Donor bone-marrow CXCR4+ Foxp3+ T-regulatory cells are essential for costimulation blockade-induced long-term survival of murine limb transplants

From replantation to transplantation: The evolution of orthoplastic extremity reconstruction

For more than six decades, the use of the operating microscope for extremity surgery has led to remarkable advances in the management of orthopedic trauma, tumors, infections, and congenital differences. The microsurgical reconstructive ladder ascends from basic microsurgical procedures such as a digital artery or nerve repair to more complex procedures such as autologous tissue transplantation. Functional muscle transfers, toe-to-hand transfers, and recently vascularized composite allotransplantation are the highest rungs on this ladder that help restore extremity function. The development of the orthoplastic approach over the last three decades simultaneously integrates the principles and practices of both orthopedic surgery and plastic surgery for optimal care and salvage of extremities. Clinical, anatomic, and basic science research in reconstructive microsurgery has resulted in significant improvements in extremity salvage, reconstruction, and restoration.

FOXP3 and CXCR4-positive regulatory T cells in the tumor stroma as indicators of tumor immunity in the conjunctival squamous cell carcinoma microenvironment

Conjunctival squamous cell carcinoma (SCC) is the most common ocular surface neoplasia. The purpose of this retrospective study was to examine the role of regulatory T cell (Treg) activity in tumor immunity and investigate the tumor microenvironment as a new treatment focus in conjunctival SCC. Cancer progression gene array and immunohistochemical analyses of FOXP3 as a Treg marker, CD8 as a tumor-infiltrating lymphocyte marker, and CXCR4 expression on activated Tregs were conducted in a series of 31 conjunctival SCC cases. The objective was to investigate the immunoreactive response in tumor cells and stromal cells in the cancer microenvironment. The stroma ratio in tumor cells was investigated by monitoring α-smooth muscle actine (SMA) expression between carcinoma in situ (Tis) and advanced carcinoma (Tadv) (P<0.01). No significant change in PD-L1 expression was observed in this study (P = 0.15). Staining patterns of FOXP3, CD8, and CXCR4 were examined separately between tumor cells and stromal cells in SCC tumors. Differences in staining of FOXP3 in Tregs and CD8 in tumor-infiltrating lymphocytes in tumor stroma in the Tis group were observed compared with the Tadv group (each P<0.01). In addition, double immunostaining of CXCR4/FOXP3 was correlated with progression-free survival (P = 0.049). Double immunostaining of CXCR4/FOXP3 correlated with American Joint Committee on Cancer T-stage, independent of age or Ki67 index (P<0.01). Our results show that FOXP3 and the CXCR4/FOXP3 axis are important pathologic and prognostic factors of ocular surface neoplasia, including SCC. The tumor microenvironment of conjunctival SCC should be considered in the future development of treatment options.

CXCR4 blockade reduces the severity of murine heart allograft rejection by plasmacytoid dendritic cell-mediated immune regulation

Allograft-specific regulatory T cells (T_reg cells) are crucial for long-term graft acceptance after transplantation. Although adoptive T_reg cell transfer has been proposed, major challenges include graft-specificity and stability. Thus, there is an unmet need for the direct induction of graft-specific T_reg cells. We hypothesized a synergism of the immunotolerogenic effects of rapamycin (mTOR inhibition) and plerixafor (CXCR4 antagonist) for T_reg cell induction. Thus, we performed fully-mismatched heart transplantations and found combination treatment to result in prolonged allograft survival. Moreover, fibrosis and myocyte lesions were reduced. Although less CD3⁺ T cell infiltrated, higher T_reg cell numbers were observed. Noteworthy, this was accompanied by a plerixafor-dependent plasmacytoid dendritic cells-(pDCs)-mobilization. Furthermore, in vivo pDC-depletion abrogated the plerixafor-mediated T_reg cell number increase and reduced allograft survival. Our pharmacological approach allowed to increase T_reg cell numbers due to pDC-mediated immune regulation. Therefore pDCs can be an attractive immunotherapeutic target in addition to plerixafor treatment.

Vascularized Bone Marrow Cellular Depletion or Discontinuity Abrogates Protection of Vascularized Composite Allografts in Nonhuman Primates

Background.

Vascularized composite allografts (VCA) have demonstrated good clinical outcomes dependent on chronic immunosuppression. Previous work by our group and others supports that cotransplanted vascularized bone marrow (VBM) as a component of VCA offers immunologic protection to prolong graft survival. We aimed to characterize the requirements and potential mechanisms of VBM-mediated protection of VCA by modifying grafts through various strategies.

Methods.

Experimental groups of mismatched cynomolgus macaque recipients received VCA transplants modified by the following approaches: heterotopic separation of the VCA and VBM components; T-cell depletion of either donor or recipient; irradiation of donor VCA; and infusion of donor bone marrow. All groups received standard immunosuppression with tacrolimus and mycophenolate mofetil.

Results.

Experimental modifications to donor, recipient, or graft all demonstrated short-graft survivals (31 d). Chimerism levels without bone marrow infusion were transient and minimal when detected and were not associated with prolonged survival. Donor bone marrow infusion increased levels of chimerism but resulted in alloantibody production and did not improve graft survival.

Conclusions.

VCA graft survival is significantly reduced compared with previously reported VCA with VBM transplants (348 d; P = 0.01) when the hematopoietic niche is removed, altered, or destroyed via irradiation, depletion, or topographical rearrangement. These experimental manipulations resulted in similar outcomes to VCA grafts without cotransplanted VBM (25 d). These data support the presence of a radiosensitive, T-cell population within the VBM compartment not reconstituted by reinfusion of bone marrow cells.