Biomimetic natural biomaterials for tissue engineering and regenerative medicine: new biosynthesis methods, recent advances, and emerging applications.

Biomimetic materials have emerged as attractive and competitive alternatives for tissue engineering (TE) and regenerative medicine. In contrast to conventional biomaterials or synthetic materials, biomimetic scaffolds based on natural biomaterial can offer cells a broad spectrum of biochemical and biophysical cues that mimic the in vivo extracellular matrix (ECM). Additionally, such materials have mechanical adaptability, microstructure interconnectivity, and inherent bioactivity, making them ideal for the design of living implants for specific applications in TE and regenerative medicine. This paper provides an overview for recent progress of biomimetic natural biomaterials (BNBMs), including advances in their preparation, functionality, potential applications and future challenges. We highlight recent advances in the fabrication of BNBMs and outline general strategies for functionalizing and tailoring the BNBMs with various biological and physicochemical characteristics of native ECM. Moreover, we offer an overview of recent key advances in the functionalization and applications of versatile BNBMs for TE applications. Finally, we conclude by offering our perspective on open challenges and future developments in this rapidly-evolving field.

Mitochondria Targeted O2 Economizer to Alleviate Tumor Hypoxia for Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) often suffers from the exacerbated tumor hypoxia and the heterogeneous distribution of photosensitizers, leading to an inefficient ROS productivity and availability. In this work, a mitochondria targeted O2 economizer (designated as Mito-OxE) is developed to improve PDT efficiency by alleviating tumor hypoxia and enhancing the subcellular localization of photosensitizers. Specifically, the photosensitizer of protoporphyrin IX (PpIX) is modified with the hydrophilic polyethylene glycol and the lipophilic cation of triphenylphosphine (TPP) to fabricate the biocompatible mitochondria targeted photosensitizers (designated as Mito-PSs). And Mito-OxE is prepared by using Mito-PSs to load the mitochondrial oxidative phosphorylation inhibitors of atovaquone (ATO). Benefiting from the targeting capability of TPP, Mito-OxE can selectively accumulate in mitochondria after cellular uptake. Subsequently, the mitochondrial respiration would be suppressed to with the participation of ATO, resulting in a local hypoxia mitigation for enhanced PDT. Compared with Mito-PSs, Mito-OxE maximizes the therapeutic effect against hypoxic tumors under light irradiation. This design of mitochondria targeted O2 economizer would advance the development of targeted drug delivery system for effective PDT regardless of hypoxic microenvironment.

Self-Delivery Nanomedicine for O2-Economized Photodynamic Tumor Therapy.

Tumor hypoxia is the Achilles heel of oxygen-dependent photodynamic therapy (PDT), and tremendous challenges are confronted to reverse the tumor hypoxia. In this work, an oxidative phosphorylation inhibitor of atovaquone (ATO) and a photosensitizer of chlorine e6 (Ce6)-based self-delivery nanomedicine (designated as ACSN) were prepared via π-π stacking and hydrophobic interaction for O2-economized PDT against hypoxic tumors. Specifically, carrier-free ACSN exhibited an extremely high drug loading rate and avoided the excipient-induced systemic toxicity. Moreover, ACSN not only dramatically improved the solubility and stability of ATO and Ce6 but also enhanced the cellular internalization and intratumoral permeability. Abundant investigations confirmed that ACSN effectively suppressed the oxygen consumption to reverse the tumor hypoxia by inhibiting mitochondrial respiration. Benefiting from the synergistic mechanism, an enhanced PDT effect of ACSN was observed on the inhibition of tumor growth. This self-delivery system for oxygen-economized PDT might be a potential appealing clinical strategy for tumor eradication.

Self-Delivery Photodynamic Nanoinhibitors for Tumor Targeted Therapy and Metastasis Inhibition.

Simultaneous inhibitions of primary tumor growth and distant metastasis are very critical for cancer patients to improve their survival and cure rates. Although photodynamic therapy (PDT) shows great potential for primary tumor treatment, it often exacerbates hypoxia with a reduced therapeutic efficacy and subsequently contributes to carcinoma progression and metastatic dissemination. To solve these issues, self-delivery photodynamic nanoinhibitors (PNI) are developed for tumor targeted therapy and metastasis inhibition. PNI are composed of a carbonic anhydrase inhibitor (CAi), a hydrophilic poly(ethylene glycol) (PEG) linker, and a hydrophobic photosensitizer protoporphyrin IX (PpIX). Such self-delivery design of PNI avoids the premature release and heterogeneous distribution of CAi and PpIX to enhance the availability and synergism. Briefly, the CAi-based nanoinhibitors improve the selectivity of CAi for specific recognition and inhibition of tumor-associated isoform carbonic anhydrase (CA) IX, which would not only facilitate the targeted drug delivery of PNI but also regulate the hypoxia-induced signaling cascade and PDT resistance. Benefiting from the CA IX inhibition and targeted PDT, PNI exhibit a robust inhibitory effect on primary tumor growth and distant metastasis. This targeted self-delivery strategy sheds light on the photosensitizer-based molecular design to overcome the defect of traditional PDT.

Epigenetics-inspired photosensitizer modification for plasma membrane-targeted photodynamic tumor therapy.

In recent years, epigenetics has attracted great attentions in the field of biomedicine, which is used to denote the heritable changes in gene expression without any variation in DNA sequence, including DNA methylation, histone modification and so on. Inspired by it, a simple and versatile amino acids modification strategy is proposed in this paper to regulate the subcellular distribution of photosensitizer for plasma membrane targeted photodynamic therapy (PDT). Particularly, the plasma membrane anchoring ability and photo toxicity of the photosensitizer against different cell lines could be effectively manipulated at a single amino acid level. Systematic researches indicate that the number and variety of amino acids have a significant influence on the plasma membrane targeting effect of the photosensitizer. Furthermore, after self-assembling into nanoparticles, the obtained nano photosensitizers (NPs) also exhibit a good biocompatibility and plasma membrane targeting ability, which are conducive to enhancing the PDT therapeutic effect under light irradiation. Both in vitro and in vivo investigations confirm a robust tumor inhibition effect of NPs with a good biocompatibility. This epigenetics-inspired photosensitizer modification strategy would contribute to the development of structure-based drug design for tumor precision therapy.

Chimeric peptide engineered exosomes for dual-stage light guided plasma membrane and nucleus targeted photodynamic therapy.

Targeted delivery of the drug to its therapeutically active site with low immunogenicity and system toxicity is critical for optimal tumor therapy. In this paper, exosomes as naturally-derived nano-sized membrane vesicles are engineered by chimeric peptide for plasma membrane and nucleus targeted photosensitizer delivery and synergistic photodynamic therapy (PDT). Importantly, a dual-stage light strategy is adopted for precise PDT by selectively and sequentially destroying the plasma membrane and nucleus of tumor cells. Briefly, plasma membrane-targeted PDT of chimeric peptide engineered exosomes (ChiP-Exo) could directly disrupt the membrane integrity and cause cell death to some extent. More interestingly, the photochemical internalization (PCI) and lysosomal escape triggered by the first-stage light significantly improve the cytosolic delivery of ChiP-Exo, which could enhance its nuclear delivery due to the presence of nuclear localization signals (NLS) peptide. Upon the second-stage light irradiation, the intranuclear ChiP-Exo would activate reactive oxygen species (ROS) in situ to disrupt nuclei for robust and synergistic PDT. Based on exosomes, this dual-stage light guided subcellular dual-targeted PDT strategy exhibits a greatly enhanced therapeutic effect on the inhibition of tumor growth with minimized system toxicity, which also provides a new insight for the development of individualized biomedicine for precise tumor therapy.

A case report of diffuse pneumocephalus induced by sneezing after brain trauma.

Pneumocephalus is the presence of air in the cranial vault. The common etiologies of pneumocephalus are brain trauma and cranial surgery. We report a case of a 26-year-old man with brain trauma who developed diffuse pneumocephalus after sneezing. CT scan was performed on arrival, and the image showed subarachnoid hemorrhage without pneumocephalus. On the seventh day after a big sneeze brain CT scan was re-performed, which showed pneumocephalus. After another ten days of treatment, the patient was discharged without any symptoms.

Long-term intraperitoneal injection of lipopolysaccharide induces high expression of Id2 in the brain of mice.

Lipopolysaccharide (LPS) from gram negative bacteria plays an important role in the pathophysiology of neurodegenerative diseases. Many evidences showed that LPS-induced neuroinflammation is related to upregulation of NF-kappaB. Here, we report that long-term treatment of lower dosage LPS mainly causes upregulation of Id2 protein. As an inhibitor of cell differentiation, Id2 plays an import role in adult olfactory neurogenesis. However, Id2 protein in brain acts as two edges in a sword, persist over-expression of Id2 in brain can induce neurodamages and may be related to neurodegeneration.

[Expression of extracellular signal-regulated protein kinases in the subcutaneous fascia of rats and their changes after acupuncture].

OBJECTIVE: To observe the effect of acupuncture on the expression of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in the subcutaneous fascia of SD rats. METHODS: Eighteen SD rats were randomly divided into 6 groups (n=3) including 5 acupuncture groups and a control group. The rats in the 5 acupuncture groups received electro-acupuncture therapy in the regions of the inguinal groove, and at 0, 1, 6, 12, and 36 h after the last therapy, the superfacial fascia surrounding the acupuncture point (about 1.5 cm in diameter) were collected. The fascia tissues at the corresponding sites and at the acupoint Zusanli (ST36) were obtained from the control rats. The expression of ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in the tissues were detected by Western blotting. RESULTS: ERK1/2 and p-ERK1/2 expressions were detected in the tissues harvested from both the acupoint and the non-acupoint in the control rats with similar expression intensities. In the rats of each acupuncture group, ERK1/2 expression was significantly increased on the acupuncture side in comparison with the control side. CONCLUSION: The normal loose connective tissue may participate in tissue proliferation and differentiation possibly via phosphorylation of ERK. Acupuncture can promote the signal transduction pathway of ERK, which can be a possible mechanism for the effect of acupuncture in modulating the physiopathological conditions.

Low concentration of lipopolysaccharide acts on MC3T3-E1 osteoblasts and induces proliferation via the COX-2-independent NFkappaB pathway.

The translocations of lipopolysaccharide (LPS) from the gut and its effects on bone healing are usually of clinical interest during bone fracture. As already widely studied, Cyclooxygenase-2 (COX-2) is a key enzyme for prostaglandin E2 (PGE(2)) production, which induces the nuclear factor kappa B (NFkappaB) activation and is beneficial to fracture healing. In order to know their roles in skeletal regeneration, mouse MC3T3-E1 osteoblasts were treated with NFkappaB inhibitor BAY 11-7082 and sc791 (a selective COX-2 inhibitor), in the presence of LPS. Interestingly, LPS could induce osteoblasts proliferation through increasing NFkappaB activation and translocation. This induction was not related to COX-2 expression, suggesting that LPS-induced NFkappaB activation is independent of COX-2. It is possible that low concentration of LPS can act as a stimulating factor of the NFkappaB pathway in nonstimulated cells such as osteoblasts. COX-2 is not necessary for the NFkappaB pathway during LPS-induced proliferation of osteoblasts since sc791 had no effects on this induction. These studies provide insight into a potential mechanism by which LPS can affect bone tissue repair in the initial phase of inflammation.

Mitochondrial AIF protein involved in skeletal muscle regeneration.

The mitochondrial flavoprotein apoptosis-inducing factor (AIF) has proved to be either the main mediator of apoptosis or an anti-apoptotic factor via its putative oxidoreductase and peroxide scavenging activities. We report here that 100 muM hydrogen peroxide (H2O2) induced the proliferation of C2C12 myoblasts and over-expression of AIF simultaneously in vitro. Immunofluorescence showed that the over-expression of AIF was located in the cytoplasm. The immunopositive AIF was detected in nuclei 27 days after denervation of skeletal muscle, but in the cytoplasm it was detected 27 days after fiber-damaged skeletal muscle. AIF may be a factor involved in skeletal muscle regeneration.

[Distribution of neuronal nitric oxide synthase-immunopositive neurons in rat corpus striatum and their ultrastructures].

OBJECTIVE: To observe the distribution of neuronal nitric oxide synthase (nNOS)-immunopositive neurons in rat corpus striatum and their ultrastructural features. METHODS: Brain tissue specimens were obtained from normal SD rats, in which nNOS-immunopositive neurons were visualized by ABC immunocytochemistry and observed under immunoelectron microscope with pre-embedding staining. RESULTS: Under light microscope, nNOS-immunopositive neurons appeared brown with distinct profiles of the cell body and processes. These neurons, mostly medium-sized and small cells, were located mainly in the lateral region of the corpus striatum. Only a few immunopositive neurons were detected in the medial region of the corpus striatum. Immunohistochemistry and transmission electron microscopy identified the nNOS-immunopositive neurons as interneurons possessing large nuclei with small amount of cytoplasma. The immunopositive granules were visualized as black plaques, and the larger ones distributed mainly in the cell bodies, some with monolayer membrane encapsulation. The small granules did not have the encapsulation, scattering in perinuclear regions and under the cell membrane, but not in the cell body. The immunopositive granules were also found in the axons and dendrites, but not in the vesicles of the synapses. In addition, many immunopositive terminals were found close to the blood vessels. CONCLUSIONS: nNOS-immunopositive neurons in rat corpus striatum are mainly medium-sized and small cells as is typical of the interneurons. The immunopositive granules locate in the cytoplasma, axons and dendrites, and larger granules have membrane coating while small ones do not, possibly in relation to their functions.

[Construction of artificial nerve bridge by three-dimensional culture of interleukin-1beta- activated Schwann cells with human hair keratins].

OBJECTIVE: To culture interleukin-1beta (IL-1beta)-activated Schwann cells (SCs) with human hair keratins (HHKs) for artificial nerve bridge construction. METHODS: SCs purified by primary culture with or without IL-1beta activation were cultured with HHKs decorated by extracellular matrix (ECM), and the artificial nerve bridge was implanted into the defect of rat sciatic nerve. The morphology of the SCs cultured with HHKs was monitored by inverted microscope, scanning electron microscope and evaluated by immunocytochemical staining, and the expression of nerve growth factor (NGF) in the sciatic nerve was observed by in situ hybridization. RESULTS: Activated SCs showed better ability to adhere to the HHKs and grew well. The HHKs component in the artificial nerve bridge underwent degradation in the sciatic nerve defect after 3 to 4 weeks, and IL-1beta activation resulted in enhanced NGF expression in the SCs. CONCLUSION: The constructed artificial nerve bridge by three-dimensional culture of IL-1beta-activiated SCs with HHKs decorated by ECM promotes the repair of sciatic nerve defects and accelerates sciatic nerve regeneration.

A new mitochondrial RNA deletion fragment accelerated by oxidative stress in rat L6 cells.

RNA deletions may be easier to detect and more extensive than DNA deletions. Two large deletion fragments (1120 and 7811 bp) of mitochondrial RNA were observed in rat L6 muscle cells. At the site of the 1120 bp deletion, the remaining RNA fragment was re-linked by a short additional section (GGTATGAAGCT). These kinds of deletions were accelerated by oxidative stress and were not observed in mitochondrial DNA.

[Oxidative stress-induced differentiation of L6 myoblasts].

OBJECTIVE: To explore the relationship between the differentiation of L6 myoblasts and oxidative stress. METHODS: MTT assay was used to determine the viability of L6 myoblasts, from which the total RNA was extracted for amplification of the myogenin gene fragment by RT-PCR. H(2)O(2)-induced morphological changes of the cells were observed. RESULTS: The myoblasts treated with low concentration of reactive oxygen (50 micromol/L H(2)O(2)) for 1 h exhibited accelerated cell growth (P<0.05), and treatment with 50 and 150 micromol/L H(2)O(2) induced the gene expression of myogenin, a molecular marker for differentiation of myoblasts. Morphological study revealed myotube formation and accelerated differentiation of the myoblasts induced by H(2)O(2). CONCLUSION: The reactive oxygen may serve as the intracellular signal molecules to induce the growth and differentiation of the myoblasts.

[Construction of artificial nerve bridge by three-dimensional culture of Schwann cells with human hair keratins].

OBJECTIVE: To culture Schwann cells (SCs) and human hair keratins (HHKs) for artificial nerve bridge construction. METHODS: SCs were purified by primary culture and labeled with BrdU, which were then cultured with HHKs decorated by ECM. The artificial nerve bridge was implanted into the defect of sciatic nerve, beneath the skin, and in the skeletal muscles of SD rat, respectively. The morphology of the SCs cultured with HHKs was monitored by inverted microscope and evaluated by immunocytochemical staining. Growth of BrdU-labeled SCs in vivo was observed by immunocytochemical staining on paraffin sections. RESULTS: In vitro cultured SCs were capable of adhering to HHKs and grew well four weeks after implantation. The HHK component in the artificial nerve bridge underwent degradation in the defect of the sciatic nerve, beneath the skin, and in the skeletal muscles of SD rat, and SC survival and proliferation were verified. CONCLUSION: SCs can survive in three-dimensional culture with HHKs for construction of artificial nerve bridge to repair nerve defects.

[FK506 promotes apoptosis of macrophages activated by homogenate of allogenic nerve].

OBJECTIVE: To study the effect of FK506 in promoting apoptosis of peripheral blood-derived macrophages activated by homogenate of allogenic nerve tissues. METHODS: Homogenate of the allogenic nerve tissues was prepared using the sciatic nerve and injected in one-month-old SD rats, from which the macrophages activated by the homogenate were collected from the abdominal cavity and cultured in vitro. The cells were divided into 4 groups according to different concentrations of FK506 for treatment, namely 0 (group A, control group), 0.25 ng/ml (group B), 0.5 ng/ml (group C), and 1.0 ng/ml (group D). The cells of the 4 groups were inoculated into 96-well plate respectively for detecting the viability of the macrophages by MTT assay and for morphological evaluation of the cell apoptosis by transmission electron microscopy and fluorescence microscopy. RESULTS: The cells in groups B and C exhibited reduced viability and signs of apoptosis, and necrosis was observed in group D. Transmission electron microscopy and fluorescence microscopy identified early apoptotic changes and the presence of apoptotic body in the macrophages. The apoptotic rates of groups B and C were much higher than that in group A found by flow cytometry. CONCLUSION: FK506 can promote the apoptosis of macrophage activated by allogenic nerve homogenate and reduce macrophage-mediated immunological rejection of peripheral nerve allograft.

[In vitro study of formalin-fixed bone tissues for allogeneic bone grafting].

OBJECTIVE: To conduct an in vitro study to assess the preliminary possibility of using formalin-fixed, instead of fresh, human bone tissues for allografting. METHODS: Fresh cadaveric bone tissues were fixed by formalin for more than 6 months and dissected into 5 mmx5 mmx5 mm pieces and 5 mmx5 mmx40 mm sticks, followed by chemical treatments to prepare the allograft bone materials. When alls treatments were completed, the bone grafts were centrifuged and their properties and cellular compatibility assessed in comparison with the currently used bone grafts clinically. RESULTS: The residual formaldehyde of the fixed allograft bone material was much below the controlled level and no significant differences were noted between the bone graft materials tested in regard to the chemical and mechanical properties and biocompatibility. CONCLUSION: This material we have prepared may meet the clinical demands for bone grafting, with good biocompatibility and less chance for infection by pathological agents.

[Amplification of brain-derived neurotrophic factor receptor trkB gene and construction of its eukaryotic expression vector].

OBJECTIVE: To construct a recombinant eukaryotic expression vector of rat brain-derived neurotrophic factor receptor trkB gene. METHODS: Using the total RNA extracted from rat brain tissue as the template, the trkB gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with a pair of specific primers containing the restriction sites of EcoRI and BamHI. The amplified fragment of trkB gene was digested with EcoRI and BamHI, and then subcloned into cloning vector pMD18-T and then expression vector pEGFP-C2. The recombinant plasmid was identified by restriction endonuclease analysis and PCR. RESULTS: The amplified DNA fragment was about 1 461 bp in length, and enzyme digestion and PCR analysis showed that trkB gene had been successfully cloned into the vectors pMD18-T and pEGFP-C2. CONCLUSION: The trkB gene of rat has been successfully amplified and cloned into the eukaryotic expression vector pEGFP-C2.