Molecular analysis of age and sex-related gene expression in meniscal tears with and without a concomitant anterior cruciate ligament tear

Abstract

Background: The meniscus plays critical roles in the knee, contributing to load transmission, shock absorption, and joint stability. Little is known about gene expression in meniscal tears, particularly in relation to injury pattern and patient age and sex. The purpose of this study was to test the hypothesis that gene expression in meniscal tears varies depending on patient age and sex and whether the anterior cruciate ligament (ACL) is also torn.

Methods: Meniscal tissue from twenty-eight patients with an isolated meniscal tear or a meniscal tear with a concomitant ACL tear was collected at the time of clinically indicated partial meniscectomy. Messenger RNA (mRNA) expression was examined by quantitative real-time polymerase chain reaction for molecular markers of osteoarthritis including proinflammatory cytokines (interleukin [IL]-1α, IL-1β, IL-6, and tumor necrosis factor-alpha [TNFα]), chemokines (IL-8, CCL3, CCL3L1, CXCL1, CXCL3, CXCL6, and CCL20), aggrecanases (ADAMTS-4 [a disintegrin and metalloproteinase with thrombospondin type-4 motifs] and ADAMTS-5), matrix metalloproteinases (MMP-1, MMP-3, MMP-9, and MMP-13), transcription factors (NFκB2 [nuclear factor kappa B2], NFκBIA [NF-kappa B inhibitor alpha], and IκBA [inhibitor of kappa B alpha]), and matrix components (bone morphogenetic protein [BMP]-2, type-I collagen alpha 1 [Col1a1], Col2a1, and aggrecan).

Results: Expression of IL-1β (p = 0.02), ADAMTS-5 (p = 0.001), MMP-1 (p = 0.007), MMP-9 (p = 0.002), MMP-13 (p = 0.01), and NFκB2 (p = 0.01) was significantly higher in patients with a meniscal tear who were under the age of forty years than it was in those over the age of forty years. Similarly, the expression of ADAMTS-4 (p = 0.002), ADAMTS-5 (p = 0.02), MMP-1 (p = 0.02), and MMP-13 (p = 0.0002) was higher in patients with a meniscal tear and an ACL tear who were under the age of forty years than it was in those over forty years. In patients with a meniscal tear and an ACL tear, the expression of IL-1β (p = 0.01), TNFα (p = 0.02), MMP-13 (p = 0.004), CCL3 (p = 0.03), and CCL3L1 (p = 0.03) was significantly higher, while that of aggrecan (p = 0.03) was lower, than that in patients with a meniscal tear alone. The only sex-based difference in gene expression was higher levels of CCL3L1 in female patients (p < 0.05) of all ages with combined injuries.

Conclusions and clinical relevance: These findings suggest clinically relevant differences in the response of the knee to meniscal tears on the basis of patient age and sex. Elevated expression levels of arthritis-related markers indicate an increased catabolic response in patients under forty years old. Higher expression of catabolic markers in patients with meniscal and ACL tears suggests this combined injury pattern is more likely to lead to the development of osteoarthritis. Catabolic activity in meniscal tissue may predict patients who are at risk for progression of osteoarthritis following partial meniscectomy.

Fig. 1

Messenger RNA gene expression of cytokines (IL-1α, IL-1β, IL-6, and TNFα), chemokines (IL-8, CCL3, CCL3L1, CXCL1, CXCL-6, and CCL20), matrix-degrading genes (ADAMTS-4, ADAMTS-5, MMP-1, MMP-3, MMP-9, and MMP-13), matrix genes (BMP-2, Col1a1, Col2a1, and aggrecan), and transcription factors (NFκB2, NFκBIA, and IκBA) in menisci obtained from young and old patients with a meniscal tear but without an ACL tear. Expression levels were determined with use of quantitative real-time polymerase chain reaction with GAPDH (glyceraldehyde 3-phosphate dehydrogenase) as the reference. Values are given as the mean and the standard error of the mean. *p < 0.05. #p < 0.01.

Fig. 2

Messenger RNA gene expression of cytokines (IL-1α, IL-1β, IL-6, and TNFα), chemokines (IL-8, CCL3, CCL3L1, CXCL1, CXCL-6, and CCL20), matrix-degrading genes (ADAMTS-4, ADAMTS-5, MMP-1, MMP-3, MMP-9, and MMP-13), matrix genes (BMP-2, Col1a1, Col2a1, and aggrecan), and transcription factors (NFκB2, NFκBIA, and IκBA) in menisci obtained from young and old patients with a meniscal tear and an ACL tear. Expression levels were determined with use of quantitative real-time polymerase chain reaction with GAPDH (glyceraldehyde 3-phosphate dehydrogenase) as the reference. Values are given as the mean and the standard error of the mean. *p < 0.05. #p < 0.01.

Fig. 3

Messenger RNA gene expression of cytokines (IL-1α, IL-1β, IL-6, and TNFα), chemokines (IL-8, CCL3, CCL3L1, CXCL1, CXCL-6, and CCL20), matrix-degrading genes (ADAMTS-4, ADAMTS-5, MMP-1, MMP-3, MMP-9, and MMP-13), matrix genes (BMP-2, Col1a1, Col2a1, and aggrecan), and transcription factors (NFκB2, NFκBIA, and IκBA) in menisci obtained from patients with combined meniscal and ACL tears (MT + ACL) and those without an ACL tear (MT). Expression levels were determined with use of quantitative real-time polymerase chain reaction with GAPDH (glyceraldehyde 3-phosphate dehydrogenase) as the reference. Values are given as the mean and the standard error of the mean. *p < 0.05. #p < 0.01.