Quarato, E. R. | bioRxiv Science

bioRxiv2025

Taurine Transporter SLC6A6 Expression Promotes Mesenchymal Stromal Cell Function

Mesenchymal stromal cell (MSC) differentiation is critical for the development, maintenance, and repair of bone tissue. This occurs within the bone marrow microenvironment, which consists of various stromal populations and structural components that support skeletal growth, repair and homeostasis. MSCs also promote self-renewal of hematopoietic stem cells and regulate their differentiation. Analysis of our own and publicly available single-cell RNA sequencing datasets of the murine non-immune bone and bone marrow indicates that Slc6a6 expression is enriched in MSCs. Slc6a6 encodes for an ion-dependent transporter of taurine (TauT). Although taurine supplements have been shown to mitigate the onset of bone defects in aged populations, the absence of TauT expression in osteolineage cells suggests that taurines effect on bone may be secondary to its function in other populations, such as MSCs. Using young TauT genetic loss-of-function murine models we find that TauT loss impacts MSC populations in vivo and impairs MSC osteogenic differentiation in vitro. This correlates with decreased bone mineral density and bone strength in young TauT knockout mice. Importantly, shRNA-based knockdown of SLC6A6 expression in primary human MSCs reduces osteogenic differentiation, indicating a key role of taurine uptake in human MSC function. Consistent with a decline in MSC function with TauT loss, we find that TauT null MSCs are unable to support self-renewal and expansion of co-cultured hematopoietic stem/progenitor populations. Mechanistically, our RNA-sequencing analysis identifies downregulation of Wnt/beta-catenin signaling in MSCs in the absence of TauT. These cells also show reduced oxidative phosphorylation, and increased ROS levels, indicating that impaired Wnt signaling and elevated oxidative stress may contribute to the observed defects in osteogenic differentiation capacity. Collectively, our data identify taurine uptake as a key regulator of mesenchymal stromal cell maintenance and osteogenic fate determination.

cell biology↗

bioRxiv2025

Local delivery of SBRT and IL-12 to Murine PDAC Tumors Modulates Hematopoiesis

BackgroundStandard of care therapies such as radiotherapy and chemotherapy have shown little efficacy against pancreatic ductal adenocarcinoma (PDAC). Immunotherapy is a newly emerging form of treatment that has shown promise; however, toxic systemic effects resulted in limited use in the clinic. Shifting from systemic to local delivery of cancer therapeutics reduces adverse systemic effects and increases response rates in multiple malignancies. Importantly, the effects of tumor-targeted therapies on distal tissues, such as the bone marrow, have not been thoroughly investigated. MethodsUsing a murine model of PDAC, we treated tumors with targeted stereotactic body radiation therapy (SBRT) and intratumoral interleukin-12 (IL-12). 13 days-13 months after tumor injection, the cells in the tumor, blood, and bone marrow were analyzed for therapy-induced changes. Hematopoietic cell numbers and lymphocytes were quantified by flow cytometry, and cytokine levels were quantified by enzyme-linked immunosorbent assays (ELISAs). ResultsWe demonstrated that although SBRT/IL-12 delivered locally to PDAC tumors successfully eradicated primary disease, it also induced significant acute and long-term effects in the bone marrow. Within days of intratumoral SBRT/IL-12 treatment, we observed acute lymphopenia in the blood, accompanied by an immunostimulatory response in the bone marrow characterized by an increase in hematopoiesis. Long-term effects included a decrease in hematopoietic stem cells (HSCs) and skewing toward a myeloid lineage bias, which could indicate premature aging of the HSC population. ConclusionsThese findings demonstrate that despite being locally delivered to the tumor, SBRT/IL-12 therapy exerts significant effects on the distal bone marrow, reinforcing the need for further investigations into the long-term systemic immunological outcomes of localized cancer treatments. Key MessagesWhat is already known on this topic: Systemic cancer therapies used to combat pancreatic ductal adenocarcinoma (PDAC) often induce toxic systemic effects. Local delivery of radiation and immunotherapy reduces adverse effects; however, the systemic spread of these therapies and the resulting effects on distal tissues such as the bone marrow have yet to be elucidated. What this study adds: Intratumoral delivery of stereotactic body radiation therapy (SBRT) and interleukin-12 (IL-12) augment hematopoiesis in the bone marrow soon after treatment and induce long-term alterations in the hematopoietic stem cells (HSCs). These effects are mainly a result of IL-12 that is transiently increased in the bone marrow after treatment. How this study might affect research, practice, or policy: Targeted SBRT/IL-12 therapy induces long-term systemic effects on the bone marrow, indicating the need for further investigation of the systemic spread of locally delivered therapeutics.

immunology↗