AJSM - 2026-08-17 - Journal Article
IL-1β-Induced Inflammatory Transcriptome and TGF-β1 Attenuation of Chemokine Expression in ACL Remnant Fibroblasts.
Cai L, Brophy RH, Tycksen ED, Rai MF
Topics
Key Takeaway
IL-1β upregulates chemokines (CXCL1/3/5/6/8, CCL20), cytokines (IL-6, IL-33), and MMPs (MMP3/12) in ACL remnant fibroblasts, while TGF-β1 pretreatment suppresses 13 of 16 assessed chemokines by up to 50%.
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Summary
This descriptive laboratory study asked whether IL-1β induces a broad inflammatory transcriptome in ACL remnant fibroblasts and whether TGF-β1 attenuates these responses. Primary fibroblasts from 10 ACL remnants were treated with IL-1β (10 ng/mL) for 24 hours, followed by RNA sequencing; TGF-β1 (10 ng/mL) was then applied for 48 hours with chemokine expression quantified by digital PCR. IL-1β drove marked upregulation of six chemokines, three cytokines, and two MMPs while suppressing five ECM genes; TGF-β1 significantly reduced 13 of 16 chemokines and downregulated NF-κB pathway transcripts NFKBIA and NFKBIZ.
Key Limitation
The study uses isolated fibroblast monocultures without immune cells, synoviocytes, or mechanical loading, so the transcriptomic responses observed may not reflect the integrated in vivo joint environment after ACL rupture.
Original Abstract
BACKGROUND
The high incidence of posttraumatic osteoarthritis after anterior cruciate ligament (ACL) injury and reconstruction suggests that biological mechanisms beyond joint instability contribute to disease progression. After injury, ACL-resident cells are exposed to inflammatory mediators within the joint and may influence the local inflammatory microenvironment; however, their global transcriptomic responses to inflammatory stimuli remain underexplored.
HYPOTHESIS
Interleukin-1 beta (IL-1β) induces inflammatory transcriptomic responses in ACL remnant-derived (ACLr) fibroblasts, and transforming growth factor beta 1 (TGF-β1) attenuates these responses.
STUDY DESIGN
Descriptive laboratory study.
METHODS
Primary ACLr fibroblasts were isolated from ACL remnants (n = 10) collected at the time of knee surgery. Near-confluent cultures were treated with IL-1β (10 ng/mL) for 24 hours to model an inflammatory joint environment. Genome-wide transcriptional changes were assessed by RNA sequencing using an Illumina NovaSeq-6000, with selected targets confirmed by microfluidic digital polymerase chain reaction (PCR). To evaluate the effects of TGF-β1, ACLr fibroblasts pretreated with IL-1β were exposed to TGF-β1 (10 ng/mL) for 48 hours, and chemokine transcript levels were assessed using digital PCR.
RESULTS
IL-1β induced broad inflammatory transcriptional responses characterized by upregulation of chemokines ( CXCL6 , CXCL8 , CXCL5 , CCL20 , CXCL1 , and CXCL3 ), cytokines ( IL33 , IL1B , and IL6 ), and matrix-degrading enzymes ( MMP3 and MMP12 ), while suppressing extracellular matrix-associated genes ( KRT14 , COL21A1 , POSTN , COL1A1 , and COL6A3 ). Functional enrichment analysis demonstrated activation of immune and inflammatory responses, cytokine and chemokine signaling, and cell activation. TGF-β1 reduced the expression of all assessed IL-1β-induced chemokines, with reduction of up to 50%, with statistically significant suppression observed for 13 of the 16 chemokines. Concomitantly, TGF-β1 treatment reduced expression of CEBPB , NFKBIA , and NFKBIZ , transcripts implicated in inflammatory gene regulation.
CONCLUSION
ACLr fibroblasts mounted a robust inflammatory transcriptomic response to IL-1β, characterized by marked induction of chemokines and inflammatory pathways. TGF-β1 attenuated many of these responses, supporting its role as a regulator of inflammatory signaling in ACL-resident cells.
CLINICAL RELEVANCE
ACL-resident cells respond to injury and may contribute to the post-injury inflammatory microenvironment. Therapeutic modulation of inflammatory signaling in these cells could represent a strategy to mitigate early molecular events associated with post-traumatic osteoarthritis following ACL tear.