A potential model of systemic sclerosis with pulmonary hypertension induced by monocrotaline plus bleomycin

The lack of a well-established animal model limits the clarification of the detailed mechanisms of the pathogenesis of systemic sclerosis with pulmonary hypertension (SSc-PH) and the development of effective treatments for it.

In this study, New Zealand rabbits were injected with monocrotaline (MCT), bleomycin (BLM), and MCT plus BLM, respectively. Three and six weeks after the first injection, the mean pulmonary artery pressure (mPAP) was measured. Skin and lung samples were isolated and the histological changes were analyzed by hematoxylin and eosin staining or Masson's trichrome staining.

All groups of rabbits showed an increased mean mPAP compared with the saline-injected rabbits. The high mPAP persisted until week six only in the MCT and MCT + BLM groups. Furthermore, persistent high Fulton's indices were found in the MCT and MCT + BLM groups, indicating that these treatments successfully induced right ventricular hypertrophy. The rabbits in the MCT + BLM group developed severe lung inflammation, as evidenced by a high level of neutrophil infiltration in the pulmonary interstitium. Importantly, pathological changes of the skin in the MCT + BLM group were observed, and further damage to the skin was caused by additional exposure to MCT plus BLM. Meanwhile, an excessive production of cytokines, including tumor necrosis factor alpha (TNF-α), and transforming growth factor beta 1 (TGF-β1), were detected in the MCT + BLM group.

These data indicate that SSc-PH induced by co-injection with MCT plus BLM shows persistent fibrosis and progressive PH, constituting a potential study model for SSc-PH.