Human immune-cell response towards diverse xenogeneic and allogeneic decellularized biomaterials.

BACKGROUND: Immunological knowledge on processed biological implants and mesh-prostheses is still mainly based on animal models, lacking information on the species-specific human immune response. We hypothesized that in contrast to human tissue even decellularized xenogenic specimens would lead to significant and tissue source dependent human immune reactions. METHODS: Specimens from processed allogenic and xenogenic pulmonary arteries, pericardium or dermis, were co-cultured with human peripheral blood mononuclear cells (PBMNC). Proliferative responses were measured in tritiated thymidine incorporation assays (n = 10). Stimulation indices (SI), calculated as counts-per-minute of co-cultured PBMNC divided by the cpm of basic cell proliferation, were compared. RESULTS: Compared to native porcine pulmonary artery tissue decellularization significantly reduced human PBMNC proliferation (mean SI: 48.7 vs. 18.0, p < 0.01), which was still higher compared to the human equivalent (SI: 0.7 vs. 1.7). Also the processed human dermal implant did not elicit immune response (SI: 1.5), whereas the decellularized and cross-linked porcine dermis lead to a significant human cell-proliferation (SI: 8.4, p < 0.01). Interestingly, both the processed human (SI: 15.2) and bovine pericardial patches (SI: 15.1) led to higher immune cell proliferation. CONCLUSION: Even decellularized or cross-linked xenogenic cardiovascular and reconstructive biomaterials elicit increased human immune responses not seen in the majority of allogenic specimens tested.

Ursolic acid causes DNA-damage, p53-mediated, mitochondria- and caspase-dependent human endothelial cell apoptosis, and accelerates atherosclerotic plaque formation in vivo.

OBJECTIVE: The plant derived triterpene ursolic acid (UA) has been intensively studied in the past; mainly as an anti-cancer compound and for its cardiovascular protective properties. Based on the controversy of reports suggesting anti-angiogenic and cytotoxic effects of UA on one side and cardiovascular and endothelial protective effects on the other side, we decided to assess UA effects on primary human endothelial cells in vitro and atherosclerotic plaque formation in vivo. METHODS AND RESULTS: Our in vitro analyses clearly show that UA inhibits endothelial proliferation and is a potent inducer of endothelial cell death. UA causes DNA-damage, followed by the activation of a p53-, BAK-, and caspase-dependent cell-death pathway. Oral application of UA in APO E knockout mice potently stimulated atherosclerotic plaque formation in vivo, which was correlated with decreased serum levels of the athero-protective cytokine IL-5. CONCLUSIONS: Due the potent endothelial cell death inducing activity of UA, a systemic application of UA in the treatment of cardiovascular diseases seems unfavourable. UA as an anti-angiogenesis, anti-cancer and - locally applied - cardiovascular drug may be helpful. The DNA damaging activity of UA may however constitute a serious problem.