Hearing loss in-a-dish model for otoprotective and otoregenerative drug development

Funding Type: 
Tools and Technologies II
Grant Number: 
ICOC Funds Committed: 
Stem Cell Use: 
Adult Stem Cell
Cell Line Generation: 
Adult Stem Cell
Public Abstract: 
Hearing impairment is the most common sensory deficit, the most common occupational disease, and the third most prevalent chronic disability of mankind, resulting in an enormous socio-economic impact. It is caused by the irreversible death of cochlear hair cells. Hair cell regeneration does not occur naturally in the mammalian cochlea, nor has it been reproducibly achieved in an experimental setting. This proposed collaborative project between California and collaborative funding partner research laboratories represents the first systematic plan to overcome the prevailing bottlenecks that impede the development of translational approaches toward novel human cell-based treatments for hearing loss. The most prevalent translational bottleneck hampering translational approaches toward curing hearing loss is the lack of purity of otic progenitor cells generated from human ES and iPS cells. The bottleneck is 1) that this heterogeneous progenitor cell pool contains tumorigenic cells, which hampers the use of the cells in in vivo repair studies. Likewise, 2) the presence of non-defined cell types renders the cell population inadequate for bioassay development, such as the development of high-throughput assays for compounds with ototoxic, but also otoprotective or otoregenerative efficacy. Ototoxic drugs are drugs such as aminoglycoside antibiotics or cisplatin, which can cause irreversible hearing loss (drug side effects). Our work will make it possible to develop ototoxicity tests with human cells; currently such tests do not exist. Otoprotective drugs prevent hair cell loss by counteracting ototoxicity. Such drugs (when discovered) could prevent hearing loss caused by, for example, loud noise, certain infections, ototoxic drugs, and perhaps even sudden hearing loss and age-related hearing degeneration. No human cell-based tests exist for otoprotection. Otoregenerative drugs directly address curing hearing loss and the identification of drug candidates with otoregenerative potential opens the door for developing a cure for hearing loss. No human cell-based tests exist for otoregeneration. Our research goals are 1) to identify novel biomarkers that are present on human ES cell-generated otic progenitor cells and to use these biomarkers to purify progenitor cells with a) high capability to generate human inner ear cells and b) no tumorigenic potential. Successful development of this novel technology will remove the bottleneck described above. 2) We will demonstrate that the purified otic progenitors are useful in bioassays for ototoxicity, otoprotection, and otoregeneration.
Statement of Benefit to California: 
This proposed collaborative project between California- and collaborative funding partner research laboratories represents the first systematic plan to overcome the prevailing bottlenecks that impede the development of translational approaches toward novel human cell-based treatments for hearing loss. Hearing loss affects one in 1,000 newborns and the same number of children lose their hearing before puberty. In adults, hearing loss can happen as a result of drug side effects (ototoxicity), loud noise exposure, certain infections, sudden hearing loss, or the effects of aging. About 3.5 million Californians have disabling hearing loss (affecting both ears); worldwide, more than 350 million people are affected. Beside the obvious medical benefit, we expect that our proposed research will lead to the development of novel techniques that can directly be adopted by existing California biotech companies. We anticipate that, in the long run, this new technology will lead to new jobs in research & development. If the new tools lead to discovery of novel treatments, they will have a long lasting effect on the California-based biotech industry including jobs, increased tax income for the state, and overall maintaining the status of California as worldwide hub for technology and innovation.
Progress Report: 
  • A key hurdle preventing translation of stem cell therapies to the clinic is the lack of efficient strategies to transplant and retain viable cells. Cell transplantation by direct injection is favored for its minimal invasiveness but commonly results in poor cell viability. Use of thixotropic hydrogels as injectable cell-delivery vehicles is one potential strategy to overcome this limitation. We report a protein-engineered hydrogel designed to meet four criteria for use in stem cell injection protocols: (i) gentle cell encapsulation at constant physiological conditions without the need for chemical crosslinkers, (ii) shear-thinning under reasonable hand-injection force through a syringe needle, (iii) rapid gel recovery to localize cells at the injection site, and (iv) cell-adhesive ligands and mechanical properties conducive to three-dimensional (3D) cell culture. This Mixing-Induced Two-Component Hydrogel (MITCH) is synthesized using protein-engineering technology to yield monodisperse block-copolymers that hetero-assemble upon simple mixing. Human and mouse adipose-derived stem cells (ASCs) remain viable and display a well-spread 3D morphology within MITCH. Use of MITCH to deliver ASCs to the subcutaneous dorsa of athymic mice resulted in significantly greater viable cell retention at the implant site compared to Type I collagen or buffer alone up to two weeks post-transplantation.
  • Although stem cells have tremendous potential to regenerate damaged or diseased tissue, scientists must develop efficient methods to deliver the stem cells to the sites in the body where they are needed. Injection of stem cells through a syringe needle directly into the tissue site is a simple procedure to perform, but it exposes the stem cells to damaging mechanical forces that can injure the cells. In year 1 of this project, we developed a gel that encapsulates stem cells and protects them from these damaging mechanical forces. This gel was able to maintain excellent viability of transplanted stem cells for up to one week. In year 2 of the project, we further developed this new gel material with the goal of extending the lifetime of transplanted stem cells. In particular, we synthesized two new gel formulations. The first gel is able to co-encapsulate the stem cells together with pro-survival factors. The presence of these pro-survival factors was found to increase the retention of transplanted stem cells. The second gel is able to stiffen after it is injected into the body; thereby enabling it to last for longer times. Our long-term goal is to increase the percentage of stem cells that can survive the transplantation process and participate in the regeneration of damaged tissue.
  • Since the previous report, efforts have focused on expanding the stem cell-protective hydrogel technology to other biomaterial formulations to confirm the broad applicability of this technology and to optimize the technology for specific disease and injury therapies.
  • During the past year, three manuscripts were accepted for publication, and an additional three manuscripts are in preparation. The technology has been protected by the Stanford Office of Technology Licensing with a patent disclosure to the US Patent Office.

© 2013 California Institute for Regenerative Medicine