23) over 24 weeks. The largest drop in FEV1 engagement came after the first week in each patient's chat experience; 65% of those that submitted an FEV1 at baseline entered a value at week one and 72% at week two. However, after this initial decline, engagement remained stable through 24 weeks (57-72%, Figure 1.A). Home spirometry FEV1 correlated closely with in-lab spirometry (rho = 0.94) (Figure 1.B) Conclusion: LT recipients engaged at high rates with a chatbot mobile health intervention and home spirometers to report their FEV1, allowing reliable home-based monitoring of LT recipients. Further investigation will be needed to improve engagement further. Given the projected need for social distancing, and increasing role of telemedicine for long-term management, a chatbot-linked home spirometer may be a powerful tool to detect early graft dysfunction.

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The phenomenon of diminishing hematocrit after in vivo liver and lung xenotransplantation and during ex vivo liver xenoperfusion has largely been attributed to action by resident liver porcine macrophages, which bind and destroy human erythrocytes. Porcine sialoadhesin (siglec‐1) was implicated previously in this interaction. This study examines the effect of porcine genetic modifications, including knockout of the CMAH gene responsible for expression of Neu5Gc sialic acid, on the adhesion of human red blood cells (RBCs) to porcine macrophages. Wild‐type (WT) porcine macrophages and macrophages from several strains of genetically engineered pigs, including CMAH gene knockout and several human transgenes (TKO+hTg), were incubated with human RBCs and “rosettes” (≥3 erythrocytes bound to one macrophage) were quantified by microscopy. Our results show that TKO+hTg genetic modifications significantly reduced rosette formation. The monoclonal antibody 1F1, which blocks porcine sialoadhesin, significantly reduced rosette formation by WT and TKO+hTg macrophages compared with an isotype control antibody. Further, desialation of human RBCs with neuraminidase before addition to WT or TKO+hTg macrophages resulted in near‐complete abrogation of rosette formation, to a level not significantly different from porcine RBC rosette formation on porcine macrophages. These observations are consistent with rosette formation being mediated by binding of sialic acid on human RBCs to sialoadhesin on porcine macrophages. In conclusion, the data predict that TKO+hTg genetic modifications, coupled with targeting of porcine sialoadhesin by the 1F1 mAb, will attenuate erythrocyte sequestration and anemia during ex vivo xenoperfusion and following in vivo liver, lung, and potentially other organ xenotransplantation.