OBJECTIVE

This review article aims to determine the properties, uses, toxicity, and other side effects of crosslinking agents in tissue scaffolds when applied in vitro and in vivo.

A literature search was performed using the PubMed-NCBI (MEDLINE) database (https://pubmed.ncbi.nlm. nih.gov/) with keywords: crosslinking reagent, collagen, hydroxyapatite, and bone regeneration. GRADE criteria were used to assess the quality of evidence.

A total of six articles were included in the study. Improved mechanical properties of collagen-hydroxyapatite scaffolds with high porosity can be achieved by employing crosslinking methods, including physical dehydrothermal (DHT) treatment, chemical treatment with glutaraldehyde (GA), Microbial Transglutaminase (mTGase), 1‐ethyl‐3‐(3‐ dimethylaminopropyl) carbodiimide (EDAC), or a combination of both DHT and EDAC. Furthermore, the crosslinking of EDAC and DHT can lead to forming ester bonds between activated carboxyl groups and hydroxyl groups.

The combination of DHT and EDAC crosslinking can increase mechanical strength, make the pore size appropriate, make the scaffold more stable, and support cell adhesion so that new cells can grow, and the process of osteogenesis can run more optimally.

Objective To explore the mechanism by which gentiopicroside (GPS) prevents macrophage-mediated hepatic fibrosis by regulating the macrophage migration inhibitory factor (MIF)-secreted phosphoprotein 1 (SPP1) signaling pathway in hepatic stellate cells. Methods LX-2 cells were divided into control group, transforming growth factor β(TGF-β) group, and TGF-β combined with GPS (25, 50, 100, 150 μmol/mL) groups. Cell proliferation was detected by EDU assay, cell invasion was assessed by Transwell^TM assay, and the protein expressions of α-smooth muscle actin (α-SMA) and type I collagen (COL1A1) were measured by Western blot. M1-type macrophage-conditioned medium (M1-CM) was used to treat LX-2 cells in the TGF-β group and TGF-β combined with GPS group. The concentrations of inducible nitric oxide synthase (iNOS) and arginase 1 (Arg1) in the cell supernatant, as well as cell proliferation, invasion ability, and the expressions of α-SMA and COL1A1 were detected. Bioinformatics analysis was performed to identify the target intersections of GPS, hepatic fibrosis, and macrophage-related genes. Drug affinity responsive target stability (DARTS) experiments and Western blot were used to verify the regulatory effect of GPS on MIF. Furthermore, LX-2 cells were divided into control group, TGF-β group, TGF-β combined with M2-CM group, TGF-β and oe-NC combined with M2-CM group, and TGF-β and oe-MIF combined with M2-CM group to analyze the concentrations of iNOS and Arg1 in the cell supernatant, as well as changes in cell proliferation, invasion, and the expressions of α-SMA and COL1A1. LX-2 cells were also divided into control group, TGF-β group, TGF-β combined with oe-NC group, TGF-β combined with oe-MIF group, and TGF-β and oe-MIF combined with GPS group to determine the protein expressions of MIF and SPP1 by Western blot. A rat model of hepatic fibrosis was constructed to explore the potential therapeutic effects of GPS on hepatic fibrosis in vivo. Results Compared with the control group, the proliferation and invasion abilities of LX-2 cells in the TGF-β group were increased, and the protein expressions of α-SMA and COL1A1 were enhanced. GPS intervention inhibited the proliferation and invasion of LX-2 cells under TGF-β conditions and reduced the expressions of α-SMA and COL1A1. Compared with the control group, the concentration of iNOS in the cell supernatant of the TGF-β group was upregulated, while the concentration of Arg1 was decreased. M1-CM treatment further increased the concentration of iNOS, decreased the concentration of Arg1, and promoted cell proliferation and invasion, as well as upregulated the expressions of α-SMA and COL1A1 on the basis of TGF-β intervention. However, GPS could reverse the effects of M1-CM intervention. Bioinformatics analysis revealed that MIF was one of the target intersections of GPS, hepatic fibrosis, and macrophage-related genes, and GPS could target and inhibit its expression. Compared with the TGF-β group, after M2-CM intervention, the concentration of iNOS in the cell supernatant decreased, the concentration of Arg1 increased, the proliferation and invasion abilities of LX-2 cells were reduced, and the expressions of α-SMA and COL1A1 were weakened. However, overexpression of MIF reversed the effects of M2-CM intervention. Western blot results showed that compared with the control group, the protein expressions of MIF and SPP1 were enhanced in the TGF-β group. Overexpression of MIF further enhanced the expressions of MIF and SPP1, while GPS intervention inhibited the expressions of MIF and SPP1. In the animal experiment, GPS intervention treatment alleviated liver injury in rats with hepatic fibrosis and inhibited the expressions of MIF and SPP1, as well as α-SMA and COL1A1 in liver tissue. Conclusion GPS may prevent macrophage-mediated hepatic fibrosis by inhibiting the MIF-SPP1 signaling pathway in hepatic stellate cells.
Hepatic Stellate Cells/metabolism* ; Signal Transduction/drug effects* ; Macrophage Migration-Inhibitory Factors/genetics* ; Liver Cirrhosis/prevention & control* ; Macrophages/drug effects* ; Iridoid Glucosides/pharmacology* ; Humans ; Cell Proliferation/drug effects* ; Animals ; Cell Line ; Collagen Type I/metabolism* ; Collagen Type I, alpha 1 Chain ; Intramolecular Oxidoreductases/genetics* ; Rats ; Transforming Growth Factor beta/pharmacology* ; Actins/metabolism*

Scar formation is characterized by dynamic alterations in collagen secretion, which critically determine scar morphology and pathological progression. In fibroblasts, collagen secretion is initiated through the activation of cytokine- and integrin-mediated signaling pathways, which promote collagen gene transcription. The procollagen polypeptide α chains undergo extensive post-translational modifications, including hydroxylation and glycosylation, within the endoplasmic reticulum (ER), followed by folding and assembly into triple-helical procollagen. Subsequent intracellular trafficking involves the sequential transport of procollagen through the ER, Golgi apparatus, and plasma membrane, accompanied by further structural refinements prior to extracellular secretion. Once secreted, procollagen is enzymatically processed to form mature collagen fibrils, which drive scar tissue remodeling. Recent advances in elucidating regulation of collagen secretion have identified pivotal molecular targets, such as transforming growth factor-beta 1 (TGF-β1), prolyl 4-hydroxylase (P4H), heat shock protein 47 (HSP47), and transport and Golgi organization protein 1 (TANGO1), providing novel therapeutic strategies to mitigate pathological scar hyperplasia and improve regenerative outcomes. This review provides a comprehensive analysis of the molecular mechanisms governing collagen secretion during scar formation, with emphasis on signaling cascades, procollagen biosynthesis, intracellular transport dynamics, and post-translational modifications, thereby offering a framework for developing targeted anti-scar therapies.
Humans ; Collagen/metabolism* ; Cicatrix/pathology* ; Signal Transduction ; Transforming Growth Factor beta1/metabolism* ; Fibroblasts/metabolism* ; Animals

OBJECTIVE: To investigate the biological effect of medical recombinant human-derived collagen functional dressings in wound healing. METHODS: MTT assay and RTCA assay were used to detect cell toxicity and proliferation. Scratch assay and Transwell cell migration assay were used to detect cell motility and migration ability. Enzyme-linked immunosorbent assay was used to detect the contents of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-endothelial cell adhesion molecule (CD31) in the supernatant of four types of cells. After animal surgery, the surgical wound was taken at 1 week, 4 weeks and 13 weeks, respectively, for hematoxylin eosin (HE) staining and immunohistochemistry to observe the inflammatory response and CD31 expression of the wound. RESULTS: Medical recombinant human-derived collagen functional dressing promotes cell proliferation and migration, enhances wound angiogenesis by upregulating the expression of VEGF, FGF, and CD31 in human dermal vascular endothelial cells (HDVEC) and human vascular endothelial cells (HVEC), thereby improving local blood supply to the wound, regulating the inflammatory response of the wound, and accelerating wound healing. CONCLUSION Recombinant type Ⅲ humanized collagen plays an important role in wound healing.
Humans ; Wound Healing/drug effects* ; Recombinant Proteins/pharmacology* ; Animals ; Cell Proliferation ; Cell Movement ; Collagen/pharmacology* ; Vascular Endothelial Growth Factor A/metabolism* ; Bandages ; Platelet Endothelial Cell Adhesion Molecule-1/metabolism* ; Endothelial Cells ; Fibroblast Growth Factors/metabolism*

OBJECTIVES: To investigate the changes in blood levels of calcium and bone metabolism biochemical markers in patients with primary osteoporosis receiving treatment with denosumab. METHODS: Seventy-three patients with primary osteoporosis treated in our Department between December, 2021 and December 2023 were enrolled. All the patients were treated with calcium supplements, vitamin D and calcitriol in addition to regular denosumab treatment every 6 months. Blood calcium, parathyroid hormone (PTH), osteocalcin (OC), type I procollagen amino-terminal propeptide (PINP), and type I collagen carboxy-terminal telopeptide β special sequence (β‑CTX) data before and at 3, 6, 9, and 12 months after the first treatment were collected from each patient. RESULTS: Three months after the first denosumab treatment, the bone turnover markers (BTMs) OC, PINP, and β-CTX were significantly decreased compared to their baseline levels by 39.5% (<i>Pi><0.001), 56.2% (<i>Pi><0.001), and 81.8% (<i>Pi><0.001), respectively. At 6, 9, and 12 months of treatment, OC, PINP, and β-CTX remained significantly lower than their baseline levels (<i>Pi><0.001). Blood calcium level was decreased (<i>Pi><0.05) and PTH level increased (<i>Pi><0.05) significantly in these patients at months of denosumab treatment, but their levels were comparable to the baseline levels at 6, 9, and 12 months of the treatment (<i>Pi>>0.05). CONCLUSIONS Denosumab can suppress BTMs and has a good therapeutic effect in patients with primary osteoporosis, but reduction of blood calcium and elevation of PTH levels can occur during the first 3 months in spite of calcium supplementation. Blood calcium and PTH levels can recover the baseline levels as the treatment extended, suggesting the importance of monitoring blood calcium and PTH levels during denosumab treatment.
Humans ; Denosumab/therapeutic use* ; Calcium/blood* ; Parathyroid Hormone/blood* ; Biomarkers/blood* ; Osteoporosis/blood* ; Osteocalcin/blood* ; Procollagen/blood* ; Female ; Collagen Type I/blood* ; Peptide Fragments/blood* ; Bone Density Conservation Agents/therapeutic use* ; Bone and Bones/metabolism* ; Male ; Middle Aged ; Vitamin D ; Peptides/blood* ; Aged

OBJECTIVES: To assess the therapeutic effect of aucubin in mice with knee osteoarthritis (KOA) and investigate the underlying mechanism. METHODS: Sixty C57BL/6J mice were randomized equally into sham operation group, KOA model group, glucosamine (positive control) treatment group, and low-, medium-, and high-dose aucubin treatment groups (2, 4, and 8 mg/kg, respectively). KOA mouse models were established by transection of the anterior cruciate ligament (ACL), and the treatment was initiated on day 1 postoperatively and administered weekly for 8 weeks. Safranin O-fast green staining, immunohistochemistry, and microCT were used to evaluate the changes in cartilage pathology, inflammatory protein expression, and subchondral bone volume fraction (BV/TV). The expression levesl of COL2, SOX9, p-P65, IL-1β and MMP13 proteins in the cartilage tissues were detected using Western blotting. In a chondrocyte model with IL-1β treatment for mimicking KOA, the effect of aucubin on chondrogenic differentiation was observed with Alcian blue and Safranin O staining, and cellular COL2, SOX9 and TNF‑α mRNA expressions were detected with RT-qPCR. RESULTS: Compared with those in the model group, the mouse models receiving aucubin treatment showed significantly upregulated COL2 and SOX9 protein levels and downregulated p-P65, IL-1β and MMP13 expressions in the cartilage tissues. In the IL-1β-induced chondrocyte model, aucubin treatment significantly upregulated the mRNA expressions of SOX9 and COL2 but lowered the mRNA expression of TNF-α. Alcian blue and Safranin O staining confirmed that aucubin promoted the synthesis of cartilage extracellular matrix and enhanced chondrogenic differentiation of the cells. CONCLUSIONS Aucubin can effectively alleviate KOA in mice by inhibiting NF‑κB-mediated cartilage inflammation, promoting cartilage matrix synthesis, and improving subchondral bone microstructure.
Animals ; Mice, Inbred C57BL ; Mice ; Osteoarthritis, Knee/drug therapy* ; Signal Transduction/drug effects* ; NF-kappa B/metabolism* ; Iridoid Glucosides/therapeutic use* ; SOX9 Transcription Factor/metabolism* ; Chondrocytes/drug effects* ; Male ; Interleukin-1beta/metabolism* ; Matrix Metalloproteinase 13/metabolism* ; Collagen Type II/metabolism* ; Disease Models, Animal

Abnormal accumulation of collagen fibrils is a hallmark feature of oral submucous fibrosis (OSF). However, the precise characteristics and underlying mechanisms remain unclear, impeding the advancement of potential therapeutic approaches. Here, we observed that collagen I, the main component of the extracellular matrix, first accumulated in the lamina propria and subsequently in the submucosa of OSF specimens as the disease progressed. Using RNA-seq and Immunofluorescence in OSF specimens, we screened the cartilage oligomeric matrix protein (COMP) responsible for the abnormal collagen accumulation. Genetic COMP deficiency reduced arecoline-stimulated collagen I deposition significantly in vivo. In comparison, both COMP and collagen I were upregulated under arecoline stimulation in wild-type mice. Human oral buccal mucosal fibroblasts (hBMFs) also exhibited increased secretion of COMP and collagen I after stimulation in vitro. COMP knockdown in hBMFs downregulates arecoline-stimulated collagen I secretion. We further demonstrated that hBMFs present heterogeneous responses to arecoline stimulation, of which COMP-positive fibroblasts secrete more collagen I. Since COMP is a molecular bridge with Fibril-associated collagens with Interrupted Triple helices (FACIT) in the collagen network, we further screened and identified collagen XIV, a FACIT member, co-localizing with both COMP and collagen I. Collagen XIV expression increased under arecoline stimulation in wild-type mice, whereas it was hardly expressed in the Comp^-/- mice, even with under stimulation. In summary, we found that COMP may mediates abnormal collagen I deposition by functions with collagen XIV during the progression of OSF, suggesting its potential to be targeted in treating OSF.
Oral Submucous Fibrosis/pathology* ; Cartilage Oligomeric Matrix Protein/genetics* ; Animals ; Mice ; Humans ; Fibroblasts/metabolism* ; Collagen Type I/metabolism* ; Arecoline/pharmacology* ; Mouth Mucosa/metabolism* ; Cells, Cultured ; Fluorescent Antibody Technique

Temporomandibular joint (TMJ) disc displacement is one of the most significant subtypes of temporomandibular joint disorders, but its etiology and mechanism are poorly understood. In this study, we elucidated the mechanisms by which destruction of inflamed collagen fibrils induces alterations in the mechanical properties and positioning of the TMJ disc. By constructing a rat model of TMJ arthritis, we observed anteriorly dislocated TMJ discs with aggravated deformity in vivo from five weeks to six months after a local injection of Freund's complete adjuvant. By mimicking inflammatory conditions with interleukin-1 beta in vitro, we observed enhanced expression of collagen-synthesis markers in primary TMJ disc cells cultured in a conventional two-dimensional environment. In contrast, three-dimensional (3D)-cultivated disc cell sheets demonstrated the disordered assembly of inflamed collagen fibrils, inappropriate arrangement, and decreased Young's modulus. Mechanistically, inflammation-related activation of the nuclear factor kappa-B (NF-κB) pathway occurs during the progression of TMJ arthritis. NF-κB inhibition reduced the collagen fibril destruction in the inflamed disc cell sheets in vitro, and early NF-κB blockade alleviated collagen degeneration and dislocation of the TMJ discs in vivo. Therefore, the NF-κB pathway participates in the collagen remodeling in inflamed TMJ discs, offering a potential therapeutic target for disc displacement.
Animals ; NF-kappa B/metabolism* ; Temporomandibular Joint Disorders/pathology* ; Temporomandibular Joint Disc/metabolism* ; Rats ; Rats, Sprague-Dawley ; Disease Models, Animal ; Male ; Collagen/metabolism* ; Cells, Cultured ; Joint Dislocations/pathology* ; Interleukin-1beta ; Arthritis, Experimental

Xerostomia (dry mouth) is frequently experienced by patients treated with radiotherapy for head and neck cancers or with Sjögren's syndrome, with no permanent cure existing for this debilitating condition. To this end, in vitro platforms are needed to test therapies directed at salivary (fluid-secreting) cells. However, since these are highly differentiated secretory cells, the maintenance of their differentiated state while expanding in numbers is challenging. In this study, the efficiency of three reversible thermo-ionically crosslinked gels: (1) alginate-gelatin (AG), (2) collagen-containing AG (AGC), and (3) hyaluronic acid-containing AG (AGHA), to recapitulate a native-like environment for human salivary gland (SG) cell expansion and 3D spheroid formation was compared. Although all gels were of mechanical properties comparable to human SG tissue (~11 kPa) and promoted the formation of 3D spheroids, AGHA gels produced larger (>100 cells/spheroid), viable (>93%), proliferative, and well-organized 3D SG spheroids while spatially and temporally maintaining the high expression of key SG proteins (aquaporin-5, NKCC1, ZO-1, α-amylase) for 14 days in culture. Moreover, the spheroids responded to agonist-induced stimulation by increasing α-amylase secretory granules. Here, we propose alternative low-cost, reproducible, and reversible AG-based 3D hydrogels that allow the facile and rapid retrieval of intact, highly viable 3D-SG spheroids.
Humans ; Hydrogels/chemistry* ; Acinar Cells/cytology* ; Spheroids, Cellular/cytology* ; Salivary Glands/cytology* ; Gelatin/chemistry* ; Collagen/chemistry* ; Alginates/chemistry* ; Cell Culture Techniques/methods* ; Hyaluronic Acid/chemistry* ; Cell Proliferation ; Cell Survival ; Cells, Cultured

Collagen-based materials, renowned for their biocompatibility and minimal immunogenicity, serve as exemplary substrates in a myriad of biomedical applications. Collagen-based micro/nanogels, in particular, are valued for their increased surface area, tunable degradation rates, and ability to facilitate targeted drug delivery, making them instrumental in advanced therapeutics and tissue engineering endeavors. Although extensive reviews on micro/nanogels exist, they tend to cover a wide range of biomaterials and lack a specific focus on collagen-based materials. The current review offers an in-depth look into the manufacturing technologies, drug release mechanisms, and biomedical applications of collagen-based micro/nanogels to address this gap. First, we provide an overview of the synthetic strategies that allow the precise control of the size, shape, and mechanical strength of these collagen-based micro/nanogels by controlling the degree of cross-linking of the materials. These properties are crucial for their performance in biomedical applications. We then highlight the environmental responsiveness of these collagen-based micro/nanogels, particularly their sensitivity to enzymes and pH, which enables controlled drug release under various pathological conditions. The discussion then expands to include their applications in cancer therapy, antimicrobial treatments, bone tissue repair, and imaging diagnosis, emphasizing their versatility and potential in these critical areas. The challenges and future perspectives of collagen-based micro/nanogels in the field are discussed at the end of the review, with an emphasis on the translation to clinical practice. This comprehensive review serves as a valuable resource for researchers, clinicians, and scientists alike, providing insights into the current state and future directions of collagen-based micro/nanogel research and development.
Collagen/chemistry* ; Drug Delivery Systems/methods* ; Humans ; Tissue Engineering/methods* ; Animals ; Biocompatible Materials/chemistry*