Reed, S. J. | bioRxiv Science

bioRxiv2023

Versatile Tissue-Injectable Hydrogels with Extended Hydrolytic Release of Bioactive Protein Therapeutics

Hydrogels generally have broad utilization in healthcare due to their tunable structures, high water content, and inherent biocompatibility. FDA-approved applications of hydrogels include spinal cord regeneration, skin fillers, and local therapeutic delivery. Drawbacks exist in the clinical hydrogel space, largely pertaining to inconsistent therapeutic exposure, short-lived release windows, and difficulties inserting the polymer into tissue. In this study, we engineered injectable, biocompatible hydrogels that function as a local protein therapeutic depot with a high degree of user-customizability. We showcase a PEG-based hydrogel functionalized with bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) handles for its polymerization and functionalization with a variety of payloads. Small-molecule and protein cargos, including chemokines and antibodies, were site-specifically modified with hydrolysable "azidoesters" of varying hydrophobicity via direct chemical conjugation or sortase-mediated transpeptidation. These hydrolysable esters afforded extended release of payloads linked to our hydrogels beyond diffusion; with timescales spanning days to months dependent on ester hydrophobicity. Injected hydrogels polymerize in situ and remain in tissue over extended periods of time. Hydrogel-delivered protein payloads elicit biological activity after being modified with SPAAC-compatible linkers, as demonstrated by the successful recruitment of murine T-cells to a mouse melanoma model by hydrolytically released murine CXCL10. These results highlight a highly versatile, customizable hydrogel-based delivery system for local delivery of protein therapeutics with payload release profiles appropriate for a variety of clinical needs. Translational ImpactWe developed injectable hydrogels that provide loco-regional, controlled release of protein therapeutics. Local delivery is especially suitable for potent, protein-based drugs like chemokines and monoclonal antibodies whose systemic toxicities can be life threatening. Our hydrogel is equipped with slowly hydrolyzing linkers for transient payload coupling, prolonging its therapeutic window and minimizing the need for repeat surgeries in a clinical setting. A range of release profiles, spanning days to over a month, and a broad compatibility to therapeutically relevant, recombinant proteins provide clinicians with flexible therapeutic options to suit a variety of circumstances.

bioengineering↗

bioRxiv2022

A blunted GPR183/oxysterol axis during dysglycemia results in delayed recruitment of macrophages to the lung during M. tuberculosis infection

We previously reported that the oxidised cholesterol-sensing receptor GPR183 is significantly downregulated in blood from tuberculosis (TB) patients with diabetes compared to TB patients without co-morbidities and that lower GPR183 expression in blood is associated with more severe pulmonary TB on chest-x-ray consistent with observations in dysglycemic mice. To further elucidate the role of this receptor and its endogenous high affinity agonist 7,25-di-hydroxycholesterol (7,25-OHC) in the lung, we studied high fat diet (HFD)-induced dysglycemic mice infected with M.tuberculosis. We found that the 7,25-OHC-producing enzymes cholesterol 25-hydroxylase (CH25H) and cytochrome P450 family 7 subfamily member B1 (CYP7B1) were highly upregulated upon M. tuberculosis infection in the lungs of normoglycemic mice, and this was associated with increased expression of GPR183 indicative of effective recruitment of GPR183-expressing immune cells to the site of infection. We demonstrated that CYP7B1 was predominantly expressed by macrophages in the centre of TB granulomas. Expression of CYP7B1 was significantly blunted in lungs from HFD-fed dysglycemic animals and this coincided with delayed recruitment of macrophages to the lung during early infection and more severe lung pathology. GPR183 deficient mice similarly had reduced macrophage recruitment during early infection demonstrating a requirement of the GPR183/oxysterol axis for macrophage infiltration into the lung in TB. Together our data demonstrate that oxidised cholesterols and GPR183 play an important role in positioning macrophages to the site of M. tuberculosis infection and that this is impaired by HFD-induced dysglycemia, adding a mechanistic explanation to the poorer TB outcomes in patients with diabetes.

immunology↗