June 1, 2006 (Vol. 26, No. 11)
Kate Marusina Ph.D.
Despite the publicity around the seemingly unlimited medical promises of embryonic stem (ES) cells, these ideas are still far from being clinically implemented. Political wrangling, religious rejections, ethical dilemmas, and technical difficulties mar research on ES cells. Meanwhile, their lesser counterpart, stem cells from umbilical cord blood (UCB), has steadily gained acceptance in the clinical and scientific community as a readily available and noncontroversial source of the mononuclear progenitor cells.
UCB contain pluripotent cells that could differentiate into epithelial, muscle, and neuronal cells, further narrowing the gap with the ES cells. Promising results of in vivo expansion and treatments with combined, partially matched units may soon propel UCB from serving primarily pediatric patients into routine treatment for adults. A large infusion of federal funds allocated by the Stem Cell Therapeutic and Research Act of 2005 should also increase the inventory of UCBs.
For many years, Thermogenesis (www.thermogenesis.com) in Rancho Cordova, CA, has been developing technologies for cord blood processing and storage. It collaborates with the National Cord Blood Program and its founder Pablo Rubinstein, M.D.
President and CEO of Thermogenesis, Philip Coelho, could be credited for making cord blood banking a national issue. A national UCB banking system with a large quality-controlled inventory could provide an 80% chance of finding a match and hence survival for patients with no matching bone marrow donor.
Clinical Applications for UCB
While bone marrow transplantation (BMT) is used as a therapy for a variety of diseases, finding the suitable HLA match can be quite difficult1 in 40,000 donors provides a perfect matchand can take up to four months. Moreover, life-threatening graft-versus-host disease (GVHD) occurs in more than 50% of transplants from unrelated donors.
Umbilical cord blood offers a viable alternative to BMT. The numbers of granulocyte-macrophage progenitor cells in UCB are equal to or greater than that of the adult bone marrow. Its transplantation requires less strict matching parameters, providing a wider pool of donor cells, and incurs fewer incidence of GVHD. UCB provides a virtually unlimited source of stem cells that can be collected without the problems associated with bone marrow collection. Once processed and stored, it is available immediately.
Some estimates place the market for cell-based therapies at $30 billion by the end of 2010, even though most of the research is still on the preclinical level.
Because the success of UCB engraftment is directly proportional to the number of cells transplanted, it was mostly given to pediatric patients. To date, 9,000 UCB transplants have been successfully grafted worldwide. However, with improved processing and storage techniques it is now conceivable to recover over 90% of the stem cells in the initial sample. In addition, ex vivo expansion of stem cells and grafting of combined samples to increase cell dose has shown increasing success in transplantation in adults. As of 2005, over a quarter of all recipients were over 18 years.
Cord Blood Cryopreservation
There are three reasons for stem cell loss during processing and preservation stages, comments Coelho. First is poor volume-reduction techniques. UCB is collected in various volumes, but the storage volume has to be consistent. Traditional methods, such as via Ficoll density gradients, result, on average, in 25% loss of viable CD34+ cells. Next, incorrect rates and temperatures of sample freezing add 10󈞀% loss of cell viability. Finally, storage conditions at above -196°C combined with transient warming events lead to another 20% loss of viability.
At the end, you may end up with only 50% of viable cells from the original collection. A patient may die just because there were not enough viable cells for transplantation.
Thermogenesis solves these issues by automating every step of the process. Its AXP AutoExpress System provides an automated, one-step procedure that separates mononuclear cells from the plasma and red blood cells into a fixed 20-mL volume and transfers them directly into the freezing bag. With its enclosing metal storage canister, the whole unit is about the size of a Palm Pilot. 20% of the sample is directed into a detachable compartment for future in vitro stem cell expansion. Each bag and canister is bar coded for easy identification through Xpress TRAK software.
Since a freezing protocol has a dramatic effect on cell viability, Thermogenesis designed an automated controlled rate freezing method. The 20-minute freezing process takes place in liquid nitrogen vapors, after which the unit is transferred by a mechanical arm into one of the 3,626 slots, deep under the �°C liquid nitrogen within the BioArchive System.
By monitoring the bag temperature via the external probes, the computer determines the actual temperatures inside the bag and derives a freezing curve to validate the process. Each BioArchive system is equipped with an autonomous power source and a manual retrieval system. In case of serious damage to the vacuum jacketing, the entire inventory could be swapped between two BioArchive dewars in less than 50 seconds. The post-thaw data provided by the company indicates that on average 96% of the cells are still viable.
Worldwide, BioArchive is installed in 76 blood banks in 29 countries. In October 2005, Thermogenesis signed the R&D and distribution agreement with GE Healthcare for the BioArchive and the AXP AutoExpress systems. Under the terms of the agreement, GE Healthcare will have exclusive global distribution rights for both systems and will also collaborate with Thermogenesis to develop new generations of the products.
The sales of its blood processing systems (including ThermoLine Freezing and Thawing systems and DAC System for semiautomated separation of blood) supports development of other blood-related products. The CryoSeal Fibrin Sealant System enables the production of autologous fibrin and thrombin from plasma in about 60 minutes. Thrombin Processing Device enables production of autologous thrombin in about 25 min, from only 11 mL of plasma. Fibrin sealants and topical thrombin are used in operating rooms to stop blood loss, promote blood clotting, and release growth factors from platelets.
Stem Cell Therapeutic and Research Act of 2005
Coelho was instrumental in drafting H.R.2520, introduced in 2003 by Representative Christopher Smith (R-NJ). The bill was signed by President Bush in December 2005. It requires the Health Resources and Services Administration to enter into contracts with qualified banks for the purposes of establishing and maintaining the National Network of Cord Blood Stem Cell banks, called C.W. Bill Young Cell Transplantation Program.
The legislation allocates $79 million over five years to increase the amount of available human cord blood stem cells to at least 150,000 high-quality units. Some of this funding will be used to purchase cryopreservation equipment, such as the $150 AXP processing disposable or $250,000 BioArchive System, which stores and preserves 3,626 cord blood units. The total cost to collect and process one unit comes to about $1,500, which includes testing for communicable diseases and tissue and DNA typing.