Preparation and characterization of small-diameter decellularized scaffolds for vascular tissue engineering in an animal model.

BACKGROUND: The development of a suitable extracellular matrix (ECM) scaffold is the first step in vascular tissue engineering (VTE). Synthetic vascular grafts are available as an alternative to autologous vessels in large-diameter arteries (>8 mm) and medium-diameter arteries (6-8 mm). In small-diameter vessels (<6 mm), synthetic vascular grafts are of limited use due to poor patency rates. Compared with a vascular prosthesis, natural tissue ECM has valuable advantages. Despite considerable progress in recent years, identifying an optimal protocol to create a scaffold for use in small-diameter (<6 mm) fully natural tissue-engineered vascular grafts (TEVG), remains elusive. Although reports on different decellularization techniques have been numerous, combination of and comparison between these methods are scarce; therefore, we have compared five different decellularization protocols for making small-diameter (<6 mm) ECM scaffolds and evaluated their characteristics relative to those of fresh vascular controls. RESULTS: The protocols differed in the choice of enzymatic digestion solvent, the use of non-ionic detergent, the durations of the individual steps, and UV crosslinking. Due to their small diameter and ready availability, rabbit arteria carotis were used as the source of the ECM scaffolds. The scaffolds were subcutaneously implanted in rats and the results were evaluated using various microscopy and immunostaining techniques. CONCLUSIONS: Our findings showed that a 2 h digestion time with 1× EDTA, replacing non-ionic detergent with double-distilled water for rinsing and the application of UV crosslinking gave rise to an ECM scaffold with the highest biocompatibility, lowest cytotoxicity and best mechanical properties for use in vivo or in situ pre-clinical research in VTE in comparison.

Recombinant IL-33 prolongs leflunomide-mediated graft survival by reducing IFN-γ and expanding CD4(+)Foxp3(+) T cells in concordant heart transplantation.

Interleukin (IL)-33 is a novel IL-1 family member, and its administration has been associated with promotion of T helper type-2 (Th2) cell activity and cytokines, particularly IL-4 and IL-5 in vivo. Recently, IL-33 was shown to increase CD4(+)Foxp3(+) regulatory T cells (Tregs) and to suppress levels of the Th1-type cytokine IFN-γ in allogeneic heart transplantation in mice. Therefore, we hypothesized that IL-33 and leflunomide (Lef) could prolong graft survival in the concordant mouse-to-rat heart transplantation model. In this model, xenografts undergo acute humoral xenograft rejection (AHXR) typically on day 3 or cell-mediated rejection approximately on day 7 if AHXR is inhibited by Lef treatment. Recipients were treated with Lef (n=6), IL-33 (n=6), IL-33 combined with Lef (n=6), or left untreated (n=6) for survival studies. Heart grafts were monitored until they stopped beating. Mouse heterotopic grafts were performed, and recipients were sacrificed on days 2 and 7 for histological and flow cytometric analyses. The combination of IL-33 and Lef significantly prolonged the grafts from 17.3±2.3 to 2.8±0.4 days, compared to untreated controls. IL-33 administration with Lef, while facilitating Th2-associated cytokines (IL-4 on day 2 but not day 7), also decreased IFN-γ on day 2 and day 7, compared with Lef treatment only. Furthermore, IL-33 with Lef administration caused an expansion of suppressive CD4(+)Foxp3(+) Tregs in rats. The IL-33 and Lef combination therapy resulted in significantly prolonged graft survival, associated with markedly decreased Th1 cells and increased IL-10 levels. In addition, the combination therapy significantly decreased the percentage of CD-45(+) B cells on days 2 and 7, compared with monotherapy. These findings reveal a new immunoregulatory property of IL-33. Specifically, it facilitates regulatory cells, particularly functional CD4(+)Foxp3(+) Tregs that underlie IL-33-mediated cardiac xenograft survival. Moreover, it can decrease Th1 cells and cytokine expression of Th1 T cells in xenograft recipients, for example IFN-γ.

Immunomodulatory Effects of Fentanyl or Dexmedetomidine Hydrochloride Infusion After Allogeneic Heart Transplantation in Mice.

BACKGROUND AND OBJECTIVES: Postoperatively, transplant recipients receive immunosuppressants, as well as sedatives and analgesics. The immunomodulatory effects of these other agents during the induction period following transplantation remain unclear. We aimed to determine whether the agents dexmedetomidine hydrochloride (Dex) and fentanyl (Fen) have immunomodulatory effects during the induction period following heart transplantation (HTx). METHODS: Fifty mice were used for antinociception tests after administration of Dex and Fen, and T cells from 3 naive animals were used for in vitro lymphocyte transformation test (study 1). Fifty-four B6 mice received HTx from BALB/c mice and were treated with Dex, Fen, or neither (study 2). Thirty-six recipients were used for graft survival data and were humanely killed at the time of cessation of heart graft contraction. The remaining 18 were humanely killed at either postoperative day (POD) 4 or 6 for histologic examination of graft survival, as well as in vitro analysis. RESULTS: Based on the results of study 1, daily intraperitoneal administration of Dex at 30 µg/kg or Fen at 0.25 mg/kg was determined to be the optimal dose to induce analgesia without oversedation following HTx. Graft survivals in both Dex- or Fen-treated animals were statistically prolonged compared with control (P < 0.01). Graft survival of Fen-treated recipients was increased up to 15 days, and graft survival of Dex-treated animals was also increased up to 10 days, whereas control mice rejected heart grafts by POD 7. Mixed lymphocyte reaction responses on POD 4 showed statistically lower responses in Dex-treated recipients and Fen-treated recipients when compared with controls (P < 0.01). Cytokine profiles of splenocytes showed markedly fewer interferon γ-positive splenocytes in Fen-treated recipients on POD 4. CONCLUSIONS: These data suggest that both Dex and Fen have immunomodulatory properties in the induction period following transplantation.