All Publications


  • 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

    Abstract

    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

  • Next-generation cancer organoids. Nature materials LeSavage, B. L., Suhar, R. A., Broguiere, N., Lutolf, M. P., Heilshorn, S. C. 2021

    Abstract

    Organotypic models of patient-specific tumours are revolutionizing our understanding of cancer heterogeneity and its implications for personalized medicine. These advancements are, in part, attributed to the ability of organoid models to stably preserve genetic, proteomic, morphological and pharmacotypic features of the parent tumour in vitro, while also offering unprecedented genomic and environmental manipulation. Despite recent innovations in organoid protocols, current techniques for cancer organoid culture are inherently uncontrolled and irreproducible, owing to several non-standardized facets including cancer tissue sources and subsequent processing, medium formulations, and animal-derived three-dimensional matrices. Given the potential for cancer organoids to accurately recapitulate the intra- and intertumoral biological heterogeneity associated with patient-specific cancers, eliminating the undesirable technical variability accompanying cancer organoid culture is necessary to establish reproducible platforms that accelerate translatable insights into patient care. Here we describe the current challenges and recent multidisciplinary advancements and opportunities for standardizing next-generation cancer organoid systems.

    View details for DOI 10.1038/s41563-021-01057-5

    View details for PubMedID 34385685

  • Engineered Matrices Enable the Culture of Human Patient-Derived Intestinal Organoids ADVANCED SCIENCE Hunt, D. R., Klett, K. C., Mascharak, S., Wang, H. Y., Gong, D., Lou, J., Li, X., Cai, P. C., Suhar, R. A., Co, J. Y., LeSavage, B. L., Foster, A. A., Guan, Y., Amieva, M. R., Peltz, G., Xia, Y., Kuo, C. J., Heilshorn, S. C. 2021
  • Engineered Matrices Enable the Culture of Human Patient-Derived Intestinal Organoids. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Hunt, D. R., Klett, K. C., Mascharak, S., Wang, H., Gong, D., Lou, J., Li, X., Cai, P. C., Suhar, R. A., Co, J. Y., LeSavage, B. L., Foster, A. A., Guan, Y., Amieva, M. R., Peltz, G., Xia, Y., Kuo, C. J., Heilshorn, S. C. 2021; 8 (10): 2004705

    Abstract

    Human intestinal organoids from primary human tissues have the potential to revolutionize personalized medicine and preclinical gastrointestinal disease models. A tunable, fully defined, designer matrix, termed hyaluronan elastin-like protein (HELP) is reported, which enables the formation, differentiation, and passaging of adult primary tissue-derived, epithelial-only intestinal organoids. HELP enables the encapsulation of dissociated patient-derived cells, which then undergo proliferation and formation of enteroids, spherical structures with polarized internal lumens. After 12 rounds of passaging, enteroid growth in HELP materials is found to be statistically similar to that in animal-derived matrices. HELP materials also support the differentiation of human enteroids into mature intestinal cell subtypes. HELP matrices allow stiffness, stress relaxation rate, and integrin-ligand concentration to be independently and quantitatively specified, enabling fundamental studies of organoid-matrix interactions and potential patient-specific optimization. Organoid formation in HELP materials is most robust in gels with stiffer moduli (G' ≈ 1 kPa), slower stress relaxation rate (t1/2 ≈ 18 h), and higher integrin ligand concentration (0.5 × 10-3-1 × 10-3 m RGD peptide). This material provides a promising in vitro model for further understanding intestinal development and disease in humans and a reproducible, biodegradable, minimal matrix with no animal-derived products or synthetic polyethylene glycol for potential clinical translation.

    View details for DOI 10.1002/advs.202004705

    View details for PubMedID 34026461

    View details for PubMedCentralID PMC8132048

  • 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

    Abstract

    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

  • Bioengineering and regeneration of gastrointestinal tissue: where are we now and what comes next? EXPERT OPINION ON BIOLOGICAL THERAPY Zakhem, E., Raghavan, S., Suhar, R. A., Bitar, K. N. 2019; 19 (6): 527–37
  • Bioengineering and regeneration of gastrointestinal tissue: where are we now and what comes next? Expert opinion on biological therapy Zakhem, E., Raghavan, S., Bitar, K. N., Suhar, R. A. 2019

    Abstract

    INTRODUCTION: The field of tissue engineering and regenerative medicine has been applied to the gastrointestinal (GI) tract for a couple decades. Several achievements have been accomplished that provide promising tools for treating diseases of the GI tract. Areas covered: The work described in this review covers the traditional aspect of using cells and scaffolds to replace parts of the tract. Several studies investigated different types of biomaterials and different types of cells. A more recent approach involved the use of gut-derived organoid units that can differentiate into all gut cell layers. The most recent approach introduced the use of organ-on-a-chip concept to understand the physiology and pathophysiology of the GI system. Expert Opinion: The different approaches tackle the diseases of the GI tract from different perspectives. While all these different approaches provide a promising and encouraging future for this field, the translational aspect is yet to be studied.

    View details for PubMedID 30880502

  • Review: Bioengineering strategies to probe T cell mechanobiology APL BIOENGINEERING de la Zerda, A., Kratochvil, M. J., Suhar, N. A., Heilshorn, S. C. 2018; 2 (2)

    View details for DOI 10.1063/1.5006599

    View details for Web of Science ID 000455057800002

  • Production of Elastin-like Protein Hydrogels for Encapsulation and Immunostaining of Cells in 3D. Journal of visualized experiments : JoVE LeSavage, B. L., Suhar, N. A., Madl, C. M., Heilshorn, S. C. 2018

    Abstract

    Two-dimensional (2D) tissue culture techniques have been essential for our understanding of fundamental cell biology. However, traditional 2D tissue culture systems lack a three-dimensional (3D) matrix, resulting in a significant disconnect between results collected in vitro and in vivo. To address this limitation, researchers have engineered 3D hydrogel tissue culture platforms that can mimic the biochemical and biophysical properties of the in vivo cell microenvironment. This research has motivated the need to develop material platforms that support 3D cell encapsulation and downstream biochemical assays. Recombinant protein engineering offers a unique toolset for 3D hydrogel material design and development by allowing for the specific control of protein sequence and therefore, by extension, the potential mechanical and biochemical properties of the resultant matrix. Here, we present a protocol for the expression of recombinantly-derived elastin-like protein (ELP), which can be used to form hydrogels with independently tunable mechanical properties and cell-adhesive ligand concentration. We further present a methodology for cell encapsulation within ELP hydrogels and subsequent immunofluorescent staining of embedded cells for downstream analysis and quantification.

    View details for PubMedID 29863669