Ian William Peall

Neural progenitor cell (NPC) fate decisions are governed by transcriptional and signaling programmes, yet the epigenetic mechanisms stabilising early neuronal versus glial lineage trajectories remain unresolved. Here, DNA methylation landscapes in two widely used human NPC models—ReNcell VM (RVM) and ReNcell CX (RCX)—were examined under several different culture conditions to define regulatory pathways shaping lineage specification. Exploratory analyses revealed that the ReNcell lines exhibited methylation similar to primary glial populations rather than neuronal subtypes, with RCX cells positioned further along a maturation trajectory and RVM cells retaining a multipotent state. RCX cultures displayed hypomethylation of neuronal markers (DCX, ENO2, MAP2), whereas RVM cultures showed consistent GFAP hypomethylation, indicative of glial or early progenitor identity. Signaling pathways regulating lineage commitment were highlighted, including TGFβ, Wnt, and Notch signaling. Within the Notch pathway, RCX cells exhibited higher gene expression of NOTCH2 and JAG ligands, consistent with active lateral induction and a developmentally advanced state. In contrast, RVM cells exhibited higher DLL1 and NOTCH1 expression, supporting lateral inhibition and cellular heterogeneity. Knockdown of syndecan-4 (SDC4) revealed opposing effects on Notch activity. Together, these findings established DNA methylation as a determinant of lineage-specific signaling in human NPCs.

Heparan sulfate proteoglycans (HSPGs) within the neuronal niche are expressed during brain development, contributing to multiple aspects of neurogenesis, yet their roles in glial lineage commitment remain elusive. This study utilised three human cell models expanded under basal culture conditions followed by media-induced lineage induction to identify a reproducible and robust model of gliogenesis. SH-SY5Y human neuroblastoma cells (neuronal control), ReNcell CX human neural progenitor cells (astrocyte inductive) and ReNcell VM human neural progenitor (mixed neural induction) models were examined. The cultures were characterised during basal and inductive states via Q-PCR, Western Blotting, immunocytochemistry (ICC) and calcium signalling activity analyses. While the ReNcell lines did not produce fully mature or homogeneous astrocyte cultures, the ReNcell CX cultures most closely resembled an astrocytic phenotype with ReNcell VM cells treated with platelet-derived growth factor (PDGF) biased toward an oligodendrocyte lineage. The glycated variant of surface-bound glypican-2 (GPC2) was found to be associated with lineage commitment, with GPC6 and 6-O HS sulfation upregulated in astrocyte lineage cultures. Syndecan-3 (SDC3) emerged as a lineage-sensitive proteoglycan, with its cytoplasmic domain enriched in progenitor-like states and lost upon differentiation, supporting a role in maintaining neural plasticity. Conversely, the persistence of transmembrane-bound SDC3 in astrocyte cultures suggest continued involvement in extracellular signalling and proteoglycan secretion, demonstrated by increased membrane-bound HS aggregates. This data supports HSPGs and HS GAGs as human neural lineage differentiation and specification markers that may enable better isolation of human neural lineage-specific cell populations and improve our understanding of human neurogenesis.

Heparan sulfate proteoglycans (HSPGs) within the neuronal niche are expressed during brain development, con-tributing to multiple aspects of neurogenesis, yet their roles in glial lineage commitment remain elusive. This study utilised three human cell models expanded under basal culture conditions followed by media induced lineage in-duction to identify a reproducible and robust model of gliogenesis. SH-SY5Y human neuroblastoma cells (neuronal control), ReNcell CX human neural progenitor cells (astrocyte inductive) and ReNcell VM human neural progenitor (mixed neural induction) models were examined. Cultures were characterised during basal and inductive states via Q-PCR, Western Blotting, immunocytochemistry (ICC), and calcium signalling activity analyses. While the ReNcell lines did not produce fully mature or homogeneous astrocyte cultures, ReNcell CX cultures most closely resembled an astrocytic phenotype with ReNcell VM cells treated with platelet derived growth factor (PDGF) biased toward an oligodendrocyte lineage. The glycated variant of surface-bound glypican-2 (GPC2) was found to be associated with lineage commitment, with GPC6 and 6-O HS sulfation upregulated in astrocyte lineage cultures. Syndecan-3 (SDC3) emerged as a lineage-sensitive proteoglycan, with its cytoplasmic domain enriched in progenitor-like states and lost upon differentiation, supporting a role in maintaining neural plasticity. Conversely, the persistence of transmem-brane-bound SDC3 in astrocyte cultures suggest continued involvement in extracellular signalling and glycan secretion, demonstrated by increased membrane-bound HS aggregates. This data supports HSPGs and HS GAGs as human neural lineage differentiation and specification markers that may enable better isolation of human neural lineage specific cell populations and improve our understanding of human neurogenesis.

Generating neurons from human stem cells has potential for brain damage therapy and neurogenesis modeling, but current efficacy is limited by culture heterogeneity and the lack of markers. We have previously reported the heparan sulfate proteoglycans (HSPGs) glypican‐1 (GPC1) and ‐4 (GPC4) as the markers of lineage‐specific human neural stem cells (hNSCs) and mediators of hNSC lineage potential. Here, we further examined phenotypical characteristics and GPC1 and GPC4 during neural differentiation of hNSCs in the presence of two neurogenic growth factors reported to bind to heparan sulfate: brain‐derived neurotrophic factor (BDNF) and platelet‐derived growth factor‐B (PDGF‐B). In hNSC neural cultures, GPC1 and GPC4 were expressed along neurites and cell bodies in long‐term (40–60 days) neural differentiation cultures demonstrating the areas of differential localization—suggesting potentially different functions. Neural differentiation cultures in the presence of BDNF or PDGF‐B generated phenotypically different neural cells with BDNF treatment associated with higher GPC4 versus GPC1 expression, increased heterogeneity, and differential neuron subtype marker expression to PDGF‐B cultures. PDGF‐B cultures exhibited higher levels of spontaneous activity and reduced heterogeneity over long‐term culture associated with decreased GPC4. Untreated neural cultures were highly variable, supporting the use of neuroregulatory growth factors for guided differentiation. Targeted siRNA downregulation of GPC1/4 reduced neural differentiation markers and altered response to exogenous BDNF and PDGF‐B. This work confirms GPC1 and GPC4 as regulators of human neural differentiation and supports their use as novel markers of neural cell characterization.

Bone marrow-derived human mesenchymal stems cells (hMSCs) are precursors to adipocyte and osteoblast lineage cells. Dysregulation of the osteo-adipogenic balance has been implicated in pathological conditions involving bone loss. Heparan sulfate proteoglycans (HSPGs) such as cell membrane-bound syndecans (SDCs) and glypicans (GPCs) mediate hMSC lineage differentiation and with syndecan-1 (SDC-1) reported in both adipogenesis and osteogenesis, these macromolecules are potential regulators of the osteo-adipogenic balance. Here, we disrupted the HSPG profile in primary hMSC cultures via temporal knockdown (KD) of SDC-1 using RNA interference (RNAi) in undifferentiated, osteogenic and adipogenic differentiated hMSCs. SDC-1 KD cultures were examined for osteogenic and adipogenic lineage markers along with changes in HSPG profile and common signalling pathways implicated in hMSC lineage fate. Undifferentiated hMSC SDC-1 KD cultures exhibited a pro-adipogenic phenotype with subsequent osteogenic differentiation demonstrating enhanced maturation of osteoblasts. In cultures where SDC-1 KD was performed following initiation of differentiation, increased adipogenic gene and protein marker expression along with increased Oil Red O staining identified enhanced adipogenesis, with impaired osteogenesis also observed in these cultures. These findings implicate SDC-1 as a facilitator of the hMSC osteo-adipogenic balance during early induction of lineage differentiation.