Theoretical study of the structural and thermodynamic properties of U-He compounds under high pressure.

Uranium is considered as a very important nuclear energy material because of the huge amount of energy it releases. As the main product of the spontaneous decay of uranium, it is difficult for helium to react with uranium because of its chemical inertness. Therefore, bubbles will be formed inside uranium, which could greatly reduce the performance of uranium or cause safety problems. Additionally, nuclear materials are usually operated in an environment of high-temperature and high-pressure, so it is necessary to figure out the exact state of helium inside uranium under extreme conditions. Here, we explored the structural stability of the U-He system under high pressure and high temperature by using density functional theory calculations. Two metastable phases are found between 50 and 400 GPa: U4He with space group Fmmm and U6He with space group P1̄. Both are metallic and adopt layered structures. Electron localization function calculation combined with charge density difference analysis indicates that there are covalent bonds between U and U atoms in both Fmmm-U4He and P1̄-U6He. Regarding the elastic modulus of α-U, the addition of helium has certain influence on the mechanical properties of uranium. Besides, first-principles molecular dynamics simulations were carried out to study the dynamical behavior of Fmmm-U4He and P1̄-U6He at high-temperature. It was found that Fmmm-U4He and P1̄-U6He undergo one-dimensional superionic phase transitions at 150 GPa. Our study revealed the exotic structure of U-He compounds beyond the formation of bubbles under high-pressure and high-temperature, which might be relevant to the performance and safety issues of nuclear materials under extreme conditions.

Microbiome Resilience and Health Implications for People in Half-Year Travel.

Travel entail change in geography and diet, both of which are known as determinant factors in shaping the human gut microbiome. Additionally, altered gut microbiome modulates immunity, bringing about health implications in humans. To explore the effects of the mid-term travel on the gut microbiome, we generated 16S rRNA gene and metagenomic sequencing data from longitudinal samples collected over six months. We monitored dynamic trajectories of the gut microbiome variation of a Chinese volunteer team (VT) in their whole journey to Trinidad and Tobago (TAT). We found gut microbiome resilience that VT's gut microbial compositions gradually transformed to the local TAT's enterotypes during their six-month stay in TAT, and then reverted to their original enterotypes after VT's return to Beijing in one month. Moreover, we identified driven species in this bi-directional plasticity that could play a role in immunity modulation, as exemplified by Bacteroides dorei that attenuated atherosclerotic lesion formation and effectively suppressed proinflammatory immune response. Another driven species P. copri could play a crucial role in rheumatoid arthritis pathogenesis, a chronic autoimmune disease. Carbohydrate-active enzymes are often implicated in immune and host-pathogen interactions, of which glycoside hydrolases were found decreased but glycosyltransferases and carbohydrate esterases increased during the travel; these functions were then restored after VT' returning to Beijing. Furthermore, we discovered these microbial changes and restoration were mediated by VT people's dietary changes. These findings indicate that half-year travel leads to change in enterotype and functional patterns, exerting effects on human health. Microbial intervention by dietary guidance in half-year travel would be conducive to immunity modulation for maintaining health.

Deep learning model based on urban multi-source data for predicting heavy metals (Cu, Zn, Ni, Cr) in industrial sewer networks.

The high concentrations of heavy metals in municipal industrial sewer networks will seriously impact the microorganisms of the activated sludge in the wastewater treatment plant (WWTP), thus deteriorating the effluent quality and destroying the stability of sewage treatment. Therefore, timely prediction and early warning of heavy metal concentrations in industrial sewer networks is crucial. However, due to the complex sources of heavy metals in industrial sewer networks, traditional physical modeling and linear methods cannot establish an accurate prediction model. Herein, we developed a Gated Recurrent Unit (GRU) neural network model based on a deep learning algorithm for predicting the concentrations of heavy metals in industrial sewer networks. To train the GRU model, we used low-cost and easy-to-obtain urban multi-source data, including socio-environmental indicator data, air environmental indicator data, water quantity indicator data, and easily measurable water quality indicator data. The model was applied to predict the concentrations of heavy metals (Cu, Zn, Ni, and Cr) in the sewer networks of an industrial area in southern China. The results are compared with the commonly used Artificial Neural Network (ANN) model. In this study, it was shown that the GRU had better prediction performance for Cu, Zn, Ni, and Cr concentrations, with the average R2 significantly increased by 12.35%, 11.94%, 9.21%, and 8.13%, respectively, compared to ANN predictions. The sensitivity analysis based on Shapley (SHAP) values revealed that conductivity (σ), temperature (T), pH, and sewage flow (Flow) contributed significantly to the prediction results of the model. Furthermore, the three input variables including air pressure (AP), land area (A), and population (Pop.) were removed without affecting the prediction performance of the model, which maximized the modeling efficiency and reduced the operational cost. This study provides an economical and feasible technical method for early warning of abnormal heavy metal concentrations in urban industrial sewer networks.

Role of MK2 signaling pathway mediating microglia/macrophages polarization in chronic compression injury of cervical spinal cord.

BACKGROUND: The role of inflammatory factors in the chronic compression injury of cervical spinal cord has drawn more attenion recently, however, the mechanism of which is still unclear. In this study, microglia/ macrophages polarization in the inflammatory responses to the injury and its regulation by MK2 signaling pathway have been investigated. METHODS: twy/twy mice at the age of 6-24 weeks were used in the animal model for the chronic compression of cervical spinal cord. ICR (Institute of Cancer Research) mice were used as the control group. MK2 inhibitor (PF-3644022, 30 mg/kg) was administrated intragastrically to twy/twy mice from weeks 20 to 24. The compression of cervical spinal cord was identified by CT/MRI. The cervical spinal cord between C2 and C3 of vertebral segments were investigated by Western blot and Real-time PCR. The animal behaviors were evaluated by BMS score. RESULTS: Western blot and Real-time PCR showed that the expressions of iNOS and Arg-1 in the compressed spinal cord of twy/twy mice were significantly higher than those of the control group. After treatment with PF-3644022, the expression of Arg1 was increased while that of iNOS decreased. Realtime PCR revealed the increased expressions of inflammation related factors (such as IL-1ß, NF-κB, TNF-α, MK2) and pro-apoptotic gene (Bax) except the decreased expression of anti-apoptotic gene (Bcl-2). Nevertheless, such increases were vanished after treatment of PF-3644022 except an increased expression of Bcl-2. The BMS score showed a reduced motor function of the twy/twy mice. The motor function was enhanced again with the treatment of PF-3644022. CONCLUSIONS: Microglia/macrophages polarization may be involved in the inflammatory response to the chronic compression of cervical spinal cord. It can be regulated by the MK2 signaling pathway. Therefore, it is possible to relieve the chronic compression of cervical spinal cord by regulating microglia/macrophages polarization through MK2 signaling pathway.

Generating Cocrystal Polymorphs with Information Entropy Driven by Molecular Dynamics-Based Enhanced Sampling.

Predicting structures of organic molecular cocrystals is a challenging task when considering the immense number of possible intermolecular orientations. Use of the Shannon information entropy, constructed from an intermolecular orientational spatial distribution function, to drive a search for crystal structures via enhanced molecular dynamics can be an efficient way to map out a landscape of putative polymorphs. Here, the Shannon entropy is used to generate a set of collective variables for differentiating polymorphs of a 1:1 cocrystal of resorcinol and urea. We show that driven adiabatic free energy dynamics, a particular enhanced-sampling approach, combined with these entropy variables, can transform the stable phase into alternate polymorphs. Density functional theory calculations confirm that a structure obtained from the enhanced molecular dynamics is stable at pressures above 1 GPa. We thus show that enhanced sampling should be considered an integral component of crystal structure searching protocols for systems with multiple independent molecules.

Synthesis of cerium oxide nanoparticles loaded on chitosan for enhanced auto-catalytic regenerative ability and biocompatibility for the spinal cord injury repair.

Biomedical applications like spinal cord injury repair; anticancer requires functional platforms and specific properties like antioxidant, autocatalytic and biocompatibility. This work demonstrated the synthesis of CeO2 nanoparticles which is shown to have promising applications in various fields exclusively biomedical field like scavenging of reactive oxygen species which is mainly responsible for carcinogenic effects. CeO2 nanoparticles were synthesized using the biocompatible ionic liquid followed by their loading with biopolymeric chitosan which was obtained by the deacetylation processing of chitin arrived from the shells of crab. The prepared CeO2 samples were characterized using FT-IR, XRD, SEM and TEM studies. FT-IR studies illustrated the formation of CeO2 nanoparticles and their loading with chitosan. A morphological study reveals the CeO2 nanoparticles are in the nano-size range of 15-20 nm with the uniformly distributed spherical shaped structure. Exploited CeO2 nanoparticles with the biocompatible property may improve outcomes profound with the pharmaceutical applications. The results of UV-visible spectrum were established that addition of cerium oxide nanoparticles into the chitosan polymer has great ability of catalytic oxidative recovery from the spectrum shifting from lower to higher and higher to lower oxidation states. This specifies that cerium oxide nanoparticles loaded material has been provided enhanced auto-regenerative and neuroprotective activity in spinal card regeneration.

Powder diffraction and crystal structure prediction identify four new coumarin polymorphs.

Coumarin, a simple, commodity chemical isolated from beans in 1820, has, to date, only yielded one solid state structure. Here, we report a rich polymorphism of coumarin grown from the melt. Four new metastable forms were identified and their crystal structures were solved using a combination of computational crystal structure prediction algorithms and X-ray powder diffraction. With five crystal structures, coumarin has become one of the few rigid molecules showing extensive polymorphism at ambient conditions. We demonstrate the crucial role of advanced electronic structure calculations including many-body dispersion effects for accurate ranking of the stability of coumarin polymorphs and the need to account for anharmonic vibrational contributions to their free energy. As such, coumarin is a model system for studying weak intermolecular interactions, crystallization mechanisms, and kinetic effects.

Intravertebral clefts in osteoporotic compression fractures of the spine: incidence, characteristics, and therapeutic efficacy.

OBJECTIVE: To determine the pathogenesis and characteristics and to assess the long-term effectiveness of polymethylmethacry late (PMMA) vertebroplasty treatment in patients with intravertebral cleft (IVC) in osteoporotic compression fractures. METHODS: A retrospective analysis of radiological and clinical parameters was performed on 388 patients who underwent percutaneous vertebroplasty or kyphoplasty to treat osteoporotic compression fractures from January 2010 to October 2012. IVC sign was observed in the MRI of 47 patients. Postoperative follow-ups were conducted for at least 2 years after surgery. RESULTS: IVC incidence was associated with older age and lower bone mineral density. Other baseline measurements, such as preoperative visual analogue scale and Oswestry Disability Index (ODI), showed no significant difference between IVC and non-IVC fracture patients. Vertebral height and kyphotic angle were corrected after percutaneous vertebroplasty or kyphoplasty with no significant difference in outcome between the two procedures. Restored vertebral height collapsed and the kyphotic angle became aggravated during the 2 years following surgery in patients with IVC. Similarly, initial improvements in visual analogue scale and ODI decreased over time. Non-IVC patients' had a slight recurrence of compression and kyphosis that began to normalize after 1 year. Visual analogue scale and ODI at 2 years' post-surgery was also significantly lower in non-IVC than IVC patients. CONCLUSION: Polymethylmethacrylate vertebroplasty treatment of osteoporotic compression fractures is initially effective for patients with signs of IVC, but compression and kyphosis gradually reoccur. Therefore, we strongly recommend strict observation and follow-up after vertebroplasty.

Cauda equina syndrome: an uncommon symptom of aortic diseases.

BACKGROUND: In order to help diagnose and deal with the fetal aortic diseases in time, we retrospectively reviewed 8 patients who presented with cauda equina syndrome (CES) but actually suffered from low spinal nerve ischemia due to aortic diseases. MATERIAL AND METHODS: 8 patients were initially diagnosed as CES. 7 patients were confirmed with aortic diseases. 1 patient was confirmed with aortic saddle embolism post emergent laminectomy. Relief of CES symptoms was evaluated during preoperation and follow-up period. RESULTS: 1 patient was diagnosed as aortic dissection and 5 patients as AAA. These 6 patients underwent endovascular aortic repair (EVAR). The CES was relieved in 5-10 d post procedure. The 7th patient was diagnosed with acute abdominal aortic occlusion and then underwent catheter directed thrombolysis with recombinant tissue plasminogen activator (rTPA) for 20 h and CES disappeared. The JOA scores of the 7 patients were recovered from preoperative 15.14±1.21 to 21.00±2.16 within 5-10 d (P<0.01), and evaluated to be 24.12±1.34, 25.88±1.21 and 26.29±1.11 at 3 m-, 6 m- and 12 m-follow-up point, respectively. The 8th patient was initially diagnosed as lumbar spinal stenosis and lumbar disc herniation. The patient underwent emergent vertebral canal decompression and presented with serious CES symptoms. CTA confirmed that the patient had been suffered from aortic saddle embolism (ASE). CONCLUSION: CES caused by abdominal aortic diseases is a special event with fetal consequences if it is not recognized and treated promptly. Orthopedists and neurosurgeons should pay attentions particularly to this issue to preserve the cauda equina functions to their maximums.

TGF-ß1 related inflammation in the posterior longitudinal ligament of cervical spondylotic myelopathy patients.

AIM: This study aimed to elucidate the pathogenesis of posterior longitudinal ligament (PLL) hypertrophy. METHODS: Cervical PLL specimens were collected from CSM patients during surgery (n = 30) and during routine autopsy (n = 14), and processed for histological examination (HE staining and Masson's Trichrome staining) and IHC (CD3, CD68, CD31, TGF-ß1 and collagen II). In addition, the mRNA expression of collagen I was detected in cervical PLL specimens from 16 CSM patients (n = 16) and from routine autopsy (n = 16) by RT-PCR. RESULTS: Obvious fibrosis, cartilage metaplasia and calcification were found in the cervical PLL of CSM patients. In the degenerated PLL, CD68(+) macrophages were frequently identified, CD3(+) T lymphocytes were occasionally found, and many newly generated small vessels were also present. In the degenerated PLL, of the number of TGF-ß1 positive cells increased markedly when compared with control group. IHC indicated TGF-ß1 was secreted by macrophages. RT-PCR showed a significantly lower mRNA expression of collagen I in the PLL of CSM patients as compared to control group. CONCLUSIONS: Macrophages are the major type of inflammatory cells involved in the cervical PLL degeneration, and TGF-ß1 is related to the cervical PLL degeneration. TGF-ß1 is mainly secreted by macrophages. Anti-inflammation may serve as an alternative non-surgical treatment and prophylactic strategy for PLL degeneration.

Evaluations of computed tomography images and lumbar specimens in mimic operations of transverse rotation laminoplasty for lumbar spinal stenosis.

BACKGROUND: Laminectomy is a major method to treat lumbar spinal stenosis (LSS), but it has lots of flaws such as scar tissue can form around the dura again or spinal instability. This study aimed to investigate the feasibility of transverse rotation laminoplasty (TRL) in the treatment of LSS. METHODS: The mimic operations of TRL were performed both in the computerized image processing and on the lumbar specimen. Computed tomography (CT) images were either collected from 80 clinical patients with complaints of lumbago or obtained from 40 sets of lumbar specimens after rebuild of spinal canals. In the CT image processing the heights of the spinous process and laminae at L3-L5 were measured. The total length of the spinous process plus one side laminae after the operation was evaluated and compared with the length of inner margin of pedical before the operation. The areas of the vertebral canal were examined before and after the operation. RESULTS: In the CT images, the height of spinous process of L3, L4 and L5 was 24.74 ± 3.45, 22.68 ± 5.96 and 21.54 ± 4.12 mm respectively, and that of laminae was 23.66 ± 2.32, 22.68 ± 5.36 and 20.99 ± 3.67 mm respectively (P > 0.05). Distance of inner border of pedical of L3, L4 and L5 was 23.01 ± 6.59, 24.65 ± 5.54 and 26.03 ± 7.34 mm respectively, and length of spinous process with laminae of those was 29.76 ± 4.91, 29.31 ± 6.43 and 32.53 ± 5.76 mm respectively (P < 0.05). Preoperative area of spinal canals of L3, L4 and L5 was 299.81 ± 10.09, 297.66 ± 9.54 and 308.22 ± 10.04 mm2 respectively, and postoperative area was 480.01 ± 9.33, 487.32 ± 8.65 and 501.03 ± 9.12 mm2 respectively (P < 0.05). In the human lumbar vertebrae specimen, the data similar to the former. CONCLUSIONS: The excised canal posterior was covered, and the lumbar canals enlarged by TRL. The TRL provided a new alternative in the treatment of LSS.

Role of MK2 signaling pathway in the chronic compression of cervical spinal cord.

OBJECTIVE: In this study, chronic compression of cervical spinal cord was introduced into twy/twy mice and the role of MK2 signaling pathway was investigated in this disease. METHODS: twy/twy mice aged 6-24 weeks were used and the inflammatory response in the cervical spinal cord was observed. The Institute of Cancer Research (ICR) mice were used as controls. MK2 inhibitor (PF-3644022, 30 mg/kg) was administered intragastrically to twy/twy mice. The motor behavior was firstly observed in these three groups by Catwalk gait analysis. And the cervical spinal cord between C2 and C3 of vertebral segments was analyzed by MRI and Western blot assay. RESULTS: The stride length of paws and interlimb coordination reduced in twy/twy mice. However, at 4 weeks after PF-3644022 treatment, a marked improvement was observed in the motor function. The expressions of inflammation related factors (such as IL-1ß, NF-κB, TNF-α, MK2 and p-MK2) and apoptosis related proteins (such as cleaved caspase-8 and bax/bcl-2) in the spinal cord of twy/twy mice significantly increased as compared to controls, but 4-week treatment with PF-3644022 markedly reduced the expressions of these factors and apoptotic proteins in the cervical spinal cord. CONCLUSION: MK2 signaling pathway is involved in the chronic compression induced inflammation of the cervical spinal cord. Thus, to inhibit the MK2 pathway may used to improve the outcome and prevent the deterioration of neurological dysfunction.

Quantitative analysis of cyclooxygenase 2 in the posterior longitudinal ligament of cervical spondylotic myelopathy.

BACKGROUND: Cervical spondylotic myelopathy (CSM), in part, results from degeneration of the posterior longitudinal ligament (PLL), which mechanically compresses the spinal cord. Much research was done on the ossification of PLL, but not concerning the non-ossifying degeneration of cervical PLL. The degeneration of cervical PLL may be related to inflammation. The aim of this study was to elucidate the pathological features of the PLL and the role of cyclooxygenase 2 (COX-2) in the degeneration of the PLL in CSM. METHODS: A total of 23 PLL specimens were collected during surgery from patients with CSM for the histological and immunohistochemical (type II collagen and Ki-67) study. For the control group 14 cervical PLL autopsy specimens were investigated in the same manner. mRNA expression of COX-2 was quantitatively measured by real-time reverse transcription-polymerase chain reaction (RT-PCR) from 18 PLL specimens of patients with CSM and 18 PLL specimens of autopsy cases. Immunohistochemistry was used to evaluate the cellular location of COX-2 in PLL. RESULTS: A distinct amount of fibrotic area, chondrometaplastic tissue and calcification were found in the PLL of the patient group, compared with the control group. Type II collagen was apparent around chondrometaplastic cells. Ki-67 positive reaction was less than 5%. A COX-2 positive reaction was found in 9 of the patient specimens (39.1%) in which the COX-2 was released from vascular endothelial cells in the PLL. However, such reactions were not found in the control group. Real-time PCR showed that the mRNA expression level of COX-2 in the patient group was significantly higher than that in the control group (P < 0.01). CONCLUSIONS: Chondrometaplastic tissue producing type II collagen was identified as the most predominant pathological feature in the degenerative PLL. The higher expression of COX-2 might be related to degeneration of the PLL in CSM.

In vitro cartilage tissue engineering using cancellous bone matrix gelatin as a biodegradable scaffold.

In this study, we constructed tissue-engineered cartilage using allogeneic cancellous bone matrix gelatin (BMG) as a scaffold. Allogeneic BMG was prepared by sequential defatting, demineralization and denaturation. Isolated rabbit chondrocytes were seeded onto allogeneic cancellous BMG, and cell-BMG constructs were harvested after 1, 3 and 6 weeks for evaluation by hematoxylin and eosin staining for overall morphology, toluidine blue for extracellular matrix (ECM) proteoglycans, immunohistochemical staining for collagen type II and a transmission electron microscope for examining cellular microstructure on BMG. The prepared BMG was highly porous with mechanical strength adjustable by duration of demineralization and was easily trimmed for tissue repair. Cancellous BMG showed favorable porosity for cell habitation and metabolism material exchange with larger pore sizes (100-500 microm) than in cortical BMG (5-15 microm), allowing cell penetration. Cancellous BMG also showed good biocompatibility, which supported chondrocyte proliferation and sustained their differentiated phenotype in culture for up to 6 weeks. Rich and evenly distributed cartilage ECM proteoglycans and collagen type II were observed around chondrocytes on the surface and inside the pores throughout the cancellous BMG. Considering the large supply of banked bone allografts and relatively convenient preparation, our study suggests that allogeneic cancellous BMG is a promising scaffold for cartilage tissue engineering.

[Collagen spatial distribution in rapid atrial pacing dogs with or without superior vena cava and aortic root fat pad].

OBJECTIVE: To observe the collagen spatial distribution, collagen volume fraction (CVF) and Cx40, Cx43mRNA expressions in rapid atrial pacing dogs post vagal denervation by removing fat pad located between the medial superior vena cava and aortic root (SVC-Ao fat pad). METHODS: Twenty-four dogs were randomly divided into unpaced sham operation group (S group, n = 8), Keeping SVC-Ao fat pad group (K group, n = 8) and Removing SVC-Ao fat pad group (R group, SVC-Ao fat pad was removed by surgical excision before pacing, n = 8). K and R groups were paced for six weeks. Six weeks later, all dogs were sacrificed, left atrium (LA), right atrium (RA), left atrial appendage (LAA), right atrial appendage (RAA) and atrial septum (AS) were collected and stained with HE or Masson Trichrome or frozen in liquid nitrogen for quantifying the expression of Cx40, Cx43 mRNA by Real-time quantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR). RESULTS: Spatial distribution of collagen fibers as well as CVF between S and R group were similar (all P > 0.05). CVF was significantly higher in K group compared to R group, especially at LAA and AS locations (all P < 0.05). Cx40mRNA expression in K group was significantly decreased in LA, RA, and significantly increased in LAA, RAA and AS compared those in S group (all P < 0.05), significantly lower in LA and RA while significantly higher in LAA and RAA compared to R group (all P < 0.05). Cx43mRNA expression in K group was significantly reduced in LA, RA, LAA and RAA while significantly increased in AS compared to S group (all P < 0.05), significantly higher in LA, RA, RAA and AS while significantly lower in LAA compared to R group. CONCLUSION: Pacing induced collagen remodeling and modulation on Cx40mRNA and Cx43 mRNA expressions could be partially attenuated by removing SVC-Ao fat pad suggesting vagal denervation plays a key role in the initiation and preservation of atrial fibrillation.

[Construction of tissue-engineered cartilage by seeding chondrocytes on allogeneic cancellous bone matrix gelatin].

OBJECTIVE: To evaluate the use of cancellous bone matrix gelatin (BMG) combined with chondrocytes in constructing tissue-engineered cartilage by observing the growth, proliferation and differentiation of chondrocytes on allogeneic cancellous BMG. METHODS: The articular chondrocytes isolated from a 1-month-old rabbit were multiplied to a monolayer and seeded onto cancellous BMG to construct tissue-engineered cartilage in vitro during a period of 6 weeks. Samples were taken from the construct after 1, 2, 4, and 6 weeks of culture and evaluated by histology, immunohistochemistry and transmission electron microscopy (TEM). RESULTS: The chondrocytes excreted matrix proteoglycan and collagen on cancellous BMG. With the prolongation of the culture time, the cells proliferated in the construct and the cells in the lacunae increased. Numerous chondrocytes were present the central region of the cancellous BMG and surrounded by extracellular matrix. By 6 weeks of culture, the BMG was covered with 15-20 layers of chondrocytes and cartilaginous tissue occurred in the pores throughout the cancellous BMG. Immunohistochemical staining showed rich and evenly distributed type II collagen around the chondrocytes, and TEM revealed an ultrastructure of the chondrocyte similar to that of native chondroctyes, with abundant extracellular matrix produced around the cells. CONCLUSION: Tissue-engineered cartilage can be constructed in vitro using allogeneic cancellous BMG combined with chondrocytes. Allogeneic cancellous BMG serves as a good scaffold material for tissue-engineered cartilage to promote the growth and proliferation of the seeded chondrocytes and allows maintenance of the differentiation phenotype of the cells.

Repairing articular cartilage defects with tissue-engineering cartilage in rabbits.

OBJECTIVE: To investigate the effect of cancellous bone matrix gelatin (BMG) engineered with allogeneic chondrocytes in repairing articular cartilage defects in rabbits. METHODS: Chondrocytes were seeded onto three-dimensional cancellous BMG and cultured in vitro for 12 days to prepare BMG-chondrocyte complexes. Under anesthesia with 2.5% pentobarbital sodium (1 ml/kg body weight), articular cartilage defects were made on the right knee joints of 38 healthy New Zealand white rabbits (regardless of sex, aged 4-5 months and weighing 2.5-3 kg) and the defects were then treated with 2.5% trypsin. Then BMG-chondrocyte complex (Group A, n=18), BMG (Group B, n=10), and nothing (Group C, n=10) were implanted into the cartilage defects, respectively. The repairing effects were assessed by macroscopic, histologic, transmission electron microscopic (TEM) observation, immunohistochemical examination and in situ hybridization detection, respectively, at 2, 4, 8, 12 and 24 weeks after operation. RESULTS: Cancellous BMG was degraded within 8 weeks after operation. In Group A, lymphocyte infiltration was observed around the graft. At 24 weeks after operation, the cartilage defects were repaired by cartilage tissues and the articular cartilage and subchondral bone were soundly healed. Proteoglycan and type II collagen were detected in the matrix of the repaired tissues by Safranin-O staining and immunohistochemical staining, respectively. In situ hybridization proved gene expression of type II collagen in the cytoplasm of chondrocytes in the repaired tissues. TEM observation showed that chondrocytes and cartilage matrix in repaired tissues were almost same as those in the normal articular cartilage. In Group B, the defects were repaired by cartilage-fibrous tissues. In Group C, the defects were repaired only by fibrous tissues. CONCLUSIONS: Cancellous BMG can be regarded as the natural cell scaffolds for cartilage tissue engineering. Articular cartilage defects can be repaired by cancellous BMG engineered with allogeneic chondrocytes. The nature of repaired tissues is closest to the normal cartilage. Local administration of trypsin can promote the adherence of repaired tissues to host tissues. Transplantation of allogeneic chondrocytes has immunogenicity, but the immune reaction is weak.