Changes in mucins and matrix metalloproteases in the endometrium of early pregnant alpacas (Vicugna pacos)

•The alpaca endometrial surface exhibits ultrastructural changes in concordance with its preparation for embryo implantation.•Relative abundance of MUC1 and MUC16 transcripts diminished in the endometrium during the early pregnancy, in correspondence to slight glycocalyx AB staining.•MMP2, MMP9 mRNA relative abundance and their presence in the uterine fluid change in response to pregnancy state.•MMP14, MMP2 and MMP9 could be involved in the first steps of alpaca embryo implantation process.•Our findings are a clear indication of alpaca uterus preparation for embryo implantation and pregnancy support, involving modifications in the glycocalyx and MMPs expression. South American Camelids (SAC) have unique reproductive features, one of which is that 98% of the pregnancies develop in the left uterine horn. Furthermore, early pregnancy is an uncharacterized process in these species, especially in regard to the ultrastructural, biochemical and genetic changes that the uterine epithelial surface undergoes to allow embryo implantation. The present study describes the uterine horn luminal surface and the characteristics of the mucinous glycocalyx in non-pregnant and early pregnant (15 days) female alpacas. In addition, the relative abundance of Mucin 1 and 16 genes (MUC1 and MUC16) was determined, as well as the relative mRNA abundance of matrix metalloproteinases (MMPs) that could be involved in MUC shedding during early pregnancy. Noticeable changes were detected in the uterine luminal epithelium and glycocalyx of pregnant alpacas in comparison to non-pregnant ones, as well as presence of MUCs and MMPs in the endometrial environment. The decrease in glycocalyx staining and in the relative abundance of MUC 1 and MUC 16 transcripts in pregnant females would allow embryo attachment to the luminal epithelium and its subsequent implantation, as has been described in other mammals. These results suggest a crucial role of MUC1 and MUC16 and a possible role of MMPs in successful embryo implantation and survival in alpacas.