Stem cells help tissues repair themselves, and researchers have asked whether their function declines with age. This guide reports what studies measured on that question: how stem cells and their supporting cells change with age, and what trials in older adults with frailty found. Frailty is the loss of strength, walking speed and reserve that often comes with age. The evidence is early. The studies here measured physical function, inflammation, safety and how cells behave [5] [10].
How stem cells change with age
Reviews describe a consistent pattern [3] [4] [12]. A 2021 systematic review of in vitro studies found that cells from older donors showed higher expression of p21, p53 and p16, along with more of a senescence marker, and lower expression of proliferation markers [3]. A 2025 systematic review of 13 preclinical papers linked senescence markers, including p16, p21 and p53, with lower bone-forming capacity and weaker regeneration in progenitor cells [4]. A 2026 narrative review argues that aging changes the chemical signals that mesenchymal stem cells release, which can weaken support for stem cells in aging tissue [12].
Mouse studies show the same idea in more detail [10] [11]. A 2026 study of muscle stem cells from young, old and geriatric mice found early changes in inflammation and late changes in gene activity and the three-dimensional structure of the genome [10]. A 2026 study of blood-forming stem cells showed that reduced Notch signaling, which is seen in aged blood-forming stem cells, can be reproduced in young mice by removing one signal from the vessel lining, with the result of more myeloid-biased stem cells and less regeneration [11]. These studies describe mechanisms in animals [10] [11]. They do not show what the same change would do in a person.
Trials in older adults with frailty
The reviews on frailty are small [1] [2]. A 2026 systematic review of three randomized trials of mesenchymal cell therapy in aging frailty found no treatment-related serious adverse events and mobility signals that varied across the trials [1]. A 2019 systematic review identified frailty trials that mostly used a single intravenous infusion of about 100 million cells, with 6 to 12 months of follow-up, and focused on safety first [2].
Randomized trials give more detail:
- A phase 2b randomized trial with 148 participants reported a 6-minute walk increase versus placebo of 63.4 meters at month 9 (95% confidence interval 17.1 to 109.6) [5]. The 6-month difference of 41.3 meters was not statistically significant [5].
- A 2017 phase 2 randomized, placebo-controlled trial in 30 adults with frailty found no therapy-related serious adverse events at one month [6]. The 100-million-cell group improved on a 6-minute walk, a short physical performance exam and forced expiratory volume (P = 0.01) [6].
- A phase I/II trial of umbilical cord tissue cells reported that grip strength and inflammatory markers differed from placebo at six months, with no difference in adverse events [7].
- A phase 2 randomized, open-label trial in frail adults compared intravenous umbilical cord cell infusions with supplements alone [8]. The publisher has issued a correction to this report, so this guide does not quote its results.
Registered studies
One more frailty study cited here is registered on ClinicalTrials.gov, and no paper is listed for it [9]. This active, not-recruiting trial lists 66 participants and has no posted results [9].
How to read an aging study
- The population. Healthy older adults, adults with frailty, and older patients with a disease are different groups.
- The outcome. Walking tests, grip strength and questionnaires measure different things. A study can improve one and not another.
- The model. Laboratory and mouse studies show mechanisms. Only trials show what happens in people.
Where to find the studies
Search frailty stem cell trials on ClinicalTrials.gov for registered designs. Search stem cell aging reviews on PubMed for published reviews. The neuropathy guide covers stem cell research and peripheral neuropathy, and the knee guide covers stem cell research and the knee.
Regulatory Status
A 2026 review of FDA regulation of biologics examines how that oversight applies to stem cell products [13]. Our stem cell therapy is not approved by the FDA.
