During bone regeneration, the periosteum acts as a carrier for key regenerative cues, delivering osteochondroprogenitor cells and crucial growth factors to the injured bone. We developed a biocompatible, 3D polycaprolactone (PCL) melt electro-written membrane to act as a mimetic periosteum. Poly (ethyl acrylate) coating of the PCL membrane allowed functionalization, mediated by fibronectin and low dose recombinant human BMP-2 (rhBMP-2) (10-25 μg/ml), resulting in efficient, sustained osteoinduction in vitro. In vivo, rhBMP-2 functionalized mimetic periosteum demonstrated regenerative potential in the treatment of rat critical-size femoral defects with highly efficient healing and functional recovery (80%-93%). Mimetic periosteum has also proven to be efficient for cell delivery, as observed through the migration of transplanted periosteum-derived mesenchymal cells to the bone defect and their survival. Ultimately, mimetic periosteum demonstrated its ability to deliver key stem cells and morphogens to an injured site, exposing a therapeutic and translational potential in vivo when combined with unprecedentedly low rhBMP-2 doses.

Numerous tissue engineering strategies aim to enable the in situ and controlled release of both cells and biologically relevant factors, mimicking physiological regenerative processes. A notable example is the release of rhBMP-2 for treating bone nonunion. By adopting a quasi-physiological approach, we can mitigate the side effects that have hindered its clinical application. Here, we present a customizable 3D-printed polycaprolactone (PCL) scaffold functionalized with poly(lactic-co-glycolic) acid (PLGA) microparticles through covalent binding, designed to mimic the periosteum structure. This scaffold was then functionalized with PLGA microparticles through covalent binding, enabling in situ delivery of rhBMP-2. This construct exhibits significant osteogenic and osteoinductive potential in vitro, promoting the differentiation of periosteum-derived mesenchymal progenitor cells into osteoblasts. Moreover, in vivo testing using a nonunion model (critical size defect) demonstrated therapeutic efficacy with a reduced net morphogen dose. Therefore, this customizable 3D scaffold represents a valuable approach for enhancing bone regeneration and holds significant potential for promoting healing in cases of nonunion fractures. This approach combines a customizable 3D scaffold with controlled rhBMP-2 release, offering a potentially more effective and safer solution for bone regeneration compared to current methods. STATEMENT OF SIGNIFICANCE: As the incidence of bone fractures continues to rise, nonunion remains a significant challenge in orthopedics, becoming a major clinical and economic burden. We present a tissue engineering strategy employing a customizable 3D-printed polycaprolactone scaffold functionalized with covalently bound poly(lactic-co-glycolic acid) microparticles for the localized release of rhBMP-2. By mimicking key features of the periosteum, this scaffold promotes bone regeneration while minimizing the risk of ectopic bone formation. In vivo tests conducted in a critical-size defect model demonstrated effective bone bridging, highlighting the therapeutic potential of the scaffold. The simple manufacturing process, potential for scale-up production, long-term storage capability, and options for customization, including combinations of different molecules or adjuvants, demonstrate that this approach possesses significant translational potential.

The bone marrow (BM) is a complex and compartmentalized tissue where spatial context plays a critical role in regulating cell behavior, signaling, and disease progression. To capture these dynamics, we apply spatial transcriptomics using the Visium Spatial Gene Expression platform on formalin-fixed paraffin-embedded (FFPE) BM sections from both healthy and Multiple Myeloma (MM) mouse models, as well as MM patient samples. Overcoming the technical challenges of working with mineralized long bone tissue, we develop a custom analytical framework integrating spatial and single-cell transcriptomic data to map cellular composition and interactions in situ. This approach enables the spatial characterization of transcriptionally heterogeneous malignant plasma cells (MM-PC) and their surrounding microenvironments. We identify spatially distinct gene programs linked to MM pathogenesis, including signatures of NETosis and IL-17 signalling, which are reduced in MM-PC-rich regions. Additionally, a transition gradient from effector to exhausted T cell phenotype is associated with increased remoteness from MM-PC. These spatial patterns are identified in FFPE BM biopsies from MM patients with varying tumor burdens. In summary, our study demonstrates both the capabilities and limitations of Visium technology in characterizing spatially regulated mechanisms underlying MM pathogenesis.

The interface tissue between bone and soft tissues, such as tendon and ligament (TL), is highly prone to injury. Although different biomaterials have been developed for TL regeneration, few address the challenges of the TL-bone interface. Here, we aim to develop novel hybrid nanocomposites based on poly(p-dioxanone) (PDO), poly(lactide-co-caprolactone) (LCL), and hydroxyapatite (HA) nanoparticles suitable for TL-bone interface repair. Nanocomposites, containing 3–10% of both unmodified and chemically modified hydroxyapatite (mHA) with a silane coupling agent. We then explored biocompatibility through in vitro and in vivo studies using a subcutaneous mouse model. Through different characterisation tests, we found that mHA increases tensile properties, creates rougher surfaces, and reduces crystallinity and hydrophilicity. Morphological observations indicate that mHA nanoparticles are attracted by PDO rather than LCL phase, resulting in a higher degradation rate for mHA group. We found that adding the 5% of nanoparticles gives a balance between the properties. In vitro experiments show that osteoblasts' activities are more affected by increasing the nanoparticle content compared with fibroblasts. Animal studies indicate that both HA and mHA nanoparticles (10%) can reduce the expression of pro-inflammatory cytokines after six weeks of implantation. In summary, this work highlights the potential of PDO/LCL/HA nanocomposites as an excellent biomaterial for TL-bone interface tissue engineering applications.

The bone marrow (BM) is a complex tissue where spatial relationships influence cell behavior, signaling, and function. Consequently, understanding the whole dynamics of cellular interactions requires complementary spatial techniques that preserve and map the architecture of cell populations in situ . We successfully conducted spatial transcriptional profiling using Visium Spatial Gene Expression in formalin-fixed paraffin-embedded (FFPE) BM samples obtained from healthy and Multiple Myeloma (MM) mouse models and patients, addressing the technical challenges of applying spatial technology to long bone samples. A custom data-analysis framework that combines spatial with single-cell transcriptomic profiles identified both the BM cellular composition and the existing cell relations. This allowed us to visualize the spatial distribution of transcriptionally heterogeneous MM plasma cells (MM-PC). We spatially delineated transcriptional programs associated with MM, including NETosis and IL-17-driven inflammatory signaling, which were inversely correlated to malignant PC-enriched regions. Furthermore, a gradient of MM-PC density spatially correlated with a shift from effector-to-exhausted T cell phenotypes. The translational relevance of our findings was confirmed using FFPE BM biopsies from MM patients with varying levels of malignant PC infiltration. In summary, we provide the first spatial transcriptomics analysis applied to a mouse and human mineralized bone tissue and illustrate the BM cellular architecture of MM, revealing deregulated mechanisms underlying MM intercellular communication.

Cardiac fibroblasts (CFs) are key mediators of heart repair following myocardial infarction (MI). A specific CF subpopulation, termed Reparative Cardiac Fibroblasts (RCFs), has been shown to orchestrate scar formation and prevent ventricular rupture after MI. However, the timing of RCF appearance and the molecular events underlying this transition remain largely undefined. Here, we present a multi-modal dataset capturing the transcriptional dynamics of CFs during the early phase post-MI. Our integrative dataset combines bulk RNA sequencing, RNAscope in situ hybridization, and spatial transcriptomics to anatomically and temporally map the gene expression changes associated with the transition into RCFs. The dataset provides resources to characterize the distinct molecular programs that guide the emergence of RCFs from Periostin ( Postn ) ⁺ activated CFs. This dataset provides a valuable resource for investigating CF heterogeneity and reparative pathways following MI. All raw and processed data, along with detailed metadata and annotations, are made available to facilitate reuse by the cardiovascular and single-cell biology communities.