Should a Stoma Be Used After Intestinal Transplant

As we all acknowledge benefits of ostomies, they can come with significant morbidity, quality of life issues, and major complications, especially during reversal procedures. In recent years, we have started to observe that similar graft and patient survival can be achieved without ostomies in certain cases. This observation and practice adopted in a few large-volume transplant centers opened a new discussion about the necessity of ostomies in intestinal transplantation. There is still more time and randomized studies will be needed to better understand and analyze the risk/benefits of "No-ostomy" approach in intestinal transplantation.

Use of Post-transplant Cyclophosphamide Treatment to Build a Tolerance Platform to Prevent Liquid and Solid Organ Allograft Rejection

Corneal transplantation (CT) is the most frequent type of solid organ transplant (SOT) performed worldwide. Unfortunately, immunological rejection is the primary cause of graft failure for CT and therefore advances in immune regulation to induce tolerance remains an unmet medical need. Recently, our work and others in pre-clinical studies found that cyclophosphamide (Cy) administered after (“post-transplant,” PTCy) hematopoietic stem cell transplantation (HSCT), i.e., liquid transplants is effective for graft vs. host disease prophylaxis and enhances overall survival. Importantly, within the past 10 years, PTCy has been widely adopted for clinical HSCT and the results at many centers have been extremely encouraging. The present studies found that Cy can be effectively employed to prolong the survival of SOT, specifically mouse corneal allografts. The results demonstrated that the timing of PTCy administration is critical for these CT and distinct from the kinetics employed following allogeneic HSCT. PTCy was observed to interfere with neovascularization, a process critically associated with immune rejection of corneal tissue that ensues following the loss of ocular “immune privilege.” PTCy has the potential to delete or directly suppress allo-reactive T cells and treatment here was shown to diminish T cell rejection responses. These PTCy doses were observed to spare significant levels of CD4⁺ FoxP3⁺ (Tregs) which were found to be functional and could readily receive stimulating signals leading to their in vivo expansion via TNFRSF25 and CD25 agonists. In total, we posit future studies can take advantage of Cy based platforms to generate combinatorial strategies for long-term tolerance induction.

Superior immune reconstitution using Treg-expanded donor cells versus PTCy treatment in preclinical HSCT models

Posttransplant cyclophosphamide (PTCy) has been found to be effective in ameliorating acute graft-versus-host disease (GVHD) in patients following allogeneic hematopoietic stem cell transplantation (aHSCT). Adoptive transfer of high numbers of donor Tregs in experimental aHSCT has shown promise as a therapeutic modality for GVHD regulation. We recently described a strategy for in vivo Treg expansion targeting two receptors: TNFRSF25 and CD25. To date, there have been no direct comparisons between the use of PTCy and Tregs regarding outcome and immune reconstitution within identical groups of transplanted mice. Here, we assessed these two strategies and found both decreased clinical GVHD and improved survival long term. However, recipients transplanted with Treg-expanded donor cells (TrED) exhibited less weight loss early after HSCT. Additionally, TrED recipients demonstrated less thymic damage, significantly more recent thymic emigrants, and more rapid lymphoid engraftment. Three months after HSCT, PTCy-treated and TrED recipients showed tolerance to F1 skin allografts and comparable immune function. Overall, TrED was found superior to PTCy with regard to weight loss early after transplant and initial lymphoid engraftment. Based on these findings, we speculate that morbidity and mortality after transplant could be diminished following TrED transplant into aHSCT recipients, and, therefore, that TrED could provide a promising clinical strategy for GVHD prophylaxis.

Marked in Vivo Donor Regulatory T Cell Expansion via Interleukin-2 and TL1A-Ig Stimulation Ameliorates Graft-versus-Host Disease but Preserves Graft-versus-Leukemia in Recipients after Hematopoietic Stem Cell Transplantation

Regulatory T cells (Tregs) are critical for self-tolerance. Although adoptive transfer of expanded Tregs limits graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HSCT), ex vivo generation of large numbers of functional Tregs remains difficult. Here, we demonstrate that in vivo targeting of the TNF superfamily receptor TNFRSF25 using the TL1A-Ig fusion protein, along with IL-2, resulted in transient but massive Treg expansion in donor mice, which peaked within days and was nontoxic. Tregs increased in multiple compartments, including blood, lymph nodes, spleen, and colon (GVHD target tissue). Tregs did not expand in bone marrow, a critical site for graft-versus-malignancy responses. Adoptive transfer of in vivo-expanded Tregs in the setting of MHC-mismatched or MHC-matched allogeneic HSCT significantly ameliorated GVHD. Critically, transplantation of Treg-expanded donor cells facilitated transplant tolerance without GVHD, with complete sparing of graft-versus-malignancy. This approach may prove valuable as a therapeutic strategy promoting transplantation tolerance.

Murine model of the Ehlers-Danlos syndrome. col5a1 haploinsufficiency disrupts collagen fibril assembly at multiple stages

The most commonly identified mutations causing Ehlers-Danlos syndrome (EDS) classic type result in haploinsufficiency of proalpha1(V) chains of type V collagen, a quantitatively minor collagen that co-assembles with type I collagen as heterotypic fibrils. To determine the role(s) of type I/V collagen interactions in fibrillogenesis and elucidate the mechanism whereby half-reduction of type V collagen causes abnormal connective tissue biogenesis observed in EDS, we analyzed mice heterozygous for a targeted inactivating mutation in col5a1 that caused 50% reduction in col5a1 mRNA and collagen V. Comparable with EDS patients, they had decreased aortic stiffness and tensile strength and hyperextensible skin with decreased tensile strength of both normal and wounded skin. In dermis, 50% fewer fibrils were assembled with two subpopulations: relatively normal fibrils with periodic immunoreactivity for collagen V where type I/V interactions regulate nucleation of fibril assembly and abnormal fibrils, lacking collagen V, generated by unregulated sequestration of type I collagen. The presence of the aberrant fibril subpopulation disrupts the normal linear and lateral growth mediated by fibril fusion. Therefore, abnormal fibril nucleation and dysfunctional fibril growth with potential disruption of cell-directed fibril organization leads to the connective tissue dysfunction associated with EDS.

Alpha 2(I) collagen deficient oim mice have altered biomechanical integrity, collagen content, and collagen crosslinking of their thoracic aorta

Collagen and elastin are the primary determinants of vascular integrity, with elastin hypothesized to be the major contributor to aortic compliance and type I collagen the major contributor to aortic strength and stiffness. Type I collagen is normally heterotrimeric composed of two alpha1(I) and one alpha2(I) collagen chains, alpha1(I)(2)alpha2(I). Recent investigations have reported that patients with recessively inherited forms of Ehlers Danlos syndrome that fail to synthesize proalpha2(I) chains have increased risks of cardiovascular complications. To assess the role of alpha2(I) collagen in aortic integrity, we used the osteogenesis imperfecta model (oim) mouse. Oim mice, homozygous for a COL1A2 mutation, synthesize only homotrimeric type I collagen, alpha1(I)3. We evaluated thoracic aortas from 3-month-old oim, heterozygote, and wildtype mice biomechanically for circumferential breaking strength (Fmax) and stiffness (IEM), histologically for morphological differences, and biochemically for collagen content and crosslinking. Circumferential biomechanics of oim and heterozygote descending thoracic aortas demonstrated the anticipated reduced Fmax and IEM relative to wildtype mice. Histological analyses of oim descending aortas demonstrated reduced collagen staining relative to wildtype aortas suggesting decreased collagen content, which hydroxyproline analyses of ascending and descending oim aortas confirmed. These findings suggest the reduced oim thoracic aortic integrity correlates with the absence of the alpha2(I)collagen chains and in part with reduced collagen content. However, oim ascending aortas also demonstrated a significant increase in pyridinoline crosslinks/collagen molecule as compared to wildtype ascending aortas. The role of increased collagen crosslinks is uncertain; increased crosslinking may represent a compensatory mechanism for the decreased integrity.

Novel collagen glomerulopathy in a homotrimeric type I collagen mouse (oim)

BACKGROUND

Oim/oim mice [osteogenesis imperfecta model; homozygous null for the proalpha2(I) collagen gene] synthesize exclusively the homotrimeric type I collagen isotype, alpha1(I)3, and are unable to synthesize the normal heterotrimeric type I collagen isotype, alpha1(I)2alpha2(I). Previous studies of the oim/oim mouse have focused on the musculoskeletal system, with no systematic evaluation of other organ systems.

METHODS

Multiple tissues from oim/oim, oim/+ (heterozygous) and +/+ (wild-type) mice were examined for gross and histological abnormalities. Tissues were stained with (1) hematoxylin and eosin (to assess lesion formation), (2) picrosirius red (collagen content), and (3) periodic acid methenamine silver (basement membrane). Kidneys were further evaluated ultrastructurally by electron microscopy and immunohistochemically with anti-alpha1(I) and anti-alpha1(III) collagen antibodies.

RESULTS

Histological analyses revealed accumulations of picrosirius red-positive material, consistent with collagen, in glomeruli of 28/29 oim/oim mice, with no evidence of mesangial cell proliferation. Only the most severely affected animals had evidence of increased capillary basement membrane thickening or mild inflammation around the affected glomeruli. Electron microscopy confirmed the presence of fibrillar collagen. Immunohistochemistry with anti-alpha1(I) collagen antibodies confirmed accumulation of type I collagen in the oim/oim glomeruli. The +/+ and oim/+ kidneys had normal mesangium with no evidence of infiltration of collagenous material.

CONCLUSIONS

This study demonstrates the first evidence, to our knowledge, of abnormal glomerular collagen deposition associated with a type I collagen defect. Further in vivo and in vitro studies are necessary to elucidate the mechanistic, functional, and pathological significance of the oim/oim collagen glomerulopathy.

The role of type I collagen in aortic wall strength with a homotrimeric

PURPOSE

Elastin and collagen (types I and III) are the primary load-bearing elements in aortic tissue. Deficiencies and derangements in elastin and type III collagen have been associated with the development of aneurysmal disease. However, the role of type I collagen is less well defined. The purpose of this study was to define the role of type I collagen in maintaining biomechanical integrity in the thoracic aorta, with a mouse model that produces homotrimeric type I collagen [alpha1(I)]3, rather than the normally present heterotrimeric [alpha1(I)]2 alpha2(I) type I collagen isotype.

METHODS

Ascending and descending thoracic aortas from homozygous (oim/oim ), heterozygous (oim /+), and wildtype (+/+) mice were harvested. Circumferential and longitudinal load-extension curves were used as a means of determining maximum breaking strength (Fmax) and incremental elastic modulus (IEM). Histologic analyses and hydroxyproline assays were performed as a means of determining collagen organization and content.

RESULTS

Circumferentially, the ascending and descending aortas of oim /oim mice demonstrated significantly reduced Fmax, with an Fmax of only 60% and 23%, respectively, of wildtype mice aortas. Oim/oim descending aortas demonstrated significantly greater compliance (decreased IEM), and the ascending aortas also exhibited a trend toward increased compliance. Reduced breaking strength was also demonstrated with longitudinal extension of the descending aorta.

CONCLUSION

The presence of homotrimeric type I collagen isotype (absence of alpha2(I) collagen) significantly weakens the aorta. This study demonstrates the integral role of type I collagen in the biomechanical and functional properties of the aorta and may help to elucidate the role of collagen in the development of aneurysmal aortic disease or dissection.