MONTREAL ¿ Clint, Arnold and Danny will perhaps never know it, but they are celebrities in the transgenic-animal world, right up there with the likes of Dolly the sheep.
The proud ¿father,¿ Nexia Biotechnologies Inc., disclosed their births recently, representing the world¿s first cloned goats and Canada¿s first cloned livestock animals using nuclear transfer.
Jeffrey Turner, president and CEO of Nexia, told BioWorld International the trio of goats was produced using a technique similar to that of Dolly the sheep, in which somatic cells were taken from the body of one goat and transferred into mature unfertilized eggs. These eggs had their original nuclei removed and replaced by nuclei derived from cells grown in culture and obtained from a separate, source goat.
The cloned goats also represent a real breakthrough for Nexia¿s BioSteel spider-silk product development program, in which the spider silk is extracted from the milk of goats, Turner said.
BioSteel, a man-made spider silk, is a new, high-performance, environmentally friendly biomaterial, and is Nexia¿s lead product.
Naturally occurring spider silk is widely recognized as the strongest, toughest fiber known. With a tensile strength of 300,000 pounds per square inch, it is stronger and lighter than steel and synthetic, petroleum-based polymers. Despite its superior mechanical properties, spider silk is not used commercially because of an absolute constraint on supply. Spider farming is simply not practical. Unlike silk worms, the spider¿s territorial and aggressive nature precludes intensive cultivation. Further, it is not the spider cocoon silk that is desired, but certain components of the web silk, namely the frame silk.
Nexia¿s technology relies on the anatomical similarities between the spider silk gland and animal¿s mammary glands. In both cases, epithelial cells manufacture and secrete water-soluble, complex proteins in large amounts. Nexia has successfully completed the first phase of its program by producing and secreting fully soluble silk protein in vitro within its patented MAC-T mammary cell lines. No truncation of the silk genes is observed.
The success of this cell-based, prototype system encouraged Nexia to continue the scale-up of manufacturing spider silk protein within its transgenic Breed Early, Lactate Early (BELE) goat system. Dairy animals have obvious utility in this application because they have a very large number of mammary cells. Nexia has the demonstrated ability to put the spider gene into all the cells of the mammary glands of goats.
Nexia is developing BioSteel to satisfy urgent medical needs for high-performance biomaterials used in artificial tendons or ligaments, prostheses, tissue repair, wound healing and super-thin, biodegradable sutures for ocular surgery or neurosurgery. It also will find application in aerospace and military applications, Turner said.
The company said that the four or five male clones in the next generation will be the founder animals, which will be bred normally, for the development of a herd of up to 500 animals that will be used for large- scale production purposes. Nexia expects to recover enough spider silk in order to begin clinically testing BioSteel next year. n