Soluble ST2 in end-stage heart failure, before and after support with a left ventricular assist device.

BACKGROUND: The interleukin-33 (IL-33)/suppressor of tumorigenicity 2 (ST2) pathway is suggested to play an important role in fibrosis, remodelling and the progression of heart failure (HF). Increased soluble (sST2) levels are associated with adverse outcome in the average HF population. Less is known about sST2 levels in end-stage HF. Therefore, we studied sST2 levels in end-stage HF and the effect of unloading by left ventricular assist device (LVAD) support on sST2 levels. METHOD AND RESULTS: Serial plasma measurements of sST2 were performed pre-implantation and 1, 3 and 6 months after (LVAD) implantation in 38 patients. sST2 levels were elevated in end-stage HF just prior to LVAD implantation (74.2 ng/mL [IQR 54.7-116.9]; normal <35 ng/mL) and decreased substantially during LVAD support, to 29.5 ng/mL [IQR 24.7-46.6](P < .001). Patients with INTERMACS profile I had significantly higher sST2 levels compared to patients in profile II and profile III. A moderate correlation was found between sST2 and C-reactive protein (r = .580, P < .010). CONCLUSION: Levels of sST2 are elevated in end-stage HF patients with variability that suggests multiple inputs to a pro-inflammatory and pro-fibrotic pathway. Cardiogenic shock and increased C-reactive protein levels are associated with higher sST2 levels. LVAD support results in a significant drop in sST2 levels with normalization within 3 months postimplantation. This suggests that LVAD support leads to lessening of fibrosis and inflammation, which might eventually be used to target medical policy: explantation of the LVAD versus permanent use or cardiac transplantation.

T-Cell Mediated Immune Rejection of Beta-2-Microglobulin Knockout Induced Pluripotent Stem Cell-Derived Kidney Organoids.

Immune evasive induced pluripotent stem cell (iPSC)-derived kidney organoids, known as "stealth" organoids, hold promise for clinical transplantation. To address immune rejection, we investigated the impact of genetically modifying human leukocyte antigen (HLA) class I in kidney organoids prior to transplantation. By using CRISPR-Cas9, we successfully knocked out beta-2-microglobulin (B2M), resulting in iPSCs devoid of HLA class I surface expression. In vitro, the B2M knockout protected kidney organoids derived from these iPSCs against T-cell rejection. To assess in vivo protection, unmodified (control) and B2M-/- kidney organoids were transplanted into humanized mice engrafted with human peripheral blood mononuclear cells (PBMCs). Successful engraftment of human PBMCs was confirmed, and after 4 weeks, we observed no discernible difference in the infiltration rate, proliferation, or cytotoxicity of CD4+ and CD8+ T cells between control and B2M-/- organoids. Both groups of organoids showed compromised tissue integrity, displaying tubulitis and loss of tubule integrity. Notably, while B2M-/- organoids failed to express HLA class I on their cell surface, there was preexisting expression of HLA class II in both control and B2M-/- organoids transplanted into mice with human PBMCs. HLA class II expression was not limited to antigen-presenting cells but also evident in epithelial cells of the kidney organoid, posing an additional immunological challenge to its transplantation. Consequently, we conclude that B2M knockout alone is insufficient to protect iPSC-derived kidney organoids from T-cell-mediated immune rejection. Additionally, our findings suggest that modulating HLA class II signaling will be necessary to prevent rejection following transplantation.

Inhibition of complement activation by CD55 overexpression in human induced pluripotent stem cell derived kidney organoids.

End stage renal disease is an increasing problem worldwide driven by aging of the population and increased prevalence of metabolic disorders and cardiovascular disease. Currently, kidney transplantation is the only curative option, but donor organ shortages greatly limit its application. Regenerative medicine has the potential to solve the shortage by using stem cells to grow the desired tissues, like kidney tissue. Immune rejection poses a great threat towards the implementation of stem cell derived tissues and various strategies have been explored to limit the immune response towards these tissues. However, these studies are limited by targeting mainly T cell mediated immune rejection while the rejection process also involves innate and humoral immunity. In this study we investigate whether inhibition of the complement system in human induced pluripotent stem cells (iPSC) could provide protection from such immune injury. To this end we created knock-in iPSC lines of the membrane bound complement inhibitor CD55 to create a transplant-specific protection towards complement activation. CD55 inhibits the central driver of the complement cascade, C3 convertase, and we show that overexpression is able to decrease complement activation on both iPSCs as well as differentiated kidney organoids upon stimulation with anti-HLA antibodies to mimic the mechanism of humoral rejection.