Screening hydrogels for antifibrotic properties by implanting cellularly barcoded alginates in mice and a non-human primate

Screening implantable biomaterials for antifibrotic properties is constrained by the need for in vivo testing. Here we show that the throughput of in vivo screening can be increased by cellularly barcoding a chemically modified combinatorial library of hydrogel formulations. The method involves the implantation of a mixture of alginate formulations, each barcoded with human umbilical vein endothelial cells from different donors, and the association of the identity and performance of each formulation by genotyping single nucleotide polymorphisms of the cells via next-generation sequencing. We used the method to screen 20 alginate formulations in a single mouse and 100 alginate formulations in a single non-human primate, and identified three lead hydrogel formulations with antifibrotic properties. Encapsulating human islets with one of the formulations led to long-term glycaemic control in a mouse model of diabetes, and coating medical-grade catheters with the other two formulations prevented fibrotic overgrowth. High-throughput screening of barcoded biomaterials in vivo may help identify formulations that enhance the long-term performance of medical devices and of biomaterial-encapsulated therapeutic cells.

Clinically translatable cytokine delivery platform for eradication of intraperitoneal tumors

Proinflammatory cytokines have been approved by the Food and Drug Administration for the treatment of metastatic melanoma and renal carcinoma. However, effective cytokine therapy requires high-dose infusions that can result in antidrug antibodies and/or systemic side effects that limit long-term benefits. To overcome these limitations, we developed a clinically translatable cytokine delivery platform composed of polymer-encapsulated human ARPE-19 (RPE) cells that produce natural cytokines. Tumor-adjacent administration of these capsules demonstrated predictable dose modulation with spatial and temporal control and enabled peritoneal cancer immunotherapy without systemic toxicities. Interleukin-2 (IL2)-producing cytokine factory treatment eradicated peritoneal tumors in ovarian and colorectal mouse models. Furthermore, computational pharmacokinetic modeling predicts clinical translatability to humans. Notably, this platform elicited T cell responses in NHPs, consistent with reported biomarkers of treatment efficacy without toxicity. Combined, our findings demonstrate the safety and efficacy of IL2 cytokine factories in preclinical animal models and provide rationale for future clinical testing in humans.

Heterogeneous toroidal spiral particles for islet encapsulation

Transplantable cell encapsulation systems present a promising approach to deliver a therapeutic solution from hormone-producing cells for the treatment of endocrine diseases like type 1 diabetes. However, the development of a broadly effective and safe transplantation system has been challenging. While some current micro-sized capsules have been optimized for adequate nutrient and metabolic transport, they lack the robustness and retrievability for the clinical safety translation that macro-devices may offer. An existing challenge to be addressed in the current macro-devices is their configuration which may lead to unsatisfactory mass transfer. Here, we design and characterize a millimeter-size particle system of poly-ethylene glycol (PEG) featuring internal toroidal spiral channels, called toroidal spiral particles (TSPs). The characteristic internal structure of the TSPs allows for large encapsulation capacity and large surface area available to all the encapsulated cell mass for effective molecular diffusion. The polymeric matrix renders the particle flexible yet robust for safe transplantation and retrieval. We demonstrate the feasibility of fabricating these particles with various polymer compositions, while optimizing their mechanical properties as well as glucose and insulin permeability. Encapsulation of islets of Langerhans is achieved with high loading capacity (∼160 IEQ per TSP) and excellent cell viability. TSP-encapsulated islets showed similar glucose-stimulated insulin secretion to the naked islets. Preliminary biocompatibility of the TSPs on naïve C57BL/6 mice shows minimal inflammatory response after 4-week transplantation into the intraperitoneal (IP) space. Long-term therapeutic efficacy of encapsulated islets needs to be confirmed in diabetic rodent models in the future, while determining minimal mass required to reverse diabetes. However, we believe from the in vitro favorable results and the TSPs' unique design that TSPs may provide a safe, effective method to transplant and retrieve therapeutic cells for type 1 diabetes treatment and may also be applicable for other cell therapies.

Evaluation of encapsulating and microporous nondegradable hydrogel scaffold designs on islet engraftment in rodent models of diabetes

Islet transplantation is a promising therapeutic option for type 1 diabetes mellitus, yet the current delivery into the hepatic portal vasculature is limited by poor engraftment. Biomaterials have been used as a means to promote engraftment and function at extrahepatic sites, with strategies being categorized as encapsulation or microporous scaffolds that can either isolate or integrate islets with the host tissue, respectively. Although these approaches are typically studied separately using distinct material platforms, herein, we developed nondegradable polyethylene glycol (PEG)-based hydrogels for islet encapsulation or as microporous scaffolds for islet seeding to compare the initial engraftment and function of islets in syngeneic diabetic mice. Normoglycemia was restored with transplantation of islets within either encapsulating or microporous hydrogels containing 700 islet equivalents (IEQ), with transplantation on microporous hydrogels producing lower blood glucose levels at earlier times. A glucose challenge test at 1 month after transplant indicated that encapsulated islets had a delay in glucose-stimulated insulin secretion, whereas microporous hydrogels restored normoglycemia in times consistent with native pancreata. Encapsulated islets remained isolated from the host tissue, whereas the microporous scaffolds allowed for revascularization of the islets after transplant. Finally, we compared the inflammatory response after transplantation for the two systems and noted that microporous hydrogels had a substantially increased presence of neutrophils. Collectively, these findings suggest that both encapsulation and microporous PEG scaffold designs allow for stable engraftment of syngeneic islets and the ability to restore normoglycemia, yet the architecture influences islet function and responsiveness after transplantation.

Retrievable hydrogels for ovarian follicle transplantation and oocyte collection

Cancer survivorship rates have drastically increased due to improved efficacy of oncologic treatments. Consequently, clinical concerns have shifted from solely focusing on survival to quality of life, with fertility preservation as an important consideration. Among fertility preservation strategies for female patients, ovarian tissue cryopreservation and subsequent reimplantation has been the only clinical option available to cancer survivors with cryopreserved tissue. However, follicle atresia after transplantation and risk of reintroducing malignant cells have prevented this procedure from becoming widely adopted in clinics. Herein, we investigated the encapsulation of ovarian follicles in alginate hydrogels that isolate the graft from the host, yet allows for maturation after transplantation at a heterotopic (i.e., subcutaneous) site, a process we termed in vivo follicle maturation. Survival of multiple follicle populations was confirmed via histology, with the notable development of the antral follicles. Collected oocytes (63%) exhibited polar body extrusion and were fertilized by intracytoplasmic sperm injection and standard in vitro fertilization procedures. Successfully fertilized oocytes developed to the pronucleus (14%), two-cell (36%), and four-cell (7%) stages. Furthermore, ovarian follicles cotransplanted with metastatic breast cancer cells within the hydrogels allowed for retrieval of the follicles, and no mice developed tumors after removal of the implant, confirming that the hydrogel prevented seeding of disease within the host. Collectively, these findings demonstrate a viable option for safe use of potentially cancer-laden ovarian donor tissue for in vivo follicle maturation within a retrievable hydrogel and subsequent oocyte collection. Ultimately, this technology may provide novel options to preserve fertility for young female patients with cancer.

Dynamic transcription factor activity networks in response to independently altered mechanical and adhesive microenvironmental cues

Multiple aspects of the local extracellular environment profoundly affect cell phenotype and function. Physical and chemical cues in the environment trigger intracellular signaling cascades that ultimately activate transcription factors (TFs) - powerful regulators of the cell phenotype. TRACER (TRanscriptional Activity CEll aRrays) was employed for large-scale, dynamic quantification of TF activity in human fibroblasts cultured on hydrogels with a controlled elastic modulus and integrin ligand density. We identified three groups of TFs: responders to alterations in ligand density alone, substrate stiffness or both. Dynamic networks of regulatory TFs were constructed computationally and revealed distinct TF activity levels, directionality (i.e., activation or inhibition), and dynamics for adhesive and mechanical cues. Moreover, TRACER networks predicted conserved hubs of TF activity across multiple cell types, which are significantly altered in clinical fibrotic tissues. Our approach captures the distinct and overlapping effects of adhesive and mechanical stimuli, identifying conserved signaling mechanisms in normal and disease states.

The enhancement of bone allograft incorporation by the local delivery of the sphingosine 1-phosphate receptor targeted drug FTY720

Poor vascularization coupled with mechanical instability is the leading cause of post-operative complications and poor functional prognosis of massive bone allografts. To address this limitation, we designed a novel continuous polymer coating system to provide sustained localized delivery of pharmacological agent, FTY720, a selective agonist for sphingosine 1-phosphate receptors, within massive tibial defects. In vitro drug release studies validated 64% loading efficiency with complete release of compound following 14 days. Mechanical evaluation following six weeks of healing suggested significant enhancement of mechanical stability in FTY720 treatment groups compared with unloaded controls. Furthermore, superior osseous integration across the host-graft interface, significant enhancement in smooth muscle cell investment, and reduction in leukocyte recruitment was evident in FTY720 treated groups compared with untreated groups. Using this approach, we can capitalize on the existing mechanical and biomaterial properties of devitalized bone, add a controllable delivery system while maintaining overall porous structure, and deliver a small molecule compound to constitutively target vascular remodeling, osseous remodeling, and minimize fibrous encapsulation within the allograft-host bone interface. Such results support continued evaluation of drug-eluting allografts as a viable strategy to improve functional outcome and long-term success of massive cortical allograft implants.