Bone fracture healing is a multistep process, including early immunological reactions, osteogenesis, and as a key factor, angiogenesis. Molecules inducing osteogenesis as well as angiogenesis are rare, but hold promise to be employed in bone tissue engineering. It has been demonstrated that the bone sialoprotein (BSP) can induce bone formation when immobilized in collagen type I, but its effect on angiogenesis still has to be characterized in detail. Therefore, the aim of this study was to analyse the effects of BSP immobilized in a collagen type I gel on angiogenesis. First, in vitro analyses with endothelial cells (HUVECs) were performed detecting enhancing effects of BSP on proliferation and gene expression of endothelial markers. A spheroid model was employed confirming these results. Finally, the inducing impact of BSP-collagen on vascular density was proved in a yolk sac membrane assay. Our results demonstrate that BSP is capable of inducing angiogenesis and confirm that collagen type I is the optimal carrier for this protein. Taking into account former results, and literature showing that BSP also induces osteogenesis, one can hypothesize that BSP couples angiogenesis and osteogenesis, making it a promising molecule to be used in bone tissue regeneration.

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Bone Sialoprotein Immobilized in Collagen Type I Enhances Angiogenesis In Vitro and In Ovo

Three-dimensional (3D) models with improved biomimicry are essential to reduce animal experimentation and drive innovation in tissue engineering. In the current study, we investigate the use of alginate-based materials as polymeric inks for 3D bioprinting of osteogenic models using human bone marrow stem/stromal cells (hBMSCs). A composite bioink incorporating alginate, nano-hydroxyapatite (nHA), type I collagen (Col) and hBMSCs was developed and for extrusion-based printing. Rheological tests perfomed on crosslinked hydrogels confirm the formation of solid-like structures consistently indicating a higher storage modulus compared to the loss modulus. The swelling behaviour analysis showed that the addition of Col and nHA into an alginate matrix can enhance the swelling rate of the resulting composite hydrogels, which maximizes cell proliferation within the structure. The LIVE/DEAD assay outcomes demonstrate that the inclusion of nHA and Col did not detrimentally affect the viability of hBMSCs over seven days post-printing. PrestoBlueTM revealed a higher hBMSCs viability in the alginate-nHA-Col hydrogel compared to the remaining groups. Gene expression analysis revealed that alginate-nHA-col bioink favoured a higher expression of osteogenic markers, including secreted phosphoprotein-1 (SPP1) and collagen type 1 alpha 2 chain (COL1A2), in hBMSCs after 14 days, indicating the pro-osteogenic differentiation potential of the hydrogel. This study demonstrates that the incorporation of nHA and Col into alginate enhances osteogenic potential and provides a bioprinted model to systematically study osteogenesis and the early stages of tissue maturation in vitro. 

3D Bioprinting of Alginate-Based Hydrogels to Investigate Osteogenic Differentiation of hBMSCS &lt;em&gt;In Vitro&lt;/em&gt;

Bone marrow-derived mesenchymal stem cells (BMSCs) exhibit multi-lineage differentiation potential and robust proliferative capacity. The late stage of differentiation signifies the functional maturation and characterization of specific cell lineages, which is crucial for studying lineage-specific differentiation mechanisms. However, the molecular processes governing late-stage BMSC differentiation remain poorly understood. This study aimed to elucidate the key biological processes involved in late-stage BMSC differentiation. Publicly available transcriptomic data from human BMSCs were analyzed after approximately 14 days of osteogenic, adipogenic, and chondrogenic differentiation. Thirty-one differentially expressed genes (DEGs) associated with differentiation were identified. Pathway enrichment analysis indicated that the DEGs were involved in extracellular matrix (ECM)-receptor interactions, focal adhesion, and glycolipid biosynthesis, a ganglion series process. Subsequently, the target genes were validated using publicly available single-cell RNA-seq data from mouse BMSCs. Lamc1 exhibited predominant distribution in adipocytes and osteoblasts, primarily during the G2/M phase. Tln2 and Hexb were expressed in chondroblasts, osteoblasts, and adipocytes, while St3gal5 was abundantly distributed in stem cells. Cell communication analysis identified two receptors that interact with LAMCI. q-PCR results confirmed the upregulation of Lamc1, Tln2, Hexb, and St3gal5 during osteogenic differentiation and their downregulation during adipogenic differentiation. Knockdown of Lamc1 inhibited adipogenic and osteogenic differentiation. In conclusion, this study identified four genes, Lamc1, Tln2, Hexb, and St3gal5, that may play important roles in the late-stage differentiation of BMSCs. It elucidated their interactions and the pathways they influence, providing a foundation for further research on BMSC differentiation. 

Lamc1 promotes osteogenic differentiation and inhibits adipogenic differentiation of bone marrow-derived mesenchymal stem cells

Bone sialoprotein (BSP) is a multi-functional extracellular matrix (ECM) protein associated with mineralized tissues, particularly bone and cementum. The amino acid sequence of BSP includes three evolutionarily conserved functional domains which contribute to functions of the protein: an N-terminal collagen-binding domain, polyglutamic acid (polyE) sequences involved in hydroxyapatite nucleation and crystal growth, and a C-terminal arginine-glycine-aspartic acid (RGD) integrin-binding domain. BSP promotes attachment and differentiation of osteogenic and osteoclastic cells. Genetic ablation of BSP in mice results in skeletal and dental developmental defects and impaired bone healing in both appendicular bone and alveolar bone of the jaw. Several studies demonstrated positive effects of BSP on bone healing in rodent models, though other experiments show negligible results. Native (harvested from rat bones) BSP cross-linked to collagen induced slight improvements in calvarial bone healing in rats. Recombinant BSP and collagen delivered in a polylactide (PLA) cylinder improved bone defect healing in rat femurs. Both native and recombinant BSP delivered in a collagen gel improved alveolar bone healing in wild-type and BSP-deficient mice. These advances suggest BSP is a new player in bone healing that has potential to be an alternative or complimentary to other bioactive factors. Future studies are necessary to understand mechanisms of how BSP influences bone healing and optimize delivery and dose in different types of bone defects and injuries. 

The Role of Bone Sialoprotein in Bone Healing

Oxidative stress and chronic inflammation are major contributors to skin aging, promoting collagen degradation and impairing dermal structure. These factors stimulate the expression of matrix metalloproteinases, accelerating collagen breakdown and leading to wrinkles, sagging, and loss of elasticity. Given the key role of collagen in maintaining skin firmness and integrity, strategies that enhance collagen synthesis are essential for anti-aging interventions. This study investigated the combined effects of Yeast/Rice Fermentation Filtrate (RFF) and sialic acid (SA) on collagen production, antioxidation, and anti-inflammation, as well as their underlying mechanisms. The combination of RFF and SA significantly increased collagen genes transcription and mRNA stability, thereby enhancing collagen accumulation in the extracellular matrix. RNA-seq analysis revealed that RFF and SA modulate genes involved in the IL-17 signaling pathway. Mechanistically, RFF enhanced collagen mRNA stability by regulating HuR, while SA promoted collagen gene transcription via the TGF-β/Smad pathway. Moreover, the combination reduced the expression of inflammatory markers (IL-1β, IL-6, IL-8, PGE2, and NO) and improved cellular resistance to oxidative and inflammatory stress. These findings support the application of RFF and SA in anti-aging cosmetics and propose a novel strategy to enhance collagen production by simultaneously upregulating gene expression and stabilizing collagen mRNA. 

In Vitro Anti-Aging Effects of Yeast/Rice Fermentation Filtrate Combined with Sialic Acid in Cosmetic Applications

The use of bioactive molecules is a promising approach to enhance the bone healing properties of biomaterials. The aim of this study was to define the role of bone sialoprotein (BSP) immobilized in collagen type I in various settings. In vitro studies with human primary osteoblasts in mono- or in co-culture with endothelial cells demonstrated a slightly increased gene expression of osteogenic markers as well as an increased proliferation rate in osteoblasts after application of BSP immobilized in collagen type I. Two critical size bone defect models were used to analyze bone regeneration. BSP incorporated in collagen type I increased bone regeneration only marginally at one concentration in a calvarial defect model. To induce the mechanical stability, three-dimensional printing was used to produce a stable porous cylinder of polylactide. The cylinder was filled with collagen type I and immobilized BSP and implanted into a femoral defect of critical size in rats. This hybrid material was able to significantly induce bone regeneration. Our study clearly shows the osteogenic effect of BSP when combined with collagen type I as carrier and thereby offers various approaches and options for its use as bioactive molecule in bone substitute materials.

Bone Sialoprotein Immobilized in Collagen Type I Enhances Bone Regeneration In vitro and In vivo

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Bone Sialoprotein Immobilized in Collagen Type I Enhances Bone Regeneration In vitro and In vivo