Citations

Abstract Organoids, which are tiny, lab-grown 3D structures that mimic some organizational and functional properties of human organs, are slowly transforming the face of systems and developmental biology, biomedical research, pharmaceutical testing, environmental toxin testing, and healthcare. Significant investments are essential for the mass production, preservation, and distribution of organoids, with the aim to accelerate innovation and progress across multiple fields—much like the investments made in cell and biologics manufacturing over the past 2 decades.

Abstract Background: Classic reports on lymphocyte development hold that B and T cells develop independently. This concept derives in part from the observation that patients with pure B cell immunodeficiency and hypogammaglobulinemia have a normal thymus and T cell numbers. Our recent findings however challenge this concept. We found that T cell development depends not only on the interaction of T cell precursors with thymic epithelial cells but also on other cells. Here we report that those other cells are B cells. Aims: The purpose of this study was to determine whether B cells drive T cell development and TCR diversification in the thymus. Methods: We compared the number of sub-populations of thymocytes and TCR repertoire diversity in B-cell deficient and B-cell proficient mice and in B cell deficient mice following immunoglobulin (Ig) injections. Total leucocytes numbers were determined with a Coulter counter and numbers of thymocytes sub-populations were calculated by flow cytometry analysis. TCR repertoire diversity was measured by a novel method based on hybridization of TCR Vβ specific cRNA on a gene chip platform. Results: In B-cell deficient mice the number of thymocytes was four times reduced and TCR Vβ chain diversity was up to one million times lower compared with wild type mice. Numbers and diversity were restored by treatment of the mice with gamma globulin (see table). Conclusions: T cell development and diversification is driven by B cells. Mice Number of total thymocytes (mean ± standard deviation) p Value β V TCR diversity of thymocytes (median; min.-max.) p Value C57BL/6 (wild mice) 1.3 x 108 ± 5.1 x 107N=7 4.7 x 106; 1.0 x 105 − 1.1 x 108N=5 JH−/− (B cell immunodeficient mice) 3.1 x 107 ± 1.7 x107N=7 0.002 5.9 x 102; 3.6 x 102 − 1.1 x 103N=5 0.0002 JH−/− treated with Ig 3.9 x 107 ± 1.4 x106N=2 0.20 1.1 x 105; 2.7 x 100 − 7.7 x 105N=4 0.08

Abstract T cell diversity was once thought to depend on the interaction of T cell precursors with thymic epithelial cells. Recent evidence suggests, however, that diversity might arise through the interaction of developing T cells with other cells, the identity of which is not known. In this study we show that T cell diversity is driven by B cells and Ig. The TCR Vβ diversity of thymocytes in mice that lack B cells and Ig is reduced to 6 × 102 from wild-type values of 1.1 × 108; in mice with oligoclonal B cells, the TCR Vβ diversity of thymocytes is 0.01% that in wild-type mice. Adoptive transfer of diverse B cells or administration of polyclonal Ig increases thymocyte diversity in mice that lack B cells 8- and 7-fold, respectively, whereas adoptive transfer of monoclonal B cells or monoclonal Ig does not. These findings reveal a heretofore unrecognized and vital function of B cells and Ig for generation of T cell diversity and suggest a potential approach to immune reconstitution.

Abstract For cardiac transplantation in infants, T cells are depleted and the thymus is removed. These manipulations should cause profound defects in the T cell compartment. To test this concept, 20 subjects who underwent cardiac transplantation in infancy and healthy age-matched subjects were studied. The number of T cells in the blood was nearly normal in all subjects 1–10 years after surgery. However, newly generated T cells were undetectable in 10 recipients and 10-fold less than controls in 10, suggesting absence of thymic function. TCRβ chain diversity, measured by a novel technique, was ∼100-fold lower than controls. T cell function, deduced from levels of human herpesvirus 7 and response to hepatitis B immunization, were notably impaired. Yet cardiac transplant recipients were generally free of opportunistic infections. Our findings demonstrate a novel approach to measuring lymphocyte diversity and suggest that understanding how these subjects resist infection could yield important insights into immune fitness.

Trafficking of cells between mother and fetus during the course of normal pregnancy is well documented. Similarly, cells are known to travel between twins that share either a placenta (i.e. monozygotic) or associated chorion (i.e. monochorionic). Transferred cells are thought to be channelled via the vessels of the placenta or vascular connections established via the chorion and the long-term presence of these cells (i.e. microchimerism) can have important consequences for immune system function and reparative capacity of the host. Whether cells can be transferred between twins with separate placentas and separate chorions (i.e. no vascular connections between placentas) has not been investigated nor have the biological consequences of such a transfer. In the present study, we tested the possibility of this type of cell transfer by injecting human cord blood-derived cells into a portion of the littermates of swine and probing for human cells in the blood and tissues of unmanipulated littermates. Human cells were detected in the blood of 78% of unmanipulated littermates. Human cells were also detected in various tissues of the unmanipulated littermates, including kidney (56%), spleen (33%), thymus (11%) and heart (22%). Human cells were maintained in the blood until the piglets were sacrificed (8 months after birth), suggesting the establishment of long-term microchimerism. Our findings show that the transfer of cells between fetuses with separate placentas and separate chorions is significant and thus such twins may be subject to the same consequences of microchimerism as monozygotic or monochorionic counterparts.

Human cells can fuse with damaged or diseased somatic cells in vivo. Whether human cells fuse in vivo in the absence of disease and with cells of disparate species is unknown. Such a question is of current interest because blood exchanges between species through direct physical contact, via insect vectors or parasitism, are thought to underlie the transmission of zoonotic agents. In a model of human‐pig chimerism, we show that some human hematopoietic stem cells engrafted in pigs contain both human and porcine chromosomal DNA. These hybrid cells divide, express human and porcine proteins, and contribute to porcine nonhematopoietic tissues. In addition, the hybrid cells contain porcine endogenous retroviral DNA sequences and are able to transmit this virus to uninfected human cells in vitro. Thus, spontaneous fusion can occur in vivo between the cells of disparate species and in the absence of disease. The ability of these cell hybrids to acquire and transmit retroviral elements together with their ability to integrate into tissues could explain genetic recombination and generation of novel pathogens.

There is a current need for a small diameter vascular graft due to the limited supply of autogenous grafts and the failure of synthetic grafts due to thrombosis and/or intimal hyperplasia. The use of living cells and tissues to fabricate a small diameter graft (i.e., tissue engineered blood vessel, TEBV) could be useful given the endothelialization potential and biocompatibility benefits of such a graft. However, while sufficient strength has been attained in a TEBV, coordinate compliance has yet to be fine-tuned. In this study we investigate the effects of biological response modifiers, retinoic acid (RA) and ascorbic acid (AA) on TEBV biomechanics as a function of time and subsequently correlate observed RA/AA induced changes in TEBV mechanics with alterations in smooth muscle cell (SMC) biochemistry. TEBVs were constructed using a fibrillar type I collagen network populated by human aortic smooth muscle cells (AoSMC). Following construction this TEBV was treated with 0.3 mM AA and 0.1 mM RA (concentrations found to induce changes in VSMC phenotype). Ultimate tensile stress (UTS), rate of relaxation (RR) and elastic efficiency (EE) of RA/AA treated and untreated TEBVs were measured following 1, 7, 15, 30, 45, and 60 days of treatment. At corresponding time points, the effect of these treatments on collagen and elastin protein synthesis and mRNA expression was examined. RA/AA treated TEBV strength increased and stiffness decreased compared to controls as a function of time. Relative collagen synthesis in treated TEBVs exceeded control levels by nearly two-fold at 15 and 30 days of incubation. RA/AA treated collagen gene expression followed a similar trend. Relative elastin synthesis was also greater in treated TEBVs as compared to untreated TEBVs at 15 and 30 days of incubation and correspondingly elastin mRNA expression was significantly elevated at 15 days of incubation. These data provide evidence that RA/AA treated TEBVs exhibit mechanical properties which more closely mimic those of a native vessel than their untreated counterparts and that changes in extracellular matrix composition and matrix gene expression in the presence of RA/AA treatment may play an important role in the development of said mechanical properties.