Early Translational II
Peripheral nerve injury is a disorder that occurs through trauma or surgical resection for cancer, causing significant loss of function and workers lost wages. The total annual cost for nerve injury treatment is $7 billion in the U.S. alone (American Paralysis Association, 1997). 50,000 peripheral nerve repair procedures/year are performed (National Center for Health Statistics, 1995). If peripheral nerve injury is not treated many patients are left with lifelong disabilities. In the clinical setting these injuries accompany upper and lower extremity trauma and are critical in evaluating for limb preservation. We have become facile at treating these injuries, yet despite some intrinsic capacity for these peripheral nerves to regenerate as well as advances in neurobiology, pathophysiology, and operative management with microsurgery, functional recovery and clinical outcomes after peripheral nerve injuries are still unsatisfactory. Generally the injury is treated by grafting donor nerve tissue from another part of the body to the damaged area often called an autograft. However, this treatment is not ideal as tissue harvesting create areas that may become numb. Many cases remain untreated. All neural diseases are complicated and difficult to cure as adult neurons go permanent senescence and do not divide. Therefore, neuron cells that are damaged or die are not replaceable. This is especially true for the central nervous system like in case of spinal cord injury. However, prospect for cure for peripheral nerve injury is not all bleak. There are some discoveries that give new hope for the cure. Stem cells can be used for successful treatment of peripheral nerve injury. Stem cells are pluripotent characterized by their ability for unlimited potential to develop all kinds of tissue types. Human liposuction is a source of stem cells known as adipose derived stem cells (ADSC). Our lab in the Aesthetic and Plastic Surgery Institute is working to harness the power of stem cells for nerve injury in the rat model but looking forward to translational research. This can be achieved in 2 ways –using this multipotent (they can differentiate into certain lineages but not all kinds of cells) stem cell. These multipotent cells will be converted to pluripotent stem cell (called iPS) by several transcription factors. This iPS will be differentiated into neuron and will be used to compensate the damaged neuron. In other way, we are using ADSC for gene delivery to the injured area. Unlike central nervous system, peripheral nerves have some ability to regenerate in the proper environment. These neuron cells need growth factors which instruct them to grow axons. Among the growth factors, nerve growth factor (NGF) is well characterized. We can deliver growth factor genes using ADSC as a vehicle. In this way, the nerve cells stimulate axon regeneration and bridge the damaged area.
Statement of Benefit to California:
California is the home of leading research centers and schools including stem cell research funded both by private and public entities. UC, Irvine has a robust stem cell program and recently a new building dedicated to stem cell research bears that testimony. There are several diseases, where stem cell have the potential for treatment including type1 diabetes, ALS, Spinal cords injury, liver failure and neuronal diseases. Adult neurons generally do not divide. So, once they are lost either by stroke, Parkinson’s (loss of dopaminergic neurons), Alzheimer’s or other kind of brain injury or pathological conditions there is no treatment that can help to regenerate neurons. Despite central neural system disorders peripheral nerve injury on the other hand is common among workers and injured soldier’s coming back from the war zones. Nerve injury equates to total annual cost of $7 billion in the U.S. alone (American Paralysis Association, 1997), while, there are 50,000 peripheral nerve repair procedures done per year (National Center for Health Statistics, 1995) Contrary to central nervous systems, peripheral nervous system nerve can regenerate to some extent with appropriate growth factors. We have delivered nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) using HEK-293 cells as a vehicle in a sciatic nerve injury model. Recently, we discovered that fat stem cells can be used as a gene carrier which offers a safe and plentiful domains of cells for translational research. We can isolate adipose derived stem cells (ADSC) from those tissues discarded in surgery or by lipoaspiration. These ADSC adult stem cells will be used as a vehicle for gene delivery to the peripheral nerve injury. Our approach to regenerate peripheral nerves in the sciatic nerve model using rats has been successful. This and other basic or translational work on stem cells will invite various biotech companies to invest more in California. This investment will create jobs (direct and indirect) and keep California’s high ranking in science and technology. It will potentially propel the future of the California economy with more advances in the biomedical field and translatable studies. Scientists in California have make progress in stem cell research and the California Institute for Regenerative Medicine (CRIM) is indispensible for supporting grants, training etc. Our research has the potential to translate directly to patient care. The spin off for California would be more money and jobs. Proposition 71 initially provided this investment into this technology, approved by the public and to support this innovative field. The purpose of this proposition was to take this research and promote translational studies. This proposal directly supports this proposition and concept by taking stem cell technology and developing potentially translational studies in peripheral nerve surgery.
This Development Candidate Feasibility (DCF) application proposes to test autologous adipose-derived stem cells (ADSC) delivering a gene therapy to improve peripheral nerve (PN) regeneration. The applicants plan to generate stably transfected ASDC expressing a cell surface protein, an inducible growth factor and a suicide gene. Next, they will test the stably transfected genes for appropriate inducible function. Finally, they will test the ability of the transfected ADSCs to promote peripheral nerve regeneration and improve functional outcomes. PN injuries are common among trauma patients and currently treated by autologous donor nerve grafting. This treatment is not always successful and can impair function at the donor site. Reviewers agreed that improved treatment for PN injuries would have major impact, and that the proposed work addresses a major unmet medical need. However, they voiced serious concerns regarding this application. One reviewer found the application poorly written. Perhaps most critically, reviewers questioned the relevance of stem cells to the proposal. They found the applicant’s rationale that ASDC are autologous and plentiful inadequate justification that stem cells were required for the project. Any cell type could be engineered to secrete a growth factor. Therefore, the panel determined this application was not responsive to the RFA. Reviewers also questioned the selection of a single growth factor to promote regeneration over published growth factor combinations, and noted the applicant did not cite evidence supporting the single chosen factor. These criticisms left the reviewers dubious that the proposed work would have meaningful impact. The group expressed unanimous disappointment in the preliminary data and poor feasibility of the proposed program. Reviewers found the data suggesting ASDC could acquire neuronal phenotypes unconvincing and questioned its relevance to the proposal’s goals. Most importantly, the investigators have not demonstrated that they have the expertise required to generate the complex, triply transfected development candidate. Rather than providing demonstration of consistent, stable and inducible triple gene expression in ASDC, the preliminary data merely show transient expression of a single gene. Given the known challenges of down-regulation in stable cell lines, reviewers found this a critical feasibility problem. Also, the applicants have not demonstrated long-term survival of ASDC in conduits. Definitive data demonstrating PN regeneration with the selected growth factor were lacking from the preliminary data. Because of these feasibility concerns, the panel found it highly unlikely that the applicants would meet the proposal’s milestones or achieve its aims. Reviewers noted the PI’s experience with the selected growth factor and nerve regeneration using tissue engineered constructs. However, they were puzzled as to why the PI’s biosketch has not provided relevant publications since 2005. Further, reviewers found it unlikely the junior co-investigator and very small bench staff would be able to successfully manage the complex scope of this study. The institutional support and research environment are strong. In summary, this DCF study proposes to use autologous ADSC as delivery vehicles for gene therapy to repair peripheral nerve damage. Reviewers found the proposed approach inadequately justified and unresponsive to the RFA. Further, feasibility was unsubstantiated by preliminary data and hindered by an inadequately experienced staff. Therefore the proposal was not recommended for funding.