Vascular Endothelial Growth Factor and Activin-A Serum Levels Following Allogeneic Hematopoietic Stem Cell Transplantation

Cytokine levels following allogeneic hematopoietic cell transplantation: a match-pair analysis of home care versus hospital care

Following allogeneic hematopoietic cell transplantation (HCT), patients living near the hospital were treated at home instead of in isolation in the hospital. We analyzed cytokines using Luminex assays for the first 3 weeks after HCT and compared patients treated at home (n = 42) with matched patients isolated in the hospital (n = 37). In the multivariate analysis, patients treated at home had decreased GM-CSF, IFN-γ (p < 0.01), IL-13, IL-5 (p < 0.05), and IL-2 (p < 0.07). Bloodstream infections, anti-thymocyte globulin, G-CSF treatment, immunosuppression, reduced-intensity conditioning (RIC), related vs. unrelated donors, and graft source affected various cytokine levels. When patients with RIC were analyzed separately, home care patients had reduced G-CSF (p = 0.04) and increased vascular endothelial growth factor (VEGF, p = 0.001) at 3 weeks compared with hospital care patients. Patients with low GM-CSF (p < 0.036) and low IFNγ (p = 0.07) had improved survival. Acute GVHD grades III-IV was seen in 7% and 16% of home care and hospital care patients, respectively. One-year transplantation-related mortality was 7% and 16% and survival at 5 years was 69% and 57% in the two groups, respectively. To conclude, patients treated in the hospital showed varying increased levels of GM-CSF, IFN-γ, IL-13, G-CSF, IL-5, and IL-2 and decreased VEGF, which may contribute to acute GVHD.

Follistatin and Soluble Endoglin Predict 1-Year Nonrelapse Mortality after Allogeneic Hematopoietic Cell Transplantation

Damage-associated angiogenic factors (AFs), including follistatin (FS) and soluble endoglin (sEng), are elevated in circulation at the onset of acute graft-versus-host disease (GVHD). We hypothesized that regimen-related tissue injury also might be associated with aberrant AF levels and sought to determine the relevance of these AF on nonrelapse mortality (NRM) in patients with acute GVHD and those without acute GVHD. To test our hypothesis, we analyzed circulating levels of FS, sEng, angiopoietin-2 (Ang2), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) A and B, placental growth factor (PlGF), and soluble VEGF receptor (sVEGFR)-1 and -2, in plasma samples from patients enrolled on Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 0402 (n = 221), which tested GVHD prophylaxis after myeloablative hematopoietic stem cell transplantation (HCT). We found that the interaction between FS and sEng had an additive effect in their association with 1-year NRM. In multivariate analysis, patients with the highest levels of day +28 FS and sEng had a 14.9-fold greater hazard ratio (HR) of NRM (95% confidence interval, 3.2 to 69.4; P < .01) when compared with low levels of FS and sEng. We validated these findings using an external cohort of patients (n = 106). Pre-HCT measurements of FS and sEng were not associated with NRM, suggesting that elevations in these factors early post-HCT may be consequences of early regimen-related toxicity. Determining the mechanisms responsible for patient-specific vulnerability to treatment toxicities and endothelial damage associated with specific AF elevation may guide interventions to reduce NRM post-HCT.

Initiation of acute graft-versus-host disease by angiogenesis

The inhibition of inflammation-associated angiogenesis ameliorates inflammatory diseases by reducing the recruitment of tissue-infiltrating leukocytes. However, it is not known if angiogenesis has an active role during the initiation of inflammation or if it is merely a secondary effect occurring in response to stimuli by tissue-infiltrating leukocytes. Here, we show that angiogenesis precedes leukocyte infiltration in experimental models of inflammatory bowel disease and acute graft-versus-host disease (GVHD). We found that angiogenesis occurred as early as day+2 after allogeneic transplantation mainly in GVHD typical target organs skin, liver, and intestines, whereas no angiogenic changes appeared due to conditioning or syngeneic transplantation. The initiation phase of angiogenesis was not associated with classical endothelial cell (EC) activation signs, such as Vegfa/VEGFR1+2 upregulation or increased adhesion molecule expression. During early GVHD at day+2, we found significant metabolic and cytoskeleton changes in target organ ECs in gene array and proteomic analyses. These modifications have significant functional consequences as indicated by profoundly higher deformation in real-time deformability cytometry. Our results demonstrate that metabolic changes trigger alterations in cell mechanics, leading to enhanced migratory and proliferative potential of ECs during the initiation of inflammation. Our study adds evidence to the hypothesis that angiogenesis is involved in the initiation of tissue inflammation during GVHD.

Angiogenic Factors Correlate with T Cell Immune Reconstitution and Clinical Outcomes after Double-Unit Umbilical Cord Blood Transplantation in Adults

Umbilical cord blood (UCB) is a valuable graft source for allogeneic hematopoietic stem cell transplantation (HSCT) in patients who lack adult donors. UCB transplantation (UCBT) in adults results in delayed immune reconstitution, leading to high infection-related morbidity and mortality. Angiogenic factors and markers of endothelial dysfunction have biologic and prognostic significance in conventional HSCT, but their role in UCBT has not been investigated. Furthermore, the interplay between angiogenesis and immune reconstitution has not been studied. Here we examined whether angiogenic cytokines, angiopoietin-1 (ANG-1) and vascular endothelial growth factor (VEGF), or markers of endothelial injury, thrombomodulin (TM) and angiopoietin-2 (ANG-2), associate with thymic regeneration as determined by T cell receptor excision circle (TREC) values and recovery of T cell subsets, as well as clinical outcomes in adult recipients of UCBT. We found that plasma levels of ANG-1 significantly correlated with the reconstitution of naive CD4+CD45RA+ and CD8+CD45RA+ T cell subsets, whereas plasma levels of VEGF displayed a positive correlation with CD4+CD45RO+ T cells and regulatory T cells and a weak correlation with TRECs. Assessment of TM and ANG-2 revealed a strong inverse correlation of both factors with naive T cells and TRECs. The angiogenic capacity of each patient's plasma, as determined by an in vitro angiogenesis assay, positively correlated with VEGF levels and with reconstitution of CD4+ T cell subsets. Higher VEGF levels were associated with worse progression-free survival and higher risk of relapse, whereas higher levels of TM were associated with chronic graft-versus-host disease and nonrelapse mortality. Thus, angiogenic factors may serve as valuable markers associated with T cell reconstitution and clinical outcomes after UCBT.

Angiogenic factors and inflammation in steroid-refractory acute graft-vs-host disease

Steroid-refractory acute graft-vs-host disease (aGVHD) remains a frequent and often fatal complication of allogeneic hematopoietic cell transplantation. Recent evidence suggests that angiogenic factors-growth factors that contribute to blood vessel development-may be involved in tissue healing and restitution after inflammatory insults such as aGVHD. However, some angiogenic factors may also be involved in inflammation and worsen clinical outcomes. In this review, we summarize the data relevant to angiogenic factors that may contribute to healing after aGVHD (epidermal growth factor and vascular endothelial growth factor A) and angiogenic factors that may promote inflammation after aGVHD (placental growth factor and follistatin). It is currently unknown whether changes in these factors are a cause or a consequence of aGVHD. Mechanistic studies in the coming years will clarify their roles and identify new pathways for improving outcomes in steroid-refractory aGVHD.

Circulating angiogenic factors associated with response and survival in patients with acute graft-versus-host disease: results from Blood and Marrow Transplant Clinical Trials Network 0302 and 0802

Circulating angiogenic factors (AF) reflect tissue healing capacity, although some AF can also contribute to inflammation and are indicative of endothelial dysfunction. The AF milieu in acute graft-versus-host disease (aGVHD) has not been broadly characterized. We hypothesized that patients with abundant AF involved in repair/regeneration versus those mediating damage/inflammation would have improved outcomes. Circulating AF known predominantly for repair/regeneration (epidermal growth factor [EGF], fibroblast growth factor-1 and -2, heparin binding-EGF-like growth factor, and vascular endothelial growth factor-A [VEGF-A], -C, and -D) and for damage/inflammation (angiopoietin-2, endothelin-1, soluble endoglin [sEng], follistatin [FS], leptin, and placental growth factor [PlGF]) were measured in a discovery set of hematopoietic cell recipients with grade III and IV aGVHD and compared with controls, then validated in 2 aGVHD cohorts enrolled in Blood and Marrow Transplant Clinical Trials Network (BMT CTN) trials 0302 (n = 105, serum) and 0802 (n = 158, plasma) versus controls without aGVHD (n = 53, serum). Levels of EGF and VEGF-A were lower than in controls at the onset of aGVHD in both trials and higher with complete response to first-line aGVHD therapy in CTN 0802. FS and PlGF were elevated in aGVHD measured in either serum or plasma. At day 28 after initial aGVHD therapy, elevated FS was an independent negative prognostic factor for survival in both cohorts (hazard ratio, 9.3 in CTN 0302; 2.8 in CTN 0802). These data suggest that circulating AF are associated with clinical outcomes after aGVHD and, thus, may contribute to both pathogenesis and recovery.

GVHD after allogeneic haematopoietic SCT for AML: angiogenesis, vascular endothelial growth factor and VEGF receptor expression in the BM

There is increasing evidence suggesting that both angiogenesis and endothelial injury are involved in GVHD. To study the dynamics of angiogenesis, we examined 26 patients with AML who had undergone allogeneic haematopoietic SCT. All were in CR and had either acute GVHD (aGVHD) or chronic GVHD (cGVHD). We performed immunohistochemical studies of BM microvessel density (MVD) using Abs against vascular-endothelial (VE)-cadherin, CD34 and CD105, and expression of vascular endothelial growth factor (VEGF) and its receptors VEGFR-1 and VEGFR-2. At the time of diagnosis, the MVD in AML patients was higher than that in the normal controls, and the MVD decreased after induction chemotherapy. Patients with aGVHD had a significantly higher MVD than patients without aGVHD. Conversely, patients with cGVHD did not have a significantly different MVD. In previous aGVHD, we also found more VEGF+ megakaryocytes. XY FISH in sex-mismatched patients showed that the BM blood vessels consisted mainly of recipient endothelial cells. Taken together, these results suggest that new vessel formation and the VEGF/VEGFR system are involved in aGVHD.

Novel treatment concepts for graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) are potentially lethal complications after stem cell transplantation (SCT). Steroids are the appropriate first-line treatment for both. However, if patients do not adequately benefit from steroid therapy, mortality is high and standardized treatment algorithms are lacking. This is mainly because of limited data from prospective, randomized clinical trials. In addition, most of the available treatment options only induce clinical benefits in a limited proportion of patients. Thus, there is an urgent clinical need to develop more potent immunosuppressive treatment strategies for patients suffering from acute or chronic steroid-refractory GVHD while maintaining the graft versus tumor effect to avoid a potential rise in relapse-related mortality. The increasing knowledge about host- as well as donor-derived variables favoring GVHD development and the increasing armamentarium of immune-modulatory agents entering preclinical and clinical research will probably allow more effective treatment of GVHD in the future. This review describes novel developments in the treatment of steroid-refractory GVHD, with a special focus on the rationale behind promising pharmacologic compounds or up-coming cellular therapies.

Small vessels, big trouble in the kidneys and beyond: hematopoietic stem cell transplantation–associated thrombotic microangiopathy

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a challenging diagnosis after hematopoietic stem cell transplantation. Although endothelial injury represents the final common pathway of disease, the exact pathophysiology of TA-TMA remains unclear. Potential causes include infections, chemotherapy, radiation, and calcineurin inhibitors. Recent literature addresses the roles of cytokines, graft-versus-host disease, the coagulation cascade, and complement in the pathogenesis of TA-TMA. Current diagnostic criteria are unsatisfactory, because patients who have received a transplant can have multiple other reasons for the laboratory abnormalities currently used to diagnose TA-TMA. Moreover, our lack of understanding of the exact mechanism of disease limits the development and evaluation of potential treatments. Short- and long-term renal complications contribute to TA-TMA's overall poor prognosis. In light of these challenges, future research must validate novel markers of disease to aid in early diagnosis, guide current and future treatments, prevent long-term morbidity, and improve outcomes. We focus on TA-TMA as a distinct complication of hematopoietic stem cell transplantation, emphasizing the central role of the kidney in this disease.

The importance of neovascularization and its inhibition for allogeneic hematopoietic stem cell transplantation

GVHD and tumor relapse are fundamental problems in allogeneic HSCT. Recent research has linked neovascularization to GVHD, tumor growth, and graft-versus-tumor (GVT) activity. Damage of the endothelium by the conditioning regimen provides the initiation stimulus for recruitment of donor-derived endothelial cells and their progenitors. During the early inflammatory phase of GVHD there is considerable neovascularization facilitating migration of inflammatory cells to target organs. In the course of GVHD, however, the vasculature itself becomes a target of alloreactive donor T cells. As a consequence, later stages of GVHD are characterized by fibrosis and rarefaction of blood vessels. Importantly, the inhibition of tumor-neovascularization by activated donor T cells that release antiangiogenic substances contributes to GVT and may be enhanced by pharmacologic inhibition of neovascularization. Furthermore, the therapeutic inhibition of neovascularization may improve immunotherapy for cancer by enhancing leukocyte infiltration in tumor tissue because of normalization of tumor vessels and stimulation of leukocyte-vessel wall interactions. These insights identify important mechanisms underlining the importance of neovascularization for allogeneic immune responses and move therapeutic approaches targeting neovascularization into the spotlight. This perspective covers current knowledge of the role of neovascularization during GVHD as well as GVT and its implications for HSCT.

The contribution of endothelial activation and injury to end-organ toxicity following allogeneic hematopoietic stem cell transplantation

Over the last 25 years, allogeneic hematopoietic stem cell transplantation (HSCT) has been used increasingly as a curative treatment option for patients with hematologic and neoplastic diseases. Despite major advances in transplant immunology and improvements in supportive and critical care medicine, HSCT is still plagued by several life-threatening complications. As such, the establishment of effective therapeutic options for these complications will be crucial as increasing numbers of high-risk transplants are performed each year. This brief review will discuss the contribution of vascular endothelial cell activation and injury to inflammation and end-organ toxicity that occurs following allogeneic HSCT, and will highlight translational research efforts that have paved the way to the development of novel strategies to treat and prevent disease. Finally, we will discuss in detail the clinical manifestations and challenges encompassed by the syndrome of thrombotic microangiopathy following HSCT.