Donor-host Lymphatic Anastomosis After Murine Lung Transplantation.

BACKGROUND: Establishing lung lymphatic drainage is thought to be important for successful lung transplantation. To date, there has been a complete absence of knowledge of how lymphatic connections are reestablished after lung transplant, despite evidence suggesting that this does indeed occur. The present study aimed to elucidate whether and how lymphatic anastomosis occurs after lung transplant. METHODS: An orthotopic murine model of lung transplant using lymphatic reporter mice and whole mount immunohistochemistry was used to evaluate the lymphatic vasculature and donor-host connections after lung transplantation. RESULTS: Immunohistochemistry of transplanted lungs demonstrated robust lymphatic vessels, and functional assays demonstrated lymphatic drainage in the transplanted lung that was comparable with that in native lungs. Lymphatic vessels in the donor lung exhibited active sprouting toward the host at the anastomosis within the first 3 days after lung transplantation, with more numerous and complex lymphatic sprouting developing thereafter. Donor lymphatic vessels were numerous at the site of anastomosis by day 14 after lung transplantation and formed physical connections with host lymphatic vessels, demonstrating a mechanism by which lymphatic drainage is reestablished in the transplanted lung. CONCLUSIONS: Lymphatic drainage after lung transplantation is established by active sprouting of donor lymphatic vessels towards the host and the formation of donor-host lymphatic connections at the level of the transplant anastomosis.

Utility of IL-2 Complexes in Promoting the Survival of Murine Orthotopic Forelimb Vascularized Composite Allografts.

BACKGROUND: Vascularized composite allografts (VCA) are novel, life-enhancing forms of transplantation (Tx). However, host immune responses to the various VCA components, especially those involving skin, are complex and make selection of appropriate therapy challenging. Although the interplay between Foxp3+ T regulatory (Treg) cells and CD4 and CD8 effector T cells is of central importance in determining the acceptance or rejection of solid organ allografts, there is little information available concerning the contribution of Treg cells to VCA survival. In addition, the effects of therapeutic expansion in vivo of host Treg cell populations on VCA survival are unknown. METHODS: We established a fully major histocompatibility complex-disparate (BALB/c- > C57BL/6) murine orthotopic forelimb Tx model to explore the benefits of pre- and post-Tx IL-2/anti-IL-2 monoclonal antibody complex (IL-2C) administration to expand the host Treg cell population and thereby attempt to promote Treg cell-dependent VCA survival. RESULTS: Both strategies expanded the Treg cell population in vivo and prolonged VCA survival (P < 0.001), but IL-2C administration pre-Tx led to significantly longer survival compared with IL-2C administration post-Tx (P < 0.01). In addition, compared with post-Tx therapy, pre-Tx therapy resulted in an increased ratio of Treg cells to CD8+ T cells (P < 0.001), reduced proliferation of CD4 and CD8 effector T cells, and reduced production of IFN-γ. Optimal effects were seen when combined with rapamycin therapy, whereas the combination of IL-2C therapy plus calcineurin inhibitor was counterproductive. CONCLUSIONS: Our studies involving different IL-2C-mediated Treg cell expansion strategies demonstrate that pre-Tx IL-2C therapy may be a useful component for developing strategies to promote VCA survival.

HDAC5 controls the functions of Foxp3(+) T-regulatory and CD8(+) T cells.

Histone/protein deacetylases (HDACs) are frequently upregulated in human malignancies and have therefore become therapeutic targets in cancer therapy. However, inhibiting certain HDAC isoforms can have protolerogenic effects on the immune system, which could make it easier for tumor cells to evade the host immune system. Therefore, a better understanding of how each HDAC isoform affects immune biology is needed to develop targeted cancer therapy. Here, we studied the immune phenotype of HDAC5(-/-) mice on a C57BL/6 background. While HDAC5(-/-) mice replicate at expected Mendelian ratios and do not develop overt autoimmune disease, their T-regulatory (Treg) cells show reduced suppressive function in vitro and in vivo. Likewise, CD4(+) T-cells lacking HDAC5 convert poorly to Tregs under appropriately polarizing conditions. To test if this attenuated Treg formation and suppressive function translated into improved anticancer immunity, we inoculated HDAC5(-/-) mice and littermate controls with a lung adenocarcinoma cell line. Cumulatively, lack of HDAC5 did not lead to better anticancer immunity. We found that CD8(+) T cells missing HDAC5 had a reduced ability to produce the cytokine, IFN-γ, in vitro and in vivo, which may offset the benefit of weakened Treg function and formation. Taken together, targeting HDAC5 weakens suppressive function and de-novo induction of Tregs, but also reduces the ability of CD8(+) T cells to produce IFN-γ.

Heat shock protein 70 is required for optimal liver regeneration after partial hepatectomy in mice.

Liver regeneration is a complex process that restores functional tissue after resection or injury, and it is accompanied by transient adenosine triphosphate depletion and metabolic stress in hepatic parenchymal cells. Heat shock protein 70 (Hsp70) functions as a chaperone during periods of cellular stress and induces the expression of several inflammatory cytokines identified as key players during early liver regeneration. We, therefore, hypothesized that Hsp70 is required for the initiation of regeneration. Investigations were carried out in a 70% partial hepatectomy mouse model with mice lacking inducible Hsp70 (Hsp70(-/-)). Liver regeneration was assessed postoperatively with the liver weight/body weight (LW/BW) ratio, and sera and tissues were collected for analysis. In addition, the expression of Hsp-related genes was assessed in a cohort of 23 human living donor liver transplantation donors. In mice, the absence of Hsp70 was associated with a reduced postoperative LW/BW ratio, Ki-67 staining, and tumor necrosis factor α (TNF-α) expression in comparison with wild-type mice. TNF-α expression was also reduced in livers from Hsp70(-/-) mice after induction with lipopolysaccharide (1 mg/kg). Clinically, the transcription of multiple Hsp genes (especially Hsp70 family members) was up-regulated after donor hepatectomy. Together, these results suggest that the early phase of successful liver regeneration requires the presence of Hsp70 to induce TNF-α. Further studies are required to determine whether Hsp70 contributes to liver regeneration as a chaperone by stabilizing specific interactions required for growth signaling or as a paracrine inflammatory signal, as can occur in models of shock.