Supplementary Material for: Interstitial Pulmonary Fibrosis and Extensive Dendriform Ossification with Persistent Viral Load: A Rare Presentation of Post-COVID-19 Condition in Need of Lung Transplantation

The incidence, presentation, and predisposing factors of post-acute sequelae of COVID-19 (PASC) are currently poorly understood. Lung explants may provide a rare insight into terminal SARS-CoV-2-associated lung damage and its pathophysiology. A 62-year-old man presented with progressively worsening respiratory symptoms after recovering from mild COVID-19 3 months earlier. No underlying pulmonary comorbidities were reported. A chest CT revealed bilateral extensive ground-glass and reticular opacities, suspicious of pulmonary fibrosis. Despite initial high-dose glucocorticoid therapy, the interstitial lung disease progressed, and after exhausting all viable therapeutic options, bilateral lung transplantation was successfully conducted. Histological analysis revealed extensive end-stage interstitial fibrosis with diffuse dendriform ossification and bronchiolar and transitional cell metaplasia. Signs of interstitial remodeling such as an increased interstitial collagen deposition, a pathological accumulation of CD163+/CD206+ M2-polarized macrophages with an increased expression of phosphorylated ERK, and an increased density of CD105+ newly formed capillaries were observed. qRT-PCR and immunohistochemistry for SARS-CoV-2 N-protein in the endothelium of medium-sized vessels confirmed a persistence of SARS-CoV-2. Our findings highlight a highly unusual presentation of SARS-CoV-2-associated lung fibrosis, implying that incomplete viral clearance in the vascular compartment may play a vital pathophysiological role in the development of PASC.

目前学界对新冠长期后遗症（post-acute sequelae of COVID-19, PASC）的发病率、临床表现及易感因素仍知之甚少。肺部切除标本可为深入解析终末期严重急性呼吸综合征冠状病毒2（SARS-CoV-2）相关肺损伤及其病理生理学机制提供罕见视角。一名62岁男性在3个月前罹患轻症新冠并康复后，出现进行性加重的呼吸道症状，无基础肺部合并症病史。胸部CT显示双侧广泛磨玻璃影及网状阴影，高度怀疑肺纤维化。尽管初始予以大剂量糖皮质激素治疗，但间质性肺病仍持续进展；在穷尽所有可行治疗方案后，成功为患者实施双肺移植术。组织病理学分析可见广泛终末期间质性纤维化，伴弥漫性树突状骨化及细支气管、移行细胞化生。同时观察到间质性重塑相关征象：间质胶原沉积增加、CD163+/CD206+ M2极化巨噬细胞病理性聚集且磷酸化ERK表达上调，以及CD105+新生毛细血管密度升高。针对中型血管内皮的SARS-CoV-2核衣壳蛋白开展实时荧光定量PCR（qRT-PCR）与免疫组化检测，证实新冠病毒仍持续存在于该部位。本研究结果揭示了一种极为罕见的新冠相关肺纤维化表型，提示血管腔内病毒清除不全可能在新冠长期后遗症的发病机制中发挥关键病理生理学作用。