Bold initiatives are afoot to transcend the rodent in favor of lab-on-chip and/or organoid models [1], and that’s a good thing. However, persistent reasons return our attention to our little whiskered helpers in many instances. True enough, cell culture studies are essential to understand how a potential therapy works. They allow researchers to examine cell behavior, molecular signaling pathways, potency, and semi-optimized dosing under controlled conditions. And for biotech/pharma discovery teams in search of the golden “needle,” primary cell models (such as with neonatal fibroblasts [2] ) dramatically shrink the size of the “haystack” of candidate molecules and cell treatments.
Yet today, even convincing data from 96-well culture plates leave many questions unanswered. Can the therapy reach the intended tissue in sufficient concentrations? Will it remain active in blood, extracellular fluid, or an inflamed organ? How will immune cells respond? Will the desired effect persist long enough to matter?
In vivo studies address these questions by placing a therapeutic concept into a complex, fully-living system. Animal models don’t fully predict human safety or efficacy, and many promising preclinical findings never become successful medicines. Even so—together with ex vivo or 3D engineered tissue models—they remain an important (if not prerequisite) translational step between biological plausibility and partially de-risked human testing.
Three exemplar publications illustrate this transition. These recent studies explored very different medical problems: ovarian damage caused by chemotherapy, irreversible retinal scarring, and antibiotic-resistant bacterial infection in cystic fibrosis. Each moved an MSC- or MSC extracellular vesicle (MSC-EV)-based concept into an animal model. Together, they encompass a range of therapeutic questions that can be explored once MSC biology moves beyond the culture vessel.
Protecting Fertility During Chemotherapy
Cancer survival has improved dramatically, [3] but successful treatment can leave lasting damage. Chemotherapy may destroy ovarian follicles, reduce hormone production, and cause ovarian insufficiency. For younger patients, the result may be permanent infertility and premature aging, even when the cancer itself has been successfully treated. And yet, current treatment options may be fraught with complex practical and/or ethical tradeoffs.
Figure 1. Graphical summary of Ghasroldasht, et al. (2026). EVs (aka “Enhanced Exosomes”) derived from umbilical cord MSCs that have been co-cultured with granulosa cells inhibit cyclophosphamide-induced damage to ovaries in live mice and restore their fertility.
Researchers led by first author Mohammad Mousaei Ghasroldasht and Dr. Ayman Al-Hendy at the University of Chicago investigated whether specially conditioned MSC-EVs (informally here called “exosomes”) could protect the ovary from chemotherapy-associated injury. [4] Rather than simple vesicle collection from conventionally cultured MSCs, the team attempted to reproduce the natural communication that occurs between mesenchymal stromal cells and ovarian granulosa cells (Figure 1).
The researchers reasoned that co-culture between human umbilical cord-derived MSCs (hUC-MSCs) and an immortalized granulosa cell line might alter the molecular cargo of the EVs and condition them toward better ovarian protection, i.e., termed “enhanced exosomes.” For this, RoosterBio hUC-MSCs were expanded in RoosterNourish™-MSC-XF medium, then transferred into RoosterCollect™-EV Pro medium for EV/exosome production. Resulting exosomes were tested across several experimental systems. These included cultured granulosa cells, cyclophosphamide-treated mice, rat ovarian tissue, and human ovarian tissue maintained outside the body. The primed EVs increased expression of cell survival and proliferation genes along with reduced apoptosis, and also yielded higher viable cell counts with in vitro and ex vivo models after the chemotherapy insult.
In the live mouse model, effects were especially striking. Compared with chemotherapy-only controls, treated animals had approximately 70% more primordial follicles and more than 20 times as many primary follicles. In the first breeding round, chemotherapy-treated mice produced only one pup, while mice receiving enhanced exosomes produced seven. Pregnancies in later breeding rounds occurred only in the enhanced-exosome group.
The researchers also observed evidence of protection in ex vivo cultured human ovarian tissue. Enhanced exosomes reduced apoptosis and preserved markers associated with granulosa-cell function and steroid hormone production. The treatment also increased expression of several ATP-binding cassette transporters, which may help cells remove cyclophosphamide or its metabolites. However, this proposed mechanism will require further confirmation, particularly to ensure that ovarian protection would not inadvertently interfere with the anticancer activity of chemotherapy.
The findings remain preclinical for now, but the study presents an intriguing possibility. MSC-derived EVs might eventually be engineered or conditioned to protect healthy reproductive tissue during cancer treatment. Reciprocally, the work demonstrates how an “educating” co-culture environment can be used to influence EV function before the product ever enters an animal. As described elsewhere, co-cultured MSCs have already been critical elements of other clinical trials in humans, e.g., post COVID interstitial lung fibrosis. [5, 6]
Interrupting Fibrosis in the Retina
Neovascular age-related macular degeneration is commonly treated by blocking vascular endothelial growth factor, or VEGF. These treatments can ablate abnormal blood-vessel growth, but they do not always prevent the development of subretinal fibrosis. Once scar tissue forms beneath the retina, vision loss may become permanent.
Figure 2. Graphical summary of Yuan, et al. (2026). Investigators at Queen’s University Belfast and Changsha Aier Eye Hospital showed that injected MSC-EVs reduce simulated macular degeneration damage via dual laser burns on the retina. In parallel, omics studies and cell data demonstrated that miRNA-21-5p and/or suppression of the TGF-beta signaling axis could contribute to a plausible therapeutic mechanism.
A study led by Xiang-Ling Yuan, David Hughes, Heping Xu, and Mei Chen asked whether MSC-derived extracellular vesicles could interrupt the inflammatory and cellular processes that lead to retinal scarring (Figure 2). [7] The researchers used a two-stage laser model to create choroidal neovascularization and subretinal fibrosis in mice. They then compared local routes of EV administration, including intravitreal injection into the eye and retroorbital injection into the venous sinus behind the eye.
The EVs were produced from human bone marrow MSCs obtained from RoosterBio. The cells were expanded initially in RoosterNourish™-MSC-XF medium before conditioned medium was collected and the vesicles were isolated by differential ultracentrifugation.
Both treatment routes reduced fibrosis, but direct intravitreal administration was more effective. Intravitreal MSC-EVs reduced collagen-positive fibrotic lesions by 46%, while retroorbital delivery produced a 30% reduction. The treatment also reduced infiltration of Iba1-positive inflammatory cells into the damaged tissue.
The researchers then explored how the vesicles might potentiate this effect. Fibrosis can arise when retinal pigment epithelial cells undergo epithelial-to-mesenchymal transition, or EMT. Macrophages similarly shift toward a scar-forming myofibroblast state through macrophage-to-myofibroblast transition, or MMT. In cell-based experiments, the MSC-EVs reduced expression of several fibrosis-associated markers in both retinal cells and macrophages. They also suppressed inflammatory cytokines in macrophages and microglia.
An EV-associated microRNA, miR-21-5p, emerged as one possible mediator in follow-up bioinformatics surveys. The vesicles were enriched in miR-21-5p, and a synthetic mimic of this microRNA reduced TGF-β-driven expression of profibrotic genes. Whether miR-21-5p cargo might trigger an amplified chain reaction of antifibrotic effect across the lesion or whether it is a “fellow traveler” with other effectors remains an interesting question. The authors therefore proposed that MSC-EVs could act pleiotropically, reducing inflammation while also interrupting the cellular transitions that convert injured tissue into scar tissue.
The work is notable because it does more than demonstrate a reduction in lesion size. It connects the in vivo result to a plausible mechanism involving suppression of the TGF-β signaling axis and it compares two potential routes of delivery. The limited performance of retroorbital administration also underscores a practical lesson in EV therapeutics: a biologically active vesicle still must reach the correct tissue at an effective dose.
Fighting Infection While Reducing Inflammation
Pseudomonas aeruginosa infection remains the major leading cause of morbidity and mortality in cystic fibrosis. The bacterium can form biofilms, resist antibiotics, and persist in the lungs. At the same time, the immune response intended to clear the infection may become excessive and propagate additional tissue damage. An ideal treatment must therefore reduce both bacterial burden and harmful inflammation.
Sharanya Sarkar and colleagues in the laboratory of Professor Bruce Stanton at Dartmouth’s Geisel School of Medicine recently tested whether MSC-derived extracellular particles (“EPs”) could provide this dual therapeutic activity in living animals (Figure 3). [8] Previously, Stanton’s group had demonstrated in cells that let-7b-5p miRNA in EPs released by airway epithelial cells can directly inhibit Pseudomonas biofilm formation—a possible example of cross-kingdom RNA interference. [9] In the latest work, the team produced particles from human bone marrow MSCs and examined both unmodified particles and preparations generated after MSCs were transfected with either a negative-control microRNA or the antimicrobial microRNA let-7b-5p.
Figure 3. MSC-EVs (aka EPs) can inhibit both the bacterial burden and pro-fibrotic inflammatory milieu of P. aeruginosa in vivo cystic fibrosis (CF) model mice. The effect of these EPs is seen irrespective of loading with the microRNA Let-7b-p, and can be observed from samples via BALF or serum.
The team then introduced a clinical mucoid strain of P. aeruginosa into the lungs of cystic-fibrosis mice. The bacterial inoculum was administered together with MSC-derived extracellular particles or a process control. Three days later, the researchers measured bacterial burden in lung tissue and bronchoalveolar lavage fluid, along with immune-cell recruitment and inflammatory cytokines.
Both the negative-control and let-7b-5p-loaded EP preparations reduced P. aeruginosa by approximately 2.5 log units compared with the process control. Interestingly, adding let-7b-5p did not produce a clear advantage over the negative-control preparation. Further sequencing showed that the transfection procedure itself altered the abundance of several other microRNAs within the particles, illustrating how an engineering step may affect EV cargo more broadly than intended.
The extracellular particles also altered the inflammatory response. Negative-control particles reduced the total number of immune cells recovered from bronchoalveolar lavage fluid by nearly 55%. Both engineered preparations significantly reduced monocytes and lymphocytes, while negative-control particles also significantly reduced neutrophils. The particles increased the anti-inflammatory cytokine IL-10 in the lungs and reduced circulating RANTES, a chemokine that attracts immune cells.
These findings suggest that MSC-derived extracellular particles may act through two complementary mechanisms. They may directly or indirectly reduce bacterial survival while also shifting the lung environment away from prolonged, damaging inflammation. That combination could be valuable in cystic fibrosis and perhaps in other diseases involving persistent, antibiotic-resistant respiratory infections.
RoosterBio provided Exosome Analytical Services to characterize the MSC-derived particles, and the authors acknowledged the company’s contribution to the analysis.
Different Diseases, a Shared Translational Step
These three studies address problems that challenge today’s armamentarium of therapy options. One seeks to preserve ovarian follicles during chemotherapy. Another attempts to prevent blindness caused by retinal fibrosis. The third targets an antibiotic-resistant lung infection while also moderating inflammation. With EVs and/or “exosomes” increasingly turned to as a bona fide clinical platform, there is reason to believe that some of these products will take their place among the mAbs, ADCs, CAR-T cells, and gene therapies that challenged us only a few years ago.
In each case, the animal model introduced challenges that could not be recapitulated in a culture dish. The ovarian study tested fertility over multiple breeding rounds. The retinal study compared delivery routes across a complex anatomical barrier. The lung study measured bacterial burden, immune-cell recruitment, and systemic cytokine responses simultaneously.
None of these findings conclusively establish that such treatments will work in patients. Each approach will require additional studies of dose, biodistribution, manufacturing, safety, reproducibility, and mechanism. Even so, these publications show how MSC and EV technologies are being applied to increasingly diverse therapeutic questions, and how in vivo models can reveal both promise and limitations before human trials are considered.
All three studies have also incorporated RoosterBio products or services. The ovarian work used RoosterBio umbilical cord MSCs and media for cell expansion and EV collection. The retinal study used RoosterBio bone marrow MSCs and expansion medium. The lung-infection study relied on RoosterBio analytical services to characterize MSC-derived particles.
Standardized, off-the-shelf raw materials from an industrialized supply chain with rigorous analytical support can help new EV/exosome translational projects succeed. Among other elements, they help researchers ask difficult biological questions with greater confidence as cell and EV therapies move from culture vessels into living systems and patients in need.
Are you curious about how RoosterBio might be able to help you along your journey to in vivo experiments and preclinical translational work? Contact us, and we will be happy to walk you through fit-for-purpose solutions for your needs.
References
- RoosterBio. How hMSCs Are Helping Power Organ-on-a-Chip Science. 2025; Available from: https://www.roosterbio.com/blog/how-hmscs-are-helping-power-organ-on-a-chip-science/.
- Carson, Jonathan. Deference to the Differences Between Fibroblasts & MSCs. 2025; Available from: https://www.roosterbio.com/blog/deference-to-the-differences-between-fibroblasts-mscs/.
- Institute, National Cancer. Annual Report to the Nation: Cancer deaths continue to decline. 2025; Available from: https://www.nih.gov/news-events/news-releases/annual-report-nation-cancer-deaths-continue-decline.
- Mousaei Ghasroldasht, M., et al., Enhanced exosomes for fertility protection against chemotherapy-induced ovarian damage. NPJ Regen Med, 2026. 10.1038/s41536-026-00477-8
- RoosterBio. RoosterBio Galvanizes Large & Small for Clinical Success. 2025; Available from: https://www.roosterbio.com/blog/roosterbio-galvanizes-large-small-for-clinical-success/.
- Candiello, Joe, Patel, Ashish. Rapid Translation of a Cellular Therapeutic: Choosing Product & Process Development Solutions for Clinical Manufacturing Readiness. 2022; Available from: https://share.hsforms.com/1YmYCcqpoQLK_tn5AfWNzYQ3564o.
- Yuan, X. L., et al., MSC-EVs attenuate subretinal fibrosis in choroidal neovascularization through miR-21-5p-mediated inhibition of EMT and MMT and suppression of inflammation. J Neuroinflammation, 2026. 23(1). 10.1186/s12974-026-03836-w
- Sarkar, S., et al., Extracellular Particles Derived From Mesenchymal Stromal Cells Reduce Pseudomonas aeruginosa Lung Infection and Inflammation in Mice. J Extracell Biol, 2026. 5(2): p. e70114. 10.1002/jex2.70114
- Koeppen, K., et al., Let-7b-5p in vesicles secreted by human airway cells reduces biofilm formation and increases antibiotic sensitivity of P. aeruginosa. Proc Natl Acad Sci U S A, 2021. 118(28). 10.1073/pnas.2105370118