Mechanisms of the circ_0042103/TAF15/NER Axis in Pulpitis: Linking Circular RNA Regulation to DNA Damage and Inflammation

Study Background and Research Question

Pulpitis is a prevalent and painful inflammatory dental disease, most often instigated by persistent microbial infection of the dental pulp. Standard therapy—removal of necrotic pulp tissue—does not address the molecular drivers of inflammation or promote tissue regeneration, underscoring the pressing need for mechanistic insights into pulpitis pathogenesis (source: Lai et al., 2026). Recent advances have identified circular RNAs (circRNAs) as emerging regulators in both inflammation and the DNA damage response (DDR), yet their exact functions in dental pulp stem cells (DPSCs) during inflammatory disease remain poorly characterized. The reference study by Lai et al. specifically investigated whether circRNAs modulate DNA damage and repair mechanisms in inflamed pulp tissue, and delineated the molecular axis through which such regulation occurs.

Key Innovation from the Reference Study

Lai et al. present the first detailed characterization of a circRNA-based regulatory axis—circ_0042103/TAF15/NER—in human dental pulp stem cells under inflammatory conditions. The study demonstrates that circ_0042103, a circular RNA upregulated during pulpitis, binds to the RNA-binding protein TAF15, ultimately impairing nucleotide excision repair (NER) by downregulating key repair proteins ERCC1 and PCNA. This axis results in heightened DNA double-strand breaks and sustained inflammation (source: Lai et al., 2026). This mechanistic link provides a new molecular framework connecting circRNA biology, DNA repair pathways, and chronic inflammation in dental tissue.

Methods and Experimental Design Insights

The study integrates transcriptomic and molecular biology approaches:

• Microarray and scRNA-seq: Used to assess global changes in DNA damage response (DDR) genes and circRNA expression in inflamed pulp tissues and DPSCs.
• qRT-PCR and Western Blot: Quantified DNA double-strand break (DSB) marker γ-H2AX and inflammatory cytokines (IL-6, IL-8, TNF-α) in tissue samples.
• Bioinformatics Analysis: Identified circ_0042103 as significantly upregulated in inflamed DPSCs and predicted its potential RNA-protein interactions.
• Functional Assays: Explored the impact of circ_0042103 overexpression and knockdown on LPS-induced DNA damage and inflammatory signaling.
• RNA FISH, Pulldown, and Fractionation: Confirmed physical interaction and subcellular localization for circ_0042103 and TAF15.
• siRNA-mediated knockdown: Dissected the functional consequences of disrupting the circ_0042103/TAF15 interaction on NER pathway activation.

This comprehensive design enabled the authors to trace causality from circRNA upregulation through protein interaction, to downstream effects on DNA repair and inflammation.

Core Findings and Why They Matter

• Activation of DDR in Pulpitis: Both inflamed pulp tissue and DPSCs exhibit increased DDR activation and DSB accumulation, evidenced by elevated γ-H2AX (source: Lai et al., 2026).
• circ_0042103 Drives Inflammatory DNA Damage: Upregulation of circ_0042103 amplifies LPS-induced DNA damage and inflammatory cytokine expression. Conversely, knockdown alleviates both outcomes (source: Lai et al., 2026).
• TAF15 Interaction and NER Suppression: circ_0042103 binds TAF15, which in turn leads to diminished levels of the NER proteins ERCC1 and PCNA, impairing DNA repair and exacerbating cellular damage (source: Lai et al., 2026).
• Integrated Axis: The circ_0042103/TAF15/NER axis directly links circRNA regulation to the cellular capacity for DNA repair in the context of inflammation.

These insights advance both the understanding of pulpitis progression and the broader field of RNA-mediated regulation in inflammatory diseases.

Comparison with Existing Internal Articles

Several recent internal articles highlight the expanding toolkit and strategies for circular RNA research:

• "Ribonuclease R (20 U/μL): Precision Tools for Circular RNA Discovery" outlines how Ribonuclease R (RNase R) enables high-fidelity circular RNA enrichment and structure analysis, which is foundational for studies like Lai et al.'s, where accurate circRNA profiling is required for mechanistic dissection (source: workflow_recommendation).
• "Ribonuclease R (20 U/μL): Advancing Circular RNA Enrichment" discusses optimized workflows for selective linear RNA degradation, troubleshooting, and integration with downstream assays, directly supporting both the identification and functional analysis of disease-relevant circRNAs (source: workflow_recommendation).
• "circ_0042103/TAF15/NER Axis Drives DNA Damage in Pulpitis" provides a complementary perspective, focusing specifically on the same regulatory pathway and reinforcing the evidence for the mechanistic role of circRNAs in inflammatory DNA damage (source: workflow_recommendation).

The reference study builds on these foundational techniques, translating high-throughput circRNA enrichment and RNA structure-function analysis into actionable insight about disease mechanisms.

Protocol Parameters

• assay: Circular RNA enrichment | value_with_unit: RNase R (20 U/μL) | applicability: selective linear RNA removal from total RNA | rationale: enriches circular RNAs by digesting linear molecules, facilitating downstream structure and function studies | source_type: workflow_recommendation
• assay: qRT-PCR for circRNA quantification | value_with_unit: ≥100 ng total RNA input | applicability: detection of low-abundance circRNAs | rationale: ensures sufficient material post-enrichment for robust quantification | source_type: workflow_recommendation
• assay: Western blot for γ-H2AX/PCNA/ERCC1 | value_with_unit: 5–20 μg protein/lane | applicability: detection of DNA damage and repair proteins in DPSCs | rationale: matches sensitivity requirements for inflammation-linked molecular readouts | source_type: paper
• assay: LPS stimulation of DPSCs | value_with_unit: 1 μg/mL, 24 h | applicability: mimics inflammatory microenvironment in vitro | rationale: replicates pulpitis-relevant cell signaling | source_type: paper

Limitations and Transferability

While the study leverages both human tissue samples and in vitro models, several limitations should be acknowledged:

• Model constraints: Functional assays were performed in cultured DPSCs and may not fully recapitulate the complex in vivo microenvironment of pulpitis (source: Lai et al., 2026).
• Specificity: The circ_0042103/TAF15/NER axis was validated in the context of dental pulp inflammation; extrapolation to other tissues or disease contexts requires further study (source: workflow_recommendation).
• Temporal resolution: The study focuses on acute responses to LPS and may not capture chronic or late-stage regulatory effects (source: workflow_recommendation).

Despite these constraints, the mechanistic insights are highly relevant to researchers investigating RNA-mediated regulation of inflammation and tissue injury.

Research Support Resources

To enable similar workflows for circular RNA enrichment and RNA structure analysis, researchers can utilize Ribonuclease R (RNase R) (20 U/μL) (SKU K3061) from APExBIO. This enzyme selectively digests linear RNA, allowing for the enrichment of circular and structured RNAs, and is compatible with downstream assays such as qRT-PCR, RNA-seq, and RNA pulldown (source: product_spec). The use of RNase R is recommended for researchers aiming to dissect RNA processing pathways or validate circular RNA function in models of inflammation and DNA damage.