Preliminary clinical experience with mesenchymal stromal cells in autoimmune hemolytic anemia: A Case series in two dogs and one cat

Abstract Autoimmune hemolytic anemia (AIHA) is a rare but potentially life-threatening immune-mediated disorder characterized by the destruction of red blood cells due to autoantibody formation. While first-line therapy typically consists of corticosteroids in combination with adjunctive immunosuppressive agents such as cyclosporine or azathioprine, a subset of patients fails to achieve sustained clinical remission. In such refractory cases, alternative immunomodulatory strategies are increasingly being investigated. This case series presents two dogs and one cat diagnosed with severe, transfusion-dependent AIHA who exhibited minimal or no response to conventional therapy. All three animals received intravenous infusions of cryopreserved allogeneic mesenchymal stromal cells (MSC) derived from adipose tissue of healthy donors. The first case involved an 8-month-old female Welsh Corgi Pembroke (8 kg) with confirmed AIHA (Coombs test 1:256). Despite two transfusions and treatment with multiple immunosuppressants including cyclosporine, her clinical status remained unstable. She was administered two doses of adipose-derived MSC, 15 days apart (4.36 × 10⁶/ml and 10.05 × 10⁶/ml). Flow cytometry confirmed expression of MSC markers CD44 (94.5–90.0 %), CD90 (91.4–91.6 %), and CD29 (94.2–92.5 %), with viability above 95 %. Gradual improvement in hematologic values and overall clinical condition followed. One-year post-treatment, the dog remains in stable remission without ongoing medication. The second case, a 10-month-old mixed-breed female dog (13 kg), developed AIHA after a suspected Anaplasma infection. She received three transfusions and immunosuppressive therapy including cyclosporine, with no significant improvement. Two MSC doses were administered 16 days apart (4.56 × 10⁶/ml and 14.77 × 10⁶/ml), with immunophenotyping showing CD44 (99.4–99.5 %), CD90 (99.2–96.8 %), CD29 (99.0–99.4 %), and viability exceeding 98 %. Hematologic parameters and clinical status progressively improved. Corticosteroid dosage was tapered, and cyclosporine was discontinued. The dog remains clinically stable 2 months after administration under regular follow-up. The third case, a 1-year-old male Maine Coon–Ragdoll mix cat (5 kg), presented with life-threatening anemia. Due to the urgency of the condition, the first dose of MSCs (1.0 × 10⁶/ml; viability 73.95 %) was administered immediately post-thaw, concurrently with a blood transfusion (blood type B).A second dose (9.739 × 10⁶/ml) was given 6 days later, with improved viability (84.8 %) and expression of CD44 (97.1 %), CD90 (92.9 %), and CD29 (96.3%). A hematologic response was evident, although complete normalization had not yet occurred one month after the second dose. The cat showed marked significant clinical improvement and continues to be monitored. No acute or delayed adverse effects associated with MSC administration were observed in any case. These preliminary findings suggest that intravenous administration of allogeneic adipose-derived MSC is a safe and feasible therapeutic approach, potentially serving as a valuable adjunctive modality for the management of refractory AIHA in veterinary patients. However, further controlled clinical trials are warranted to confirm efficacy, optimize dosing regimens, and comprehensively evaluate long-term safety profiles. Given the shared pathophysiology of AIHA across species, these data may provide important translational insights relevant to the development of MSC-based therapies for human autoimmune hemolytic conditions.