Early Translational I
Medical care for burn patients has advanced in the last few decades. This is due, in large part, to medical research that has contributed to the management of fluid loss and infection. Now, morbidity rather than mortality is the main issue in burn care. Technology has advanced so we can save lives by replacing damaged or missing skin with skin autografting or dermal equivalent products made from animal products. However, grafted skin is unable to completely restore normal skin function. For skin to function normally, it requires multiple skin appendage organs. These include hair, sebaceous gland, etc. Sebaceous glands are necessary for normal skin lubrication and patient without glands will have lifelong requirement for daily moisturizer to replace skin oils. Hair functions in direct relationship to external appearance which directly influences a patient’s quality of life. We have recently developed a new method of growing hair from newborn mouse skin cells. The cells can organize themselves and form skin which contains normal hairs distributed in a cosmetically acceptable fashion. We will also apply the concept of improving the "macro-environmental regulation of hair stem cell activity", based on a paper we just published in Nature this January. By preparing the soil to be more fertile, we increase the success of stem cell regeneration. Together these represent major advances in skin appendage regeneration. Here we propose to bring this progress from basic research to the pre-clinical research phase, so that the technology can be ready for clinical trials at the end of the 3 year funding period. This work offers another significant step in the saga of stem cell engineering. As of today, bone marrow stem cells have already been in clinical use because no spatial organization is needed. However, for many organs, tissue architecture is essential for function. While scientists can exert some control over the stem cell differentiation, our inability to turn a population of stem cells into topologically-organized tissues becomes a bottleneck preventing their use in therapy. The success of this work will be the first in this category of stem cell engineering. One of the major concerns in the use of stem cells is their potential to form tumors. Therefore there is a great need to develop imaging methods that can track stem cells once they are in the body, so one can detect any early changes. Since the skin is on the surface, we can verify that the cells contribute to appropriate skin structure, and biopsy can be done easier to verify changes in radiological imaging. Principles learned this way can also be applied to the stem cell research of other organs. The ability to reconstruct skin appendages has profound implications to benefit patients. In addition to burn patients, there are numerous congenital, post-traumatic and acquired deficiencies of hair. Success would allow clinicians to treat these patients as well.
Statement of Benefit to California:
The recent firestorms in southern California remind us of the dangers from natural disasters in our environment. An article published in the Insurance Journal, May 2008, estimates that a 7.8 magnitude earthquake could cause over $87 billion worth of damage from fires ignited by ruptured gas lines and other sources. Currently, over 100,000 patients are treated for burn injury in the United States per year. In the event of a catastrophe such as wildfire, earthquake or even terrorist attack, that number could skyrocket beyond what medical practitioners can handle. Burns can cause lasting appearance and functional defects to visible areas on the skin. Research has taken today’s burn care beyond just keeping the patient alive and fighting against infection and fluid loss. Appearance can profoundly affect one’s physical and psychological well-being, especially when altered after a severe disfiguring injury. Current technology has improved the mortality rate of burns tremendously, but improvement of the morbidity rate of burn injuries has a long way to go. Our goal is to create normal skin for burn victims. Currently, burn victims have scars, which never look or feel like normal skin. The main difference between scar and normal skin lies in the fact that scar does not have hair, sweat glands, or oil glands. While we may find these to be ancillary, lack of any or all of these causes significant suffering in a patient with scars. Evolutionarily, hair kept people warm. Today, billions of dollars are spent nationwide in the grooming and restoration of hair. It is conceivable that the benefit of our ability to use stem cells to grow hairs can be extended beyond restoration of normal skin architecture. The current gold standard of treatment for hair loss is hair transplantation, which is a laborious and expensive procedure. Essentially, a strip of hair bearing skin is surgically taken from the patient. The individual hair follicles are then painstakingly dissected out one by one and planted into small slits are made on the recipient’s skin. Patients who do not have enough hair as a result of previous injury (such as burn), cannot spare extra hair to transplant. There is just no way to increase the total number of hairs. In contrast, our stem cell based hair growth can generate many more new hairs from the stem cell pool. We seek to generate completely new hairs from a patient’s own stem cells, although we also will pursue other strategies. The hair will be permanent and will look and behave like natural hair. Hair restoration has profound implications for both the medical field and the cosmetic industry. The ability to harness stem cells toward forming normal looking, hair-containing skin has a huge potential market. The people of California not only will benefit from having new therapeutic treatment for hair restoration following traumatic injury, but also can reap financial benefit from their stake in supporting the development of this technology.
The goal of this project is to generate normal skin, containing functional, properly patterned hair to treat victims of burns, trauma or disease such as alopecia (loss of hair). The Principle Investigator (PI) has developed an assay (“planar hair forming procedure”) using a slurry of dissociated and re-aggregated newborn mouse skin cells on a scaffold that can engraft onto a wound bed and generate apparently normal hair. The PI proposes 3 aims utilizing the mouse skin cell assay, and a fourth aim to translate the findings to human cells. In the first aim, the existing assay will be optimized by altering the ratio of epidermal to dermal cells and by utilizing different matrices. In the second aim, the number and size of the resulting hair follicles will be optimized, by manipulating the cells and the graft environment using various growth factor conditions and small molecules. Some active compounds have already been discovered and others will be identified. The goal of the third aim is to track the fate and location of grafted cells, using various imaging methods and to evaluate the generation of teratomas. In aim four, attempts will be made to determine whether human embryonic stem cells (hESC), human induced pluripotent stem cells (hiPSC), other human cells, or their derivates can be used to generate grafts of normal skin with hair, using assays similar to the ones described for newborn mouse skin cells. This is a well-written proposal targeting an important clinical problem that the PI plans to address using an interesting tissue engineering approach. However, reviewers identified several issues that reduced their enthusiasm for this application. First, they were not convinced that an emphasis on normal hair pattern is justified when considering approaches for treating burn victims. While the desire for “normal” skin is obvious, generation of healthy skin with imperfect hair patterning may still be very useful for treating burn victims. Second, reviewers considered it a major problem that very little consideration is given to the stem cell biology of the “planar hair forming procedure”, calling the responsiveness of this application to the RFA into question. Although the PI proposes to track the fate of stem cells in the graft, the proposed approach is flawed in that labeling of the cells to be tracked does not target stem cells, but rather will label all cells in the transplanted cell mixture. While this is useful for evaluating the graft, it is not helpful for understanding its stem cell biology. The study would have gained in significance if some of the reporter genes for cell tracking were to be placed under the control of a cell type-specific promoter. The experiments in the final aim are based on stems cells in that they seek to determine whether hESC or hiPSC, amongst other human cells, can be used to generate skin and hair forming cells, but it remains unclear how this is related to the mouse work proposed for aims 1 through 3, and whether the derivatives will have hair-forming potential similar to that of mouse skin samples. The proposed optimization of the graft in the first two aims is well thought out and supported by strong preliminary data, although one reviewer felt not enough information was provided about the composition of the slurry. Overall, as presented, the assay seems to be quite robust, and it was not obvious to the reviewers what needs to be optimized. With regard to aim 3, the reviewers appreciated that due to its surface transplantation, the skin patch paradigm is uniquely suited for non-invasive imaging to follow the fate of cells over time. Therefore, reviewers felt that much can be learned about the behavior for transplanted cells, which may have wider implications for the field. For instance, discoveries related to early processes of teratoma formation based on monitoring early dysplastic or malignant changes could be applicable to teratomas formed by other stem cells. A reviewer pointed out, though, that the applicant discussed analysis of teratoma formation in the context of the transplants involving newborn mouse skin cells, when teratoma formation is not expected. The applicant proposes to use various relevant imaging modalities, but did not provide a rationale for the use of PET imaging, when the use of bioluminescence and GFP imaging seems sufficient. Reviewers further pointed out that this proposal is presented as addressing a bottleneck, identified by the PI as the “long-term care of burn victims”, but felt that instead this project pursues a development candidate, i.e. skin with normal hair. The PI is highly qualified to lead this translational research team, is an expert and long-time contributor to the field of hair follicle patterning and has published extensively. Many of his/her studies have used the avian feather model, while recent work has also shed light on the molecular regulation of hair follicle regeneration in the mouse. The strong multi-disciplinary research team includes investigators with interests in skin and hair and with expertise in surgery and imaging, with small molecule screens, hESC and hiPSC work. However, the roles of the stem cell biologists are rather poorly developed, and it would have been helpful if there were a clear experimental strategy for using hESC in this work. The stem cell environment at the applicant institution is very strong. The PI has adequate resources and research facilities to conduct the experiments and clinical connections to make the transition to human studies. In summary, reviewers felt that the applicant proposes an interesting tissue engineering project that addresses a very important clinical problem. However, enthusiasm was reduced because this proposal is not particularly focused on stem cell biology, and it remained unclear how the planar hair forming procedure will be translated toward a stem cell-based clinical therapy. Additional concerns about experimental details contributed to an overall moderate level of enthusiasm.