Intravenous adipose-derived mesenchymal stem cell therapy for the treatment of feline asthma: a pilot study

Objectives The aim of this study was to evaluate the feasibility and efficacy of serially administered adipose-derived mesenchymal stem cells (MSCs) in an experimental feline asthma model. Methods Allergic asthma was acutely induced with Bermuda grass allergen in six purpose-bred cats. Five intravenous infusions of allogeneic MSCs (n = 4; MSC-treated) or saline (n = 2; placebo-treated) were administered over the first 130 days after asthma induction. Infusions contained 2 x 10(6), 4 x 10(6), 4.7 x 10(6), 1 x 10(7) and 1 x 10(7) cryopreserved MSCs/cat. For thoracic imaging additional cats were enrolled as control groups: four untreated, experimentally asthmatic cats (combined with placebo-treated cats), and six healthy, non-asthmatic cats. Outcome measures included airway eosinophilia, pulmonary mechanics, thoracic computed tomography and several immunologic assays. Results Cats were assessed for 9 months after treatment. At early points, airway eosinophil percentage was not affected by MSC administration (post-treatment average of days 12, 26, 47, 108 and 133 in MSC-treated cats was 41 +/- 15% and in placebo-treated cats it was 34 +/- 16%). By month 9, eosinophil percentages in all MSC-treated cats decreased to normal reference intervals (MSC-treated 6%; placebo-treated 20%; normal < 17%). Diminished airway hyper-responsiveness was noted in all MSC-treated compared with placebo-treated cats at day 133 (dose of methacholine to double baseline airway resistance: MSC-treated median 22.9 mg/ml [range 6.4-64.0]; individual placebo-treated cats 1.1 and 5.0 mg/ml). Lung attenuation (mean +/- SEM MSC-treated -865 +/- 12 Hounsfield units [HU]; untreated asthmatics -820 +/- 11 HU; P = 0.004) and bronchial wall thickening scores (median [interquartile range] MSC-treated 0 [0-1.5]; untreated asthmatic 11.6 [7.3-27.3]; P = 0.010) were significantly reduced in MSC-treated vs untreated asthmatic cats, consistent with decreased airway remodeling at month 9. No clear immunologic mechanisms by which MSCs act were determined. Conclusions and relevance MSCs may have a delayed effect in reducing airway inflammation, airway hyper-responsiveness and remodeling in experimentally induced asthmatic cats. Results warrant additional investigation of MSC therapy for asthma in cats.