21 Functional and structural characterization of equine clone placentas with regards to foal outcome

E. Muñoz; M. Estrade; M. Soriano; J. Rivière; M. Vilotte; N. Mucci; P. Chavatte-Palmer

doi:10.1071/RDv37n1Ab21

RESEARCH ARTICLE

21 Functional and structural characterization of equine clone placentas with regards to foal outcome

E. Muñoz ^A ^B , M. Estrade ^B , M. Soriano ^A , J. Rivière ^C , M. Vilotte ^C , N. Mucci ^A and P. Chavatte-Palmer ^D ^E

+ Author Affiliations

- Author Affiliations

^A Clonargen Biotech, Equine Cloning Company, Luján, Buenos Aires, Argentina

^B Unidad Académica Reproducción Animal, Facultad de Veterinaria, UDELAR, Montevideo, Uruguay

^C Paris-Saclay University, INRAE, AgroParisTech, GABI, Jouy-en-Josas, France

^D Paris-Saclay University, UVSQ, INRAE, BREED, Jouy-en-Josas, France

^E Ecole Nationale Vétérinaire d’Alfort, BREED, Maisons-Alfort, France

Reproduction, Fertility and Development 37, RDv37n1Ab21 https://doi.org/10.1071/RDv37n1Ab21

Cloning in various species is associated with placental abnormalities. The objective of this study was to describe term placental functionality and structure related to foal outcome in a commercial equine cloning company. Fibroblasts (one to three passages) were used as donor cells during conventional somatic cell nuclear transfer procedure, as described by Galli et al. (2008 Reprod. Domest. Anim. 43, 331–337). Light crossbreed mares were used as recipients and routinely monitored during pregnancy. Recipients between 260 and 280 days of gestation and without any previously detected pregnancy pathology were selected for this study. Placentas were collected and weighed at delivery after foaling, and their gross surface measured. Variables analyzed were assigned to two groups according to foal outcome: viable foals (V, n = 17) that remained alive after 1 month, and nonviable foals (NV, n = 16) that were stillborn or were euthanized because of medical issues. A limited number of placental samples were fixed for histology (V, 4; NV, 7) or snap-frozen for candidate gene expression (V, 4; NV, 6). Paraffin-embedded sections (7 μm) were stained with HES and Masson’s trichrome and scanned using NanoZoomer Digital Pathology®. Statistical analyses were performed by Mann-Whitney tests using GraphPad Prism v.10.2.3. Gestational length did not differ significantly (P = 0.08) between groups (median: V, 349 days; NV, 318.5 days). Viable foals tended (P = 0.068) to be heavier than NV foals (median: V, 44 kg; NV, 37.8 kg). Placentas were heavier (P = 0.002) in NV foals (median: V, 5.1 kg; NV, 7.2 kg) and placental efficiency (placenta/foal weight ratio) was significantly (P = 0.004) reduced in NV foals (median: V, 13; NV, 8.4). Overall, the foal neutrophil/lymphocyte (N/L) ratio at birth, which is used clinically as an index for foal maturation, did not differ between groups (V, 3.5; NV, 3.9; P = 0.41), but N/L values were lower than standard references in equine literature for viable foals (>6). Histological observations of placentas did not show any sign of infection or inflammation in either group. Results are pending for surface density and volume fraction of the different components of the chorioallantoid, as quantified by One Stop stereology using Mercator® software, and RT-qPCR expression of genes involved in growth (H19, IGF-2, IGF-1R), transplacental exchange (SLC2A1, SLC2A3, SIC38A2, CD36, LPL), and vascularization (ENG, Flt1, KDR). In conclusion, although gestational length did not significantly differ between groups, V foals tended to be heavier with higher placental efficiency, whereas NV foals tended to be lighter with heavier placentas. Pending results from stereology and gene expression analyses will help us explore the reduced placental efficiency in NV foals.