Towards using 3D cellular cultures to model the activation and diverse functions of macrophages

Self-healing, 3D printed bioinks from self-assembled peptide and alginate hybrid hydrogels

There is a pressing need for new cell-laden, printable, biomaterials that are rigid and highly biocompatible. These materials can mimic stiffer tissues such as cartilage, fibrotic tissue and cancer microenvironments, and thus have exciting applications in regenerative medicine, wound healing and cancer research. Self-assembled peptides (SAPs) functionalised with aromatic groups such as Fluorenyl-9-methoxycarbonyl (Fmoc) show promise as components of these biomaterials. However, the harsh basic conditions often used to solubilise SAPs leads to issues with toxicity and reproducibility. Here, we have designed a hybrid material comprised of self-assembled Fmoc-diphenylalanine (Fmoc-FF) assemblies dispersed throughout a sodium alginate matrix and investigated the influence of different organic solvents as peptide solubilising agents. Bioinks fabricated from peptides dissolved in 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) showed improved biocompatibility compared to those made from Dimethyl Sulfoxide (DMSO) peptide stocks, due to the increased volatility and reduced surface tension of HFIP, allowing for more efficient expulsion from the system. Through optimisation of assembly and solvent conditions we can generate hybrid bioinks with stiffnesses up to 8 times greater than sodium alginate alone that remain highly printable, even when laden with high concentrations of cells. In addition, the shear-thinning nature of the self-assembled peptide assemblies gave the hybrid bioinks highly desirable self-healing capabilities. Our developed hybrid materials allow the bioprinting of materials previously considered too stiff to extrude without causing shear induced cytotoxicity with applications in tissue engineering and biosensing.

Macrophage Polarization: Learning to Manage It 3.0

Macrophages are cells of the innate immune system with very peculiar characteristics, so plastic that they respond rapidly to environmental changes by assuming different and sometimes contrasting functions, such as initiating a physiological inflammatory response or interrupting it and repairing damaged tissues [...].

Tissue-Resident Macrophages in Cancer: Friend or Foe?

INTRODUCTION

Macrophages are essential in maintaining homeostasis, combating infections, and influencing the process of various diseases, including cancer. Macrophages originate from diverse lineages: Notably, tissue-resident macrophages (TRMs) differ from hematopoietic stem cells and circulating monocyte-derived macrophages based on genetics, development, and function. Therefore, understanding the recruited and TRM populations is crucial for investigating disease processes.

METHODS

By searching literature databses, we summarized recent relevant studies. Research has shown that tumor-associated macrophages (TAMs) of distinct origins accumulate in tumor microenvironment (TME), with TRM-derived TAMs closely resembling gene signatures of normal TRMs.

RESULTS

Recent studies have revealed that TRMs play a crucial role in cancer progression. However, organ-specific effects complicate TRM investigations. Nonetheless, the precise involvement of TRMs in tumors is unclear. This review explores the multifaceted roles of TRMs in cancer, presenting insights into their origins, proliferation, the latest research methodologies, their impact across various tumor sites, their potential and strategies as therapeutic targets, interactions with other cells within the TME, and the internal heterogeneity of TRMs.

CONCLUSIONS

We believe that a comprehensive understanding of the multifaceted roles of TRMs will pave the way for targeted TRM therapies in the treatment of cancer.

Shaping the immune landscape: Multidimensional environmental stimuli refine macrophage polarization and foster revolutionary approaches in tissue regeneration

In immunology, the role of macrophages extends far beyond their traditional classification as mere phagocytes; they emerge as pivotal architects of the immune response, with their function being significantly influenced by multidimensional environmental stimuli. This review investigates the nuanced mechanisms by which diverse external signals ranging from chemical cues to physical stress orchestrate macrophage polarization, a process that is crucial for the modulation of immune responses. By transitioning between pro-inflammatory (M1) and anti-inflammatory (M2) states, macrophages exhibit remarkable plasticity, enabling them to adapt to and influence their surroundings effectively. The exploration of macrophage polarization provides a compelling narrative on how these cells can be manipulated to foster an immune environment conducive to tissue repair and regeneration. Highlighting cutting-edge research, this review presents innovative strategies that leverage the dynamic interplay between macrophages and their environment, proposing novel therapeutic avenues that harness the potential of macrophages in regenerative medicine. Moreover, this review critically evaluates the current challenges and future prospects of translating macrophage-centered strategies from the laboratory to clinical applications.

Composite Bioprinted Hydrogels Containing Porous Polymer Microparticles Provide Tailorable Mechanical Properties for 3D Cell Culture

The mechanical and architectural properties of the three-dimensional (3D) tissue microenvironment can have large impacts on cellular behavior and phenotype, providing cells with specialized functions dependent on their location. This is especially apparent in macrophage biology where the function of tissue resident macrophages is highly specialized to their location. 3D bioprinting provides a convenient method of fabricating biomaterials that mimic specific tissue architectures. If these printable materials also possess tunable mechanical properties, they would be highly attractive for the study of macrophage behavior in different tissues. Currently, it is difficult to achieve mechanical tunability without sacrificing printability, scaffold porosity, and a loss in cell viability. Here, we have designed composite printable biomaterials composed of traditional hydrogels [nanofibrillar cellulose (cellulose) or methacrylated gelatin (gelMA)] mixed with porous polymeric high internal phase emulsion (polyHIPE) microparticles. By varying the ratio of polyHIPEs to hydrogel, we fabricate composite hydrogels that mimic the mechanical properties of the neural tissue (0.1-0.5 kPa), liver (1 kPa), lungs (5 kPa), and skin (10 kPa) while maintaining good levels of biocompatibility to a macrophage cell line.