Generation of HLA-Universal iPSC-Derived Megakaryocytes and Platelets for Survival Under Refractoriness Conditions.

Platelet (PLT) transfusion is indispensable to maintain homeostasis in thrombocytopenic patients. However, PLT transfusion refractoriness is a common life-threatening condition observed in multitransfused patients. The most frequent immune cause for PLT transfusion refractoriness is the presence of alloantibodies specific for human leukocyte antigen (HLA) class I epitopes. Here, we have silenced the expression of HLA class I to generate a stable HLA-universal induced pluripotent stem cell (iPSC) line that can be used as a renewable cell source for the generation of low immunogenic cell products. The expression of HLA class I was silenced by up to 82% and remained stable during iPSC cultivation. In this study, we have focused on the generation of megakaryocytes (MK) and PLTs from a HLA-universal iPSC source under feeder- and xeno-free conditions. On d 19, differentiation rates of MKs and PLTs with means of 58% and 76% were observed, respectively. HLA-universal iPSC-derived MKs showed polyploidy with DNA contents higher than 4n and formed proPLTs. Importantly, differentiated MKs remained silenced for HLA class I expression. HLA-universal MKs produced functional PLTs. Notably, iPSC-derived HLA-universal MKs were capable to escape antibody-mediated complement- and cellular-dependent cytotoxicity. Furthermore, HLA-universal MKs were able to produce PLTs after in vivo transfusion in a mouse model indicating that they might be used as an alternative to PLT transfusion. Thus, in vitro produced low immunogenic MKs and PLTs may become an alternative to PLT donation in PLT-based therapies and an important component in the management of severe alloimmunized patients.

miR-145 Is a Promising Therapeutic Target to Prevent Cornea Scarring.

Corneal scarring is an expected outcome of corneal injury or infection and is one of the major causes for visual loss. The formation of light-scattering myofibroblasts is thought to be the underlying cause of corneal haze formation. Recently, microRNA (miRNA) gene therapies have been proposed as novel approach for complex processes such as fibrosis and scarring. In this study, we focused on the role of miR-145 in corneal myofibroblast differentiation and function. Analysis of human corneal scar tissue and transforming growth factor (TGF)-ß1-induced corneal myofibroblasts showed a 13- and 4-fold increase of miR-145, respectively, compared with healthy cornea and nonstimulated fibroblasts (p<0.01). Furthermore, myofibroblasts showed an increase in α-smooth muscle actin (α-SMA) expression and a decreased expression of Kruppel-like factor 4 (KLF4). These results indicated that TGF-ß1 increases miR-145 expression, which indirectly induces α-SMA expression via downregulation of KLF4, a known negative regulator of α-SMA. Consistently, miR-145 silencing in corneal myofibroblasts using a specific antimiR resulted in increased KLF4 and strongly decreased α-SMA expression. In addition, miR-145 inhibition also significantly decreased myofibroblast contractility, migratory capacity, and TGF-ß1 secretion, which are all thought to contribute to corneal scarring. Hence, miR-145 plays an important role in TGF-ß1-stimulated corneal myofibroblast differentiation and activation, which can be reversed by miR-145 silencing. Therefore, we suggest miR-145 as a promising therapeutic target for miRNA-based gene therapy to prevent or treat visual loss caused by corneal fibrosis.

Local substitution of GDF-15 improves axonal and sensory recovery after peripheral nerve injury.

The growth/differentiation factor-15, GDF-15, has been found to be secreted by Schwann cells in the lesioned peripheral nervous system. To investigate whether GDF-15 plays a role in peripheral nerve regeneration, we substituted exogenous GDF-15 into 10-mm sciatic nerve gaps in adult rats and compared functional and morphological regeneration to a vehicle control group. Over a period of 11 weeks, multiple functional assessments, including evaluation of pinch reflexes, the Static Sciatic Index and of electrophysiological parameters, were performed. Regenerated nerves were then morphometrically analyzed for the number and quality of regenerated myelinated axons. Substitution of GDF-15 significantly accelerated sensory recovery while the effects on motor recovery were less strong. Although the number of regenerated myelinated axons was significantly reduced after GDF-15 treatment, the regenerated axons displayed advanced maturation corroborating the results of the functional assessments. Our results suggest that GDF-15 is involved in the complex orchestration of peripheral nerve regeneration after lesion.