The effects of human skin fibroblast monolayers on human sperm motility and mouse zygote development

A new system for co-culture in human in-vitro fertilization (IVF), using human skin fibroblasts, is described and tested pre-clinically. The first test involved the development of 1-cell mouse embryos which exhibit the 2-cell developmental block in vitro. Passage through this block (pb1-ratio) was determined by the ratio of compacted morula stages on day 4 of incubation. For nine human skin cell lines tested (fetal, neonatal and adult), the pb1-ratio was approximately 0.45 (0.07 in culture medium alone; P less than 0.0005). At the compacted morula stage, a second developmental block was observed. The ratio of passing this block (pb2-ratio) was 0.70 +/- 0.09 on skin fibroblasts obtained from fetal or neonatal tissue. On fibroblasts from adult patients the pb2-ratio was 0.30 +/- 0.04 (P less than 0.0005). The second test examined the influence of skin fibroblasts from fetal or neonatal tissue on human sperm motility. After 24 h of incubation, all skin cell lines had a positive influence (P less than 0.01) on the percentage motility compared to culture medium alone. The curvilinear velocity was not significantly increased. From the results we conclude that (i) human skin fibroblasts (especially from fetal tissue) have a positive influence on the development of mouse embryos in vitro, (ii) there is a positive influence of human skin fibroblasts on the percentage motility of human spermatozoa, and (iii) a clinical trial of co-culture with human skin fibroblasts can be justified.