👤 Dongrim Seol

Focal damage to articular cartilage incurred during joint injuries frequently progresses to post-traumatic osteoarthritis (PTOA) due to the limited intrinsic repair capacity of cartilage. Chondrogenic progenitor cells (CPCs) residing within the cartilage can contribute to repair if effectively recruited and activated. Early interventions that enhance CPC homing and their subsequent chondrogenesis offer a regenerative strategy to prevent PTOA progression, addressing the current lack of effective early clinical therapies. GDF5 stands out as a key protein involved in cartilage development, yet its potential to mobilize CPC-mediated regeneration remains underexplored. We evaluated the effects of GDF5 on CPC migration, proliferation, chondrogenic differentiation, and anti-catabolic activity using in vitro CPC models. To assess CPC chemotaxis in a clinically relevant biomaterial context, GDF5 was incorporated into a hyaluronic acid/fibrin interpenetrating network (IPN) hydrogel and tested in an ex vivo cartilage defect model. GDF5 acted as a potent chemoattractant for CPCs, promoting their recruitment toward cartilage defects when delivered via a hyaluronic acid/fibrin IPN hydrogel in an ex vivo model. GDF5 also enhanced CPC proliferation, consistent with activation of a glycolysis-associated transcriptional program. In addition, GDF5 significantly upregulated chondrogenic markers, including SOX9, COL2a1, and ACAN, and elevated extracellular matrix components in CPCs, potentially through activation of the PI3K/AKT signaling pathway. Furthermore, GDF5 reduced expression of a key catabolic enzyme ADAMTS5, possibly through the WWP2/miR-140 axis. These findings highlight the versatile role of GDF5 on endogenous CPCs. When combined with a hydrogel platform, GDF5 may serve as an early therapeutic strategy to convert injured cartilage from a passive site of degeneration into one of active regeneration. Show less

We used next-generation sequencing (NGS) to investigate the genetic causes of suspected genetic short stature in 37 patients, and we describe their phenotypes and various genetic spectra. We reviewed the medical records of 50 patients who underwent genetic testing using NGS for suspected genetic short stature from June 2019 to December 2022. Patients with short stature caused by nongenetic factors or common chromosomal abnormalities were excluded. Thirty-seven patients from 35 families were enrolled in this study. We administered one of three genetic tests (2 targeted panel tests or whole exome sequencing) to patients according to their phenotypes. Clinical and molecular diagnoses were confirmed in 15 of the 37 patients, for an overall diagnostic yield of 40.5%. Fifteen pathogenic/likely pathogenic variants were identified in 13 genes (ACAN, ANKRD11, ARID1B, CEP152, COL10A1, COL1A2, EXT1, FGFR3, NIPBL, NRAS, PTPN11, SHOX, SLC16A2). The diagnostic rate was highest in patients who were small for their gestational age (7 of 11, 63.6%). Genetic evaluation using NGS can be helpful in patients with suspected genetic short stature who have clinical and genetic heterogeneity. Further studies are needed to develop patient selection algorithms and panels containing growth-related genes. Show less

p53 regulates various cellular responses through transcriptional regulation of distinct sets of target genes. Dual specificity phosphatase 6 (DUSP6) is a cytosolic phosphatase that inactivates the extracellular-signal-regulated kinase 1/2 (ERK1/2). This study demonstrates that p53 transactivates DUSP6 in human colorectal HCT116 cells to regulate ERK1/2 in p53-mediated cell death. DUSP6 is transactivated by p53 overexpression and genotoxic agents, and chromatin immunoprecipitation revealed two p53-binding sites in the DUSP6 promoter responsible for DUSP6 induction. Expression of shDUSP6 inhibited 5'-FU-induced cell death, whereas overexpression of DUSP6 increased susceptibility to 5'-FU. 5'-FU treatment dephosphorylated ERK in a DUSP6-dependent manner, resulting in destabilization of Bcl-2 and stabilization of Bad. These results provide insights on the modulatory role of p53 in the survival pathway by up-regulating DUSP6. Show less

The dynamic exchange of histone lysine methylation status by histone methyltransferases and demethylases has been previously implicated as an important factor in chromatin structure and transcriptional regulation. Using immunoaffinity TAP analysis, we purified the WHISTLE-interacting protein complexes, which include the heat shock protein HSP90α and the jumonji C-domain harboring the histone demethylase JMJD1C. In this study, we demonstrate that JMJD1C specifically demethylates histone H3K9 mono- and di-methylation, and mediates transcriptional activation. We also provide evidence suggesting that both WHISTLE and JMJD1C performs functions in the development of mouse testes by regulating the expression of the steroidogenesis marker, p450c17, via SF-1-mediated transcription. Furthermore, we demonstrate that WHISTLE is recruited to the p450c17 promoter via SF-1 and represses the transcription of prepubertal stages of steroidogenesis, after which JMJD1C replaces WHISTLE and activates the expression of target genes via SF-1-mediated interactions. Our results demonstrate that the histone methylation balance mediated by HMTase WHISTLE and demethylase JMJD1C perform a transcriptional regulatory function in mouse testis development. Show less