Academic Appointments

All Publications

  • Hyaluronan and elastin-like protein (HELP) gels significantly improve microsphere retention in the myocardium. Biomaterials science Suhar, R. A., Doulames, V. M., Liu, Y., Hefferon, M. E., Figueroa, O. 3., Buabbas, H., Heilshorn, S. C. 2022


    Heart disease is the leading cause of death globally, and delivery of therapeutic cargo (e.g., particles loaded with proteins, drugs, or genes and cells) through direct injection into the myocardium is a promising clinical intervention. However, retention of deliverables to the contracting myocardium is low, with as much as 60-90% of payload being lost within 24 hr. Commercially-available injectable hydrogels, including Matrigel, have been hypothesized to increase payload retention but have not yielded significant improvements in quantified analyses. Here, we assess a recombinant hydrogel composed of chemically modified hyaluronan and elastin-like protein (HELP) as an alternative injectable carrier to increase cargo retention. HELP is crosslinked using dynamic covalent bonds, and tuning the hyaluronan chemistry significantly alters hydrogel mechanical properties including stiffness, stress relaxation rate, and ease of injectability through a needle or catheter. These materials can be injected even after complete crosslinking, extending the time window for surgical delivery. We show that HELP gels significantly improve in vivo retention of microsphere cargo compared to Matrigel, both 1 day and 7 days post-injection directly into the rat myocardium. These data suggest that HELP gels may assist with the clinical translation of therapeutic cargo designed for delivery into the contracting myocardium by preventing acute cargo loss.

    View details for DOI 10.1039/d1bm01890f

    View details for PubMedID 35411353

  • Elastin-like Proteins to Support Peripheral Nerve Regeneration in Guidance Conduits. ACS biomaterials science & engineering Suhar, R. A., Marquardt, L. M., Song, S., Buabbas, H., Doulames, V. M., Johansson, P. K., Klett, K. C., Dewi, R. E., Enejder, A. M., Plant, G. W., George, P. M., Heilshorn, S. C. 2021; 7 (9): 4209-4220


    Synthetic nerve guidance conduits (NGCs) offer an alternative to harvested nerve grafts for treating peripheral nerve injury (PNI). NGCs have been made from both naturally derived and synthesized materials. While naturally derived materials typically have an increased capacity for bioactivity, synthesized materials have better material control, including tunability and reproducibility. Protein engineering is an alternative strategy that can bridge the benefits of these two classes of materials by designing cell-responsive materials that are also systematically tunable and consistent. Here, we tested a recombinantly derived elastin-like protein (ELP) hydrogel as an intraluminal filler in a rat sciatic nerve injury model. We demonstrated that ELPs enhance the probability of forming a tissue bridge between the proximal and distal nerve stumps compared to an empty silicone conduit across the length of a 10 mm nerve gap. These tissue bridges have evidence of myelinated axons, and electrophysiology demonstrated that regenerated axons innervated distal muscle groups. Animals implanted with an ELP-filled conduit had statistically higher functional control at 6 weeks than those that had received an empty silicone conduit, as evaluated by the sciatic functional index. Taken together, our data support the conclusion that ELPs support peripheral nerve regeneration in acute complete transection injuries when used as an intraluminal filler. These results support the further study of protein engineered recombinant ELP hydrogels as a reproducible, off-the-shelf alternative for regeneration of peripheral nerves.

    View details for DOI 10.1021/acsbiomaterials.0c01053

    View details for PubMedID 34510904

  • Designer, injectable gels to prevent transplanted Schwann cell loss during spinal cord injury therapy. Science advances Marquardt, L. M., Doulames, V. M., Wang, A. T., Dubbin, K., Suhar, R. A., Kratochvil, M. J., Medress, Z. A., Plant, G. W., Heilshorn, S. C. 2020; 6 (14): eaaz1039


    Transplantation of patient-derived Schwann cells is a promising regenerative medicine therapy for spinal cord injuries; however, therapeutic efficacy is compromised by inefficient cell delivery. We present a materials-based strategy that addresses three common causes of transplanted cell death: (i) membrane damage during injection, (ii) cell leakage from the injection site, and (iii) apoptosis due to loss of endogenous matrix. Using protein engineering and peptide-based assembly, we designed injectable hydrogels with modular cell-adhesive and mechanical properties. In a cervical contusion model, our hydrogel matrix resulted in a greater than 700% improvement in successful Schwann cell transplantation. The combination therapy of cells and gel significantly improved the spatial distribution of transplanted cells within the endogenous tissue. A reduction in cystic cavitation and neuronal loss were also observed with substantial increases in forelimb strength and coordination. Using an injectable hydrogel matrix, therefore, can markedly improve the outcomes of cellular transplantation therapies.

    View details for DOI 10.1126/sciadv.aaz1039

    View details for PubMedID 32270042

  • Human iPSC-Derived Corticospinal Neuronal Grafts To Repair Cervical Spinal Cord Injury Doulames, V., Weimann, J., Plant, G. W. SAGE PUBLICATIONS INC. 2019: 492
  • Stem cell therapies for acute spinal cord injury in humans: a review NEUROSURGICAL FOCUS Jin, M. C., Medress, Z. A., Azad, T. D., Doulames, V. M., Veeravagu, A. 2019; 46 (3): E10


    Recent advances in stem cell biology present significant opportunities to advance clinical applications of stem cell-based therapies for spinal cord injury (SCI). In this review, the authors critically analyze the basic science and translational evidence that supports the use of various stem cell sources, including induced pluripotent stem cells, oligodendrocyte precursor cells, and mesenchymal stem cells. They subsequently explore recent advances in stem cell biology and discuss ongoing clinical translation efforts, including combinatorial strategies utilizing scaffolds, biogels, and growth factors to augment stem cell survival, function, and engraftment. Finally, the authors discuss the evolution of stem cell therapies for SCI by providing an overview of completed (n = 18) and ongoing (n = 9) clinical trials.

    View details for DOI 10.3171/2018.12.FOCUS18602

    View details for Web of Science ID 000460130200010

    View details for PubMedID 30835679

  • Induced Pluripotent Stem Cell Therapies for Cervical Spinal Cord Injury. International journal of molecular sciences Doulames, V. M., Plant, G. W. 2016; 17 (4)


    Cervical-level injuries account for the majority of presented spinal cord injuries (SCIs) to date. Despite the increase in survival rates due to emergency medicine improvements, overall quality of life remains poor, with patients facing variable deficits in respiratory and motor function. Therapies aiming to ameliorate symptoms and restore function, even partially, are urgently needed. Current therapeutic avenues in SCI seek to increase regenerative capacities through trophic and immunomodulatory factors, provide scaffolding to bridge the lesion site and promote regeneration of native axons, and to replace SCI-lost neurons and glia via intraspinal transplantation. Induced pluripotent stem cells (iPSCs) are a clinically viable means to accomplish this; they have no major ethical barriers, sources can be patient-matched and collected using non-invasive methods. In addition, the patient's own cells can be used to establish a starter population capable of producing multiple cell types. To date, there is only a limited pool of research examining iPSC-derived transplants in SCI-even less research that is specific to cervical injury. The purpose of the review herein is to explore both preclinical and clinical recent advances in iPSC therapies with a detailed focus on cervical spinal cord injury.

    View details for DOI 10.3390/ijms17040530

    View details for PubMedID 27070598

    View details for PubMedCentralID PMC4848986