Neovascularization is influenced by androgenic hormones in the tissue implant response

The objective of this investigation was to demonstrate the effect of androgens on the neovascularization of the fibrous tissue surrounding tricalcium phosphate (TCP) implants. Sixteen animals in four experimental groups (n = 4/group) were implanted with one TCP implant each. Group I animals were implanted with the sham TCP ceramic (Control). Group II animals received a testosterone-loaded ceramic. Group III animals were implanted with a dihydrotestosterone containing bioceramic. Group IV animals received the androstenedione filled bioceramic. At 90 days post-implantation, the fibrous tissue surrounding the implants were evaluated microscopically following staining with routine hematoxylin and eosin (H&E), Masson’s trichrome, and Papanicolaou stains. Using Image Pro (Media Cybernetics, Silver Spring, MD) digital analysis software, data were collected to compare the hormonal effects on the number (per high power field) and size of blood vessels (micrometers, µm) within the fibrous tissue surrounding all four groups. The presence of androgens greatly affected the angiogenic response within the fibrous tissue. All three hormones exhibited less neovascularization compared to the control. Though not as dramatic as androstenedione (3±0), both testosterone (12±1) and dihydrotestosterone (10±1) suppressed the number of blood vessels present in the fibrous tissue capsule compared to control (13±1). However, the circumference of the vessels was much larger for the testosterone (236µm ±8µm) and dihydrotestosterone (256µm±4µm) treated groups compared to the androstenedione (146µm ±7µm) or control (163µm±3µm) groups. The results of this study demonstrate androgens strongly vary in their effect on neovascularization by limiting the number of new vessels developed while contributing to the presence of larger vessels within the fibrous tissue surrounding TCP implants loaded with testosterone and dihydrotestosterone.