RESOURCES

Abstract
Deciphering breast cancer treatment resistance remains hindered by the lack of models that can successfully capture the four-dimensional dynamics of the tumor microenvironment. Here, we show that microextrusion bioprinting can reproducibly generate distinct cancer and stromal compartments integrating cells relevant to human pathology. Our findings unveil the functional maturation of this millimeter-sized model, showcasing the development of a hypoxic cancer core and an increased surface proliferation. Maturation was also driven by the presence of cancer-associated fibroblasts (CAF) that induced elevated microvascular-like structures complexity. Such modulation was concomitant to extracellular matrix remodeling, with high levels of collagen and matricellular proteins deposition by CAF, simultaneously increasing tumor stiffness and recapitulating breast cancer fibrotic development. Importantly, our bioprinted model faithfully reproduced response to treatment, further modulated by CAF. Notably, CAF played a protective role for cancer cells against radiotherapy, facilitating increased paracrine communications. This model holds promise as a platform to decipher interactions within the microenvironment and evaluate stroma-targeted drugs in a context relevant to human pathology.

Abstract
Producing oral soft tissues using tissue engineering could compensate for the disadvantages of autologous grafts (limited availability and increased patient morbidity) and currently available substitutes (shrinkage). However, there is a lack of in vitro-engineered oral tissues due to the difficulty of obtaining stable pre-vessels that connect to the host and enable graft success. The main objective was to assess the connection of pre-vascularised 3D-bioprinted gingival substitutes to the host vasculature when subcutaneously implanted in immunodeficient mice. This study produced vascularised connective tissue substitutes using extrusion-based 3D-bioprinting of primary human gingival fibroblasts (hGFs) and fluorescent human endothelial cells (RFP-HUVEC) co-cultures. Pre-vascularised (hGF + RFP-HUVEC-CC grids) and control (hGF only -HG grids) grids were bioprinted and pre-cultivated for 14 d to enable pre-vessels formation. In vitro vessel formation follow-up was performed. Eight-week-old female NOG mice were used for in vivo experiments. One grid per mouse was subcutaneously implanted in 20 mice (10HG/10CC). The fluorescent activity of RFP-HUVEC was monitored. Samples were retrieved at 7, 14 and 21 d. Histological, immunohistochemical, and immunofluorescent staining was performed. CC-grids formed efficient and stable pre-vessel networks within 14 d of static pre-culture. HG-grids did not contain any vessel, while CC-grids successfully connected to the host vasculature by presenting erythrocytes within the vessel lumen inside the grids starting day 7. From days 7–21, vessel density was stable. Human pre-vessels were present at 7 d and were progressively replaced by murine ECs. This study showed that primary hGF-HUVEC co-cultures can be successfully 3D-bioprinted within biomimetic hydrogels having a close composition to the gingival connective tissue, and HUVEC organise themselves into pre-vessel networks that connect to the murine vasculature when implanted in vivo. This approach represents a promising strategy to enhance current and future oral soft tissue substitutes for prospective clinical applications.

Abstract
Reliable and predictive experimental models are urgently needed to study metastatic mechanisms of ovarian cancer cells in the omentum. Although models for ovarian cancer cell adhesion and invasion were previously investigated, the lack of certain omental cell types, which influence the metastatic behavior of cancer cells, limits the application of these tissue models. Here, we describe a 3D multi-cellular human omentum tissue model, which considers the spatial arrangement of five omental cell types. Reproducible tissue models were fabricated combining permeable cell culture inserts and bioprinting technology to mimic metastatic processes of immortalized and patient-derived ovarian cancer cells. The implementation of an endothelial barrier further allowed studying the interaction between cancer and endothelial cells during hematogenous dissemination and the impact of chemotherapeutic drugs. This proof-of-concept study may serve as a platform for patient-specific investigations in personalized oncology in the future.

Abstract
Abstract Bioprinting applications in the clinical field generate great interest, but developing suitable biomaterial inks for medical settings is a challenge. Placental tissues offer a promising solution due to their abundance, stability, and status as medical waste. They contain basement membrane components, have a clinical history, and support angiogenesis. This study formulates bioinks from two placental tissues, amnion (AM) and chorion (CHO), and compares their unique extracellular matrix (ECM) and growth factor compositions. Rheological properties of the bioinks are evaluated for bioprinting and maturation of human endothelial cells. Both AM and Cho-derived bioinks sustained human endothelial cell viability, proliferation, and maturation, promoting optimal vasculogenesis. These bioinks derived from human sources have significant potential for tissue engineering applications, particularly in supporting vasculogenesis. This research contributes to the advancement of tissue engineering and regenerative medicine, bringing everyone closer to clinically viable bioprinting solutions using placental tissues as valuable biomaterials.

Abstract
The field of bioprinting has shown a tremendous development in recent years, focusing on the development of advanced in vitro models and on regeneration approaches. In this scope, the lack of suitable biomaterials that can be efficiently formulated as printable bioinks, while supporting specific cellular events, is currently considered as one of the main limitations in the field. Indeed, extracellular matrix (ECM)-derived biomaterials formulated to enable printability and support cellular response, for instance via integrin binding, are eagerly awaited in the field of bioprinting. Several bioactive laminin sequences, including peptides such as YIGSR and IKVAV, have been identified to promote endothelial cell attachment and/or neurite outgrowth and guidance, respectively. Here, we show the development of two distinct bioinks, designed to foster vasculogenesis or neurogenesis, based on methacrylated collagen and hyaluronic acid (CollMA and HAMA, respectively), both relevant ECM-derived polymers, and on their combination with cysteine-flanked laminin-derived peptides. Using this strategy, it was possible to optimize the bioink printability, by tuning CollMA and HAMA concentration and ratio, and modulate their bioactivity, through adjustments in the cell-active peptide sequence spatial density, without compromising cell viability. We demonstrated that cell-specific bioinks could be customized for the bioprinting of both human umbilical vein cord endothelial cells (HUVECs) or adult rat sensory neurons from the dorsal root ganglia, and could stimulate both vasculogenesis and neurite outgrowth, respectively. This approach holds great potential as it can be tailored to other cellular models, due to its inherent capacity to accommodate different peptide compositions and to generate complex peptide mixtures and/or gradients.