Joo Hyun Kim

Metastasis is a leading cause of mortality in breast cancer and is critically influenced by cell–extracellular matrix (ECM) interactions, mechanical forces, and cellular motility. In this study, we present a cell surface engineering approach using tris(2-carboxyethyl)phosphine (TCEP), a biocompatible thiol-modifying agent, to modulate the biomechanical behavior of breast cancer cells. TCEP treatment increased surface thiol availability, enhanced phosphorylation of focal adhesion kinase (FAK), and promoted the elongation of pFAK-positive focal adhesions, along with cytoskeletal remodeling and stronger cell–ECM adhesion. These molecular and structural changes corresponded with significantly reduced migration and invasion of MCF7 and MDA-MB-231 cells. Using traction force microscopy (TFM), we further observed increased intracellular tension and traction stress, providing quantitative insight into how surface modification regulates mechanotransduction. These findings highlight the potential of cell surface thiol engineering to control cancer cell adhesion and motility, providing a platform for future identification of clinically applicable redox-modulating agents.

Chronic wound healing is a complex and tightly regulated process requiring coordinated epithelial and stromal regeneration. Photobiomodulation (PBM) using low-level red light-emitting diode (LED) therapy has emerged as a non-invasive approach to enhancing skin repair. In this study, we evaluated the therapeutic efficacy of a pulsed, multi-wavelength LED system on full-thickness excisional wound healing in a normal murine model. Daily LED treatment significantly accelerated wound closure, promoted re-epithelialization, and improved dermal architecture. Histological and immunohistochemical analyses revealed enhanced epidermal stratification, reduced inflammation, and improved collagen organization. Molecular profiling demonstrated increased expression of proliferation marker Ki67, keratins CK14 and CK17, and extracellular matrix-related genes including MMPs, Col1a1, and Col3a1. In vitro assays using HaCaT keratinocytes showed accelerated scratch wound closure and cytoskeletal remodeling following PBM exposure. These findings suggest that pulsed PBM promotes coordinated epithelial regeneration and matrix remodeling, highlighting its potential as a tunable and effective therapeutic modality for accelerating cutaneous wound healing under physiological conditions.

Therapeutic advances for vocal fold (VF) disorders are limited by the scarcity of VF-derived epithelial cells (VFEs). Despite their substantial self-renewal capability in vivo, VFEs expand for only a few passages in vitro before succumbing to growth arrest. This has led to the extensive use of alternative cellular sources that are not exposed to physiological stresses of phonation. To address this, we developed an ideal culture strategy that enables long-term expansion of rabbit VFEs (rbVFEs), by utilizing Rho kinase inhibitor (ROCKi), epidermal growth factor (EGF), and mitomycin-treated STO cells or its conditioned media (STO-CM). ROCKi only could support short-term proliferation, and rbVFEs eventually underwent senescence. Further enhancement to ROCKi-containing media with EGF or STO-CM promoted sustained proliferation of rbVFEs. Mechanistically, non-self-renewing rbVFEs exhibited cytoskeletal remodeling associated with increased nuclear YAP localization, elevated focal adhesion, and higher traction forces, whereas self-renewing rbVFEs had cytoplasmic YAP retention, decreased adhesion, and reduced cellular tension. Our optimized culture strategy provides a robust supply of rbVFEs for advancing regenerative approaches in VF research.

Three-dimensional (3D) spheroid cultures are crucial for modeling salivary gland (SG) morphogenesis and advancing regenerative medicine. This study evaluated the effects of varying ratios of mouse SG-derived epithelial cells co-cultured with human dermal fibroblasts (hDFs), identifying a 2:1 ratio (spheroids containing 67% EpCAM^pos cells with 33% hDFs) as optimal for preserving native SG-derived epithelial cell phenotypes. At this ratio, 67% EpCAM^pos spheroids maintained structural integrity and demonstrated a significant reduction in apoptosis and senescence markers, specifically, cleaved caspase-3 (Cc3) and Serpine1, alongside an enhanced expression of the progenitor marker Keratin 5 (KRT5). This highlights the pivotal role of fibroblasts in supporting epithelial cell function in 3D cultures. These spheroids provide a useful model for developing SG tissues that closely mimic physiological properties. Despite promising results, these findings are preliminary and require further validation under diverse conditions and across different SG models.

Tongue cancer is a significant threat to human health due to its propensity to spread throughout the oral cavity and to other regions of the head and neck. The challenges posed by its high invasion, metastasis, and late clinical detection underscore the urgency for effective clinical interventions. In this study, we elucidate the promising anti‐cancer properties of artemisinin, an anti‐malarial drug, in inhibiting cellular interactions within a tongue cancer cell line. Our findings reveal that artemisinin treatment effectively suppresses phosphorylated focal adhesion kinase and its downstream AKT pathway, thereby enhancing apoptotic processes and inducing cell cycle arrest, consequently impeding cellular proliferation. Moreover, artemisinin treatment induces focal adhesion rearrangement and diminishes the cell's capacity to generate traction stress, consequently restraining cell migration on the matrix, as determined via traction force microscopy. Additionally, a transition from N‐cadherin to E‐cadherin expression occurs at cellular junctions, lowering intracellular stress, as measured by monolayer stress microscopy. This transition significantly curtails cellular migratory capabilities. Our in vivo studies corroborate these findings, showing a significant reduction in tumor volume following artemisinin treatment. Our study highlights the therapeutic potential of artemisinin use as a novel strategy for tongue cancer treatment, which acts via modulating both intracellular and intercellular interactions.

Objectives. To compare the surgical outcomes of externally monitored and conventional buried flaps with the goal of determining the usefulness of external monitoring of buried flaps.Methods. In this case-control study with propensity score matching, 30 patients were evenly divided into externally monitored buried flap and conventional buried flap groups. The total operative time for free flap reconstruction, the flap survival rate, the length of hospital stay, the initial time of a reliable visual assessment, complications, the final diet achieved, and the duration until diet initiation were compared between the groups.Results. The mean operative time for reconstruction was 115 minutes (interquartile range, 85–150 minutes) and 142 minutes (interquartile range, 95–180 minutes) in the externally monitored and conventional groups, respectively (P= 0.245). The median length of hospital stay was 24 days (interquartile range, 18–30 days) and 27 days (interquartile range, 20–41 days) in the externally monitored and conventional groups, respectively (P=0.298). The median duration until diet initiation was 15 days (interquartile range, 15–21 days) and 18 days (interquartile range, 15–34 days) in the externally monitored and conventional groups, respectively (P=0.466). The final diet, initial time of a reliable visual assessment, and complications were comparable between the groups, but the external skin paddle provided an excellent visual assessment immediately postoperatively in all cases.Conclusion. The outcomes were comparable between the groups, indicating that externalization of the cutaneous component of a buried flap may be a straightforward and useful technique for monitoring a buried anterolateral thigh free flap in laryngopharyngeal reconstructions. The salvage and false-positive rates of compromised flaps should be compared in large subject groups in future studies to prove that the use of an external skin paddle improves flap monitoring.

Large-sized or deep skin wounds require skin substitutes for proper healing without scar formation. Therefore, multi-layered skin substitutes that mimic the genuine skin anatomy of multiple layers have attracted attention as suitable skin substitutes. In this study, a novel skin substitute was developed by combining the multi-layer skin tissue reconstruction method with the combination of a human-derived keratinic extract-loaded nano- and micro-fiber using electrospinning and a support structure using 3D printing. A polycaprolactone PCL/keratin electrospun scaffold showed better cell adhesion and proliferation than the keratin-free PCL scaffold, and keratinocytes and fibroblasts showed better survival, adhesion, and proliferation in the PCL/keratin electrospun nanofiber scaffold and microfiber scaffold, respectively. In a co-culture of keratinocytes and fibroblasts using a multi-layered scaffold, the two cells formed the epidermis and dermal layer on the PCL/keratin scaffold without territorial invasion. In the animal study, the PCL/keratin scaffold caused a faster regeneration of new skin without scar formation compared to the PCL scaffold. Our study showed that PCL/keratin scaffolds co-cultured with keratinocytes and fibroblasts promoted the regeneration of the epidermal and dermal layers in deep skin defects. Such finding suggests a new possibility for artificial skin production using multiple cells.

Due to the morphological resemblance between the electrospun nanofibers and extracellular matrix (ECM), electrospun fibers have been widely used to fabricate scaffolds for tissue regeneration. Relationships between scaffold morphologies and cells are cell type dependent. In this study, we sought to determine an optimum electrospun fiber diameter for human vascular smooth muscle cell (VSMC) regeneration in vascular scaffolds. Scaffolds were produced using poly(caprolactone) (PCL) electrospun fiber diameters of 0.5, 0.7, 1, 2, 2.5, 5, 7 or 10 μm, and VSMC survivals, proliferations, infiltrations, and phenotypes were recorded after culturing cells on these scaffolds for one, four, seven, or 10 days. VSMC phenotypes and macrophage infiltrations into scaffolds were evaluated by implanting scaffolds subcutaneously in a mouse for seven, 14, or 28 days. We found that human VSMC survival was not dependent on the electrospun fiber diameter. In summary, increasing fiber diameter reduced VSMC proliferation, increased VSMC infiltration and increased macrophage infiltration and activation. Our results indicate that electrospun PCL fiber diameters of 7 or 10 µm are optimum in terms of VSMC infiltration and macrophage infiltration and activation, albeit at the expense of VSMC proliferation.

Hematopoietic stem cell (HSC) maintenance requires a specific microenvironment. HSC niches can be activated by tissue damaging chemotherapeutic drugs and various cell signaling molecules such as SDF-1 and FGF, which might also result in bone marrow stress. Recent research has insufficiently shown that endosteal osteolineage cells and other niche constituents recover after marrow injury. We investigated the role of FGF2 in the osteoblastic niche cells during hematopoietic homeostasis recovery after bone marrow injury. Mice were treated with 5-fluorouracil (5FU) to eliminate actively cycling cells in the bone marrow. Primary osteoblasts were isolated and subjected to cell culture. Real-time PCR, western blot and immunohistochemical staining were performed to study niche-related genes, osteoblast markers, and FGF2 signaling. Proliferation rate were analyzed by marker gene Ki67 and colony formation assay. Also, osterix-positive osteoprogenitor cells were isolated by FACS from Osx-GFP-Cre mice after 5FU treatment, and subjected to RNA-sequencing and analyzed for Fgf receptors and niche markers. The endosteal osteolineage cells isolated from 5FU-treated mice showed increased expression of the niche-related genes Sdf-1, Jagged-1, Scf, N-cad, Angpt1 and Vcam-1 and the osteoblast marker genes Osx, Opn, Runx2, and Alp, indicating that BM stress upon 5FU treatment activated the osteoblastic niche. Endosteal osteoblast expanded from a single layer to several layers 3 and 6 days after 5FU treatment. During the early recovery phase in 5FU-activated osteoblastic niches increased FGF2 expression and activated its downstream pERK. FGF2 treatment resulted in increased proliferation rate and the expression of niche marker genes in 5FU-activated osteoblastic niche cells. RNA-seq analysis in Osterix-positive osteoprogenitor cells isolated from 5FU-treated Osx-GFP mice showed significantly increased expression of Fgf receptors Fgfr1, 2 and 3. Although osteoblastic niche cells were damaged by 5FU treatment in the beginning, the increased number of OB layers in the recovery phase may be derived from resident osteoprogenitor cells by FGF2 activation under stress. Taken together, FGF2 signaling can regulate osteoblastic niche cells to support HSC homeostasis in response to bone marrow damage.