Long intergenic non-coding RNAs mediate the human chondrocyte inflammatory response and are differentially expressed in osteoarthritis cartilage

ABSTRACT
Objective: To identify long non-coding RNAs (lncRNAs) including intergenic
lncRNAs (lincRNAs), antisense and pseudogenes associated with the inflammatory
response in human primary OA chondrocytes and to explore their expression and
function in OA.

Methods: OA cartilage was obtained from hip and knee OA patients following joint replacement surgery. Non-OA cartilage was obtained from post-mortem donors and neck of femur fracture patients. Primary OA chondrocytes were isolated by collagenase digestion. LncRNA expression analysis was performed by RNA sequencing (RNAseq) and qRT-PCR. Modulation of lncRNA chondrocyte expression was achieved using LNA longRNA GapmeRs (Exiqon). Cytokine production was measured by Luminex.

Results: RNAseq identified 983 lncRNAs in primary human hip OA chondrocytes, of which 183 had previously not been identified. Following IL-1β stimulation we
identified 125 lincRNAs that were differentially expressed. The lincRNAs PACER,
and two novel chondrocyte inflammation-associated lincRNAs (CILinc01 and
CILinc02) were differentially expressed in both knee and hip OA cartilage compared to non-OA cartilage. In primary OA chondrocytes, these lincRNAs were rapidly and transiently induced in response to multiple pro-inflammatory cytokines. Knockdown of CILinc01 and CILinc02 expression in human chondrocytes significantly enhanced the IL-1-stimulated secretion of pro-inflammatory cytokines.

Conclusion: The inflammatory response in human OA chondrocytes is associated
with widespread changes in the profile of lncRNAs including PACER, CILinc01 and
CILinc02. Differential expression of CILinc01 and CIinc02 in hip and knee OA
cartilage, and their role in modulating cytokine production during the chondrocyte inflammatory response suggest they may play an important role in mediating inflammation driven cartilage degeneration in OA.