Department of Experimental Rheumatology, Radboud University Medical Center, Nijmegen, The Netherlands.
Department of Medical Imaging, Radboud University Medical Center, Nijmegen, The Netherlands.
Arthritis Res Ther. 2023 Aug 31;25(1):158. doi: 10.1186/s13075-023-03147-y.
Rheumatoid arthritis (RA) is one of the most prevalent and debilitating joint diseases worldwide. RA is characterized by synovial inflammation (synovitis), which is linked to the development of joint destruction. Magnetic resonance imaging and ultrasonography are widely being used to detect the presence and extent of synovitis. However, these techniques do not reveal the activation status of inflammatory cells such as macrophages that play a crucial role in synovitis and express CD64 (Fc gamma receptor (FcγR)I) which is considered as macrophage activation marker.
We aimed to investigate CD64 expression and its correlation with pro-inflammatory cytokines and pro-damaging factors in human-derived RA synovium. Furthermore, we aimed to set up a molecular imaging modality using a radiolabeled CD64-specific antibody as a novel imaging tracer that could be used to determine the extent and phenotype of synovitis using optical and nuclear imaging.
First, we investigated CD64 expression in synovium of early- and late-stage RA patients and studied its correlation with the expression of pro-inflammatory and tissue-damaging factors. Next, we conjugated an anti-CD64 antibody with IRDye 800CW and diethylenetriamine penta-acetic acid (DTPA; used for In labeling) and tested its binding on cultured THP1 cells, ex vivo RA synovium explants and its imaging potential in SCID mice implanted with human RA synovium explants obtained from RA patients who underwent total joint replacement.
We showed that CD64 is expressed in synovium of early and late-stage RA patients and that FCGR1A/CD64 expression is strongly correlated with factors known to be involved in RA progression. Combined, this makes CD64 a useful marker for imaging the extent and phenotype of synovitis. We reported higher binding of the [In]In-DTPA-IRDye 800CW anti-CD64 antibody to in vitro cultured THP1 monocytes and ex vivo RA synovium compared to isotype control. In human RA synovial explants implanted in SCID mice, the ratio of uptake of the antibody in synovium over blood was significantly higher when injected with anti-CD64 compared to isotype and injecting an excess of unlabeled antibody significantly reduced the antibody-binding associated signal, both indicating specific receptor binding.
Taken together, we successfully developed an optical and nuclear imaging modality to detect CD64 in human RA synovium in vivo.
类风湿关节炎（RA）是全球最普遍和使人虚弱的关节疾病之一。RA 的特征为滑膜炎症（滑膜炎），这与关节破坏的发展有关。磁共振成像和超声检查被广泛用于检测滑膜炎的存在和程度。然而，这些技术并不能显示巨噬细胞等炎症细胞的激活状态，巨噬细胞在滑膜炎中起着至关重要的作用，并表达 CD64（FcγR I），这被认为是巨噬细胞激活的标志物。
我们旨在研究 CD64 在人源 RA 滑膜中的表达及其与促炎细胞因子和促损伤因子的相关性。此外，我们旨在建立一种分子成像方式，使用放射性标记的 CD64 特异性抗体作为新型成像示踪剂，通过光学和核成像来确定滑膜炎的程度和表型。
首先，我们研究了早期和晚期 RA 患者滑膜中 CD64 的表达，并研究了其与促炎和组织损伤因子表达的相关性。接下来，我们将抗 CD64 抗体与 IRDye 800CW 和二乙三胺五乙酸（DTPA；用于 In 标记）连接，并在培养的 THP1 细胞、离体 RA 滑膜标本以及在接受全关节置换的 RA 患者获得的人 RA 滑膜标本植入的 SCID 小鼠中检测其结合和成像潜力。
我们表明 CD64 在早期和晚期 RA 患者的滑膜中表达，并且 FCGR1A/CD64 表达与已知参与 RA 进展的因子密切相关。综合来看，这使得 CD64 成为成像滑膜炎程度和表型的有用标志物。我们报告说，与同型对照相比，[In]In-DTPA-IRDye 800CW 抗 CD64 抗体对体外培养的 THP1 单核细胞和离体 RA 滑膜的结合更高。在 SCID 小鼠中植入人 RA 滑膜标本中，与同型对照相比，注射抗 CD64 时滑膜对抗体的摄取与血液的比值明显更高，并且注射过量未标记的抗体可显著降低与抗体结合相关的信号，这都表明了特异性受体结合。
综上所述，我们成功开发了一种光学和核成像方式，用于在体内检测人 RA 滑膜中的 CD64。
