Major histocompatibility complex class I in the horse (Equus caballus) placenta during pregnancy and parturition.

BACKGROUND: Major histocompatibility protein class I (MHC-I) is believed to be expressed in the horse allantochorion only in limited areas at limited times. However, its expression has only been investigated in early pregnancy with non-quantitative techniques that cannot reliably detect small amounts of protein. OBJECTIVE: To quantify the relative expression of MHC-I in the allantochorion and endometrium during days 90-240 of pregnancy (PREG), parturition with physiological delivery of fetal membranes (PHYS), and parturition with retention of these membranes (FMR). Also, to visualize protein expression and determine whether classical or non-classical MHC-I mRNA is expressed. ANIMALS: Heavy draft horses. SETTING: PREG horses (n = 12) were sampled postmortem at a slaughterhouse. PHYS (n = 6) and FMR (n = 5) horses were sampled at farms in the vicinity of Olsztyn, Poland. METHODS: For relative quantification of MHC-I, western blotting with densitometry was used. To visualize MHC-I, immunohistochemistry was used. For mRNA identification, RT-PCR was performed. RESULTS: Although the quantity of MHC-I was lower during PREG than parturition, it was present in the allantochorion and endometrium during PREG. During parturition, MHC-I expression was upregulated in the allantochorion (PHYS vs. PREG: 2.7-times higher, 95% confidence interval, 1.3- to 5.7-times higher; FMR vs. PREG: 3.2-times higher, 95% confidence interval, 1.5- to 6.7-times higher). At parturition, staining for MHC-I was detected in the microcotyledons. Classical and non-classical MHC-I were expressed in both tissues during PREG, PHYS, and FMR. CONCLUSION: MHC-I protein is present in the horse allantochorion and endometrium for at least the first two-thirds of pregnancy and at parturition.

Differences in extracellular matrix remodeling in the placenta of mares that retain fetal membranes and mares that deliver fetal membranes physiologically.

INTRODUCTION: In mammals, placenta separation at term may involve degradation of the extracellular matrix by matrix metalloproteinases (MMPs). The activity of MMPs is modulated by TIMPs. We hypothesized that the placentas of mares that deliver fetal membranes physiologically and those that retain fetal membranes (FMR) differ in terms of histology; mRNA expression of MMP-2 and MMP-9; protein expression of MMP-2, MMP-9, and TIMP-2; and the potential activity of both MMPs. METHODS: Placenta biopsies were taken from mares (n = 9; 4 FMR, 5 controls) immediately after foal expulsion. Retention was defined as failure to expel all fetal membranes within 3 h of expulsion. All mares were monitored for time of expulsion. The degree of allantochorial/endometrial adhesion was determined in FMR mares, and biopsies from all mares were histologically examined. mRNA expression, protein immunolocalization, protein amount and potential enzyme activity were determined with RT-PCR, immunohistochemistry, Western Blotting and zymography, respectively. RESULTS: FMR mares had strong to extremely strong allantochorial/endometrial adhesion, and significantly more connective tissue in the allantochorial villi than controls. The range of MMP-2 mRNA expression levels was more than 13 times greater in FMR mares than in controls. Protein content of both MMPs and TIMP-2 differed significantly between groups. The range of potential MMP-2 and MMP-9 activity was larger in FMR mares, and MMP-2 potential activity was 1.4 times higher in controls (P = 0.02). DISCUSSION: These results indicate differences in extracellular matrix remodeling in FMR mares and controls, and suggest dysregulation of MMP expression and activation in FMR mares.