Captopril mitigates splenomegaly and myelofibrosis in the Gata1low murine model of myelofibrosis

Abstract

Allogeneic stem cell transplantation is currently the only curative therapy for primary myelofibrosis (MF), while the JAK2 inhibitor, ruxolitinib. Has been approved only for palliation. Other therapies are desperately needed to reverse life-threatening MF. However, the cell(s) and cytokine(s) that promote MF remain unclear. Several reports have demonstrated that captopril, an inhibitor of angiotensin-converting enzyme that blocks the production of angiotensin II (Ang II), mitigates fibrosis in heart, lung, skin and kidney. Here, we show that captopril can mitigate the development of MF in the Gata1^low mouse model of primary MF. Gata1^low mice were treated with 79 mg/kg/d captopril in the drinking water from 10 to 12 months of age. At 13 months of age, bone marrows were examined for fibrosis, megakaryocytosis and collagen expression; spleens were examined for megakaryocytosis, splenomegaly and collagen expression. Treatment of Gata1^low mice with captopril in the drinking water was associated with normalization of the bone marrow cellularity; reduced reticulin fibres, splenomegaly and megakaryocytosis; and decreased collagen expression. Our findings suggest that treating with the ACE inhibitors captopril has a significant benefit in overcoming pathological changes associated with MF.

Keywords: drug repurposing; myelofibrosis; myeloproliferative neoplasms.

Figure 1

Effects of captopril administration on Gata1 ^low mouse model of myelofibrosis. Wild‐type (wt) or Gata1 ^low mice were treated from 10 to 12 mo with either captopril 72 mg/kg/d or vehicle in drinking water. Mice were killed at 13 mo, and tissues were harvested. (A) Haematoxylin and eosin staining of bone marrow from the humeri of the three mouse cohorts. Magnification is 40×. (B, C) Gomori staining of the same histological sections shows reticulin deposition in vehicle‐treated Gata1 ^low mice. Under blinded conditions, a board‐certified pathologist (T.A.S.) scored bone marrow for reticulin. Captopril treatment resulted in decreased reticulin fibre score, with *P value < .05 (one‐tailed Mann‐Whitney test). (D) Haematoxylin and eosin staining of spleens from the three mouse cohorts. Magnification is 60×. (E) Gomori staining of the same histological sections shows reticulin deposition in vehicle‐treated Gata1 ^low mice. (F) Spleens from the three mouse cohorts were weighed, with *P value < .05

Figure 2

Effects of captopril administration on peripheral blood counts. Wild‐type (wt) or Gata1 ^low mice were treated from 10 to 12 mo with either captopril 72 mg/kg/d or vehicle in drinking water. Mice were killed at 13.5 mo, and tissues were harvested. Complete blood cell counts with differentials were obtained. (A) white blood cells (WBC); (B) lymphocytes; (C) eosinophils; (D) neutrophils; (E) platelets; and (F) red blood cells (RBC). Means are indicated; *indicates P < .05

Figure 3

Effects of captopril administration of megakaryocytes and collagen. Wild‐type (wt) or Gata1 ^low mice were treated from 10 to 12 mo with either captopril 72 mg/kg/d or vehicle in drinking water. Mice were killed at 13.5 mo, and tissues were harvested. (A) Flow cytometric analysis was performed on femur bone marrow cells to measure percentage of CD45⁺ cells expressing CD41⁺ cells. Representative FACS data are presented for wt, Gata1 ^low‐untreated mice and Gata1 ^low captopril‐treated mice. (B‐E) qPCR of mRNA isolated from bone marrow of Gata1 ^low mice treated ± captopril, as described above. Interrogated transcripts were CD41, CD61, Col 1a and Col 3a. Data show Gata1 ^low qPCR transcript levels from untreated mice compared to the ratio of Gata1 ^low transcript levels from mice treated with captopril relative to Gata1 ^low‐untreated mice. *P value .05. (F) Flow cytometric analysis was performed on spleen‐derived cells to measure percentage of CD45⁺ cells expressing CD41⁺ cells. Representative FACS data are presented for wt, Gata1 ^low‐untreated mice and Gata1 ^low captopril‐treated mice. (G‐J) qPCR of mRNA isolated from spleens of Gata1 ^low mice treated ± captopril, as described above. Interrogated transcripts were CD41, CD61, Col1a and Col3a. Data show Gata1 ^low qPCR transcript levels from untreated mice compared to the ratio of Gata1 ^low transcript levels from mice treated with captopril relative to Gata1 ^low‐untreated mice. *P value .05