The xenotransplantation of porcine tissues may help overcome the shortage of human organs for transplantation. However, there are some concerns about recipient safety because the risk of porcine endogenous retrovirus (PERV) transmission to human cells remains unknown. Although, to date, no PERV infections have been noted in vivo, the possibility of such infections has been confirmed in vitro. Better understanding of the structure and replication cycle of PERVs is a prerequisite for determining the risk of infection and planning PERV-detection strategies. This review presents the current state of knowledge about the structure and replication cycle of PERVs in the context of retroviral infection risk.

Epigenetic modifications are responsible for the modulation of gene expression without affecting the nucleotide sequence. The observed changes in transcriptional activity of genes in tumor tissue compared to normal tissue, are often the result of DNA methylation within the promoter sequences of these genes. This modification by attaching methyl groups to cytosines within CpG islands results in silencing of transcriptional activity of the gene, which in the case of tumor suppressor genes is manifested by abnormal cell cycle, proliferation and excessive destabilization of the repair processes. Further studies of epigenetic modifications will allow a better understanding of mechanisms of their action, including the interdependence between DNA methylation and activity of proteins crucial to the structure of chromatin and gene activity. Wider knowledge of epigenetic mechanisms involved in the process of malignant transformation and pharmacological regulation of the degree of DNA methylation provides an opportunity to improve the therapeutic actions in the fight against cancer.

This review article provides an overview on adipose-derived stem cells (ADSCs) for implications in bone tissue regeneration. Firstly this article focuses on mesenchymal stem cells (MSCs) which are object of interest in regenerative medicine. Stem cells have unlimited potential for self-renewal and develop into various cell types. They are used for many therapies such as bone tissue regeneration. Adipose tissue is one of the main sources of mesenchymal stem cells (MSCs). Regenerative medicine intends to differentiate ADSC along specific lineage pathways to effect repair of damaged or failing organs. For further clinical applications it is necessary to understand mechanisms involved in ADSCs proliferation and differentiation. Second part of manuscript based on osteogenesis differentiation of stem cells. Bones are highly regenerative organs but there are still many problems with therapy of large bone defects. Sometimes there is necessary to make a replacement or expansion new bone tissue. Stem cells might be a good solution for this especially ADSCs which manage differentiate into osteoblast in in vitro and in vivo conditions.