Biology subjects

Sevlever, G. E.

Publications and source records attributed to Sevlever, G. E..

4 recordsLinked to original sources

bioRxiv2026

Modulating SPARC Expression in Mesenchymal Stem Cells Improves Secretome-Mediated Skin Regeneration and Wound Repair

Mesenchymal stem cells (MSCs) have garnered significant attention over the past three decades due to their robust regenerative potential, primarily mediated by their paracrine activity by releasing soluble bioactive factors and extracellular vesicles (EVs). The MSC secretome plays a pivotal role in wound healing by influencing cellular migration, inflammation, angiogenesis, extracellular matrix (ECM) remodeling, and re-epithelialization. SPARC (Secreted Protein Acidic and Rich in Cysteine), a multifunctional ECM glycoprotein involved in tissue repair and remodeling, regulates key processes such as cell migration, proliferation, angiogenesis, and survival. Despite its known role in ECM dynamics, the impact of SPARC expression on the regenerative properties of MSCs remains underexplored. In this study, we hypothesized that SPARC overexpression in MSCs enhances their secretomes regenerative capacity. Using lentiviral systems, we generated SPARC-overexpressing (+SPARC) and SPARC-knockdown (KD-SPARC) MSCs to investigate SPARCs role in wound healing. Conditioned media (CM) derived from these MSCs were analyzed in vitro for their effects on human skin keratinocytes and fibroblasts. Our results revealed that SPARC expression significantly influences cell-specific migration and cell cycle. Furthermore, in an in vivo wound healing model, CM from +SPARC MSCs accelerated regeneration, while SPARC absence in MSCs CM delayed the healing process. These findings underscore the critical role of SPARC in modulating MSC secretome composition and enhancing its regenerative efficacy. This study highlights SPARC as a promising therapeutic target for the development of advanced regenerative therapies aimed at improving cutaneous wound healing outcomes.

cell biology↗

bioRxiv2024

Identification of microRNAs regulated by E2F transcription factors in human pluripotent stem cells

Human pluripotent stem cells (hPSCs), which include embryonic and induced pluripotent stem cells (hESCs and hiPSCs, respectively), have an unusual cell cycle structure which consists of a short G1 phase and the absence of the G1/S checkpoint regulation. E2F transcription factors (E2Fs) play an important role in the G1/S transition. G1 duration contributes to hPSC fate determination, and microRNAs (miRNAs) play critical roles in this commitment. As little is known about the interplay between E2Fs and miRNAs in hPSCs, we aimed to identify miRNAs that are regulated by E2Fs in these cells. We first found that mRNA expression levels of canonical E2F repressors were more expressed than most E2F activators in G1-arrested hPSCs. Moreover, we observed higher mRNA and protein expression levels of canonical E2F2, E2F3A, and E2F5 in G1 synchronized hPSCs compared to human fibroblasts (HF). However, E2F1 and E2F4 protein expression levels were higher in HF. We next found that E2F inhibition with HLM006474 induced an increase in the G1 cell population without affecting hPSC viability, concomitantly with a decrease in OCT-4 mRNA levels and the percentage of OCT-4+ hPSCs. Next, by RNA-seq analysis we found 52 differentially expressed (DEGs) miRNAs in HLM006474-treated hESCs. RT-qPCR validation of some of the DEGs let us conclude that miR-19a-3p, miR-19b-3p, miR-4454, miR-1260a, miR-1260b, miR-454-3p and miR-301a-3p are regulated by E2Fs in hPSCs. Interestingly, gene target and ontology analysis of these miRNAs revealed a possible implication in proliferation and cell cycle regulation, development, and neural differentiation.

developmental biology↗

bioRxiv2023

The transcription factor OCT6 promotes the dissolution of the naive pluripotent state by repressing Nanog and activating a formative state gene regulatory network.

Animal development relies on complex gene regulatory networks (GRNs) that govern the nearly irreversible changes that occur during cell differentiation. In this work we aimed to determine key transcription factors (TFs) associated with the dissolution of the naive pluripotent state and the acquisition of a formative identity. We identified OCT6 as one of the earliest TFs induced during the onset of mouse embryonic stem cell (mESCs) differentiation. To investigate its role, we generated an Oct6 knockout mESC line, which failed to acquire the characteristic cell morphology associated with the formative state. Transcriptome analysis of differentiating cells revealed nearly 300 differentially expressed genes compared to wild-type cells, including pluripotency TFs Nanog, Klf2, Nr5a2, Prdm14, and Esrrb, that failed to correctly downregulate. Notably, premature expression of OCT6 in naive cells triggered a rapid morphological transformation mirroring differentiation, accompanied by self-induction of Oct6 and expression of TFs such as Sox3, Zic2/3, Foxp1, as well as the formative genes Dnmt3A and FGF5. Strikingly, the majority of OCT6 expressing cells did not express NANOG. Gene expression and single molecule RNA-FISH analysis confirmed that this regulation was at the transcriptional level. Collectively, our results establish OCT6 as a key TF in the dissolution of the naive pluripotent state and support a model where Oct6 and Nanog form a double negative feedback loop which could act as a toggle switch important for the transition to the formative state. HighlightsO_LIOct6 is rapidly induced as mESCs exit ground state pluripotency. C_LIO_LILoss of OCT6 negatively affects the transition to formative pluripotency. C_LIO_LIPremature expression of OCT6 in mESCs is sufficient to induce a formative-like phenotype. C_LIO_LIOCT6 and NANOG repress each other forming a double negative feedback loop. C_LI

developmental biology↗

bioRxiv2020

Downregulation of E-cadherin in pluripotent stem cells triggers partial EMT

Epithelial to mesenchymal transition (EMT) is a critical cellular process that has been well characterized during embryonic development and cancer metastasis and it also is implicated in several physiological and pathological events including embryonic stem cell differentiation. During early stages of differentiation, human embryonic stem cells pass through EMT where deeper morphological, molecular and biochemical changes occur. Though initially considered as a decision between two states, EMT process is now regarded as a fluid transition where cells exist on a spectrum of intermediate states. In this work, using a CRISPR interference system in human embryonic stem cells, we describe a molecular characterization of the effects of downregulation of E-cadherin, one of the main initiation events of EMT, as a unique start signal. Our results suggest that the decrease and delocalization of E-cadherin causes an incomplete EMT where cells retain their undifferentiated state while expressing several characteristics of a mesenchymal-like pheno-type. Namely, we found that E-cadherin downregulation induces SNAI1 and SNAI2 upregulation, promotes MALAT1 and LINC-ROR downregulation, modulates the expression of tight junction occludin 1 and gap junction connexin 43, increases human embryonic stem cells migratory capacity and delocalize b-catenin. Altogether, we believe our results provide a useful tool to model the molecular events of an unstable intermediate state and further identify multiple layers of molecular changes that occur during partial EMT.

cell biology↗