Scientists continue to make progress in this first phase of tissue engineering, in which real and mock tissues of various types grown from cells will largely be used to expand and speed up further research rather than in treatment:
Researchers have reported development of the first three-dimensional tissue system that reproduces the complex structure and physiology of human bone marrow and successfully generates functional human platelets. Using a biomaterial matrix of porous silk, the new system is capable of producing platelets for future clinical use and also provides a laboratory tissue system to advance study of blood platelet diseases. "There are many diseases where platelet production or function is impaired. New insight into the formation of platelets would have a major impact on patients and healthcare. In this tissue system, we can culture patient-derived megakaryocytes - the bone marrow cells that make platelets - and also endothelial cells, which are found in bone marrow and promote platelet production, to design patient-specific drug administration regimes."
The new system can also provide an in vitro laboratory tissue system with which to study mechanisms of blood disease and to predict efficacy of new drugs - providing a more precise and less costly alternative to in vivo animal models. The new system combined microtubes spun of silk, collagen and fibronectin surrounded by a porous silk sponge. Megakaryocytes - some of which were derived from patients - were seeded into the engineered microvasculature. The researchers were able to increase platelet production in the bioreactor by embedding the silk with active endothelial cells and endothelial-related molecular proteins that support platelet formation.
Laboratory tests showed that the platelets being generated and recovered from the tissue system were able to aggregate and clot. While the number of platelets produced per megakaryocyte was lower than normally made in the body, the researchers note that the system represents a significant advance over previous models. The scalable nature of the bioreactor system provides engineering options to increase yields of platelets in ongoing studies. In addition to providing a platform for studying the processes that regulate platelet production and related diseases, the researchers hope the platelets produced can be used as a source of growth factors for wound healing in regenerative medicine, including healing of ulcers and burns.