SummaryTo evaluate the influence of types of sera and the donors age on proliferation and re-differentiation capacities of equine chondrocytes, cartilage tissue from 10 horses was obtained in the age range 2.5 to 19 years. Chondrocytes were isolated from the fetlock-joints and expanded in media containing different types of sera: fetal calf serum (FCS), fetal equine serum (FES), adult equine serum (AES) and autologous serum. Cells were expanded in monolayers at low and high seeding densities. Chondrocytes re-differentiation capacities were assessed in micromass pellet cultures after 4 weeks of incubation in chondrogenic medium supplemented with or without 5ng/ml TGFβ1. The neocartilagineous tissue formation was evaluated through proteoglycan and collagen type II deposition, and Berne score visual evaluation system. Results showed that the low seeding density allows for higher proliferation rates in FCS, FES and AES. In addition chondrocytes from younger horses proliferate faster independently of the serum type. Re-differentiation capacities are influenced by the animals age, type of serum during expansion, and the presence of TGFβ1 in pellet cultures. Cells from young horses appear to produce better neocartilage upon expansion in autologous serum, while cells from older horses re-differentiated better upon expansion in FCS. The expansion conditions of potential clinical relevance include the correct choice of sera according to the age of horse during monolayer culture for better subsequent re-differentiation and lower seeding densities allowing for smaller biopsy sampling and therefore less injury to the donor site.