Sistiana Aiello

In the early 1970s, aspirin (acetylsalicylic acid) was shown to inhibit platelet aggregation by irreversibly acetylating platelet cyclooxygenase (COX), thereby suppressing the synthesis of its pro-aggregating product thromboxane A₂ (TxA₂)...

Transplanted organs carry donor immune cells into the recipient, the majority of which are tissue-resident macrophages (TRMs). The role they play in guiding the fate of the transplanted organ toward acceptance or rejection remains elusive. TRMs originate from both embryonic and bone marrow-derived precursors. Embryo-derived TRMs retain the embryonic capability to proliferate, so they are able to self-renew and, theoretically, persist for extended periods of time after transplantation. Bone marrow-derived TRMs do not proliferate and must constantly be replenished by adult circulating monocytes. Recent studies have aimed to clarify the different roles and interactions between donor TRMs, recipient monocytes, and monocyte-derived macrophages (MFs) after organ transplantation. This review aims to shed light on how MFs affect the fate of a transplanted organ by differentiating between the role of donor TRMs and that of MFs derived from graft infiltrating monocytes.

Induced pluripotent stem cells (iPSC) have huge potential as cell therapy for various diseases, given their potential for unlimited self-renewal and capability to differentiate into a wide range of cell types. Although autologous iPSCs represents the ideal source for patient-tailored regenerative medicine, the high costs of the extensive and time-consuming production process and the impracticability for treating acute conditions hinder their use for broad applications. An allogeneic iPSC-based strategy may overcome these issues, but it carries the risk of triggering an immune response. So far, several approaches based on genome-editing techniques to silence human leukocyte antigen class I (HLA-I) or II (HLA-II) expression have been explored to overcome the immune rejection of allogeneic iPSCs. In this study, we employed the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9) system to delete the β2-Microglobulin (B2M) and the Class II Major Histocompatibility Complex Transactivator (CIITA) genes, essential for the correct surface expression of HLA-I and HLA-II proteins. The resulting hypoimmunogenic iPSC line has a normal karyotype, expresses the pluripotency stem cell markers, and is capable of differentiating into the three embryonic germ layers. Furthermore, we showed that it specifically retains the ability to differentiate towards different liver cells, such as endothelial-like cells, hepatocyte-like cells, and hepatic stellate-like cells. Our results indicate that hypoimmunogenic iPSCs could give a new cost-effective and off-the-shelf opportunity for cell therapy in liver diseases.

Kidney transplantation is the therapy of choice for patients who suffer from end-stage renal diseases. Despite improvements in surgical techniques and immunosuppressive treatments, long-term graft survival remains a challenge. A large body of evidence documented that the complement cascade, a part of the innate immune system, plays a crucial role in the deleterious inflammatory reactions that occur during the transplantation process, such as brain or cardiac death of the donor and ischaemia/reperfusion injury. In addition, the complement system also modulates the responses of T cells and B cells to alloantigens, thus playing a crucial role in cellular as well as humoral responses to the allograft, which lead to damage to the transplanted kidney. Since several drugs that are capable of inhibiting complement activation at various stages of the complement cascade are emerging and being developed, we will discuss how these novel therapies could have potential applications in ameliorating outcomes in kidney transplantations by preventing the deleterious effects of ischaemia/reperfusion injury, modulating the adaptive immune response, and treating antibody-mediated rejection.

Increased expression of the enzyme autotaxin (ATX) and the consequently increased levels of its product, lysophosphatidic acid (LPA), have been reported in several primary tumors. The role of LPA as a direct modulator of tumor cell functions—motility, invasion and migration capabilities as well as resistance to apoptotic death—has been recognized by numerous studies over the last two decades. Notably, evidence has recently been accumulating that shows that LPA also contributes to the development of the tumor microenvironment (TME). Indeed, LPA plays a crucial role in inducing angiogenesis and lymphangiogenesis, triggering cellular glycolytic shift and stimulating intratumoral fibrosis. In addition, LPA helps tumoral cells to escape immune surveillance. Treatments that counter the TME components, in order to deprive cancer cells of their crucial support, have been emerging among the promising new anticancer therapies. This review aims to summarize the latest knowledge on how LPA influences both tumor cell functions and the TME by regulating the activity of its different elements, highlighting why and how LPA is worth considering as a molecular target for new anticancer therapies.

Background: Tissue fibrosis is the final common phase of chronic allograft injury, the leading cause of late graft loss in kidney transplantation. Preclinical evidence points to the involvement of lysophosphatidic acid (LPA), a bioactive phospholipid, in the development of renal fibrosis. Objectives: We assessed whether treatment with an orally available inhibitor of autotaxin (ATXi), the main LPA-producing enzyme, could slow the progression of chronic allograft injury in a fully major histocompatibility complex-mismatched rat kidney transplant model and compared its effects with those of the angiotensin-converting enzyme inhibitor lisinopril. Methods: Kidney allograft recipients were given ciclosporin for the first 15 postoperative days to prevent early acute rejection. Thereafter, they received either no treatment or ATXi or lisinopril and were followed for 180 days after transplantation. Results: Renal LPA levels were increased in allograft rats, providing the rationale for using ATXi in this model. Chronic treatment with ATXi or lisinopril limited progressive proteinuria and ameliorated tubulointerstitial fibrosis compared with allograft rats, although the effects were more robust under ATX inhibition. The administration of ATXi, but not lisinopril, attenuated systemic hypertension, reduced intragraft T cell infiltration, and eventually improved renal graft survival. Conclusions: In summary, ATXi had protective effects on indices of chronic allograft injury and could be of therapeutic add-on value in the kidney transplant setting. Notably, an ATX inhibitor is currently being investigated in 2 large phase 3 studies in idiopathic pulmonary fibrosis, underscoring the clinical relevance of our findings.

Danger molecules from ischemic tissues activate innate immunity by increasing dendritic cell (DC) immunogenicity. To evaluate whether hypoxia directly impacts on DC antigen presentation capacity, we used mouse B6-OVA-DCs, expressing chicken OVA peptides in the context of class I and II MHC, and OVA-specific TCR-transgenic B6 syngeneic CD8 (OTI) and CD4 (OTII) T cells. Bone-marrow derived OVA-DCs were pre-exposed for 4hr to 1% (hypoxia) or 20% O2 (normoxia) and then used as stimulators of OTI or OTII T cells for 2 days. Higher numbers of IFNγ-producing CD8 and CD4 T cell clones emerged (p<0.05) in response to hypoxic than to normoxic OVA-DCs (OTI 162±26, OTII 72±20 vs: OTI 115±23, OTII 36±15 spots/50000 cells, n=4). A larger increase of IFNγ-producing clones was found in response to hypoxic OVA-DCs exposed to conditioned medium (cm) from hypoxic OVA-B6 renal tubuli vs normoxic OVA-DC exposed to cm from normoxic tubuli (p<0.01). Similarly, non-transgenic B6-DCs pre-incubated with OVA protein (plus hypoxic tubular cm) during hypoxia, induced higher numbers of IFNγ-producing T cell clones than normoxic B6 DCs (pre-incubated with OVA plus normoxic tubular cm): OTI 60±15, OTII 50±10 vs OTI 31±8, OTII 23±6 spots, n=3, p<0.05. This indicates that hypoxia augmented the capacity of DCs to present and cross-present antigens to CD4 and CD8 T cells, respectively. Altogether these results suggest that hypoxia increases antigen presentation by DCs both by direct action on DCs and through release of soluble factors from injured tissues. Such events eventually translate into an augmented adaptive T cells immune response.

Ischemia/reperfusion injury (IRI), occurring after transplantation, activates TLRs/IL-1R on inflammatory leukocytes amplifying adaptive immune response. In a mouse model of renal artery clamp deficiency of Tir8, a IL-1R/TLR negative regulator, aggravated post-ischemic acute renal failure in association with intrarenal leukocyte accumulation. We investigated the role of TIR8 in modulating post-transplant IRI and inflammatory response in mouse model of syngeneic kidney transplant. Donor and recipient C57BL/6 mice were congenic for CD45 leukocyte antigen to allow discriminating between intragraft recipient and donor leukocytes. Wild-type (wt-group n=5) or Tir8-/- (Tir8-/--group, n=5) donor kidneys were exposed to 30 min cold ischemia before transplant. Transient impairment of graft function was found at 1day post-transplant in wt-group (BUN: 1day 53±19, 30day: 27±3mg/dl). At variance the Tir8-/--group showed irreversible severe graft dysfunction (BUN: 1day 95±23, 30day: 67±23 mg/dl, P<0.05 vs wt-group). Both at 10 and 30 days post-transplant lower numbers (P<0.05) of intragraft leukocytes were found in the wt-group (20±9/field, 61±18/field, respectively) vs the Tir8-/--group (104±17/field, 117±24/field, respectively). At 10 days the majority of leukocytes were of donor origin both in the wt and the Tir8-/- groups (79±8%, 78±2%, respectively). At 30days, in the wt-group the majority of intragraft leukocytes were of recipient origin (63±6%) while 63±2% of intragraft leukocytes were of donor origin in the Tir8-/--group. These results indicate that TIR8 modulates post-transplant IRI possibly by suppressing expansion and activation of resident leukocytes within the kidney graft.