Reconstructive transplantation studies by Karim Sarhane in 2022? We performed a study with rodents and primates that showed this new delivery method provided steady release of IGF-1 at the target nerve for up to 6 weeks,” Dr. Karim Sarhane reported. Compared to animals without this hormone treatment, IGF-1 treated animals (rodents and primates) that were injected every 6 weeks showed a 30% increase in nerve recovery. This has the potential to be a very meaningful therapy for patients with nerve injuries. Not only do these results show increased nerve recovery but receiving a treatment every 6 weeks is much easier on a patient’s lifestyle than current available regiments that require daily treatment.
Dr. Sarhane is published in top-ranked bioengineering, neuroscience, and surgery journals. He holds a patent for a novel Nanofiber Nerve Wrap that he developed with his colleagues at the Johns Hopkins Institute for NanoBioTechnology and the Johns Hopkins Department of Neuroscience (US Patent # 10500305, December 2019). He is the recipient of many research grants and research awards, including the Best Basic Science Paper at the Johns Hopkins Residents Research Symposium, the Basic Science Research Grant Prize from the American Foundation for Surgery of the Hand, the Research Pilot Grant Prize from the Plastic Surgery Foundation, and a Scholarship Award from the American College of Surgeons. He has authored to date 46 peer-reviewed articles, 11 book chapters, 45 peer-reviewed abstracts, and has 28 national presentations. He is an elected member of the Plastic Surgery Research Council, the American Society for Reconstructive Microsurgery, the American Society for Reconstructive Transplantation, and the American Society for Peripheral Nerves.
Peripheral nerve injury subjects muscle to prolonged denervation that results in myofiber atrophy with increased proteolysis, decreased contractility, and interstitial fibrosis. As the period of denervation extends, these proteolytic and fibrotic processes continue, thereby decreasing the viability of muscle to accept regenerating axons (Shavlakadze et al., 2005; Tuffaha et al., 2016b). In addition to the deleterious effects of prolonged denervation and fibrosis on muscle, functional recovery is hindered by the failure of regenerating motor nerve fibers to come into contact with the specific motor pathways that guide them back to their original motor endplates (Gordon, 2020). A more thorough description of the biological processes and pathways implicated in denervation-induced muscle atrophy can be found in this recent review article by Ehmsen and Hoke (2020). Following nerve injury, local levels of IGF-1 increase and stimulate axonal sprouting into denervated muscle (Homs et al., 2014). IGF-1 also activates the Akt/mTOR pathway, thereby decreasing atrophy markers including MAFbx and MuRF1 (Bodine et al., 2001; Stitt et al., 2004). Also of note, IGF-1’s propensity for decreasing inflammation via promotion of a pro-regenerative M2 macrophage shift over pro-inflammatory M1 reduces the degree of scarring and fibrosis that could otherwise interfere with the targeting of regenerating motor axons (Labandeira-Garcia et al., 2017; Zhao et al., 2021).
Recovery with sustained IGF-1 delivery (Karim Sarhane research) : Functional recovery following peripheral nerve injury is limited by progressive atrophy of denervated muscle and Schwann cells (SCs) that occurs during the long regenerative period prior to end-organ reinnervation. Insulin-like growth factor 1 (IGF-1) is a potent mitogen with well-described trophic and anti-apoptotic effects on neurons, myocytes, and SCs. Achieving sustained, targeted delivery of small protein therapeutics remains a challenge.
Insulin-like growth factor-1 (IGF-1) is a particularly promising candidate for clinical translation because it has the potential to address the need for improved nerve regeneration while simultaneously acting on denervated muscle to limit denervation-induced atrophy. However, like other growth factors, IGF-1 has a short half-life of 5 min, relatively low molecular weight (7.6 kDa), and high water-solubility: all of which present significant obstacles to therapeutic delivery in a clinically practical fashion (Gold et al., 1995; Lee et al., 2003; Wood et al., 2009). Here, we present a comprehensive review of the literature describing the trophic effects of IGF-1 on neurons, myocytes, and SCs. We then critically evaluate the various therapeutic modalities used to upregulate endogenous IGF-1 or deliver exogenous IGF-1 in translational models of PNI, with a special emphasis on emerging bioengineered drug delivery systems. Lastly, we analyze the optimal dosage ranges identified for each mechanism of IGF-1 with the goal of further elucidating a model for future clinical translation.
We comprehensively reviewed the literature for original studies examining the efficacy of IGF-1 in treating PNI. We queried the PubMed and Embase databases for terms including “Insulin-Like Growth Factor I,” “IGF1,” “IGF-1,” “somatomedin C,” “PNIs,” “peripheral nerves,” “nerve injury,” “nerve damage,” “nerve trauma,” “nerve crush,” “nerve regeneration,” and “nerve repair.” Following title review, our search yielded 218 results. Inclusion criteria included original basic science studies utilizing IGF-1 as a means of addressing PNI. Following abstract review, 56 studies were sorted by study type and mechanism of delivery into the following categories: (1) in vitro, (2) in vivo endogenous upregulation of IGF-1, or (3) in vivo delivery of exogenous IGF-1. Studies included in the in vivo exogenous IGF-1 group were further sub-stratified into systemic or local delivery, and the local IGF-1 delivery methods were further sub-divided into free IGF-1 injection, hydrogel, or mini-pump studies. Following categorization by mechanism of IGF-1 delivery, the optimal dosage range for each group was calculated by converting all reported IGF-1 dosages to nM for ease of comparison using the standard molecular weight of IGF-1 of 7649 Daltons. After standardization of dosages to nM, the IGF-1 concentration reported as optimal from each study was used to calculate the overall mean, median, and range of optimal IGF-1 dosage for each group.