Adaptive remodeling of retrodiscal tissue following anterior disc displacement (ADD) of the temporomandibular joint (TMJ) has been recognized for decades, yet the underlying cellular dynamics and molecular mechanisms remain unclear. Using a porcine ADD model, this study investigated the cellular and molecular basis driving retrodiscal tissue adaptation. Histological staining revealed adaptive remodeling of retrodiscal tissue after ADD induction, with dense connective tissue and cartilaginous masses replacing loose connective tissue. Furthermore, single-cell RNA sequencing (scRNA-seq) captured pronounced fibroblast expansion during tissue remodeling, notably the FB2 subcluster with high developmental potential, and the emergence of a mural cell subcluster MC4 associated with extracellular matrix (ECM) remodeling. CellChat analysis highlighted MC4-FB2 crosstalk via FGF2 and BMP5 signaling. The combination of pathway-aware multi-layered hierarchical network (P-NET) and Seurat with drug database screening identified five promising compounds. Among them, Zaprinast demonstrated the most robust effects by enhancing the remodeling capability of fibroblasts in vitro, and also alleviated TMJ deformation in vivo. Collectively, fibroblast activation is pivotal for early retrodiscal tissue adaptation following ADD, which is driven by MC4-derived FGF2/BMP5 signaling. Zaprinast treatment potentiates this remodeling process. These findings provide new insights into cellular basis of TMJ adaptation and identify potential therapeutic targets for ADD management.

Mesenchymal stem cell (MSCs) transplantation shows promise for meniscus repair, but their inadaptability to the in vivo mechanical environment complicates differentiation regulation. This study developed a mechanical priming strategy to enhance MSCs fibrochondrogenic differentiation and promote meniscus repair. Synovial-derived MSCs (SMSCs) were co-cultured with meniscal fibrochondrocytes and exposed to cyclic tensile strain (10%, 0.5 Hz, 4h/day) for 5 days as a "stem cell warm-up system". Differentiation and mechanical adaptation were assessed through gene expression, cytoskeletal and nuclear morphology, and YAP-mediated mechanical transduction in vitro. A 2-mm meniscus defect model in New Zealand white rabbits was used, with histological analysis for repair evaluation. Mechanical priming inhibited SMSCs hypertrophy and promoted fibrochondrogenesis, with effects lasting 72 h post-loading. Meanwhile, priming induced actin cap formation, nuclear flattening, and nuclear pore expansion, facilitating mechanical adaptation. YAP-mediated transduction was essential for the sustained upregulation of differentiation-related genes, alongside increased expression of its downstream targets, Ctgf and Cyr61. siRNA silencing of Ctgf and Cyr61 led to a downregulation of differentiation-related genes, with YAP inhibition further suppressing differentiation, underscoring its pivotal role in regulating this process. Primed SMSCs exhibited faster activation and better phenotype maintenance during secondary loading. In vivo, primed SMSCs demonstrated superior performance in meniscus regeneration, equivalent to the outcomes of growth factor-treated groups. This biomimetic priming system enhances MSC differentiation and mechanical adaptability, offering a clinically translatable strategy for meniscus repair and load-bearing tissue regeneration.

Developing fibrochondrogenic serum-free media is important for regenerating diseased and injured fibrocartilage but no defined protocols exist. Towards this goal, we characterized the effect of four candidate fibrochondrogenic serum-free media containing transforming growth factor beta-3 (TGF-β3), insulin-like growth factor-1 (IGF-1), and fibroblast growth factor-2 (FGF-2) with high/low glucose and with/without dexamethasone on human mesenchymal stem cells (hMSCs) via proliferation and differentiation assays. In Ki67 proliferation assays, serum-free media containing low glucose and dexamethasone exhibited the highest growth. In gene expression assays, serum-free media containing low glucose and commercially available chondrogenic media (COM) induced high fibrochondrogenic transcription factor expression (scleraxis/SCX and SRY-Box Transcription Factor 9/SOX9) and extracellular matrix (ECM) protein levels (aggrecan/ACAN, collagen type I/COL1A1, and collagen type II/COL2A1), respectively. In immunofluorescence staining, serum-free media containing high glucose and COM induced high fibrochondrogenic transcription factor (SCX and SOX9) and ECM protein (COL1A1, COL2A1, and collagen type X/COL10A1) levels, respectively. In cytochemical staining, COM and serum-free media containing dexamethasone showed a high collagen content whereas serum-free media containing high glucose and dexamethasone exhibited high glycosaminoglycan (GAG) levels. Altogether, defined serum-free media containing high glucose exhibited the highest fibrochondrogenic potential. In summary, this work studied conditions conducive for fibrochondrogenesis, which may be further optimized for potential applications in fibrocartilage tissue engineering.

Meniscal injury presents a formidable challenge and often leads to functional impairment and osteoarthritic progression. Meniscus tissue engineering (MTE) is a promising solution, as conventional strategies for modulating local immune responses and generating a conducive microenvironment for effective tissue repair are lacking. Recently, magnesium-containing bioactive glass nanospheres (Mg-BGNs) have shown promise in tissue regeneration. However, few studies have explored the ability of Mg-BGNs to promote meniscal regeneration. First, we verified the anti-inflammatory and fibrochondrogenic abilities of Mg-BGNs in vitro. A comprehensive in vivo evaluation of a rabbit critical-size meniscectomy model revealed that Mg-BGNs have multiple effects on meniscal reconstruction and effectively promote fibrochondrogenesis, collagen deposition, and cartilage protection. Multiomics analysis was subsequently performed to further explore the mechanism by which Mg-BGNs regulate the regenerative microenvironment. Mechanistically, Mg-BGNs first activate the TRPM7 ion channel through the PI3K/AKT signaling pathway to promote the cellular function of synovium-derived mesenchymal stem cells and then activate the PPARγ/NF-κB axis to modulate macrophage polarization and inflammatory reactions. We demonstrated that Mg2+ is critical for the crosstalk among biomaterials, immune cells, and effector cells in Mg-BGN-mediated tissue regeneration. This study provides a theoretical basis for the application of Mg-BGNs as nanomedicines to achieve in situ tissue regeneration in complex intrajoint pathological microenvironments.

To explore the genetic etiology of a fetus with short limbs identified by prenatal ultrasonography. A fetus detected with short limb malformations at Shengjing Hospital Affiliated to China Medical University on October 25, 2021 was selected as the study subject. Prenatal ultrasound and post-abortion imaging were carried out to determine the phenotypic characteristics of the fetus. Amniotic fluid sample of the fetus and peripheral blood samples of its parents were collected. Following extraction of genomic DNA, whole-exome sequencing was carried out. Candidate variants were verified by Sanger sequencing. Online software was used to predict the structural changes of the mutant proteins. Prenatal ultrasound showed that the fetus had a small bell-shaped thorax, markedly shortened limbs, flat midface, a small nose with anteriorly tilted nostrils, and a small mandible. Post-abortion CT showed typical short and wide fetal ribs, cupped metaphyses at both ends, short long bones with wide metaphyses, resulting in a dumbbell-shaped appearance and curved thoracic vertebrae. Whole-exome sequencing revealed that the fetus had harbored compound heterozygous variants of the COL11A1 gene, namely c.2251G>T and c.3790G>T, both of which were predicted to alter the important Gly-X-Y structure of collagen protein. Sanger sequencing confirmed that the variants were respectively inherited from its parents. A rare fetus with Fibrochondrogenesis type 1 due to compound heterozygous variants of the COL11A1 gene has been diagnosed. Above finding has enabled genetic counseling and reproductive guidance for this family.