Low back pain is closely associated with intervertebral disc (IVD) degeneration, in which inflammation and neovascularization within the annulus fibrosus (AF) contribute to pain generation. Platelet-derived growth factor (PDGF)-BB plays a crucial role in tissue repair and cellular homeostasis, but its role in AF cell biology remains poorly understood. To investigate the effects of PDGF-BB on human AF cells, healthy and degenerated AF cells were treated with PDGF-BB for 3 or 5 days, followed by bulk RNA sequencing. Functional enrichment of differentially expressed genes, transcription factor activity analysis, and protein–protein interaction network analysis was performed. Publicly available single-cell RNA-seq data were used to compare the transcriptomic profiles of native healthy and degenerated AF samples. In addition, TNF-α stimulation was conducted to validate the anti-inflammatory effects of PDGF-BB. Our findings suggest that PDGF-BB induced both common and context-dependent transcriptional responses in healthy and degenerated AF cells. In healthy AF cells, PDGF-BB consistently upregulated genes associated with cell cycle and developmental growth. In degenerated AF cells, PDGF-BB also induced these responses, while additionally it downregulated the genes related to extracellular matrix remodeling and collagen degradation. Meanwhile, PDGF-BB showed common effects in both healthy and degenerated cells by modulating the expression of genes within G protein-coupled receptor (GPCR) networks that are linked to complement, inflammation, and neurotransmitter signaling. In addition, PDGF-BB also suppressed the expression of genes involved in inflammatory-neurogenic signaling, including nerve growth factor (NGF), C-X-C motif chemokine ligand 12 (CXCL12), and apolipoprotein E (APOE). To relate these PDGF-BB induced responses to disc degeneration, we reanalyzed publicly available single-cell RNA-seq datasets from native human AF tissues and found that NGF-positive cells showed increased tumor necrosis factor (TNF)-α signaling activity. When AF cells were stimulated with TNF-α, PDGF-BB treatment significantly inhibited the expression of NGF, endothelin-1 (EDN1), and interleukin 6 (IL6) under both baseline and TNF-α-stimulated conditions. These results suggest that PDGF-BB modulates gene expression associated with inflammatory and neurogenic signaling as well as ECM remodeling in human AF cells, providing a transcriptomic insight into the PDGF-BB’s function in AF biology.
Zhang et al. (Sat,) studied this question.