Anterior cruciate ligament (ACL) and meniscus tears are common knee injuries. Despite the high rate of post-traumatic osteoarthritis (PTOA) following these injuries, the contributing factors remain unclear. In this study, we characterized the immune cell profiles of normal and injured joints at the time of ACL and meniscal surgeries. Twenty-nine patients (14 meniscus-injured and 15 ACL-injured) undergoing ACL and/or meniscus surgery but with a normal contralateral knee were recruited. During surgery, synovial fluid was aspirated from both normal and injured knees. Synovial fluid cells were pelleted, washed, and stained with an antibody cocktail consisting of fluorescent antibodies for cell surface proteins. Analysis of immune cells in the synovial fluid was performed by polychromatic flow cytometry. A broad spectrum immune cell panel was used in the first 10 subjects. Based on these results, a T cell-specific panel was used in the subsequent 19 subjects. Using the broad spectrum immune cell panel, we detected significantly more total viable cells and CD3 T cells in the injured compared to the paired normal knees. In addition, there were significantly more injured knees with T cells above a 500-cell threshold. Within the injured knees, CD4 and CD8 T cells were able to be differentiated into subsets. The frequency of total CD4 T cells was significantly different among injury types, but no statistical differences were detected among CD4 and CD8 T cell subsets by injury type. Our findings provide foundational data showing that ACL and meniscus injuries induce an immune cell-rich microenvironment that consists primarily of T cells with multiple T helper phenotypes. Future studies investigating the relationship between immune cells and joint degeneration may provide an enhanced understanding of the pathophysiology of PTOA following joint injury.

中文翻译：

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前交叉韧带和半月板损伤后滑液中的免疫细胞谱

前交叉韧带 (ACL) 和半月板撕裂是常见的膝关节损伤。尽管这些损伤后创伤后骨关节炎 (PTOA) 的发生率很高，但其影响因素仍不清楚。在这项研究中，我们表征了 ACL 和半月板手术时正常和受伤关节的免疫细胞谱。招募了 29 名接受 ACL 和/或半月板手术但对侧膝关节正常的患者（14 名半月板损伤和 1​​5 名 ACL 损伤）。在手术过程中，从正常和受伤的膝盖中抽出滑液。滑液细胞被沉淀、洗涤并用由细胞表面蛋白的荧光抗体组成的抗体混合物染色。通过多色流式细胞术对滑液中的免疫细胞进行分析。在前 10 名受试者中使用了广谱免疫细胞组。基于这些结果，在随后的 19 名受试者中使用了 T 细胞特异性组合。使用广谱免疫细胞面板，与配对的正常膝盖相比，我们在受伤者中检测到明显更多的总活细胞和 CD3 T 细胞。此外，T 细胞超过 500 细胞阈值的受伤膝盖明显更多。在受伤的膝盖内，CD4 和 CD8 T 细胞能够分化成亚群。总CD4 T细胞的频率在不同损伤类型之间存在显着差异，但不同损伤类型的CD4和CD8 T细胞亚群之间没有检测到统计学差异。我们的研究结果提供了基础数据，表明 ACL 和半月板损伤会诱导富含免疫细胞的微环境，该微环境主要由具有多种 T 辅助表型的 T 细胞组成。未来研究免疫细胞与关节退化之间的关系可能会加深对关节损伤后 PTOA 病理生理学的理解。