Growth Plate Morphogens as Potential Modulators of Cellular Tissue Remodeling by Annulus Fibrosus Cells.
BMP-2, TGF-β1, and FGF-2 significantly influence AF cell behavior in vitro, suggesting potential roles in tissue remodeling relevant to AIS development.
Where it sits
this study against the rest of the abaloparatide (tymlos) corpusSummary and findings
The study investigated the effects of growth plate morphogens (GPMs) on annulus fibrosus (AF) cells in vitro. BMP-2, TGF-β1, and FGF-2 significantly altered gene expression related to ECM remodeling and cell proliferation. BMP-2 and TGF-β1 increased DNA content and sGAG levels, suggesting potential roles in tissue remodeling.
Abstract
<h4>Background</h4>Adolescent Idiopathic Scoliosis (AIS) is a spinal deformity of unknown etiology that begins in the intervertebral disc and emerges during pubertal growth. In the vertebral growth plate, adjacent to the disc, powerful growth plate morphogens (GPMs) modulate this growth. We evaluated whether GPMs can also alter the capacity of annulus fibrosus (AF) disc cells to proliferate and/or remodel their extracellular matrix (ECM).<h4>Methods</h4>AF cell responsiveness to seven GPMs was screened in monolayer culture by RT-qPCR for downstream signaling markers. GPMs and concentrations eliciting significant transcriptional responses were selected for deeper analysis. Bulk RNA sequencing (RNA-seq) was conducted on AF cells cultured in a 2.5D environment to preserve their native elongated phenotype. Differentially expressed genes (DEGs) were identified and subjected to Gene Ontology enrichment, focusing on ECM remodeling and cell-proliferation processes. Transcriptomic findings were corroborated by assessments of cell proliferation (DNA content), sulfated glycosaminoglycan (sGAG) levels, and matrix metalloproteinase (MMP) activity.<h4>Results</h4>BMP-2, TGF-β1, and FGF-2 significantly altered AF cell expression of downstream target genes, whereas Ihh, PTHrP, Wnt-1, and FGF-18 did not. IGF-1 induced modest, dose-dependent gene expression changes that were not replicated by RNA-seq. BMP-2 and TGF-β1 upregulated genes associated with anabolic ECM remodeling. BMP-2 promoted a cartilage-like ECM with increased expression of type II-associated collagens, aggrecan, and hyaluronan synthesis. TGF-β1 promoted type I collagen-associated genes, collagen cross-linking, and myofibroblast activation. In contrast, FGF-2 activated transcriptional programs related to cell-cycle progression, collagen degradation, and increased GAG turnover. Functionally, we observed higher DNA content under BMP-2 and TGF-β1 stimulation and higher sGAG levels under BMP-2, TGF-β1, and FGF-2 treatment.<h4>Conclusion</h4>BMP-2, TGF-β1, and FGF-2 can modulate AF cell behavior, influencing tissue remodeling and implicating their involvement in disc wedging during AIS onset.
Background
Adolescent Idiopathic Scoliosis (AIS) is a spinal deformity that begins in the intervertebral disc and emerges during pubertal growth. Growth plate morphogens (GPMs) are known to modulate growth in the vertebral growth plate, which is adjacent to the disc. This study explores whether GPMs can influence the proliferation and extracellular matrix (ECM) remodeling capacity of annulus fibrosus (AF) cells, potentially contributing to AIS development.
Methods
The study screened AF cell responsiveness to seven GPMs in monolayer culture using RT-qPCR for downstream signaling markers. GPMs and concentrations eliciting significant transcriptional responses were selected for further analysis. Bulk RNA sequencing was conducted on AF cells in a 2.5D environment to maintain their native phenotype. Differentially expressed genes were identified and analyzed for Gene Ontology enrichment, focusing on ECM remodeling and cell proliferation. Transcriptomic findings were validated by measuring cell proliferation, sulfated glycosaminoglycan levels, and matrix metalloproteinase activity.
Results
BMP-2, TGF-β1, and FGF-2 significantly altered AF cell expression of downstream target genes, while other GPMs did not. BMP-2 promoted a cartilage-like ECM with increased type II collagen, aggrecan, and hyaluronan synthesis. TGF-β1 upregulated type I collagen-associated genes and myofibroblast activation. FGF-2 activated transcriptional programs related to cell-cycle progression and collagen degradation. Functionally, BMP-2 and TGF-β1 increased DNA content, and BMP-2, TGF-β1, and FGF-2 increased sGAG levels.
Interpretation
The study suggests that BMP-2, TGF-β1, and FGF-2 can modulate AF cell behavior, potentially influencing tissue remodeling and contributing to disc wedging in AIS. While the findings are statistically significant, the clinical significance remains uncertain due to the in vitro nature of the study. The results align with previous knowledge of GPMs' roles in growth plate modulation but require further validation in vivo to confirm their relevance to AIS.
Key findings
- BMP-2, TGF-β1, and FGF-2 significantly altered AF cell gene expression.
- BMP-2 promoted cartilage-like ECM with increased type II collagen and aggrecan.
- TGF-β1 upregulated type I collagen-associated genes and myofibroblast activation.
- FGF-2 activated genes related to cell-cycle progression and collagen degradation.
- Higher DNA content observed under BMP-2 and TGF-β1 stimulation.
Limitations
- In vitro study, limiting clinical applicability.
- Cellular models may not replicate in vivo conditions.
- No direct clinical endpoints assessed.