Meir Ohana

THE EFFECT OF HALOFUGINONE, AN INHIBITOR OF COLLAGEN TYPE I SYNTHESIS, ON URETHRAL STRICTURE FORMATION: IN VIVO AND IN VITRO STUDY IN A RAT MODEL

PURPOSE Urethral strictures are narrowing of the urethra caused by fibrosis due to excessive collagen production in response to an insult. We evaluated the effects of halofuginone, a potent inhibitor of collagen alpha1(I) gene expression, on experimentally induced urethral strictures in vivo and on rat urethral fibroblasts in vitro. MATERIALS AND METHODS Applying coagulation current to the male rat urethra produced urethral strictures. Halofuginone was given to the animals for 7 days, starting on the day of stricture formation, either orally at 1 and 5 ppm in the diet or by injection of 0.03% halofuginone solution into the urethra. All rats were sacrificed on day 21. Collagen alpha1(I) gene expression was evaluated by in situ hybridization, collagen content by sirius red staining and urethral morphology by urethrogram. RESULTS Coagulation current produced reproducible strictures with a typical urethrogram appearance, which were associated with increases in collagen alpha1(I) gene expression and collagen content at the stricture site. Halofuginone injected into the urethra or orally at 5 ppm normalized the urethrogram and prevented increases in collagen alpha1(I) gene expression and collagen content. Halofuginone at a concentration of 10-8 M. inhibited the collagen secreted by fibroblasts derived from the rat male urethra, which was due to inhibition of the collagen alpha1(I) gene expression. CONCLUSIONS Halofuginone prevented stricture formation and may become an important mode of therapy in the prevention of restenosis during urethral stricture formation.

Reduction in dermal fibrosis in the tight-skin (Tsk) mouse after local application of halofuginone.

The effect of dermal application of halofuginone-an inhibitor of collagen type I synthesis-on skin collagen and collagen alpha1(I) gene expression in an animal model of scleroderma and chronic graft versus host disease (cGvHD) was evaluated. Halofuginone-containing cream was applied on the tight-skin mouse (Tsk) and skin biopsies were taken for collagen staining by sirius red and for collagen alpha1(I) gene expression by in situ hybridization. In addition, cell proliferation was evaluated by immunostaining for proliferation cell nuclear antigen (PCNA) alone or in combination with collagen alpha1(I) probe. The number of mast cells was assessed by toluidine blue. Dermal application of halofuginone (0.01%) for 60 days was as good as systemic administration (1 microg/mouse/day) in reducing collagen alpha1(I) gene expression in skin biopsy and almost as good in reducing skin width. Halofuginone was stable and effective only at acidic pH. The effect of halofuginone (0.03%) was time-dependent. After 40 days of daily treatment, a significant reduction in the collagen alpha1(I) gene expression was observed and further decrease was observed after 60 days. The reduction in collagen alpha1(I) gene expression and the reduction in the proliferation of dermal fibroblasts probably occur in the same subset of cells. No effect of halofuginone on the proliferation of keratinocytes or on mast cell number was observed. These results suggest that target-oriented application of halofuginone may become a novel therapy for fibrotic disorders in general and for scleroderma in particular.

Alleviation of acute and chronic graft-versus-host disease in a murine model is associated with glucocerebroside-enhanced natural killer T lymphocyte plasticity.

Background. Natural killer T (NKT) lymphocytes play a role in graft-versus-host disease GVHD (GVHD). Glucocerebroside (GC) is a naturally occurring glycolipid that plays a role in the immune modulation of NKT lymphocytes. This study aims to determine the effect of GC in murine models of semiallogeneic/acute and chronic GVHD. Methods. Acute and chronic GVHD were generated by fusion of splenocytes from C57BL/6 to (C57BL/6xBalb/c) F1 mice, and from B10.D2 donor mice into Balb/c, respectively. Recipients were treated daily with GC. Histological and immunological parameters of GVHD were assessed. Results. Treatment with GC significantly alleviated GVHD in both models The beneficial effect of GC was associated with an increase in the intrahepatic/peripheral NKT lymphocyte ratio in the semiallogeneic/acute model. This ratio was decreased in the chronic GVHD model. A significant increase in intrahepatic CD8+ lymphocyte trapping was noted in the semiallogeneic/acute model, whereas the opposite effect was observed in the chronic GVHD model. Administration of GC led to decreased serum interferon-&ggr; and increased serum interleukin-4 levels in the Th1-mediated model, whereas the opposite effect was observed in the Th2-mediated models. Conclusions. GC ameliorates GVHD in both Th1- and Th2-mediated murine models, suggesting it is able to differentially affect the immune system. GC may alleviate immunologically incongruous disorders, and may be associated with “fine tuning” of immune responses.

Adoptive transfer of small numbers of DX5+ cells alleviates graft-versus-host disease in a murine model of semiallogeneic bone marrow transplantation : a potential role for NKT lymphocytes

Summary:Natural killer T (NKT) lymphocyte cells are a subset of regulatory lymphocytes with important immunemodulatory effects. Our aim was to evaluate the effect of transplantation of NKT lymphocytes on graft versus host disease (GVHD) in a murine model of semiallogeneic BMT. GVHD was generated by infusion of 2 × 107 splenocytes from C57BL/6 donor mice into irradiated (C57BL/6 × Balb/c)F1 recipient mice. Adoptive transfer of increasing numbers of DX5+ cells was performed. Recipient mice were followed for histological parameters of GVHD-associated liver, bowel, and cutaneous injury. Intrahepatic and intrasplenic lymphocytes were isolated and analyzed by FACS for CD4+ and CD8+ subpopulations. It was seen that adoptive transfer of 4.5 × 106 DX5+ cells significantly alleviated GVHD-related hepatic, bowel, and cutaneous injury, and improved survival (85% survival on day 28). In contrast, depletion of DX5+ cells led to severe GVHD-associated multiorgan injury and 100% mortality. A direct correlation with the number of transplanted DX5+ cells was noted (maximal effect with transplantation of 4.5 × 106 DX5+ cells). Tolerance induction was associated with an increased peripheral CD4/CD8 ratio, intrahepatic trapping of CD8 lymphocytes and a shift towards a Th2-type cytokine profile, manifested by decreased IL-12/IL10, IL-12/IL-4, IFNγ/IL-10, and IFNγ/IL-4 ratios. Transplantation of DX5+ cells holds promise as a novel therapeutic measure for GVHD.

NK Cell Receptor NKp46 Regulates Graft-versus-Host Disease

SUMMARY Hematopoietic stem cell transplantation (HSCT) is often the only curative treatment for a wide variety of hematologic malignancies. Donor selection in these diseases is crucial, given that transplanted cells can mediate not only the desired graft-versus-leukemia effect but also graft-versus-host disease (GVHD). Here, we demonstrate that in the absence of NKp46, a major killer receptor expressed by human and mouse natural killer (NK) cells, GVHD is greatly exacerbated, resulting in rapid mortality of the transplanted animals because of infection with commensal bacteria. Furthermore, we demonstrate that the exacerbated GVHD is the result of an altered ability of immune cells to respond to stimulation by immature dendritic cells. Because high and low expression of NKp46 on NK cells is observed in different individuals, our data indicate that choosing NKp46-high donors for the treatment of different hematologic malignancies might lead to better tumor eradication while minimizing GVHD.

Prevention of esophageal strictures in a caustic burn model using halofuginone, an inhibitor of collagen type I synthesis

Objective: Esophageal strictures caused by caustic injury continue to be a plaguing problem. Halofuginone (HF) has been proven to inhibit the formation of fibrosis in various animal models and human diseases. Its mechanism appears to be through the suppression of the production of collagen α1(I) and transforming growth factor‐β signaling pathway. We tried to assess whether HF would have an effect on the formation of strictures after inducing caustic esophageal.

Induction of oral tolerance in bone marrow transplantation recipients suppresses graft-versus-host disease in a semiallogeneic mouse model

Summary:Graft-versus-host disease (GVHD) is the major obstacle for successful allogeneic stem cell transplantation (SCT). Morbidity and mortality are high, and novel therapeutic strategies are required. Current therapy, which is based mainly on immunosuppression, is associated with a high degree of complications. Immune hyporesponsiveness induced by oral antigen administration has recently been shown to prevent the development of chronic GVHD (cGVHD) in a murine model. The aim of the present study was to evaluate whether it is possible to induce tolerance and to alleviate GVHD in a semiallogeneic transplantation model in mice. GVHD was generated by infusing 2 × 107 splenocytes from C57BL/6 donor mice into (C57BL/6 × Balb/c)F1 recipient mice, which received 7 Gy 60Co total body irradiation (TBI) prior to transplantation. Oral tolerance was induced by feeding recipient F1 mice with five oral doses of proteins, 50 μg/mouse, extracted from C57BL/6 splenocytes on alternate days following transplantation. In vitro mixed lymphocyte reaction (MLR) from tolerized and nontolerized mice was performed. Recipient mice were followed for chimerism, and for clinical and histological parameters of GVHD. Induction of tolerance was documented by a significant reduction in MLR response of tolerated vs nontolerated splenocytes. A significant alleviation of the clinical and pathological manifestation of GVHD was observed in the liver, small bowel, and skin. Tolerance induction did not jeopardize engraftment. These results may constitute a step towards reducing the frequency of GVHD via manipulation of the immune system.

Effect of Halofuginone, a Collagen α1(I) Inhibitor, on Wound Healing in Normal and Irradiated Skin: Implication for Hematopoietic Stem Cell Transplantation

It is a major interest in the field of hematopoietic stem cell transplantation to reduce scarring of healing wounds with overdeposition of collagen due to radiation injury or graft-versus-host disease. Halofuginone (HF) inhibits collagen α1(I) gene expression and overdeposition of collagen. We examined the effect of HF on the healing of full-depth incision wounds inflicted in normal skin or skin areas compromised by local preirradiation with 18 Gy. Preirradiation significantly decreased the tensile strength of the healing wounds at day 14 (by ∼60%, p < 0.0001). In contrast, HF treatment did not significantly decrease the strength of wounds inflicted in both normal and preirradiated skin. Histological evaluation revealed that HF induced moderate thinning of the dermis accompanied by elevated thickness of the epidermis and enhanced rejoining of subdermal muscles in the wound area. HF only minimally reduced total collagen deposition in both groups, with minor changes in the level of more matured fibrillar collagen network. Our study demonstrates that HF does not significantly affect wound strength. This encourages the possible use of HF as an antifibrotic agent with minimal complications for post-hematopoietic stem cell transplantation complications including radiation toxicity and graft-versus-host disease.