Maternal dendritic cells influence fetal allograft response following murine in-utero hematopoietic stem cell transplantation.

BACKGROUND: Intrauterine hematopoietic stem cell transplantation (IUT), potentially curative in congenital haematological disease, is often inhibited by deleterious immune responses to donor cells resulting in subtherapeutic donor cell chimerism (DCC). Microchimerism of maternal immune cells (MMc) trafficked into transplanted recipients across the placenta may directly influence donor-specific alloresponsiveness, limiting DCC. We hypothesized that dendritic cells (DC) among trafficked MMc influence the development of tolerogenic or immunogenic responses towards donor cells, and investigated if maternal DC-depletion reduced recipient alloresponsiveness and enhanced DCC. METHODS: Using transgenic CD11c.DTR (C57BL/6) female mice enabled transient maternal DC-depletion with a single dose of diphtheria toxin (DT). CD11c.DTR females and BALB/c males were cross-mated, producing hybrid pups. IUT was performed at E14 following maternal DT administration 24 h prior. Bone marrow-derived mononuclear cells were transplanted, obtained from semi-allogenic BALB/c (paternal-derived; pIUT), C57BL/6 (maternal-derived; mIUT), or fully allogenic (aIUT) C3H donor mice. Recipient F1 pups were analyzed for DCC, while maternal and IUT-recipient immune cell profile and reactivity were examined via mixed lymphocyte reactivity functional assays. T- and B-cell receptor repertoire diversity in maternal and recipient cells were examined following donor cell exposure. RESULTS: DCC was highest and MMc was lowest following pIUT. In contrast, aIUT recipients had the lowest DCC and the highest MMc. In groups that were not DC-depleted, maternal cells trafficked post-IUT displayed reduced TCR & BCR clonotype diversity, while clonotype diversity was restored when dams were DC-depleted. Additionally, recipients displayed increased expression of regulatory T-cells and immune-inhibitory proteins, with reduced proinflammatory cytokine and donor-specific antibody production. DC-depletion did not impact initial donor chimerism. Postnatal transplantation without immunosuppression of paternal donor cells did not increase DCC in pIUT recipients; however there were no donor-specific antibody production or immune cell changes. CONCLUSIONS: Though maternal DC depletion did not improve DCC, we show for the first time that MMc influences donor-specific alloresponsiveness, possibly by expanding alloreactive clonotypes, and depleting maternal DC promotes and maintains acquired tolerance to donor cells independent of DCC, presenting a novel approach to enhancing donor cell tolerance following IUT. This may have value when planning repeat HSC transplantations to treat haemoglobinopathies.

Enhancing mesenchymal stem cell response using uniaxially stretched poly(ε-caprolactone) film micropatterns for vascular tissue engineering application.

Regeneration of tunica media with anisotropic architecture still remains a challenging issue for vascular tissue engineering (TE). Herein, we present the development of flexible poly(ε-caprolactone) (PCL) film micropatterns to regulate mesenchymal stem cells (MSCs) function for tunica media construction. Results showed that uniaxial thermal stretching of PCL films resulted in topographical micropatterns comprising of ridges/grooves, and improved mechanical properties, including yield stress, Young's modulus, and fracture stress without sacrificing film elasticity. Culturing on such PCL film micropatterns, MSCs self-aligned along the ridges with a more elongated morphology as compared to that of the un-stretched film group. Moreover, MSCs obtained a contractile SMCs-like phenotype, with ordered organization of cellular stress filaments and upregulated expression of the contractile makers, including SM-α-actin, calponin, and SM-MHC. The PCL film micropatterns could be rolled into a small-diameter 3D tubular scaffold with circumferential anisotropy of ridges/grooves, and in the incorporation of MSCs, which facilitated a hybrid sandwich-like vascular wall construction with ordered cell architecture similar to that of the tunica media. These results provide insights of how geometric cues are able to regulate stem cells with desired functions and have significant implications for the designing of a functionalized vascular TE scaffold with appropriate topographical geometries for guiding tunica media regeneration with microscale control of cell alignment and genetic expression.