Cryopreserved exosomes derived from hypoxically preconditioned Wharton's jelly mesenchymal stromal cells (WJ‑MSC) were isolated and used to treat human dermal fibroblasts in an in vitro experiment, with an initial preparation containing 1.5 × 10^9 exosomes/ml (~350 μg/ml total protein). Fibroblasts were treated with three dilutions of exosomes 1:90 (~4 ng/µl), 1:30 (~12 ng/µl) and 1:10 (~30 ng/µl) for 72 hours and assessed for proliferation, COL1A2 gene expression and β-galactosidase activity. Exosome treatment promoted fibroblast proliferation in a dose-dependent manner, with significant increases observed at 1:30 (p < 0.05) and 1:10 (p < 0.01) dilutions. COL1A2 expression was increased at 1:30 (p = 0.0418) and 1:10 (p = 0.0002) dilutions, while the 1:90 dilution showed no difference from control. β-galactosidase activity in senescent fibroblasts was significantly reduced at 1:30 and 1:10 dilutions, with the strongest reduction at 1:10 dilution (p = 0.0010). The authors report these results as supporting the use of hypoxia-conditioned, cryopreserved WJ‑MSC exosomes as scalable agents for regenerative therapies and suggest further comparative studies to elucidate the effect of storage method on efficacy.