Regenerative Strategies for Vascular and Lung Tissues Laura E Niklason MD, PhD
Disclosure: Some of this work in this presentation is from Humacyte Inc. Niklason is a founder of Humacyte, and holds stock in the company.
Composition, Design Requirements for Arteries: - Must have adequate mechanical strength: 3 billion stress cycles over our lifetimes - Must prevent blood clotting functions of the endothelium, heparin, nitric oxide - If cellular, must be autologous. The Grand Challenge is the off-the-shelf, small caliber vascular graft
Rupture strengths of native arteries > 2,000 mm Hg
A blood vessel model constructed from collagen and cultured vascular cells Weinberg & Bell, Science 1986; 231: 397.
Transplantation of a tissue-engineered pulmonary artery Shin oka, Imai, Ikada, New England Journal of Medicine 2001; 344: 532.
Late-term results of tissue-engineered vascular grafts in humans. J. Thoracic Cardiovascular Surgery 2101; 139: 431. Extracardiac cavo-pulmonary shunts Pediatric patients, low pressure system. Autologous marrow- derived cells on a biodegradable polymer scaffold culture time of hours.
Technology insight: The evolution of tissue engineered vascular grafts, from research to practice Nature Clinical Practice 2007; 4: 389. Revolutionary dialysis graft in adults. Drawbacks: cells from the patient; long culture time (6 months or more)
Mechanically strong vessels that do not require cells from the patient: Rupture > 3,000 mm Hg
Readily available tissue engineered vascular grafts, Science Translational Medicine 2011; 2;3(68). Overall patency in baboons > 80%, follow-up 1 to 6 months; grafts are off-the-shelf.
Allogeneic, acellular arteries do they meet design criteria? - Must have adequate mechanical strength - Must prevent blood clotting - If cellular, must be autologous. At larger calibers (eg. > 6 mm, high flow rates), presence of anti-coagulation provided by endothelium is not critical. However, for small calibers the Grand Challenge anti-coagulation is essential.
Ongoing work covalent chemistry on the graft lumen to mimic some of the actions of native endothelial cells..... all with the goal of producing an artery off-the-shelf...
Human Lung is a tremendously complex organ regeneration of the solid organ presents new challenges: - 23 generations of airway branching - 70 square meters surface area for gas exchange - 100 million air sacs, each 200 microns in size - Blood-gas barrier is protein membrane 50 nm thick
First attempt at human lung replacement the polio epidemic :
Attempts at intra-vascular oxygenation limited by low surface areas, thrombosis around the capillary tubes :
Functional Lung design criteria: Adequate surface area for O 2 /CO 2 exchange Maintain barrier function between blood and air Proper mechanics not emphysematous or fibrotic Cellular components must be autologous Grand Challenge Produce an autologous organ that can support long-term gas exchange, without rejection.
Lung matrix has anatomic complexity retained - Vascular architecture Air-sac architecture
Paradigm for lung regeneration: eventually, cells to populate the matrix will come from stem cells that we create for each patient, from a small biopsy of skin
Native Re-populated Native Decell Engineered
Implantation of engineered lung into rat recipient - Petersen, et al, Science 2010
To approach the challenge of human lung regeneration, we need a source of pulmonary epithelial cells - Yamanaka 2006, 2008
Differentiation of human ips into pulmonary epithelium: A Trophic Factors SB431542(10µM) Activin A NOGGIN (200ng/ml) EGF(10ng/ml),FGF10 (10ng/ml) (100ng/ml) 0 6 8 KGF (10ng/ml),WNT3a (100ng/ml) 21 ips Definitive endoderm Anterior foregut endoderm Differentiation Alveolar progenitor Maturation days AETII
Human lung bioreactor development stepping stone for meeting the grand challenge :
Bioreactor supports organ growth and survival, and provides for ventilation of liquid medium (or air) similar to native:
Outstanding Laboratory Group: Liqiong Gui PhD Sumati Sundaram PhD Julio Mendez PhD Jenna Balistrini PhD Mahboobe Ghaedi PhD Ashley Gard BS Elizabeth Calle BS Liping Zhao MS - Sam Raredon BSE - Thomas Petersen MD, PhD - Shannon Dahl PhD - Juliana Blum PhD - Justin Strader BSE - Heather Prichard PhD Key Collaborators: Jeffrey Lawson MD, PhD Alan Kypson MD Tai Yi MD Erica Herzog MD, PhD