Skin health is closely tied to collagen production, which maintains firmness and elasticity. Cell therapies often leverage the “secretome,” a cocktail of growth factors, proteins, and signaling molecules released by cells. Among these, extracellular vesicles (EVs)—especially bacterial EVs (bEVs)—have emerged as potent, stable carriers of bioactive molecules. bEVs from the microbiome mediate cross-kingdom communication and influence human cellular functions. While several therapeutic effects have been observed in diseases, their potential for promoting skin health through collagen enhancement has not been fully explored. This study investigates bEVs from eight Lactobacillales strains for their therapeutic relevance in skin applications.
Methods
bEVs were isolated from eight gram-positive Lactobacillales strains grown in MRS medium and purified via tangential flow filtration. Nanoparticle Tracking Analysis (NTA) measured vesicle size and count; protein and lipid content were quantified. Cytotoxicity was assessed in HEK293T, LX-2, and keloid fibroblast cells. Microarray-based transcriptomic profiling in HEK293T cells was used for Connectivity Map (CMap) analysis to predict therapeutic roles. Collagen production effects were validated via Sirius Red staining and ELISA in NIH3T3 and LX-2 cells. Proteomic analyses and host-pathogen interaction mapping (HPIDB, STRING) were used to uncover collagen-regulating molecular pathways.
Key Findings
- Strain-Specific Features:
Distinct bEV profiles were observed: L. paracasei yielded the largest bEVs (82.5 nm), L. lactis the highest vesicle count (3.2 × 10⁹/mL), L. plantarum the highest protein content (0.124 pg/particle), and L. salivarius the most lipids (16.3 µg/particle). Lipid-rich bEVs showed higher cytotoxicity in HEK293T cells. Larger bEVs had better delivery to fibroblasts. - CMap Predictions for Skin Health:
Transcriptomic analysis connected bEVs from L. rhamnosus, L. fermentum, L. acidophilus, and S. thermophilus with skin-related drug signatures, involving Ras, PI3K-AKT, JAK-STAT, mTOR, and focal adhesion signaling—all essential to skin elasticity and collagen dynamics. - Experimental Validation:
All eight bEVs significantly boosted collagen in NIH3T3 cells. Four strains (L. rhamnosus, L. fermentum, L. acidophilus, S. thermophilus) showed up to 1.25-fold collagen increase in LX-2 cells (p < 0.001). However, effects were not consistently dose-dependent across concentrations. - Mechanistic Insights:
Proteomic mapping showed bEV proteins interact with human pathways like JAK-STAT, PI3K-AKT, and focal adhesion. For example, L. rhamnosus bEVs upregulated Ras and PI3K-AKT; L. fermentum activated PI3K-AKT and mTOR; L. acidophilus enhanced JAK-STAT; S. thermophilus increased ribosomal activity while reducing oxidative stress. Regulators like pSmad3 and Hsp47 were upregulated, and Mmp1 (collagenase) was downregulated.
This study pioneers the integration of CMap bioinformatics with experimental work to uncover the collagen-boosting potential of Lactobacillales-derived bEVs. It reveals strain-specific molecular cargo capable of activating key skin regeneration pathways. These findings suggest bEVs could be leveraged as next-generation bioactive ingredients in skincare. Moving forward, deeper cargo profiling (including RNA and metabolites), broader bacterial screening, and phase-based culturing will further refine their therapeutic applications.
Link to the study: https://www.nature.com/articles/s41598-025-12873-z
