Studies in the Pathogenesis of Systemic Capillary Leak Syndrome

一些证据表明，免疫失调可能是导致SCLS病理生理学改变的原因之一。首先，在大多数SCLS病例中存在一种意义不明的单克隆性伽马病(MGUS)。MGUS是多发性骨髓瘤(MM)的癌前病变，在MM中，克隆性浆细胞群分泌大量可在患者血清中检测到的单克隆性免疫球蛋白(Ig，也称为副蛋白)。几名小细胞淋巴瘤患者中，MGUS进展为原始骨髓瘤或浆细胞白血病的患者在化疗后因其造血功能障碍而出现较少的毛细血管漏事件。这些发现表明，来自失调浆细胞群体的单克隆性副蛋白可能是观察到的病理生理结果的直接或间接来源。我们正在通过检测单抗Ig在体外血管病理发展中的作用来探索SCLS的分子机制。使用来自SCLS患者的单抗Ig，我们将确定它是否与特定的细胞类型、靶抗原(如果有)结合，以及由此产生的对内皮细胞的影响(直接或间接)。我们还对发病前和发病后的血细胞RNA转录组和SCLS血清/血浆的蛋白质组进行了鉴定，以确定是否可以识别急性症状的特定生物标志物。在过去的4年里，我们已经在NIH临床中心评估了35名与该方案相关的患者。我们是全球主要的SCLS研究转介中心。 SCLS中的一过性低血压休克和无症状性发作被认为是可逆性微血管屏障功能障碍引起的。我们的主要发现是，应用间歇性SCLS血清，但无论是纯化的免疫球蛋白部分还是缓解期患者的血清，都不能引起血管内皮细胞钙粘附素内化，内皮细胞间连接的破坏，肌动蛋白应激纤维的形成，以及补充功能分析中通透性的增加，而不会诱导内皮细胞凋亡。静脉注射免疫球蛋白是治疗SCLS的一种有前景的治疗方法，可以减轻发作性血清的通透性影响。与内源性、非免疫球蛋白、循环通透性因子(S)的存在相一致，我们发现血管内皮生长因子(VEGFs)和血管生成素2(Ang2)在SCLS发作期血清中升高，而在缓解期血清中不升高。基于AB的Ang2抑制作用抵消了发作期SCLS血清诱导的通透性。我们的结果支持SCLS的发病模型，在该模型中，非免疫球蛋白体液因子如血管内皮生长因子和Ang2促进了一过性内皮收缩，提示了这种高度致命性疾病的分子机制。 由于缺乏特异的生物标志物，临床上诊断为SCLS。我们搜索了可以帮助识别活动的SCL的放射学模式。弥漫性心肌纤维化，以及程度较轻的全身性心肌水肿，很难用常规的晚期Gd增强(LGE)或T1标测的心血管磁共振(CMR)进行评估或量化。心肌细胞外体积分数(ECV)的测量避开了混淆T1加权像或T1-MAP的因素。我们假设心肌ECV的定量评估将在临床上用于检测各种常见和罕见心脏疾病中的局限性和弥漫性心肌异常。62例正常人ECV平均值为25.4，2.5%(m，sd)，正常值范围为20.4%~30.4%。在16例非缺血性扩张型心肌病患者中，有4例发现ECV异常升高(38.1%，1.9%；P&lt；0.001比正常)。心脏淀粉样变性(N=4)、全身性毛细血管渗漏综合征(N=2)、心肌炎异常部位(N=7)的ECV值分别为32~60%、40~41%、39~56%。这项研究表明，ECV标测似乎有望在弥漫性更均匀的疾病病例中补充LGE成像。

Several lines of evidence suggest that immune dysregulation may contribute to the pathophysiologic findings seen in SCLS. First, a monoclonal gammopathy of unknown significance (MGUS) is present in a majority of SCLS cases. MGUS is a premalignant precursor to multiple myeloma (MM), in which a clonal plasma cell population secretes large amounts of monoclonal immunoglobulin (Ig, also referred to as a paraprotein) detectable in patient sera. Several patients with SCLS in whom MGUS evolved into frank myeloma or plasma cell leukemia experienced fewer capillary leak episodes after chemotherapy for their hematopoietic disorder. These findings suggest that the monoclonal paraprotein from the dysregulated plasma cell population may be the direct or indirect source of the pathophysiologic findings observed. We are exploring the molecular mechanisms of SCLS by examining the function of the monoclonal Ig in the development of vascular pathology in vitro. Using monoclonal Ig from SCLS patients, we will determine whether it binds to a specific cell type, target antigen (if any), and resulting effect (direct or indirect) on endothelial cells. We are also characterizing the transcriptome of blood cell RNA and the proteome of SCLS serum/plasma, both pre- and post-attack, to determine whether specific biomarkers of acute symptoms can be identified. We have now evaluated 35 patients at the NIH clinical center in association with this protocol in the last 4 years. We are the primary worldwide referral center for research on SCLS. The transient episodes of hypotensive shock and anasarca in SCLS are thought to arise from reversible microvascular barrier dysfunction. Our principal findings were that application of episodic SCLS sera, but neither the purified immunoglobulin fraction nor sera obtained from patients during remission, to human microvascular endothelial cells caused vascular endothelial cadherin internalization, disruption of interendothelial junctions, actin stress fiber formation, and increased permeability in complementary functional assays without inducing endothelial apoptosis. Intravenous immunoglobulin, one promising therapy for SCLS, mitigated the permeability effects of episodic sera. Consistent with the presence of endogenous, nonimmunoglobulin, circulating permeability factor(s) constrained to SCLS episodes, we found that vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2), were elevated in episodic SCLS sera but not in remission sera. Ab-based inhibition of Ang2 counteracted permeability induced by episodic SCLS sera. Our results support a model of SCLS pathogenesis in which nonimmunoglobulin humoral factors such as VEGF and Ang2 contribute to transient endothelial contraction, suggesting a molecular mechanism for this highly lethal disorder. Due to the lack of specific biomarkers, the diagnosis of SCLS is made clinically. We searched for radiographic modalities that could aid in identifying active SCLS. Diffuse myocardial fibrosis, and to a lesser extent global myocardial edema, are difficult to assess or quantify with cardiovascular magnetic resonance (CMR) using conventional late gadolinium enhancement (LGE) or T1-mapping. Measurement of the myocardial extracellular volume fraction (ECV) circumvents factors that confound T1-weighted images or T1-maps. We hypothesized that quantitative assessment of myocardial ECV would be clinically useful for detecting both focal and diffuse myocardial abnormalities in a variety of common and uncommon heart diseases. We found that the mean ECV of 62 normal individuals was 25.4, 2.5% (m, SD), normal range 20.4%-30.4%. Abnormally elevated ECV was identified in 4 of 16 patients with non-ischemic dilated cardiomyopathy (38.1, 1.9%; p<0.001 vs normal). Mean ECV values in other disease entities ranged 32-60% for cardiac amyloidosis (N=4), 40-41% for systemic capillary leak syndrome (N=2), and 39-56% within abnormal regions affected by myocarditis (N=7). This study suggests that ECV mapping appears promising to complement LGE imaging in cases of more homogenously diffuse disease.