Abnormal Chondrocyte Proliferation Research Articles

Molecular mechanism of thiram-induced abnormal chondrocyte proliferation via lncRNA MSTRG.74.1-BNIP3 axis

Thiram, a widely used organic pesticide in agriculture, exhibits both bactericidal and insecticidal effects. However, prolonged exposure to thiram has been linked to bone deformities and cartilage damage, contributing to the development of tibial dyschondroplasia (TD) in broilers and posing a significant threat to global agricultural production. TD, a prevalent nutritional metabolic disease, manifests as clinical symptoms like unstable standing, claudication, and sluggish movement in affected broilers. In recent years, there has been growing recognition of the regulatory role of long non-coding RNA (lncRNA) in tibial cartilage formation among broilers through diverse signaling pathways. This study employs in vitro experimental models, growth performance analysis, and clinical observation to assess broilers' susceptibility to thiram pollution. Transcriptome sequencing analysis revealed a significant elevation in the expression of lncRNA MSTRG.74.1 in both the con group and the thiram-induced in vitro group. The results showed that lncRNA MSTRG.74.1 plays a pivotal role in influencing the proliferation and abnormal differentiation of chondrocytes. This regulation occurs through the negative modulation of apoptotic genes, including Bax, Cytc, Bcl2, Apaf1, and Caspase3, along with genes Atg5, Beclin1, LC3b, and protein p62. Moreover, the overexpression of lncRNA MSTRG.74.1 was found to regulate broiler chondrocyte development by upregulating BNIP3. In summary, this research sheds light on thiram-induced abnormal chondrocyte proliferation in TD broilers, emphasizing the significant regulatory role of the lncRNA MSTRG.74.1-BNIP3 axis, which will contribute to our understanding of the molecular mechanisms underlying TD development in broilers exposed to thiram.

Microstructure changes and miRNA-mRNA network in a developmental dysplasia of the hip rat model

MicroRNAs (miRNAs) interact with mRNAs in various pathophysiological processes. In developmental dysplasia of the hip (DDH), the miRNA-mRNA pairs affecting acetabular cartilage (AC) development remain unknown. We investigated dynamic microstructure changes and mRNA and miRNA expression profiles in the AC proliferative zone in a DDH rat model. Abnormal chondrocyte proliferation was observed, and several differentially expressed mRNAs and miRNAs were identified. Downregulated mRNAs and target genes of upregulated miRNAs were primarily enriched in bone and cartilage development. Six hub genes were identified using the predicted miRNA-mRNA interaction network and gene expression pattern analysis. The expression levels of these hub genes and paired miRNAs aligned with our predictions, and most of the pairs were significantly negatively correlated. Excessive chondrocyte proliferation in the AC proliferative zone can delay AC ossification, which might be crucial to DDH development. Specific miRNA-mRNA interaction pairs may serve as diagnostic biomarkers and therapeutic targets.

Mechanism of Abnormal Chondrocyte Proliferation Induced by Piezo1-siRNA Exposed to Mechanical Stretch.

Objective To investigate the effect of small interfering RNA targeting mechanosensitive ion channel protein Piezo1 (Piezo1-siRNA) on abnormal chondrocyte proliferation exposed to mechanical stretch. Methods Construct and screen effective Piezo1-siRNA sequences and explore an appropriate method to transfect lentiviral vector into chondrocytes exposed to mechanical stretch. Western blot and RT-PCR were used to detect the mRNA and protein expression of Piezo1, Kif18A, and β-tubulin, respectively. Flow cytometry was used to measure the changes in the chondrocyte cycle. The proliferation of chondrocyte was evaluated by cell counting kit-8. Results According to the mRNA and protein expression of Piezo1, the effective siRNA sequence was successfully screened. Compared with the 0 h group, mechanical stretch upregulated the expression of Piezo1, Kif18A, and β-tubulin, resulting in chondrocyte cycle arrest and eventually inhibiting chondrocyte proliferation. Moreover, Piezo1-siRNA transfection effectively blocks this process and promotes the proliferation of chondrocyte. Conclusion Piezo1-siRNA can reduce the inhibition of chondrocyte proliferation induced by mechanical stretch via downregulating the expression of Kif18A and inhibiting the depolymerization of microtubules. Piezo1-siRNA plays a protective role in chondrocytes, which provides a potential method for the treatment of OA under abnormal mechanical stimulation.

The Indispensable Role of Cyclin-Dependent Kinase 1 in Skeletal Development

Skeletal development is tightly regulated through the processes of chondrocyte proliferation and differentiation. Although the involvement of transcription and growth factors on the regulation of skeletal development has been extensively studied, the role of cell cycle regulatory proteins in this process remains elusive. To date, through cell-specific loss-of-function experiments in vivo, no cell cycle regulatory proteins have yet been conclusively shown to regulate skeletal development. Here, we demonstrate that cyclin-dependent kinase 1 (Cdk1) regulates skeletal development based on chondrocyte-specific loss-of-function experiments performed in a mouse model. Cdk1 is highly expressed in columnar proliferative chondrocytes and is greatly downregulated upon differentiation into hypertrophic chondrocytes. Cdk1 is essential for proper chondrocyte proliferation and deletion of Cdk1 resulted in accelerated differentiation of chondrocytes. In vitro and ex vivo analyses revealed that Cdk1 is an essential cell cycle regulatory protein for parathyroid hormone-related peptide (PTHrP) signaling pathway, which is critical to chondrocyte proliferation and differentiation. These results demonstrate that Cdk1 functions as a molecular switch from proliferation to hypertrophic differentiation of chondrocytes and thus is indispensable for skeletal development. Given the availability of inhibitors of Cdk1 activity, our results could provide insight for the treatment of diseases involving abnormal chondrocyte proliferation, such as osteoarthritis.

3β-Hydroxysterol-Delta24 reductase plays an important role in long bone growth by protecting chondrocytes from reactive oxygen species

Desmosterolosis is an autosomal recessive disease caused by mutations in the 3β-hydroxysterol-Delta24 reductase (DHCR24) gene, with severe developmental anomalies including short limbs. We utilized DHCR24 knockout (KO) mice to study the underlying bone pathology. Because the KO mice died within a few hours after birth, we cultured metatarsal bones from newborn mice. The growth of bones from KO mice was significantly retarded after 1week of culture. Absence of proliferating chondrocytes in the growth plate and abnormal hypertrophy of prehypertrophic chondrocytes were observed in the bones from KO mice. Hypertrophic differentiation was evidenced by higher expression of Indian hedgehog, alkaline phosphatase, and matrix metalloproteinase 13. Since elevated levels of reactive oxygen species (ROS) during chondrogenesis are known to inhibit proliferation and to initiate chondrocyte hypertrophy in the growth plate, and since DHCR24 acts as a potent ROS scavenger, we hypothesized that the abnormal chondrocyte proliferation and differentiation in KO mice were due to decreased ROS scavenging activity. Treatment with an antioxidant, N-acetyl cysteine, could correct the abnormalities observed in the bones from KO mice. Treatment of bones from wild-type mice with U18666A, a chemical inhibitor of DHCR24, resulted in short broad bones with a disrupted proliferating zone. Treatment of ATDC cells with hydrogen peroxide (H(2)O(2)) induced hypertrophic changes as evidenced by the expression of the marker genes specific for hypertrophic chondrocyte differentiation. H(2)O(2)-induced hypertrophic change was prevented by adenoviral delivery of DHCR24. Induction of chondrocyte differentiation in ATDC cells by insulin was associated with increased ROS production that was markedly enhanced by treatment of ATDC5 cells with DHCR24 siRNA. This is the first demonstration that DHCR24 plays an important role in long bone growth by protecting chondrocytes from ROS.

Mutation analyses of the NFAT1 gene in chondrosarcomas and enchondromas

Mice lacking nuclear factor of activated T cell 1 (NFAT1) showed an abnormal proliferation of chondrocytes in articular cartilage and formed an extraosseous cartilaginous mass resembling a neoplastic lesion, suggesting that the NFAT1 gene is a tumor suppressor gene in cartilaginous neoplasms. Here we performed mutation analyses of the NFAT1 gene in human cartilaginous tumors including 30 chondrosarcomas and 15 enchondromas. Reverse transcription–polymerase chain reaction (PCR) analysis revealed the expression of the NFAT1 gene in 15/15 chondrosarcomas and 12/13 enchondromas. To find subtle alterations, the genomic structure of the NFAT1 gene was determined using human genome draft sequences, and a mutation analysis was performed using the exon-by-exon PCR-single-strand conformation polymorphism method. Two heterozygous missense mutations, A1557T (His446Leu) and C2859T (Pro880Leu), were found in eight tumor samples, but the same mutation was also present in the constitutional cells of corresponding patients. The incidence of the mutant alleles in the patient and control groups showed no significant difference, suggesting that these mutations are rare single nucleotide polymorphisms unrelated with tumorigenesis. These results suggest that the NFAT1 gene is not likely to be a tumor suppressor gene in human cartilaginous tumors.

Spontaneous osteoarthritic lesions in a new mutant strain of the mouse.

In our laboratory, mice showing signs of osteoarthritic lesions with cinnamon colored (yellowish-brown) hair were discovered in a colony of B6C3F1 mice. This mouse is characterized by tiptoe walking and swelling and ankylotic changes in the ankle joint. As to radiographic findings, osteoarthritic changes, such as erosion and/or fusion of the bone tissue, were evident in the ankle joints. Histopathological characteristics included irregularity of articular surfaces caused by fissuring and/or erosion with degeneration of articular cartilage, as well as osteophytes with abnormal proliferation of chondrocytes in joint margin regions. Subsequently, ankylotic changes in the ankle joints were completed in the formation of a cartilaginous bridge and fusion of articular cavity with abnormal proliferation of cartilaginous or bone tissues. This mouse strain may provide an additional animal model that is valuable in the study of human osteoarthritis (OA).

Basic calcium phosphate crystals stimulate cell proliferation and collagenase message accumulation in cultured adult articular chondrocytes.

To investigate BCP (basic calcium phosphate) crystal-stimulated mitogenesis and collagenase gene transcription in primary cultures of porcine chondrocytes. The role of protein kinases in BCP crystal-stimulated DNA synthesis was investigated using thymidine incorporation, kinase inhibitors, and protein kinase C (PKC) assays. Northern blot analysis was used to determine the levels of collagenase c-fos and c-jun message. BCP crystals stimulated chondrocyte proliferation in a PKC-dependent manner. Increased levels of collagenase message were preceded by an increased accumulation of c-fos, but not c-jun. BCP crystals could contribute to the abnormal chondrocyte proliferation and collagenase secretion observed in some rheumatic diseases.