BACKGROUND:As tissue engineering brings new hope to the worldwide problem of articular cartilage repair,the construction of light-curing 3D printed hydrogel scaffolds with biomimetic composition is of great significance for cartilage tissue engineering. OBJECTIVE:To construct a biomimetic methacryloylated hyaluronic acid/acellular Wharton's jelly composite hydrogel scaffold by digital light processing 3D printing technology,and to evaluate its biocompatibility. METHODS:Wharton's jelly was isolated and extracted from human umbilical cord,then decellulated,freeze-dried,ground into powder,and dissolved in PBS to prepare 50 g/L acellular Wharton's jelly solution.Methylallylated hyaluronic acid was prepared,lyophilized and dissolved in PBS to prepare 50 g/L methylallylated hyaluronic acid solution.Acellular Wharton's jelly solution was mixed with methacrylyacylated hyaluronic acid solution at a volume ratio of 1:1,and was used as bio-ink after adding photoinitiator.Methylacrylylated hyaluronic acid hydrogel scaffolds(labeled as HAMA hydrogel scaffolds)and methylacrylylated hyaluronic acid/acellular Wharton's jelly gel scaffolds(labeled as HAMA/WJ hydrogel scaffolds)were prepared by digital light processing 3D printing technology,and the microstructure,swelling performance,biocompatibility,and cartilage differentiation performance of the scaffolds were characterized. RESULTS AND CONCLUSION:(1)Under scanning electron microscope,the two groups of scaffolds showed a three-dimensional network structure,and the fiber connection of HAMA/WJ hydrogel scaffold was more uniform.Both groups achieved swelling equilibrium within 10 hours,and the equilibrium swelling ratio of HAMA/WJ hydrogel scaffold was lower than that of HAMA hydrogel scaffold(P＜0.05).(2)CCK-8 assay showed that HAMA/WJ hydrogel scaffold could promote the proliferation of bone marrow mesenchymal stem cells compared with HAMA hydrogel scaffold.Dead/live staining showed that bone marrow mesenchymal stem cells grew well on the two groups of scaffolds,and the cells on the HAMA/WJ hydrogel scaffolds were evenly distributed and more cells were found.Phalloidine staining showed better adhesion and spread of bone marrow mesenchymal stem cells in HAMA/WJ hydrogel scaffold than in HAMA.(3)Bone marrow mesenchymal stem cells were inoculated into the two groups for chondrogenic induction culture.The results of qRT-PCR showed that the mRNA expressions of agglutinoglycan,SOX9 and type Ⅱ collagen in the HAMA/WJ hydrogel scaffold group were higher than those in the HAMA hydrogel scaffold group(P＜0.05,P＜0.01).(4)These findings indicate that the digital light processing 3D bioprinting HAMA/WJ hydrogel scaffold can promote the proliferation,adhesion,and chondrogenic differentiation of bone marrow mesenchymal stem cells.

BACKGROUND:Tissue engineering has brought new hope to the clinical challenge of liver failure,and the preparation of plant-derived decellularized fiber scaffolds holds significant importance in liver tissue engineering. OBJECTIVE:To prepare apple tissue decellularized scaffold material by using fresh apple slices and a solution of sodium dodecyl sulfate,and assess its biocompatibility. METHODS:Fresh apples were subjected to decellularization using phosphate buffer saline and sodium dodecyl sulfate solution,separately.Afterwards,the decellularized apple tissues and apple decellularized scaffold materials were decontaminated with phosphate buffer saline.Subsequently,scanning electron microscopy was used to assess the effectiveness of decellularization of the apple materials.Adipose-derived mesenchymal stem cells were extracted from the inguinal fat BALB/C of mice,and their expression of stem cell-related markers(CD45,CD34,CD73,CD90,and CD105)was identified through flow cytometry.The cells were then divided into a scaffold-free control group and a scaffold group.Equal amounts of adipose-derived mesenchymal stem cells were seeded onto both groups.The biocompatibility of the decellularized scaffold with adipose-derived mesenchymal stem cells was evaluated using CCK-8 assay,hematoxylin-eosin staining,and phalloidine staining.Cell adhesion and growth on the scaffold were observed under light microscopy and scanning electron microscopy.Furthermore,the scaffold was subdivided into the non-induced group and the hepatogenic-induced group.Adipose-derived mesenchymal stem cells were cultured on the decellularized apple scaffold,and they were cultured for 14 days in regular culture medium or hepatogenic induction medium for comparison.Immunofluorescent staining using liver cell markers,including albumin,cytokeratin 18,and CYP1A1,was performed.Enzyme-linked immunosorbent assay was used to detect the secretion of alpha fetoprotein and albumin.Additionally,scanning electron microscopy was employed to observe the morphology of the induced cells on the scaffold,verifying the expression of liver cell-related genes on the decellularized scaffold material.Finally,the cobalt-60 irradiated and sterilized decellularized apple scaffolds were transplanted onto the surface of mouse liver and the degradation of the scaffold was observed by gross observation and hematoxylin-eosin staining after 28 days. RESULTS AND CONCLUSION:(1)The scanning electron microscopy results revealed that the decellularized apple scaffold material retained a porous structure of approximately 100 μm in size,with no residual cells observed.(2)Through flow cytometry analysis,the cultured cells were identified as adipose-derived mesenchymal stem cells.(3)CCK-8 assay results demonstrated that the prepared decellularized apple tissue scaffold material exhibited no cytotoxicity.Hematoxylin-eosin staining and phalloidine staining showed that adipose-derived mesenchymal stem cells were capable of adhering and proliferating on the decellularized apple tissue scaffold.(4)The results obtained from immunofluorescence staining and enzyme-linked immunosorbent assay revealed that adipose-derived mesenchymal stem cells cultured on the decellularized apple scaffolds exhibited elevated expression of liver-specific proteins,including albumin,alpha-fetoprotein,cytokeratin 18,and CYP1A1.These results suggested that they were induced differentiation into hepatocyte-like cells possessing functional characteristics of liver cells.(5)The decellularized apple scaffold implanted at 7 days has integrated with the liver,with partial degradation of the scaffold observed.By 28 days,the decellularized apple scaffold has completely degraded and has been replaced by newly-formed tissue.(6)The results indicate that the decellularized scaffold material derived from apple tissue demonstrates favorable biocompatibility,promoting the proliferation,adhesion,and hepatic differentiation of adipose-derived mesenchymal stem cells.

Articular cartilage (AC) injuries often lead to cartilage degeneration and may ultimately result in osteoarthritis (OA) due to the limited self-repair ability. To date, numerous intra-articular delivery systems carrying various therapeutic agents have been developed to improve therapeutic localization and retention, optimize controlled drug release profiles and target different pathological processes. Due to the complex and multifactorial characteristics of cartilage injury pathology and heterogeneity of the cartilage structure deposited within a dense matrix, delivery systems loaded with a single therapeutic agent are hindered from reaching multiple targets in a spatiotemporal matched manner and thus fail to mimic the natural processes of biosynthesis, compromising the goal of full cartilage regeneration. Emerging evidence highlights the importance of sequential delivery strategies targeting multiple pathological processes. In this review, we first summarize the current status and progress achieved in single-drug delivery strategies for the treatment of AC diseases. Subsequently, we focus mainly on advances in multiple drug delivery applications, including sequential release formulations targeting various pathological processes, synergistic targeting of the same pathological process, the spatial distribution in multiple tissues, and heterogeneous regeneration. We hope that this review will inspire the rational design of intra-articular drug delivery systems (DDSs) in the future.

With the emergence of DNA nanotechnology in the 1980s, self-assembled DNA nanostructures have attracted considerable attention worldwide due to their inherent biocompatibility, unsurpassed programmability, and versatile functions. Especially promising nanostructures are tetrahedral framework nucleic acids (tFNAs), first proposed by Turberfield with the use of a one-step annealing approach. Benefiting from their various merits, such as simple synthesis, high reproducibility, structural stability, cellular internalization, tissue permeability, and editable functionality, tFNAs have been widely applied in the biomedical field as three-dimensional DNA nanomaterials. Surprisingly, tFNAs exhibit positive effects on cellular biological behaviors and tissue regeneration, which may be used to treat inflammatory and degenerative diseases. According to their intended application and carrying capacity, tFNAs could carry functional nucleic acids or therapeutic molecules through extended sequences, sticky-end hybridization, intercalation, and encapsulation based on the Watson and Crick principle. Additionally, dynamic tFNAs also have potential applications in controlled and targeted therapies. This review summarized the latest progress in pure/modified/dynamic tFNAs and demonstrated their regenerative medicine applications. These applications include promoting the regeneration of the bone, cartilage, nerve, skin, vasculature, or muscle and treating diseases such as bone defects, neurological disorders, joint-related inflammatory diseases, periodontitis, and immune diseases.
Nucleic Acids/chemistry* ; Regenerative Medicine ; Consensus ; Reproducibility of Results ; DNA/chemistry*

Due to good mechanical properties and biocompatibility, tissue engineering scaffolds have become the vital method for repairing and regenerating articular cartilage defects. With the continuous development of tissue engineering technology, many scaffolds preparation and formation methods have been developed and tested in the past decade, however, the preparation of ideal regenerative scaffolds remain controversial. As load-bearing tissue inside the body joints, the matrix structure and cell composition of articular cartilage are hierarchical, and there are several smooth natural gradients from the cartilage surface to the subchondral bone layer, including cell phenotype and number, specific growth factors, matrix composition, fiber arrangement, mechanical properties, nutrient and oxygen consumption. Therefore, in the design of regenerative scaffolds, it is necessary to achieve these gradients to regenerate articular cartilage in situ. In recent studies, many new biomimetic gradient scaffolds have been used to simulate the natural gradient of articular cartilage. These scaffolds show different mechanical, physicochemical or biological gradients in the structure, and have achieved good repair effects. The related articles on tissue engineering for the treatment of articular cartilage defects were retrieved by searching databases with key wordsarticular cartilage injury, cartilage repair and gradient scaffolds. In this work,the structural, biochemical, biomechanical and nutrient metabolism gradients of natural articular cartilage were studied and summarized firstly. Then, the latest design and construction of articular cartilage gradient scaffolds were classified. Besides that, the material composition (such as hydrogels, nanomaterials, etc.) and the preparation process (such as electrospinning, 3D printing, etc.) of grandient scaffolds were further enhanced. Finally, the prospect and challenge of biomimetic gradient scaffolds in cartilage engineering are discussed, which provides a theoretical basis for the successful application of gradient scaffolds in clinical transformation.

Objective:Establishment of a new model of human primary colon cancer transplantation tumor in normal immune mice and to provide a reliable experimental animal model for studying the pathogenesis of colon cancer under normal immunity.Methods:Human colon cancer cells come from colon cancer patients who underwent surgery in the Affiliated Hospital of Jining Medical College in 2017. The mice in the cell control group were inoculated with phosphate buffered solution (PBS) containing colon cancer cells, the microcarrier control group was inoculated with PBS containing microcarrier 6, and the cell-microcarrier complex group was inoculated with the PBS containing colon cancer cell-microcarrier complex. The cells of each group were inoculated under the skin of the right axilla of mice by subcutaneous injection, and the time, size, tumor formation rate and pathological changes under microscope were recorded. The transplanted tumor tissue was immunohistochemically stained with the EnVisiion two-step method, and the tumor formation rate of the transplanted tumor was judged according to the proportion of positive cells in the visual field. The polymerase chain reaction (PCR) method was used to detect the expression of human-specific Alu sequence in mice tumor tissue.Results:After inoculation with tumor cells, the mice in the cell control group and the microcarrier control group did not die and did not form tumors; the mice in the cell-microcarrier complex group had palpable subcutaneous tumors in the right axillary subcutaneously on the 5th to 7th days after inoculation, and tumor formation rate is 67% (10/15), and the tumor volume can reach about 500 mm 3 2 to 3 weeks after vaccination. The immunohistochemistry results showed that CK20, CDX-2 and carcinoembryonic antigen were all positively expressed. The PCR results showed that the expression of human-specific Alu sequence can be detected in the transplanted tumor tissue of tumor-bearing mice. Conclusion:Human primary colon cancer cells used microcarrier 6 as a carrier to form tumors in normal immunized mice, and successfully established a new model of human colon cancer transplantation tumor in normal immune mice.

Objective:Establishment of a new model of human primary colon cancer transplantation tumor in normal immune mice and to provide a reliable experimental animal model for studying the pathogenesis of colon cancer under normal immunity.Methods:Human colon cancer cells come from colon cancer patients who underwent surgery in the Affiliated Hospital of Jining Medical College in 2017. The mice in the cell control group were inoculated with phosphate buffered solution (PBS) containing colon cancer cells, the microcarrier control group was inoculated with PBS containing microcarrier 6, and the cell-microcarrier complex group was inoculated with the PBS containing colon cancer cell-microcarrier complex. The cells of each group were inoculated under the skin of the right axilla of mice by subcutaneous injection, and the time, size, tumor formation rate and pathological changes under microscope were recorded. The transplanted tumor tissue was immunohistochemically stained with the EnVisiion two-step method, and the tumor formation rate of the transplanted tumor was judged according to the proportion of positive cells in the visual field. The polymerase chain reaction (PCR) method was used to detect the expression of human-specific Alu sequence in mice tumor tissue.Results:After inoculation with tumor cells, the mice in the cell control group and the microcarrier control group did not die and did not form tumors; the mice in the cell-microcarrier complex group had palpable subcutaneous tumors in the right axillary subcutaneously on the 5th to 7th days after inoculation, and tumor formation rate is 67% (10/15), and the tumor volume can reach about 500 mm 3 2 to 3 weeks after vaccination. The immunohistochemistry results showed that CK20, CDX-2 and carcinoembryonic antigen were all positively expressed. The PCR results showed that the expression of human-specific Alu sequence can be detected in the transplanted tumor tissue of tumor-bearing mice. Conclusion:Human primary colon cancer cells used microcarrier 6 as a carrier to form tumors in normal immunized mice, and successfully established a new model of human colon cancer transplantation tumor in normal immune mice.

The treatment of articular cartilage (AC) injury caused by various reasons is still a major clinical problem. The emergence of cartilage tissue engineering brings new hope for the treatment of AC injury. In general, AC tissue engineering can be divided into two categories, including cell-based tissue engineering and cell-free tissue engineering. Although cell-based tissue engineering can repair cartilage damage to a certain extent, existing therapeutic strategies still suffer from limited cell sources, high costs, risk of disease transmission, and complex procedures. However, the cell-free tissue engineering avoids these shortcomings and brings hope for in-situ AC regeneration. Non-cellular tissue engineering is mainly used to recruit endogenous stem cells/progenitor cells (SCPCs) to reach the site of cartilage injury, and provide a suitable regenerative microenvironment to promote cell proliferation and chondrogenic differentiation, then the maturation of new cartilage tissue was promoted. Therefore, it is also called as cell-homing in situ tissue engineering. Successful recruitment of endogenous SCPCs is the first step in in-situ cartilage tissue engineering. This review aims to introduce chemokine response of cartilage injury, systematically summarize traditional chemoattractant (chemokines and growth factors etc.) and emerging chemoattractant (functional peptides, exosomes and nucleic acid adapters etc.), evaluate the combination mode between chemoattractant and delivery devices, discuss the prospects and challenges of chemoattractant-mediated in situ tissue engineering and provide theoretical basis for the design of endogenous SCPCs homing-based in situ tissue engineering.

Objective: To evaluate the anti-tumor activity of mouse multi-subtype heat shock protein/peptide (mHSP/P) vaccine in combination with a programmed death ligand 1 (PD-L1) inhibitor in mouse sarcoma. Methods: Immunohistochemical staining and en-zyme-linked immunosorbent assay (Elisa) was used to quantitatively identify the expression of heat shock proteins (HSP70, HSP90, Grp94) in the sarcoma cell line MCA207. From the protein suspension prepared, mHSP/P and Grp94/peptide (Grp94/P) sarcoma vac-cines were isolated using chromatography and were identified by Western blot (WB). Flow cytometry was used to determine their cy-totoxic effects. The levels of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) produced upon mHSP/P and Grp94/P stimulation were measured by Elisa. The effect of sarcoma vaccines on the growth and survival of sarcoma was evaluated in mice. The expression of PD-L1 on the surface of MCA207 sarcoma cells was evaluated by immunofluorescent staining. The effect of IFN-γ treatment on the expression of PD-L1 was determined by WB. Animal experiments explored the effects of PD-L1 inhibitor in combination with mHSP/P treatment on tumors. Results: Tumor tissue carries a variety of HSP subtypes (HSP70, HSP90, Grp94). We successfully isolated sarco-ma tissue-derived mHSP/P and Grp94/P tumor vaccines, which were identified by WB; flow cytometry analysis demonstrated their cy-totoxicity. The levels of IFN-γ and TNF-α cytokines upon mHSP/P stimulation were significantly higher than that observed upon Grp94/P stimulation (P<0.05). The expression of PD-L1 on the surface of sarcoma cells increased with IFN-γ treatment. Animal experiments demonstrated that PD-L1 inhibitor in combination with mHSP/P significantly increased the immune response against tumor (P<0.05). Conclusions: Tumor-derived mHSP/P and Grp94/P can be used as tumor vaccines in animal models. The mHSP/P can elicit a stronger anti-tumor immune response than Grp94/P. IFN-γ stimulates the expression of PD-L1 in sarcoma cells, which results in immune eva-sion. The PD-L1 inhibitor in combination with mHSP/P increased the anti-tumor effect in the tumor microenvironment.

BACKGROUND:Accumulative evidence supports that co-culture technology can be applied to construct the tissue-engineered cartilage with excellent biological characters. OBJECTIVE:To elaborate the co-culture concept and conclude and analyze seed cell sources, cel mixed ratio, spatial y-defined co-culture models and biomaterials in co-culture systems to conclude and analyze the biological characters of tissue-engineered cartilage, and to prospect progression of co-culture systems in cartilage tissue engineering. METHODS:The first author retrieved the databases of PubMed, Web of Science, and CNKI for relative papers published from January 1976 to May 2016 using the keywords ofco-culture, co-culture systems;articular cartilage, chondrocytes, mesenchymal stem cells;tissue engineering, articular cartilage tissue engineeringin English and Chinese, respectively. Finally 60 literatures were included in result analysis, including 1 Chinese and 59 English articles. RESULTS AND CONCLUSION:Co-culture technology emphasizes the role of microenvironment in terms of various physical, chemical and biological factors in the cell processing. In cartilage tissue engineering, co-culture systems contribute to maintain the viability and natural cell phenotype of chondrocytes and induce cartilage differentiation of mesenchymal stem cells. In addition, co-culture technology provides a novel way for cartilage tissue engineering to overcome the shortage of chondrocytes and repair injury to the cartilage-subchondral bone. However, the mechanisms of cell-cell interaction in co-culture systems still need to be explored in depth, so as to optimize the co-culturing conditions and construct perfect tissue-engineered cartilage.