Solid organ transplantation following end-organ failure in recipients of hematopoietic stem cell transplantation in children

The intragraft vascularized bone marrow induces secondary donor-specific mystacial pad allograft tolerance

Introduction

Vascularized bone marrow (VBM) is essential in tolerance induction through chimerism. We hypothesized that the inclusion of VBM contributes to the induction of mystacial pad allotransplantation tolerance.

Method

In this study, 19 VBM, nine mystacial pad, and six sequential VBM and mystacial pad allografts were transplanted from Brown Norway (BN) rats to Lewis (LEW) rats to test our hypothesis. The VBM recipients were divided into antilymphocyte serum (ALS) monotherapy group (two doses of ALS on day 3 pretransplantation and day 1 posttransplantation), immunosuppressant group [a week of 2 mg/kg/day tacrolimus (Tac) and 3 weeks of 3 mg/kg/day rapamycin (RPM)], and combined therapy group. The mystacial pad recipients were divided into VBM and non-VBM transplantation groups, and both groups were treated with an immunosuppression regimen that consists of ALS, Tac, and RPM. For the recipients of sequential VBM and mystacial pad allotransplantations, additional Tac was given 1 week after mystacial pad transplantation. Allograft survival, donor-specific tolerance, and chimerism level were evaluated.

Results

With the administration of ALS and short-term Tac and RPM treatments, VBM recipients demonstrated long-term graft survival (>120 days) with persistent chimerism for 30 days. CD3+ T cells from tolerant rats showed donor-specific hyporesponsiveness and tolerance to donor skin grafts but not to third-party counterparts. Furthermore, mystacial pad graft recipients with VBM transplantation exhibited a higher allograft survival rate than those without VBM transplantation [median survival time (MST) >90 days vs. 70 days, p < 0.05].

Conclusion

This study demonstrated that VBM transplantation is an efficient strategy to induce and maintain donor-specific tolerance for an osseous-free allograft.

Hematopoietic stem cell transplantation: graft versus host disease and pathology of gastrointestinal tract, liver, and lung

Hematopoietic stem cell transplantation (HCT), formerly known as bone marrow transplantation, is an integral part of treatment for many hematological malignancies. HCT is associated with several complications and comorbidities with differential effects on a wide spectrum of organs and tissues. We present an update on HCT-associated complications such as graft versus host disease (GVHD) and infection, with focus on the surgical pathology of the gastrointestinal (GI) tract, liver, and lung. Although the grading system for GI tract acute GVHD was proposed 40 years ago, recent studies have shed light on minimal histologic criteria for diagnosis of GVHD, as well as its differential diagnosis, including histologic effects of various medications. GI dysfunction in autologous transplant recipients is increasingly appreciated and patients are often biopsied. Acute liver injury in HCT is often due to sinusoidal obstruction syndrome (previously known as venoocclusive disease), or acute GVHD. Liver dysfunction at later time posttransplantation may be associated with acute or chronic GVHD, iron overload, or other causes of hepatitis. Lung injury in HCT is multifactorial, and it remains crucially important to diagnose and treat pulmonary infections. The pulmonary biopsy yields clinically unsuspected diagnoses in the majority of cases and its utilization is likely to increase. The pathology of the skin and kidney in HCT patients are detailed in accompanying articles.

Renal pathology associated with hematopoietic stem cell transplantation

The kidney is subject to a large variety of injurious factors before, during, and after hematopoietic stem cell transplantation (HCT), leading to a high incidence of acute kidney injury in the peritransplant period. Chronic kidney disease is estimated to impact 15% to 20% of HCT recipients. Although renal biopsies may be deferred in the setting of thrombotic microangiopathy, acute self-limited impairment, or slowly progressive functional decline, in many patients renal biopsy yields important diagnostic insight to guide treatment. Light microscopic, immunofluorescence, and ultrastructural analysis often reveals a number of concurrent abnormalities in glomeruli, tubules, interstitium, and vessels. Meta-analysis of the literature reveals that membranous nephropathy is the most commonly reported glomerular lesion in the setting of HCT, followed by minimal change disease. Autopsy and biopsy studies show that clinical criteria lack sensitivity and specificity for renal acute and chronic thrombotic microangiopathy. Viral infection and other causes of interstitial nephritis and tubular injury are important findings in HCT renal biopsies, which in many instances may not be clinically suspected. Given the complexity and variability of HCT protocols, clinicopathologic correlation is needed.