There has been a resurgence of interest in bioactive peptides as therapeutic agents. This is particularly interesting for tyrosinase, which can be inhibited by thiol-containing peptides. This work demonstrates that an N-terminal cysteine-containing tetrapeptide can be rationally designed to inhibit tyrosinase activity in vitro and in cells. The tetrapeptide cysteine (C), arginine (R), asparagine (N) and leucine (L) or CRNL is a potent inhibitor of tyrosinase activity with an IC₅₀ value of 39.62 ± 6.21 μM, which is comparable to currently used tyrosinase inhibitors. Through structure-activity studies and computational modeling, we demonstrate the peptide interacts with the enzyme via electrostatic (R with E322), hydrogen bonding (N with N260) and hydrophobic (L with V248) intermolecular interactions and that a combination of these is required for potent activity. Moreover, copper chelating activity might be one of the mechanisms of tyrosinase inhibition by CRNL. Kinetic studies show that tetrapeptide is a competitive inhibitor with two-step irreversible inhibition. In addition, CRNL had no toxicity and could reduce melanin levels in the murine melanoma cell line (B16F1). Overall, CRNL is a very promising candidate for hyperpigmentation treatment.

There is a desire to develop new molecules that can combat hyperpigmentation. To this end, the N-terminal cysteine-containing heptapeptide TILI-2 has shown promising preliminary results. In this work, the mechanism by which it works was evaluated using a series of biochemical assays focusing on known biochemical pathways, followed by LC-MS/MS proteomics to discover pathways that have not been considered before. We demonstrate that TILI-2 is a competitive inhibitor of tyrosinase’s monophenolase activity and it could potentially scavenge ABTS and DPPH radicals. It has a very low cytotoxicity up to 1400 µM against human fibroblast NFDH cells and macrophage-like RAW 264.7 cells. Our proteomics study revealed that another putative mechanism by which TILI-2 may reduce melanin production involves the disruption of the TGF-β signaling pathway in mouse B16F1 cells. This result suggests that TILI-2 has potential scope to be used as a depigmenting agent.

We evaluated the potential of Fourier-transform infrared (FTIR) microspectroscopy for non-invasive biochemical profiling of rhesus macaque embryonic stem cells (rhESCs) cultured in either conventional FGF2/KOSR medium or a novel formulation, ALGöX. Cells from both conditions were analyzed by immunocytochemistry, RNA sequencing, and high-resolution FTIR profiling. Molecular marker expression patterns and transcriptional profiles revealed that rhESCs maintained in FGF2/KOSR were in the primed pluripotent state, whereas those cultured in ALGöX adopted a naïve-like state. FTIR spectra showed consistent differences in protein, lipid, and nucleic acid signatures, with ALGöX-cultured cells displaying higher amide I/II and nucleic acid absorbance and FGF2/KOSR-cultured cells exhibiting stronger lipid-associated bands. Principal component analysis (PCA) separated the two groups along PC−1 (64% variance), and partial least squares discriminant analysis (PLS-DA) classified samples with 100% specificity and 100% sensitivity. These findings demonstrate that FTIR microspectroscopy can reliably discriminate pluripotent state–specific biochemical features in non-human primate PSCs, providing a rapid and label-free approach for monitoring stem cell identity and quality.

We evaluated the potential of Fourier-transform infrared (FTIR) microspectroscopy for non-invasive biochemical profiling of rhesus macaque embryonic stem cells (rhESCs) cultured in either conventional FGF2/KOSR medium or a novel formulation, ALGöX. Cells from both conditions were analyzed by immunocytochemistry, RNA sequencing, and high-resolution FTIR profiling. Molecular marker expression patterns and transcriptional profiles revealed that rhESCs maintained in FGF2/KOSR were in the primed pluripotent state, whereas those cultured in ALGöX adopted a naïve-like state. FTIR spectra showed consistent differences in protein, lipid, and nucleic acid signatures, with ALGöX-cultured cells displaying higher amide I/II and nucleic acid absorbance, and FGF2/KOSR-cultured cells exhibiting stronger lipid-associated bands. Principal component analysis (PCA) separated the two groups along PC1 (64% variance), and partial least squares-discriminant analysis (PLS-DA) classified samples with 100% specificity and 100% sensitivity. These findings demonstrate that FTIR microspectroscopy can reliably discriminate pluripotent state–specific biochemical features in non-human primate PSCs, providing a rapid and label-free approach for monitoring stem cell identity and quality.

The conversion of primed pluripotent stem cells to a naive-like state has emerged as a critical strategy for enhancing developmental potential and broadening applications in regenerative medicine. Conditioned media (CM)-based approaches provide a supportive microenvironment enriched with secreted factors that may facilitate this state transition without extensive genetic or chemical manipulation. In this study, we investigated the potential of human Wharton’s Jelly-derived mesenchymal stem cell-conditioned media (hWJ-MSCs-CM) and mouse embryonic fibroblasts CM (MEFs-CM) to support the conversion of primed rhesus monkey embryonic stem cells (rhESCs) into a naive-like state. The rhESCs were cultured under feeder-free and feeder conditions using both hWJ-MSCs-CM and MEFs-CM, exhibiting distinct morphological changes during conversion. Immunofluorescence analysis demonstrated the expression of pluripotency and naive markers under both conditions. Gene expression analysis further confirmed the upregulation of naive-specific genes and downregulation of primed markers, with statistically significant differences between groups. Additionally, epigenetic reprogramming was assessed, revealing differential effects of the CM sources on the reversion to a naive state. These findings highlight the potential of hWJ-MSCs-CM as a supportive system for naive-like state induction in primate ESCs.

This study aimed to examine the potential of human Wharton’s Jelly-derived mes-enchymal stem cells (hWJ-MSCs) in supporting the conversion of the primed state of rhesus monkey embryonic stem cells (rhESCs) to a naïve-like state. The rhESCs were cultured under feeder-free and feeder conditions using hWJ-MSC-conditioned media (hWJ-MSCs-CM) and mouse embryonic fibroblasts CM (MEFs-CM) exhibited distinct morphological changes during conversion. Immunofluorescence analysis demonstrated the expression of pluripotency and naïve markers under both condi-tions. Gene expression analysis further confirmed the upregulation of naïve-specific genes and downregulation of primed markers, with statistically significant differ-ences between groups. Additionally, epigenetic reprogramming was assessed, re-vealing differential effects of the CM sources on the reversion to a naïve state. These findings highlight the potential of hWJ-MSCs-CM as a supportive system for na-ïve-state induction in primate ESCs.