A new study has demonstrated a way to reduce vitamin D receptor activity selectively in bone or muscle in living mice, using engineered adeno-associated viral vectors. The work, reported by O’Donohue, Chu, Norris and colleagues in Gene Therapy, provides a molecular toolkit for studying how vitamin D signaling operates in different tissues without disrupting the pathway throughout the entire body. By directing genetic cargo to specific tissues, the approach could help researchers separate the effects of vitamin D signaling in the skeleton from those in muscle and other organs.
The vitamin D receptor, or VDR, is a transcription factor that regulates gene activity after binding the active form of vitamin D. It is present in many cell types and influences processes including mineral metabolism, bone remodeling, muscle biology and immune function. When activated, VDR binds regulatory regions of DNA together with partner proteins, altering the expression of genes involved in calcium handling, differentiation and tissue maintenance. Because the receptor performs distinct functions in different tissues, conventional whole-body genetic deletion can make it difficult to determine which biological effects arise from bone, muscle or systemic changes.
The researchers addressed this problem through adeno-associated virus, commonly known as AAV. AAVs are small, non-pathogenic viral vectors widely used to deliver genetic instructions to mammalian cells. They do not normally cause disease and can persist in tissues primarily as episomal DNA, although their ability to remain active and their distribution depend on the vector design, dose and target tissue. In this study, the vectors were engineered to carry gene-silencing instructions directed against Vdr, the gene encoding the vitamin D receptor, while also incorporating targeting features intended to favor bone or skeletal muscle.
Rather than simply delivering a conventional gene-editing enzyme, the vectors were designed to reduce production of the receptor within selected cells. Such knockdown strategies can use regulatory RNA molecules, including short hairpin RNAs or microRNA-adapted sequences, to guide the cellular RNA-interference machinery toward the target messenger RNA. Once targeted, the messenger RNA is degraded or destabilized, lowering the amount of VDR protein available for gene regulation. This approach is potentially reversible and may avoid some of the permanent genomic changes associated with nuclease-based editing, although the duration and completeness of suppression remain important experimental considerations.
The central achievement reported by the study is tissue selectivity. Bone-targeted vectors were able to deliver VDR-suppressing activity to skeletal tissues, while muscle-targeted vectors enabled knockdown in skeletal muscle. This distinction is technically significant because bone and muscle are closely connected biologically and anatomically, yet they respond differently to hormones and mechanical signals. A vector that reaches both tissues indiscriminately could produce overlapping effects that are difficult to interpret. Selective delivery offers a way to ask more precise questions, such as whether a change in bone density results from altered vitamin D signaling inside bone cells or from secondary effects originating in muscle.
AAV targeting is governed by several layers of vector biology. The viral capsid, which surrounds the genetic payload, influences which cells can be entered and how efficiently the vector is taken up. Tissue-selective promoters and other regulatory DNA elements can further restrict where the silencing construct is expressed after delivery. The resulting specificity is rarely absolute: vectors may reach non-target tissues, and promoter activity can vary between cell types, developmental stages and disease states. For that reason, successful tissue targeting must be assessed experimentally by measuring vector distribution, transgene activity and the resulting reduction in the target protein.
The mouse experiments described in the paper establish these vectors as research tools for dissecting VDR biology in vivo. Tissue-restricted knockdown can complement existing models in which VDR is removed throughout the body or deleted from a particular cell lineage using recombinase-based genetics. AAV-mediated suppression may also allow investigators to manipulate adult animals after development is complete, helping distinguish developmental functions of VDR from its roles in mature tissue maintenance. This flexibility could be valuable in studies of osteoporosis, muscle weakness, mineral disorders and conditions in which vitamin D signaling is altered.
The findings also illustrate both the promise and the challenges of using viral vectors for biological discovery. AAV platforms have become increasingly important in medicine because they can deliver genetic payloads to selected organs, but immune responses, limited packaging capacity, pre-existing antibodies and variable tissue distribution can restrict their performance. In a research setting, additional questions include how long VDR knockdown lasts, whether suppression is uniform across different bone and muscle cell populations, and whether the vectors produce unintended effects in the liver or other organs. These issues will determine how broadly the system can be applied and how confidently physiological outcomes can be attributed to a particular tissue.
For now, the study’s importance lies in providing a targeted method rather than a therapy for vitamin D-related disease. By combining AAV delivery with gene-specific knockdown, the researchers have created a means of perturbing vitamin D receptor signaling in anatomically distinct tissues in mice. The platform could help clarify why the same hormone can influence bone strength, muscle performance and whole-body mineral balance through different cellular mechanisms. Such information is essential for designing future interventions that enhance beneficial vitamin D responses while limiting unwanted effects elsewhere in the body.
Subject of Research: Tissue-selective vitamin D receptor knockdown in mouse bone and skeletal muscle using adeno-associated viral vectors.
Article Title: Bone- and muscle-targeted adeno-associated viral vectors enable tissue-selective vitamin D receptor knockdown in mice.
Article References: O’Donohue, A.K., Chu, J., Norris, N. et al. “Bone- and muscle-targeted adeno-associated viral vectors enable tissue-selective vitamin D receptor knockdown in mice.” Gene Therapy (2026). https://doi.org/10.1038/s41434-026-00636-y
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41434-026-00636-y
Keywords: adeno-associated virus, AAV vectors, vitamin D receptor, VDR knockdown, bone targeting, muscle targeting, gene therapy, RNA interference, skeletal biology, mice
Tags: adeno-associated viral vectorsgene delivery in living micegene therapy for bone and muscleimmune response to viral vectorsmolecular toolkit for tissue-specific gene knockdownTargeted viral vectorstissue-specific gene regulationtissue-specific genetic modificationVDR in bone remodelingVDR signaling in skeletal musclevitamin D pathway in health and diseasevitamin D receptor silencing
