Production and rearing of germ-free X-SCID pigs

Abstract

Pigs with X-linked severe combined immunodeficiency (X-SCID) caused by a mutation of the interleukin-2 receptor gamma chain gene (IL2RG) are of value for a wide range of studies. However, they do not survive longer than 8 weeks because of their susceptibility to infections. To allow longer survival of X-SCID pigs, the animals must be born and reared under germ-free conditions. Here, we established an efficient system for piglet derivation by hysterectomy and used it to obtain and maintain a germ-free X-SCID pig. In four trials using pregnant wild-type pigs, 66% of piglets after hysterectomy started spontaneous breathing (range of 20–100% per litter). The resuscitation rate was found to negatively correlate with elapsed time from the uterus excision to piglet derivation (r=−0.97, P<0.05). Therefore, it is critical to deliver piglets within 5 min to achieve a high resuscitation rate (82% estimated from regression analysis). In a fifth trial with an IL2RG+/− pig, four piglets were delivered within 4.2 min of uterus excision and three were alive (75%). One of the live born piglets was genotypically and phenotypically determined to be X-SCID and was reared for 12 weeks. The X-SCID piglet was free from both bacteria and fungi at all time points tested by microbial culture and grew without any abnormal signs or symptoms. This study showed successful production and rearing of germ-free pigs, enabling experiments involving long-term follow-up of X-SCID pigs.

Update regarding xenotransplantation in Japan

“…However, there are no DPF pig herds in Japan. Hara et al established an efficient piglet derivation system involving hysterectomy of wild‐type pigs to optimize the piglet delivery conditions . In this system, they excised the uterus with the fetus from the anesthetized mother pig just before birth and transferred it to a plastic isolator through a tank for decontamination.…”

Development of Severe Combined Immunodeficient (SCID) Pig Models for Translational Cancer Modeling: Future Insights on How Humanized SCID Pigs Can Improve Preclinical Cancer Research

“…Survivability of previous IL2RG knock out pigs has varied from 2 to 7 weeks ( 16 ) and derivation of animals and available housing likely impacts outcome. Recently Hara et al ( 27 ) used small isolators and developed piglet delivery protocols to help extend the lifespan of IL2RG knock out SCID pigs. To achieve this goal, excised uteruses were brought into isolators units, piglets were delivered, and reared within these isolators.…”

“…To achieve this goal, excised uteruses were brought into isolators units, piglets were delivered, and reared within these isolators. One SCID piglet raised in the isolators was raised to a planned endpoint of 12 weeks of age without incidence of bacterial or fungal disease ( 27 ).…”

“…One of the hurdles to working with SCID pigs is maintaining viability due to susceptibility to disease. The use of positive-pressure biocontainment facilities ( 31 ) and standard animal isolators ( 27 ) have improved SCID pig health and viability. The ability to house immunodeficient pigs in a controlled environment increases their lifespan allowing them to be utilized for long-term biomedical research.…”

Novel Engraftment and T Cell Differentiation of Human Hematopoietic Cells in ART−/−IL2RG−/Y SCID Pigs

“…Within the past few years, such SCID pigs are now being utilized by cancer (13), disease model (12), and stem cell therapy (7) researchers. Biocontainment facilities (14), isolators (12), and Cesarean section (15) techniques have allowed survival of animals, enabling longer term studies. An important step in further developing the SCID pig model is to immunologically humanize these animals through the introduction of human CD34 + hematopoietic stem cells.…”