Engineering Targeted Nanoparticles for Adipose Stromal Cells Subsets to Reprogram Fibrotic and Inflammatory Niches in Obese Adipose Tissue

Introduction: : Obesity is a major public health challenge characterized by the expansion of white adipose tissue (WAT) and an increased risk of metabolic disorders, including diabetes, cardiovascular disease, and cancer. Within obese WAT, adipose stromal cells (ASCs) exhibit heterogeneity, with distinct subpopulations responding uniquely to altered extracellular matrix (ECM) cues. Our research investigates integrin alpha 7 (ITGA7) as a central mediator of this process and as a targeting strategy. We hypothesize ASCs expressing high levels of ITGA7 (ITGA7high) represent a pro-inflammatory, pro-fibrotic subpopulation contributing to obesity-associated dysfunction in WAT. By leveraging ITGA7 as a marker, we can engineer nanoparticles to selectively target and modulate the activity of this ASC subset, offering a novel therapeutic approach to reduce inflammation and fibrosis in obesity.

Materials and

Methods: : ITGA7 expression in WAT from ob/ob mice was evaluated using immunofluorescence in tissue sections and isolated adipose stem cells (ASCs). ASCs were sorted into ITGA7high and ITGA7low populations and analyzed for adipogenic, inflammatory, and fibrotic markers using molecular techniques including RT-PCR and ELISA for adipokine secretion. To selectively target ITGA7high ASCs, we engineered lipid-coated mesoporous silica nanoparticles (LCMSNs) functionalized with anti-ITGA7 antibodies. Mesoporous silica nanoparticles (MSNPs) were synthesized via a surfactant-directed self-assembly method, coated with liposomes through electrostatic interactions, and conjugated to ITGA7 antibodies via biotin-neutravidin binding (Fig 1A). LCMSNs were loaded with siRNA against plasminogen activator inhibitor-1 (PAI-1), a key pro-inflammatory adipokine implicated in fibrosis and metabolic dysfunction in obesity. ITGA7-LCMSNs were administered subcutaneously to obese (ob/ob) mice to evaluate in vivo silencing of PAI-1 and therapeutic efficacy.

Results, Conclusions, and Discussions:: Immunofluorescence staining revealed significantly greater ITGA7 expression in subcutaneous white adipose tissue (sWAT) of obese mice compared to WT controls. Gene expression and cell sorting analyses confirmed a 50% increase in ITGA7high ASCs in obese mice indicating that obesity enhances the presence of this subpopulation (Fig1B-C). The results revealed that ITGA7high ASCs exhibited elevated expression of ECM genes (Col1a1, Col3a1), decreased adipogenic markers (Pparg, Adiponectin), and increased inflammatory markers (PAI-1, Ccl2, Il6). ITGA7high ASCs were also CD9high, a marker associated with progenitor pools linked to fibrosis and metabolic dysfunction in obesity. In contrast, ITGA7low ASCs displayed higher adipogenic potential, lipolysis, and glucose uptake. In-vitro studies demonstrated specific targeting and enhanced uptake of targeted LCMSNs by ITGA7high ASCs compared to ITGA7low ASCs. Silencing PAI-1 led to a significant (50%) reduction in PAI-1 expression and a corresponding decrease in inflammatory markers. In-vivo, ITGA7-targeted LCMSNs demonstrated strong retention in obese sWAT 48h after subcutaneous injection (Fig1D). Notably, LCMSN treatment led to a significant reduction in PAI-1 expression within obese WAT, confirming effective target engagement and gene silencing (Fig1E).

In conclusion, our study identifies ITGA7 ASC as central mediators of inflammation, fibrosis, and metabolic dysfunction in obesity. We developed a novel nanomedicine-based gene silencing platform using ITGA7-targeted LCMSNs loaded with PAI-1 siRNA, which preferentially accumulated in ITGA7high ASCs and achieved over 50% silencing of Pai-1 in-vivo. Targeting this pathogenic ASC subpopulation significantly reduced pro-inflammatory signaling, highlighting the therapeutic potential of precision nanomedicine to reprogram the obese adipose tissue microenvironment and improve systemic metabolic health.

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