Clinical and molecular characterization of a re-established line of sheep exhibiting hemophilia A

BACKGROUND

Large animal models that accurately mimic human hemophilia A (HA) are in great demand for developing and testing novel therapies to treat HA.

OBJECTIVES

To re-establish a line of sheep exhibiting a spontaneous bleeding disorder closely mimicking severe human HA, fully characterize their clinical presentation, and define the molecular basis for disease.

PATIENTS/METHODS

Sequential reproductive manipulations were performed with cryopreserved semen from a deceased affected ram. The resultant animals were examined for hematologic parameters, clinical symptoms, and responsiveness to human FVIII (hFVIII). The full coding region of sheep FVIII mRNA was sequenced to identify the genetic lesion.

RESULTS AND CONCLUSIONS

The combined reproductive technologies yielded 36 carriers and 8 affected animals. The latter had almost non-existent levels of FVIII:C and extremely prolonged aPTT, with otherwise normal hematologic parameters. These animals exhibited bleeding from the umbilical cord, prolonged tail and nail cuticle bleeding time, and multiple episodes of severe spontaneous bleeding, including hemarthroses, muscle hematomas and hematuria, all of which responded to hFVIII. Inhibitors of hFVIII were detected in four treated animals, further establishing the preclinical value of this model. Sequencing identified a premature stop codon and frame-shift in exon 14, providing a molecular explanation for HA. Given the decades of experience using sheep to study both normal physiology and a wide array of diseases and the high homology between human and sheep FVIII, this new model will enable a better understanding of HA and facilitate the development and testing of novel treatments that can directly translate to HA patients.

145 REESTABLISHMENT OF AN EXTINCT STRAIN OF SHEEP UTILIZING ASSISTED REPRODUCTIVE TECHNOLOGIES

The objective of this study was to reestablish an extinct strain of sheep that exhibits spontaneous X-linked factor VIII deficiency closely mimicking human hemophilia A. Twenty female carriers of the trait, produced in a previous study (Bormann et al. 2006 Reprod. Fertil. Dev. 18, 201–202), were backcrossed using 3 straws of semen from their affected sire using either IVF or multiple ovulation embryo transfer (MOET). Eleven oocyte donors were synchronized with CIDRs (15 days) and superovulated with a declining dose of FSH (204 mg) twice daily for 3.5 days. Nine MOET donors were synchronized using CIDRs (14 days), superovulated with a declining dose of FSH (184 mg) BID for 3 days with pregnant mare serum gonadotropin (PMSG; 200 IU) given with the final dose of FSH, and given 1000 IU of hCG 12 h post-CIDR removal. Recipient ewes were synchronized using sponges (Ovakron, HeriotAgvet, Rowville, Victoria, Australia) containing 30 mg of flugestone acetate (14 days) and given PMSG (400 IU) at sponge removal, followed by 1000 IU of hCG 12 h post-sponge removal. Oocytes were collected via follicular aspiration during midventral laparotomy and matured as previously reported. Semen for IVF was prepared by centrifugation on a Percoll gradient. Oocytes and sperm were incubated in mTALP with 20% estrus sheep serum (modified from Bavister et al. 1977 Bio. Reprod. 16, 228–237) for 20 h, then vortexed to remove cumulus cells, and cultured in G1.3 medium (Vitrolife, Englewood, CO) with BSA until transfer. Embryos were surgically transferred into oviducts of recipients 24 to 48 h following IVF. The 9 MOET donors were surgically inseminated at the uterotubal junction with approximately 1–2.0 � 106 spermatazoa. Oviducts of eight of these ewes were flushed 48 h post-insemination with warm M199 containing Hanks salts, 25 mm HEPES, 10% FBS, and 0.5 µg mL–1 gentamicin. MOET embryos were surgically transferred to synchronized recipients within 5 h. One MOET donor was not flushed due to poor response and did not produce an offspring. Utilizing 140 ova, IVF produced 54 embryos for an embryo/oocyte rate of 38.6%. All IVF embryos were transferred into 15 recipients resulting in 3 lambs for a lamb/embryo rate of 5.5%. The MOET donors produced 38 embryos and 13 apparently unfertilized ova, generating an embryo/oocyte rate of 74.5%. MOET embryos were transferred into 21 synchronized recipients. MOET produced 16 lambs for a lamb/embryo rate of 42.1%. Co-transfer of 1 IVF and 1 MOET embryo into a single recipient produced one offspring. Utilizing multiple reproductive technologies over a two-year period, 8 hemophilic offspring (7 females and 1 male), 6 carrier females, and 6 unaffected males were produced. This strain of sheep will be used to produce affected offspring for stem cell-based therapies.

187 RE-ESTABLISHMENT OF AN EXTINCT STRAIN OF SHEEP FROM A LIMITED SUPPLY OF FROZEN SEMEN

The objective of this study was to restore a line of sheep that exhibits spontaneous X-linked factor VIII deficiency closely mimicking human hemophilia A. Six straws of frozen semen from an affected Alpine White male were obtained from Switzerland. In the first experiment the straw of semen thawed was of poor quality. Two ewes were synchronized for use as embryo donors (MOET) by means of CIDRs for 14 days and superovulated with declining doses of FSH (184 mg) twice daily for 3 days. PMSG (200 IU) was given with the final dose of FSH and 1000 IU of hCG 12 h post-CIDR removal. The ewes were surgically inseminated 24 h later. Oviducts were flushed 48 h post-insemination producing 13 unfertilized ova (UFO). Spermatozoa were used for intracytoplasmic sperm injection (ICSI) utilizing oocytes collected from superstimulated ewes by laporatomy. These ewes were synchronized with CIDRs (15 days) and superovulated with a declining dose of FSH (204 mg) twice daily for 3.5 days. Utilizing 236 oocytes, ICSI produced 189 embryos, an 80% embryo/oocyte rate. Embryos were transferred surgically to the oviducts of 17 synchronized recipients. Recipients were synchronized using sponges (Ovakron; Heriot Agvet, Rowville, Victoria, Australia) containing 30 mg of flugestone acetate (14 days) and given PMSG (400 IU) at sponge removal, followed by 1000 IU of hCG 12 h post-sponge removal. Eleven recipients produced 17 lambs for a lamb/embryo rate of 8.9%. The straw of semen utilized for the second experiment was of higher quality. Three ewes were superstimulated for use as MOET donors, as above, with increased doses of FSH (228 mg) and PMSG (500 IU). Donors were surgically inseminated and oviductal flushes were performed 40 h post-insemination, yielding 19 UFO and 12 embryos for an embryo/oocyte rate of 38.7%. Embryos were transferred to four recipients, synchronized as above with an increased dose of PMSG (600 IU). These MOET recipients produced nine lambs for a lamb/embryo rate of 75%. Semen was used to produce embryos via in vitro fertilization (IVF) using oocytes collected from superstimulated ewes (as above with an increase of FSH to 252 mg). IVF produced 91 embryos from 247 oocytes for an embryo/oocyte rate of 36.8%. Embryos were transferred to 20 recipients 24 to 48 h post-fertilization. Seven recipients maintained pregnancy and produced 10 lambs with a lamb/embryo rate of 11%. ICSI was also utilized, producing 54 embryos from 98 oocytes, an embryo/oocyte rate of 55.1%. Embryos were transferred to eight recipients; none maintained pregnancy. Through the use of multiple reproductive technologies, 36 lambs (22 carriers) were produced from two straws of semen. Carriers will be bred back to their sire in a similar program to produce affected lambs. The authors would like to acknowledge J. Liu and M. Ridha for their contributions. This work was supported by NIH Grant HL073737-12.

Simulation of lean lamb production systems

A series of simulations were performed to evaluate the effects of mature size (WMA; 60, 70, 80 and 90 kg), slaughter weight (SW; 55, 60 and 65 kg) and three diets fed to feedlot lambs. Rations included a traditional diet (C2L) or placing weaned lambs on alfalfa for either 30 (A30) or 60 (A60) d before placing them on the C2L diet (A30-C2L and A60-C2L). Two lamb pricing schemes were used in the financial analysis of the biological results: sale price based on weight with or without adjustment for carcass fat. Placing lambs on alfalfa pasture increased ownership by 22 d on average compared to C2L. As WMA and SW increased, ownership increased from 3 to 11 d. Across nutritional treatments, fat decreased by 5.8 to 9.0% as WMA increased from 60 and 90 kg. When market lambs were priced on weight, net returns per lamb were greatest for A30-C2L or A60-C2L ($2.34 and $5.21, respectively above C2L) and for greater SW ($4.77 and $7.16 greater for SW 60 and 65 kg than for SW 55). The combination WMA of 90 kg, a SW of 65 kg and nutritional treatment of A60-C2L proved most profitable. However, when sale price was discounted for excessive fat content, the combinations WMA of 60 or 70 with a SW of 65 and A60-C2L were most profitable. The rank correlation between biological efficiency (weight gain/dry matter feed consumption) and net return, when sale price was based on weight, was found to be -.51. This was because lambs slaughtered at lighter weights had high biological efficiencies but low net returns due to a negative price margin. With negative price margins but positive feeding margins, net returns are greatest for heavier, fatter lambs fed longer.