Biomedical subjects

Koichiro Higasa

Publications and source records attributed to Koichiro Higasa.

3 recordsLinked to original sources

PubMed2026

Differential regulation of CYP46A1 in ischemic core and peri-infarct regions of male mouse brain after permanent middle cerebral artery occlusion.

Cholesterol 24-hydroxylase (CYP46A1) regulates brain cholesterol homeostasis and synaptic plasticity, playing a crucial role in ischemic stroke. Although previous studies have reported post-ischemic CYP46A1 upregulation, its spatiotemporal dynamics remain poorly defined. To elucidate these dynamics, we investigated the expression of CYP46A1 and other essential cholesterol homeostasis-related genes from 6 h to 3 days after permanent middle cerebral artery occlusion (pMCAO) in CB-17 mice. We utilized single-cell and single-nucleus transcriptomics, regional quantitative PCR, and high-resolution immunohistochemistry. CYP46A1 is predominantly expressed in neurons. Following ischemia, the cholesterol network exhibited a dynamic spatiotemporal divergence. Acutely (6 h post-ischemia), surviving regions transiently upregulated cell-autonomous cholesterol synthesis genes and CYP46A1. Subacutely (3 days), this response shifted toward a widespread upregulation of glia-dependent cholesterol transport genes and general CYP46A1 downregulation. At 24 h, CYP46A1 protein was substantially reduced in the necrotic core and superficial layer II/III of the peri-infarct cortex, but upregulated in deeper layer V, hippocampus, and lateral striatum. Notably, this localized upregulation spatially coincided with reactive microglial hypertrophy. These findings indicate that CYP46A1 is dynamically modulated in viable tissues following ischemic stress. This spatial divergence likely reflects a synergistic interaction between inflammatory propagation and neural circuit-mediated oxidative stress. Resolving these spatiotemporal profiles provides a rigorous foundation for evaluating CYP46A1 functionality and developing stage-specific therapeutic interventions.

Cholesterol 24-hydroxylase↗

PubMed2026

Primary Cerebral Pleomorphic-Myxoid Sarcoma With Many Hyaline Globules.

A case of primary sarcoma that arose in the right temporal lobe of a 59-year-old man is reported. The patient had a history of resection of a "pituitary tumor" and postoperative radiotherapy about 40 years earlier. The cerebral tumor consisted of loose and diffuse proliferation of large pleomorphic cells in a matrix showing a markedly myxoid change and containing a variable amount of delicate collagen fibers. Some tumor cells had a large intracytoplasmic vacuole containing acid mucopolysaccharide, thus featuring "pseudolipoblasts." Differentiation along other specific mesenchymal lineages was not found. Many tumor cells contained densely eosinophilic hyaline globules in the cytoplasm. Tumor cells showed a loss of the nuclear expression of H3K27me3. Although cerebral sarcomas showing similar histopathological features have not been previously reported, a markedly myxoid change of the stroma admixed with delicate collagen fibers and "pseudolipoblasts" suggests a close pathological kinship to myxofibrosarcoma. Another notable finding was the appearance of many hyaline globules, which has been considered a characteristic finding of primary intracranial sarcoma, DICER1-mutant. In the cytogenetic study of the present case, however, no DICER1 gene mutations were demonstrated.

Humans↗

PubMed2025

HMGA2 links morphological evolution and microenvironment dynamics to systemic therapy response in clear cell renal cell carcinoma.

BACKGROUND: Clear cell renal cell carcinoma (ccRCC) exhibits significant heterogeneity due to morphological changes and tumor microenvironment dynamics, influencing systemic therapy responses. While the role of high-mobility group AT-hook 2 (HMGA2) in tumor progression has been implicated in other cancers, its significance in ccRCC remains unclear. This study investigates the role of HMGA2 in these processes and its clinical impact. METHODS: Spatial transcriptomics (ST) was performed on primary ccRCC samples to investigate expression trajectories associated with HMGA2 expression and morphological evolution. In metastatic ccRCC cohorts treated with systemic therapy, immunohistochemistry and bulk RNA sequencing data were analyzed to evaluate molecular and clinical features in relation to HMGA2. Single-cell RNA sequencing (scRNA-seq) data were used to explore immune cell populations and their interactions. Based on these findings, multiplex immunohistochemistry (mIHC) assessed spatial distribution, cell-cell interactions, and pathological responses of key immune populations. RESULTS: HMGA2 expression was associated with aggressive morphological patterns, such as solid sheets and rhabdoid/sarcomatoid. ST revealed a progressive increase in HMGA2 expression along the morphological trajectory, marked by a shift from clear to eosinophilic cytoplasm, with eccentric nuclei and prominent nucleoli, and loss of vascular architecture. HMGA2-high tumors exhibited aggressive phenotypes driven by cell cycle, epithelial-mesenchymal transition, and inflammatory signaling pathways. Clinically, patients with high HMGA2 had worse progression-free survival but responded better to immune checkpoint inhibitor combination (Combo-ICI) therapy than to tyrosine kinase inhibitor monotherapy. To assess the immune landscape, scRNA-seq data revealed that HMGA2-high tumors were enriched with progenitor exhausted CD8+ T cells (Tpex), along with increased frequencies of conventional dendritic cell type 1 (cDC1) and inflammatory cDC type 2, which were found to interact with Tpex via ICAM-1. mIHC confirmed that Tpex were enriched among Combo-ICI responders in HMGA2-high tumors, with higher densities and closer proximity to ICAM-1+ cDC1. CONCLUSIONS: These findings suggest that dynamic HMGA2 expression contributes to morphological evolution and modulates immune responses through enhanced Tpex-cDCs engagement, serving as a potential marker for systemic therapy response in ccRCC. However, additional experimental studies are required to validate these mechanisms.

Humans↗