Type I Collagen and Collagen Mimetics as Angiogenesis Promoting Superpolymers

Versatile Triblock Peptide Self-Assembly System to Mimic Collagen Structure and Function

The construction of collagen mimetic peptides has been a hot topic in tissue engineering due to their attractive advantages, such as virus-free nature and low immunogenicity. However, all of the reported self-assembled peptides rely on the inclusion of risky elements of potential safety concerns or lack the capability of incorporating critical functional motifs. A versatile self-assembly design of pure synthetic peptides that can mimic the collagen structure and function remains an insurmountably challenging target. We have herein created a type of triblock peptide consisting of a central triple helical block and N-terminal/C-terminal blocks with oppositely charged amino acids. Favorable electrostatic interactions between the two terminal blocks have been demonstrated to trigger the triblock peptides to form collagen-like nanofibers with a distinct D-banding pattern. A length of 3 or above charged amino acid pairs as well as the maintenance of the triple helical conformation are required for the self-assembly of triblock peptides. Notably, integrin and discoidin domain receptor (DDR) binding sequences GFOGER and GVMGFO have been well demonstrated as vivid examples of convenient incorporation of functional motifs into the triblock peptides without interfering with their self-assembly. These triblock peptides provide a robust and versatile strategy to create next-generation peptide-based biomaterials that can recapitulate the structure and function of collagen, which have promising applications in the fields of tissue engineering and regenerative medicine.

A Gelatin/Alginate Double Network Hydrogel Nerve Guidance Conduit Fabricated by a Chemical-Free Gamma Radiation for Peripheral Nerve Regeneration

Nerve guidance conduits (NGCs) are widely developed using various materials for the functional repair of injured or diseased peripheral nerves. Especially, hydrogels are considered highly suitable for the fabrication of NGCs due to their beneficial tissue-mimicking characteristics (e.g., high water content, softness, and porosity). However, the practical applications of hydrogel-based NGCs are hindered due to their poor mechanical properties and complicated fabrication processes. To bridge this gap, a novel double-network (DN) hydrogel using alginate and gelatin by a two-step crosslinking process involving chemical-free gamma irradiation and ionic crosslinking, is developed. DN hydrogels (1% alginate and 15% gelatin), crosslinked with 30 kGy gamma irradiation and barium ions, exhibit substantially improved mechanical properties, including tensile strength, elastic modulus, and fracture stain, compared to single network (SN) gelatin hydrogels. Additionally, the DN hydrogel NGC exhibits excellent kink resistance, mechanical stability to successive compression, suture retention, and enzymatic degradability. In vivo studies with a sciatic defect rat model indicate substantially improved nerve function recovery with the DN hydrogel NGC compared to SN gelatin and commercial silicone NGCs, as confirm footprint analysis, electromyography, and muscle weight measurement. Histological examination reveals that, in the DN NGC group, the expression of Schwann cell and neuronal markers, myelin sheath, and exon diameter are superior to the other controls. Furthermore, the DN NGC group demonstrates increased muscle fiber formation and reduced fibrotic scarring. These findings suggest that the mechanically robust, degradable, and biocompatible DN hydrogel NGC can serve as a novel platform for peripheral nerve regeneration and other biomedical applications, such as implantable tissue constructs.

African Swine Fever Virus I267L Is a Hemorrhage-Related Gene Based on Transcriptome Analysis

African swine fever (ASF) is an acute and severe disease transmitted among domestic pigs and wild boars. This disease is notorious for its high mortality rate and has caused great losses to the world's pig industry in the past few years. After infection, pigs can develop symptoms such as high fever, inflammation, and acute hemorrhage, finally leading to death. African swine fever virus (ASFV) is the causal agent of ASF; it is a large DNA virus with 150-200 genes. Elucidating the functions of each gene could provide insightful information for developing prevention and control methods. Herein, to investigate the function of I267L, porcine alveolar macrophages (PAMs) infected with an I267L-deleted ASFV strain (named ∆I267L) and wild-type ASFV for 18 h and 36 h were taken for transcriptome sequencing (RNA-seq). The most distinct different gene that appeared at both 18 hpi (hours post-infection) and 36 hpi was F3; it is the key link between inflammation and coagulation cascades. KEGG analysis (Kyoto encyclopedia of genes and genomes analysis) revealed the complement and coagulation cascades were also significantly affected at 18 hpi. Genes associated with the immune response were also highly enriched with the deletion of I267L. RNA-seq results were validated through RT-qPCR. Further experiments confirmed that ASFV infection could suppress the induction of F3 through TNF-α, while I267L deletion partially impaired this suppression. These results suggest that I267L is a pathogenicity-associated gene that modulates the hemorrhages of ASF by suppressing F3 expression. This study provides new insights into the molecular mechanisms of ASFV pathogenicity and potential targets for ASFV prevention and control.

Multi-organ hereditary hemorrhagic telangiectasia: A case report

BACKGROUND

Type 2 hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant disease and is associated with ALK1 gene mutations. Type 2 HHT patients primarily suffer from recurrent bleeding. There is currently no promising treatment.

CASE SUMMARY

A 5-year-old Chinese patient (III23) was admitted to Zhongshan Hospital for recurrent melena occurring over 2 mo. She had been experiencing epistaxis for years and had been diagnosed with idiopathic pulmonary hypertension 4 mo before presentation. Abdominal computed tomography examination showed hepatic arteriovenous malformation. Gene testing revealed a c.1121G>A mutation on the ALK1 gene. According to the international diagnostic criteria, this patient was diagnosed with HHT. In addition, 8 more family members exhibited HHT symptoms to varying degrees. Gene testing in 5 family members (2 with HHT symptoms and 3 without HHT symptoms) revealed the ALK1 c.1121G>A mutation in the 2 family members with HHT symptoms. This missense mutation results in the substitution of arginine for glutamine at amino acid position 374 (R374Q) in the conserved functional kinase domain of ALK1. Biological studies revealed that this mutation decreased the kinase activity of ALK1 and impeded the phosphorylation of its substrate Smad1. Moreover, the R374Q mutant downregulated the protein level of collagen-1, a fibrogenic factor, indicating abnormal fiber generation during vascular formation.

CONCLUSION

The R374Q mutant of ALK1 and its subsequent influence on fiber generation highly indicated its pathogenic role in this family with type 2 HHT. Detection of this gene mutation will facilitate early diagnosis of suspected type 2 HHT patients, and mechanistic studies will provide insights for future therapy.

The hemostatic effect and wound healing of novel collagen-containing polyester dressing

Collagen plays an important role in hemostasis and tissue repair processes. Traditional passive wound dressings like gauze, bandage, and cotton wool could hardly fit the open wounds and exerted no active effect on wound healing. Even worse, they would adhere to the skin tissue, causing dehydration and second injury upon replacement. Polyester is commonly used in the medical field and is a safe and inexpensive polymer. Due to the hydrophobic surface, polyester does not adhere to tissue; however, polyester does not have the hemostatic properties. We designed a material composed of collagen and polyester, encapsulated hydrolyzed collagen in polyester particles, and made collagen-polyester non-woven fabric by melt blowing method, The collagen content was 1% and the collagen-polyester dressing exhibited a hydrophobic nature, preventing moisture from sticking to its surface. The purpose of this study was to compare the hemostatic effect of collagen-polyester nonwovens with conventional polyester pads, and to observe the adhesion of the pads to the wound. The wound healing and shrinkage rates of collagen-polyester dressings and conventional pads were compared in a rat wound healing test. The hemostatic test showed that the polyester pads containing 1% collagen significantly shortened the bleeding time compared with the traditional polyester pads, and retained the hydrophobicity and non-adhesion properties. The collagen-polyester dressing had better angiogenesis and granulation degree than the control group on the 14th day, and reduced the wound shrinkage rate. Collagen polyester dressings have excellent hemostasis, regeneration, shrinkage reduction and non-adhering for wounds. Overall, the novel collagen-containing polyester dressing is ideal choice for wound dressings.

Effects of collagen, chitosan and mixture on fibroblast responses and angiogenic activities in 2D and 3D in vitro models

Despite accumulating evidences have demonstrated the potential of collagen and chitosan on tissue repair, it remains unclear on their combination effects. Here, we examined the regenerative effects of single collagen, chitosan and their mixture on fibroblasts and endothelial cells at cellular levels. The results showed that fibroblast responses, as indicated by high proliferative rate, increased spheroid diameter and migrated area existing from spheroid edge, and decreased wound area, were significantly promoted by either collagen or chitosan stimulation. Similarly, both collagen and chitosan resulted in increased endothelial cell proliferation and migration with accelerated tube-like network formation and upregulated VE-cadherin expression, although collagen strongly provided this effect. While the 1:1 mixture (100:100 μg/mL of chitosan to collagen) treatment caused a reduction in fibroblast viability, the lower ratio of chitosan (1:10 mixture; 10:100 μg/mL) did not produce any impact on both fibroblast and endothelial cell viabilities. The 1:10 mixture also significantly enhanced the additional effects on fibroblast responses and angiogenic activities as shown by higher endothelial growth, proliferation and migration with accelerated capillary-like network formation than those treated with the single substance. Further investigation of signaling proteins found that collagen significantly increased expressions of p-Fak, p-Akt and Cdk5 whereas chitosan upregulated p-Fak and Cdk5 expressions. Comparing to the single treatments, p-Fak, p-Akt and Cdk5 were higher expressed in the 1:10 mixture. These observations indicate that proper collagen-chitosan mixture provides the combination effects on fibroblast responses and angiogenic activities when a high concentration of collagen is used, possibly through Fak/Akt and Cdk5 signaling pathways. Therefore, this study helps to define the clinical use of collagen and chitosan as promising biomaterials for tissue repair.

Mesoporous Composite Bioactive Compound Delivery System for Wound-Healing Processes

Currently, the treatment of wounds is still a challenge for healthcare professionals due to high complication incidences and social impacts, and the development of biocompatible and efficient medicines remains a goal. In this regard, mesoporous materials loaded with bioactive compounds from natural extracts have a high potential for wound treatment due to their nontoxicity, high loading capacity and slow drug release. MCM-41-type mesoporous material was synthesized by using sodium trisilicate as a silica source at room temperature and normal pressure. The synthesized mesoporous silica was characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2 absorption-desorption (BET), Dynamic Light Scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR), revealing a high surface area (BET, 1244 m2/g); pore diameter of approx. 2 nm; and a homogenous, ordered and hexagonal geometry (TEM images). Qualitative monitoring of the desorption degree of the Salvia officinalis (SO) extract, rich in ursolic acid and oleanolic acid, and Calendula officinalis (CO) extract, rich in polyphenols and flavones, was performed via the continuous recording of the UV-VIS spectra at predetermined intervals. The active ingredients in the new composite MCM-41/sage and marigold (MCM-41/SO&CO) were quantified by using HPLC-DAD and LC-MS-MS techniques. The evaluation of the biological composites' activity on the wound site was performed on two cell lines, HS27 and HaCaT, naturally involved in tissue-regeneration processes. The experimental results revealed the ability to stimulate collagen biosynthesis, the enzymatic activity of the main metalloproteinases (MMP-2 and MMP-9) involved in tissue remodeling processes and the migration rate in the wound site, thus providing insights into the re-epithelializing properties of mesoporous composites.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Biological Macromolecule-Based Scaffolds for Urethra Reconstruction

Urethral reconstruction strategies are limited with many associated drawbacks. In this context, the main challenge is the unavailability of a suitable tissue that can endure urine exposure. However, most of the used tissues in clinical practices are non-specialized grafts that finally fail to prevent urine leakage. Tissue engineering has offered novel solutions to address this dilemma. In this technology, scaffolding biomaterials characteristics are of prime importance. Biological macromolecules are naturally derived polymers that have been extensively studied for various tissue engineering applications. This review discusses the recent advances, applications, and challenges of biological macromolecule-based scaffolds in urethral reconstruction.

Collagen as a Biomaterial for Skin and Corneal Wound Healing

The cornea and the skin are two organs that form the outer barrier of the human body. When either is injured (e.g., from surgery, physical trauma, or chemical burns), wound healing is initiated to restore integrity. Many cells are activated during wound healing. In particular, fibroblasts that are stimulated often transition into repair fibroblasts or myofibroblasts that synthesize extracellular matrix (ECM) components into the wound area. Control of wound ECM deposition is critical, as a disorganized ECM can block restoration of function. One of the most abundant structural proteins in the mammalian ECM is collagen. Collagen type I is the main component in connective tissues. It can be readily obtained and purified, and short analogs have also been developed for tissue engineering applications, including modulating the wound healing response. This review discusses the effect of several current collagen implants on the stimulation of corneal and skin wound healing. These range from collagen sponges and hydrogels to films and membranes.

Application of Hydrogels as Sustained-Release Drug Carriers in Bone Defect Repair

Large bone defects resulting from trauma, infection and tumors are usually difficult for the body's repair mechanisms to heal spontaneously. Generally, various types of bones and orthopedic implants are adopted to enhance bone repair and regeneration in the clinic. Due to the limitations of traditional treatments, bone defect repair is still a compelling challenge for orthopedic surgeons. In recent years, bone tissue engineering has become a potential option for bone repair and regeneration. Amidst the various scaffolds for bone tissue engineering applications, hydrogels are considered a new type of non-toxic, non-irritating and biocompatible materials, which are widely used in the biomedicine field currently. Some studies have demonstrated that hydrogels can provide a three-dimensional network structure similar to a natural extracellular matrix for tissue regeneration and can be used to transport cells, biofactors, nutrients and drugs. Therefore, hydrogels may have the potential to be multifunctional sustained-release drug carriers in the treatment of bone defects. The recent applications of different types of hydrogels in bone defect repair were briefly reviewed in this paper.

Comparison of Two Bovine Commercial Xenografts in the Regeneration of Critical Cranial Defects

Autologous bone is the gold standard in regeneration processes. However, there is an endless search for alternative materials in bone regeneration. Xenografts can act as bone substitutes given the difficulty of obtaining bone tissue from patients and before the limitations in the availability of homologous tissue donors. Bone neoformation was studied in critical-size defects created in the parietal bone of 40 adult male Wistar rats, implanted with xenografts composed of particulate bovine hydroxyapatite (HA) and with blocks of bovine hydroxyapatite (HA) and Collagen, which introduces crystallinity to the materials. The Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated the carbonate and phosphate groups of the hydroxyapatite and the amide groups of the collagen structure, while the thermal transitions for HA and HA/collagen composites established mainly dehydration endothermal processes, which increased (from 79 °C to 83 °C) for F2 due to the collagen presence. The xenograft’s X-ray powder diffraction (XRD) analysis also revealed the bovine HA crystalline structure, with a prominent peak centered at 32°. We observed macroporosity and mesoporosity in the xenografts from the morphology studies with heterogeneous distribution. The two xenografts induced neoformation in defects of critical size. Histological, histochemical, and scanning electron microscopy (SEM) analyses were performed 30, 60, and 90 days after implantation. The empty defects showed signs of neoformation lower than 30% in the three periods, while the defects implanted with the material showed partial regeneration. InterOss Collagen material temporarily induced osteon formation during the healing process. The results presented here are promising for bone regeneration, demonstrating a beneficial impact in the biomedical field.

Label-free second harmonic generation imaging of cerebral vascular wall in local ischemia mouse model in vivo

Second harmonic generation (SHG) imaging is label-free and non-invasive, and it has been extensively applied in multiple biological and medical studies, but not in the brain in vivo. In this study, we modified classical two photon excited fluorescence (TPEF) system to perform in vivo simultaneous TPEF and SHG imaging in the local ischemia mouse model. In cerebral vascular walls, we found strong SHG signal, which co-localized with collagen. In the continuous 2 days' in vivo imaging, this SHG signal remained stable in the local ischemic blood vessel in the initial 4 hours, then its signal abruptly increased and got spatially thickened 5 hours after thrombosis, and this tendency continued in the following 48 hours. This study provides direct and precise timeline of rapid collagen change in cerebral vascular walls in vivo, and reveals the subtle but significant temporal-spatial dynamics of this structural signal during local ischemia. Thus, this cerebral in vivo SHG imaging provides a powerful tool to identify the early and subtle pathological change of collagen around clinical key therapeutic time window.

SARS-CoV-2 Brain Regional Detection, Histopathology, Gene Expression, and Immunomodulatory Changes in Decedents with COVID-19

Brains of 42 COVID-19 decedents and 107 non-COVID-19 controls were studied. RT-PCR screening of 16 regions from 20 COVID-19 autopsies found SARS-CoV-2 E gene viral sequences in 7 regions (2.5% of 320 samples), concentrated in 4/20 subjects (20%). Additional screening of olfactory bulb (OB), amygdala (AMY) and entorhinal area for E, N1, N2, RNA-dependent RNA polymerase, and S gene sequences detected one or more of these in OB in 8/21 subjects (38%). It is uncertain whether these RNA sequences represent viable virus. Significant histopathology was limited to 2/42 cases (4.8%), one with a large acute cerebral infarct and one with hemorrhagic encephalitis. Case-control RNAseq in OB and AMY found more than 5000 and 700 differentially expressed genes, respectively, unrelated to RT-PCR results; these involved immune response, neuronal constituents, and olfactory/taste receptor genes. Olfactory marker protein-1 reduction indicated COVID-19-related loss of OB olfactory mucosa afferents. Iba-1-immunoreactive microglia had reduced area fractions in cerebellar cortex and AMY, and cytokine arrays showed generalized downregulation in AMY and upregulation in blood serum in COVID-19 cases. Although OB is a major brain portal for SARS-CoV-2, COVID-19 brain changes are more likely due to blood-borne immune mediators and trans-synaptic gene expression changes arising from OB deafferentation.

Crosslinked Collagenic Scaffold Behavior Evaluation by Physico-Chemical, Mechanical and Biological Assessments in an In Vitro Microenvironment

Wound healing-associated difficulties continue to drive biotechnological creativeness into complex grounds. The sophisticated architecture of skin wound sites and the intricate processes involved in the response to the use of regenerative devices play a critical role in successful skin regeneration approaches and their possible outcomes. Due to a plethora of complications involved in wound healing processes as well as the coordination of various cellular mechanisms, biomimetic approaches seems to be the most promising starting ground. This study evaluates the behavior of a crosslinked, porous collagen scaffold obtained by lyophilization and dehydrothermal reticulation (DHT). We address the key physio-chemical and mechanical factors, such as swelling, density and porosity, mechano-dynamic properties, SEM and TG-DSC, as well as important biological outcomes regarding scaffold biocompatibility and cellular metabolic activity, cytokine expression in inflammation, apoptosis and necrosis, as well as hemocompatibility and biodegradation. The mechanical and visco-elastic behavior are correlated, with the samples found to present similar thermal behavior and increased rigidity after DHT treatment. High biocompatibility rates were obtained, with no inflammatory stimulation and a reduction in necrotic cells. Higher percentages of cellular early apoptosis were observed. The hemocompatibility rate was under 2%, coagulation effects expressed after 4 min, and the DHT scaffold was more resistant to the biodegradation of collagenase compared with the untreated sample.

Targeting tumor innervation: premises, promises, and challenges

A high intratumoral nerve density is correlated with poor survival, high metastasis, and high recurrence across multiple solid tumor types. Recent research has revealed that cancer cells release diverse neurotrophic factors and exosomes to promote tumor innervation, in addition, infiltrating nerves can also mediate multiple tumor biological processes via exosomes and neurotransmitters. In this review, through seminal studies establishing tumor innervation, we discuss the communication between peripheral nerves and tumor cells in the tumor microenvironment (TME), and revealed the nerve-tumor regulation mechanisms on oncogenic process, angiogenesis, lymphangiogenesis, and immunity. Finally, we discussed the promising directions of ‘old drugs newly used’ to target TME communication and clarified a new line to prevent tumor malignant capacity.

In Vitro Direct and Indirect Cytotoxicity Comparative Analysis of One Pre-Hydrated versus One Dried Acellular Porcine Dermal Matrix

Aim: The aim of the present study was to compare the direct and indirect cytotoxicity of a porcine dried acellular dermal matrix (PDADM) versus a porcine hydrated acellular dermal matrix (PHADM) in vitro. Both are used for periodontal and peri-implant soft tissue regeneration. Materials and methods: Two standard direct cytotoxicity tests—namely, the Trypan exclusion method (TEM) and the reagent WST-1 test (4-3-[4-iodophenyl]-2-[4-nitrophenyl]-2H-[5-tetrazolio]-1,3-benzol-desulphonated)—were performed using human primary mesenchymal stem cells (HPMSCs) seeded directly onto a PDADM and PHADM after seven days. Two standard indirect cytotoxicity tests—namely, lactate dehydrogenase (LTT) and MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazoliumbromide)—were performed using HPMSCs cultivated in eluates from the matrices incubated for 0.16 h (10 min), 1 h, and 24 h in a serum-free cell culture medium. Results: The WST and the TEM tests revealed significantly lower direct cytotoxicity values of HPMSCs on the PHADM compared with the PDADM. The indirect cytotoxicity levels were low for both the PHADM and PDADM, peaking in short-term eluates and decreasing with longer incubation times. However, they were lower for the PHADM with a statistically significant difference (p < 0.005). Conclusions: The results of the current study demonstrated a different biologic behavior between the PHADM and the PDADM, with the hydrated form showing a lower direct and indirect cytotoxicity.

Targeting Type I Collagen for Cancer Treatment

Collagen is the most abundant protein in animals. Interactions between tumor cells and collagen influence every step of tumor development. Type I collagen is the main fibrillar collagen in the extracellular matrix and is frequently up-regulated during tumorigenesis. The binding of type I collagen to its receptors on tumor cells promotes tumor cell proliferation, epithelial-mesenchymal transition, and metastasis. Type I collagen also regulates the efficacy of tumor therapies, such as chemotherapy, radiotherapy, and immunotherapy. Furthermore, type I collagen fragments are diagnostic markers of metastatic tumors and have prognostic value. Inhibition of type I collagen synthesis has been reported to have anti-tumor effects in animal models. However, collagen has also been shown to possess anti-tumor activity. Therefore, the roles that type I collagen plays in tumor biology are complex and tumor type-dependent. In this review, we discuss the expression and regulation of synthesis of type I collagen, as well as the role up-regulated type I collagen plays in various stages of cancer progression. We also discuss the role of collagen in tumor therapy. Finally, we highlight several recent approaches targeting type I collagen for cancer treatment. This article is protected by copyright. All rights reserved.

Adding collagen to adipose tissue transplant increases engraftment by promoting cell proliferation, neovascularisation and macrophage activity in a rat model

To clarify the effect of collagen addition to transplanted adipose tissue on angiogenesis, cell proliferation and tissue remodelling process and reveal whether collagen addition contributes to improving transplanted adipose tissue engraftment in rats. Adipose tissue was harvested from the inguinal and injected into the back of the rat, in addition to collagen. Engraftment tissue was harvested, semi-quantitatively evaluated and underwent haematoxylin and eosin or Perilipin staining. Moreover, we evaluated viable adipocyte counts and neovascularisation. Macrophages were evaluated using flow cytometry, and the adiponectin or vascular endothelial growth factor (VEGF) mRNA was detected using real-time polymerase chain reaction. By collagen addition to transplanted adipose tissue, higher engraftment rate semi-quantitatively and a greater number of new blood vessels histologically were identified. Perilipin staining revealed a higher adipocyte number. The total cell, M1 macrophage and M2 macrophage count were higher. There was increased adiponectin mRNA significantly at week 4 compared to that at week 1 after transplantation. Note that the expression levels of VEGF mRNA increased. In rats, adding collagen enhanced cell proliferation, induced M2 macrophages, which are involved in wound healing, and promoted adipocytes and neovascularisation. Therefore, collagen addition to transplanted adipose tissue could increase the engraftment rate of adipose tissue.

Olfactory Bulb and Amygdala Gene Expression Changes in Subjects Dying with COVID-19

In this study we conducted RNA sequencing on two brain regions (olfactory bulb and amygdala) from subjects who died from COVID-19 or who died of other causes. We found several-fold more transcriptional changes in the olfactory bulb than in the amygdala, consistent with our own work and that of others indicating that the olfactory bulb may be the initial and most common brain region infected. To some extent our results converge with pseudotime analysis towards common processes shared between the brain regions, possibly induced by the systemic immune reaction following SARS-CoV-2 infection. Changes in amygdala emphasized upregulation of interferon-related neuroinflammation genes, as well as downregulation of synaptic and other neuronal genes, and may represent the substrate of reported acute and subacute COVID-19 neurological effects. Additionally, and only in olfactory bulb, we observed an increase in angiogenesis and platelet activation genes, possibly associated with microvascular damages induced by neuroinflammation. Through coexpression analysis we identified two key genes (CAMK2B for the synaptic neuronal network and COL1A2 for the angiogenesis/platelet network) that might be interesting potential targets to reverse the effects induced by SARS-CoV-2 infection. Finally, in olfactory bulb we detected an upregulation of olfactory and taste genes, possibly as a compensatory response to functional deafferentation caused by viral entry into primary olfactory sensory neurons. In conclusion, we were able to identify transcriptional profiles and key genes involved in neuroinflammation, neuronal reaction and olfaction induced by direct CNS infection and/or the systemic immune response to SARS-CoV-2 infection.

Diverse energy metabolism patterns in females in Neodon fuscus, Lasiopodomys brandtii, and Mus musculus revealed by comparative transcriptomics under hypoxic conditions

The effects of global warming and anthropogenic disturbance force animals to migrate from lower to higher elevations to find suitable new habitats. As such migrations increase hypoxic stress on the animals, it is important to understand how plateau- and plain-dwelling animals respond to low-oxygen environments. We used comparative transcriptomics to explore the response of Neodon fuscus, Lasiopodomys brandtii, and Mus musculus skeletal muscle tissues to hypoxic conditions. Results indicate that these species have adopted different oxygen transport and energy metabolism strategies for dealing with a hypoxic environment. N. fuscus promotes oxygen transport by increasing hemoglobin synthesis and reduces the risk of thrombosis through cooperative regulation of genes, including Fga, Fgb, Alb, and Ttr; genes such as Acs16, Gpat4, and Ndufb7 are involved in regulating lipid synthesis, fatty acid β-oxidation, hemoglobin synthesis, and electron-linked transmission, thereby maintaining a normal energy supply in hypoxic conditions. In contrast, the oxygen-carrying capacity and angiogenesis of red blood cells in L. brandtii are promoted by genes in the CYP and COL families; this species maintains its bodily energy supply by enhancing the pentose phosphate pathway and mitochondrial fatty acid synthesis pathway. However, under hypoxia, M. musculus cannot effectively transport additional oxygen; thus, its cell cycle, proliferation, and migration are somewhat affected. Given its lack of hypoxic tolerance experience, M. musculus also shows significantly reduced oxidative phosphorylation levels under hypoxic conditions. Our results suggest that the glucose capacity of M. musculus skeletal muscle does not provide sufficient energy during hypoxia; thus, we hypothesize that it supplements its bodily energy by synthesizing ketone bodies. For the first time, we describe the energy metabolism pathways of N. fuscus and L. brandtii skeletal muscle tissues under hypoxic conditions. Our findings, therefore, improve our understanding of how vertebrates thrive in high altitude and plain habitats when faced with hypoxic conditions.

Positive Effects of Three-Dimensional Collagen-Based Matrices on the Behavior of Osteoprogenitors

Recent research has demonstrated that reinforced three-dimensional (3D) collagen matrices can provide a stable scaffold for restoring the lost volume of a deficient alveolar bone. In the present study, we aimed to comparatively investigate the migratory, adhesive, proliferative, and differentiation potential of mesenchymal stromal ST2 and pre-osteoblastic MC3T3-E1 cells in response to four 3D collagen-based matrices. Dried acellular dermal matrix (DADM), hydrated acellular dermal matrix (HADM), non-crosslinked collagen matrix (NCM), and crosslinked collagen matrix (CCM) did all enhance the motility of the osteoprogenitor cells. Compared to DADM and NCM, HADM and CCM triggered stronger migratory response. While cells grown on DADM and NCM demonstrated proliferative rates comparable to control cells grown in the absence of a biomaterial, cells grown on HADM and CCM proliferated significantly faster. The pro-proliferative effects of the two matrices were supported by upregulated expression of genes regulating cell division. Increased expression of genes encoding the adhesive molecules fibronectin, vinculin, CD44 antigen, and the intracellular adhesive molecule-1 was detected in cells grown on each of the scaffolds, suggesting excellent adhesive properties of the investigated biomaterials. In contrast to genes encoding the bone matrix proteins collagen type I (Col1a1) and osteopontin (Spp1) induced by all matrices, the expression of the osteogenic differentiation markers Runx2, Alpl, Dlx5, Ibsp, Bglap2, and Phex was significantly increased in cells grown on HADM and CCM only. Short/clinically relevant pre-coating of the 3D biomaterials with enamel matrix derivative (EMD) or recombinant bone morphogenetic protein-2 (rBMP-2) significantly boosted the osteogenic differentiation of both osteoprogenitor lines on all matrices, including DADM and NCM, indicating that EMD and BMP-2 retained their biological activity after being released from the matrices. Whereas EMD triggered the expression of all osteogenesis-related genes, rBMP-2 upregulated early, intermediate, and late osteogenic differentiation markers except for Col1a1 and Spp1. Altogether, our results support favorable influence of HADM and CCM on the recruitment, growth, and osteogenic differentiation of the osteoprogenitor cell types. Furthermore, our data strongly support the biofunctionalization of the collagen-based matrices with EMD or rBMP-2 as a potential treatment modality for bone defects in the clinical practice.

Restoring Endogenous Repair Mechanisms to Heal Chronic Wounds with a Multifunctional Wound Dressing

Current treatment of chronic wounds has been critically limited by various factors, including bacterial infection, biofilm formation, impaired angiogenesis, and prolonged inflammation. Addressing these challenges, we developed a multifunctional wound dressing-based three-pronged approach for accelerating wound healing. The multifunctional wound dressing, composed of nanofibers, functional nanoparticles, natural biopolymers, and selected protein and peptide, can target multiple endogenous repair mechanisms and represents a promising alternative to current wound healing products.

Architecture of Cancer-Associated Fibroblasts in Tumor Microenvironment: Mapping Their Origins, Heterogeneity, and Role in Cancer Therapy Resistance

The tumor stroma, a key component of the tumor microenvironment (TME), is a key determinant of response and resistance to cancer treatment. The stromal cells, extracellular matrix (ECM), and blood vessels influence cancer cell response to therapy and play key roles in tumor relapse and therapeutic outcomes. Of the stromal cells present in the TME, much attention has been given to cancer-associated fibroblasts (CAFs) as they are the most abundant and important in cancer initiation, progression, and therapy resistance. Besides releasing several factors, CAFs also synthesize the ECM, a key component of the tumor stroma. In this expert review, we examine the role of CAFs in the regulation of tumor cell behavior and reveal how CAF-derived factors and signaling influence tumor cell heterogeneity and development of novel strategies to combat cancer. Importantly, CAFs display both phenotypic and functional heterogeneity, with significant ramifications on CAF-directed therapies. Principal anti-cancer therapies targeting CAFs take the form of: (1) CAFs' ablation through use of immunotherapies, (2) re-education of CAFs to normalize the cells, (3) cellular therapies involving CAFs delivering drugs such as oncolytic adenoviruses, and (4) stromal depletion via targeting the ECM and its related signaling. The CAFs' heterogeneity could be a result of different cellular origins and the cancer-specific tumor microenvironmental effects, underscoring the need for further multiomics and biochemical studies on CAFs and the subsets. Lastly, we present recent advances in therapeutic targeting of CAFs and the success of such endeavors or their lack thereof. We recommend that to advance global public health and personalized medicine, treatments in the oncology clinic should be combinatorial in nature, strategically targeting both cancer cells and stromal cells, and their interactions.

3D bioprinting and microscale organization of vascularized tissue constructs using collagen-based bioink

Bioprinting three-dimensional (3D) tissue equivalents have progressed tremendously over the last decade. 3D bioprinting is currently being employed to develop larger and more physiologic tissues, and it is of particular interest to generate vasculature in biofabricated tissues to aid better perfusion and transport of nutrition. Having an advantage over manual culture systems by bringing together biological scaffold materials and cells in precise 3D spatial orientation, bioprinting could assist in placing endothelial cells in specific spatial locations within a 3D matrix to promote vessel formation at these predefined areas. Hence, in the present study, we investigated the use of bioprinting to generate tissue-level capillary-like networks in biofabricated tissue constructs. First, we developed a bioink using collagen type-1 supplemented with xanthan gum (XG) as a thickening agent. Using a commercial extrusion-based multi-head bioprinter and collagen-XG bioink, the component cells were spatially assembled, wherein the endothelial cells were bioprinted in a lattice pattern and sandwiched between bioprinted fibroblasts layers. 3D bioprinted constructs thus generated were stable, and maintained structural shape and form. Post-print culture of the bioprinted tissues resulted in endothelial sprouting and formation of interconnected capillary-like networks within the lattice pattern and between the fibroblast layers. Bioprinter-assisted spatial placement of endothelial cells resulted in fabrication of patterned prevascularized constructs that enable potential regenerative applications in the future.

Three dimensional porous scaffolds derived from collagen, elastin and fibrin proteins orchestrate adipose tissue regeneration

Current gold standard to treat soft tissue injuries caused by trauma and pathological condition are autografts and off the shelf fillers, but they have inherent weaknesses like donor site morbidity, immuno-compatibility and graft failure. To overcome these limitations, tissue-engineered polymers are seeded with stem cells to improve the potential to restore tissue function. However, their interaction with native tissue is poorly understood so far. To study these interactions and improve outcomes, we have fabricated scaffolds from natural polymers (collagen, fibrin and elastin) by custom-designed processes and their material properties such as surface morphology, swelling, wettability and chemical cross-linking ability were characterised. By using 3D scaffolds, we comprehensive assessed survival, proliferation and phenotype of adipose-derived stem cells in vitro. In vivo, scaffolds were seeded with adipose-derived stem cells and implanted in a rodent model, with X-ray microtomography, histology and immunohistochemistry as read-outs. Collagen-based materials showed higher cell adhesion and proliferation in vitro as well as higher adipogenic properties in vivo. In contrast, fibrin demonstrated poor cellular and adipogenesis properties but higher angiogenesis. Elastin formed the most porous scaffold, with cells displaying a non-aggregated morphology in vitro while in vivo elastin was the most degraded scaffold. These findings of how polymers present in the natural polymers mimicking ECM and seeded with stem cells affect adipogenesis in vitro and in vivo can open avenues to design 3D grafts for soft tissue repair.

Collagen in Wound Healing

Normal wound healing progresses through inflammatory, proliferative and remodeling phases in response to tissue injury. Collagen, a key component of the extracellular matrix, plays critical roles in the regulation of the phases of wound healing either in its native, fibrillar conformation or as soluble components in the wound milieu. Impairments in any of these phases stall the wound in a chronic, non-healing state that typically requires some form of intervention to guide the process back to completion. Key factors in the hostile environment of a chronic wound are persistent inflammation, increased destruction of ECM components caused by elevated metalloproteinases and other enzymes and improper activation of soluble mediators of the wound healing process. Collagen, being central in the regulation of several of these processes, has been utilized as an adjunct wound therapy to promote healing. In this work the significance of collagen in different biological processes relevant to wound healing are reviewed and a summary of the current literature on the use of collagen-based products in wound care is provided.

Collagen Type I Biomaterials as Scaffolds for Bone Tissue Engineering

Collagen type I is the main organic constituent of the bone extracellular matrix and has been used for decades as scaffolding material in bone tissue engineering approaches when autografts are not feasible. Polymeric collagen can be easily isolated from various animal sources and can be processed in a great number of ways to manufacture biomaterials in the form of sponges, particles, or hydrogels, among others, for different applications. Despite its great biocompatibility and osteoconductivity, collagen type I also has some drawbacks, such as its high biodegradability, low mechanical strength, and lack of osteoinductive activity. Therefore, many attempts have been made to improve the collagen type I-based implants for bone tissue engineering. This review aims to summarize the current status of collagen type I as a biomaterial for bone tissue engineering, as well as to highlight some of the main efforts that have been made recently towards designing and producing collagen implants to improve bone regeneration.

Collagen Structure-Function Mapping Informs Applications for Regenerative Medicine

Type I collagen, the predominant protein of vertebrates, assembles into fibrils that orchestrate the form and function of bone, tendon, skin, and other tissues. Collagen plays roles in hemostasis, wound healing, angiogenesis, and biomineralization, and its dysfunction contributes to fibrosis, atherosclerosis, cancer metastasis, and brittle bone disease. To elucidate the type I collagen structure-function relationship, we constructed a type I collagen fibril interactome, including its functional sites and disease-associated mutations. When projected onto an X-ray diffraction model of the native collagen microfibril, data revealed a matrix interaction domain that assumes structural roles including collagen assembly, crosslinking, proteoglycan (PG) binding, and mineralization, and the cell interaction domain supporting dynamic aspects of collagen biology such as hemostasis, tissue remodeling, and cell adhesion. Our type III collagen interactome corroborates this model. We propose that in quiescent tissues, the fibril projects a structural face; however, tissue injury releases blood into the collagenous stroma, triggering exposure of the fibrils' cell and ligand binding sites crucial for tissue remodeling and regeneration. Applications of our research include discovery of anti-fibrotic antibodies and elucidating their interactions with collagen, and using insights from our angiogenesis studies and collagen structure-function model to inform the design of super-angiogenic collagens and collagen mimetics.

Improved bone regeneration using collagen-coated biphasic calcium phosphate with high porosity in a rabbit calvarial model

Many growth factors have been paired with synthetic bone grafts to accelerate the healing process in vivo. Collagen has been particularly examined as a mediator of the enhancement of bone regeneration. This study investigated the new bone formation potential of micro-macroporous biphasic calcium phosphate (m-BCP), high porosity biphasic calcium phosphate (p-BCP), and collagen-coated p-BCP (cp-BCP) using a rabbit calvarial defect model. At 2 or 8 weeks after surgery, bone tissue was collected. The three-dimensional analysis of new bone formation using synchrotron radiation micro-computed tomography and histological study were conducted. The new bone formation values observed at 2 and 8 weeks in the negative control, m-BCP, p-BCP, and cp-BCP groups were 11.21 ± 1.36 mm³, 21.75 ± 1.18 mm³, 24.59 ± 1.26 mm³, and 29.54 ± 2.72 mm³, respectively, and 18.34 ± 3.99 mm³, 32.27 ± 3.78 mm³, 43.12 ± 1.61 mm³, and 58.20 ± 3.84 mm³, respectively. New bone formation was greatest in the cp-BCP group, while the amount of new bone at 8 weeks was higher than at 2 weeks in each group. The use of cp-BCP to enhance new bone formation during the healing period could improve bone regeneration.

Heterotopic autotransplantation of ovarian tissue in a large animal model: Effects of cooling and VEGF

Heterotopic and orthotopic ovarian tissue autotransplantation techniques, currently used in humans, will become promising alternative methods for fertility preservation in domestic and wild animals. Thus, this study describes for the first time the efficiency of a heterotopic ovarian tissue autotransplantation technique in a large livestock species (i.e., horses) after ovarian fragments were exposed or not to a cooling process (4°C/24 h) and/or VEGF before grafting. Ovarian fragments were collected in vivo via an ultrasound-guided biopsy pick-up method and surgically autografted in a subcutaneous site in both sides of the neck in each mare. The blood flow perfusion at the transplantation site was monitored at days 2, 4, 6, and 7 post-grafting using color-Doppler ultrasonography. Ovarian grafts were recovered 7 days post-transplantation and subjected to histological analyses. The exposure of the ovarian fragments to VEGF before grafting was not beneficial to the quality of the tissue; however, the cooling process of the fragments reduced the acute hyperemia post-grafting. Cooled grafts compared with non-cooled grafts contained similar values for normal and developing preantral follicles, vessel density, and stromal cell apoptosis; lower collagen type III fibers and follicular density; and higher stromal cell density, AgNOR, and collagen type I fibers. In conclusion, VEGF exposure before autotransplantation did not improve the quality of grafted tissues. However, cooling ovarian tissue for at least 24 h before grafting can be beneficial because satisfactory rates of follicle survival and development, stromal cell survival and proliferation, as well as vessel density, were obtained.

Human Retinal Microvasculature-on-a-Chip for Drug Discovery

Retinal cells within neurovascular units generate the blood-retinal barrier (BRB) to regulate the local retinal microenvironment and to limit access to inflammatory cells. Breakdown of the endothelial junctional complexes in the BRB negatively affects neuronal signaling and ultimately causes vision loss. As new therapeutics are being developed either to prevent barrier disruption or to restore barrier function, access to physiologically relevant human in vitro tissue models that recapitulate important features of barrier biology is essential for disease modeling, target validation, and toxicity assessment. Here, a tunable organ-on-a-chip model of the retinal microvasculature using human retinal microvascular endothelial cells with integrated flow is described. Automated imaging and image analysis methods are employed for facile screening of leakage mediators and cytokine inhibitors on barrier properties. The developed retinal microvasculature-on-a-chip will enable improved understanding of BRB biology and provide an additional tool for drug discovery.

Biomaterials for Bioprinting Microvasculature

Microvasculature functions at the tissue and cell level, regulating local mass exchange of oxygen and nutrient-rich blood. While there has been considerable success in the biofabrication of large- and small-vessel replacements, functional microvasculature has been particularly challenging to engineer due to its size and complexity. Recently, three-dimensional bioprinting has expanded the possibilities of fabricating sophisticated microvascular systems by enabling precise spatiotemporal placement of cells and biomaterials based on computer-aided design. However, there are still significant challenges facing the development of printable biomaterials that promote robust formation and controlled 3D organization of microvascular networks. This review provides a thorough examination and critical evaluation of contemporary biomaterials and their specific roles in bioprinting microvasculature. We first provide an overview of bioprinting methods and techniques that enable the fabrication of microvessels. We then offer an in-depth critical analysis on the use of hydrogel bioinks for printing microvascularized constructs within the framework of current bioprinting modalities. We end with a review of recent applications of bioprinted microvasculature for disease modeling, drug testing, and tissue engineering, and conclude with an outlook on the challenges facing the evolution of biomaterials design for bioprinting microvasculature with physiological complexity.

A collagen-based hydrogel containing tacrolimus for bone tissue engineering

Bone tissue engineering aims to develop bone graft structure that can heal bone defects without using autografts or allografts. The current study was conducted to promote bone regeneration using a collagen type I hydrogel containing tacrolimus. For this purpose, different amounts of tacrolimus (10 μg/ml, 100 μg/ml, and 1000 μg/ml) were loaded into the hydrogel. The resulting drug-loaded hydrogels were characterized for their porosity, swelling capacity, weight loss, drug release, blood compatibility, and cell proliferation (MTT). For functional analysis, the developed hydrogel surrounded by a film made of gelatin and polycaprolactone (PCL) was administrated in the calvarias defect of Wistar rats. The results indicated that the hydrogel has a porosity of 89.2 ± 12.5% and an appropriate swelling, drug release, and blood compatibility behavior. The in vitro results indicated that the collagen hydrogel containing 1000 μg tacrolimus was adequate in terms of cell proliferation. Finally, in vivo studies provided some evidence of the potential of the developed hydrogel for bone healing.

Nerves in cancer

The contribution of nerves to the pathogenesis of malignancies has emerged as an important component of the tumour microenvironment. Recent studies have shown that peripheral nerves (sympathetic, parasympathetic and sensory) interact with tumour and stromal cells to promote the initiation and progression of a variety of solid and haematological malignancies. Furthermore, new evidence suggests that cancers may reactivate nerve-dependent developmental and regenerative processes to promote their growth and survival. Here we review emerging concepts and discuss the therapeutic implications of manipulating nerves and neural signalling for the prevention and treatment of cancer.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

Mesoglycan induces the secretion of microvesicles by keratinocytes able to activate human fibroblasts and endothelial cells: A novel mechanism in skin wound healing

Mesoglycan is a fibrinolytic compound but recently promising pro-healing effects in skin wound repair have been reported. Previously, we have showed that mesoglycan activates human keratinocytes, fibroblasts and endothelial cells and induces the secretion of microvesicles (EVs), particularly exosomes, from keratinocytes. These EVs may contribute to wound healing since they further activate cells generating an autocrine loop with a positive feedback. In this work, EVs isolated from keratinocytes, treated with mesoglycan, have been tested on human fibroblasts and endothelial cells. The in vitro investigation has been carried out through Wound-Healing/invasion assays to analyze cell motility and assess the differentiation process. Then, the formation of capillary-like structures by human endothelial cells has been performed to evaluate in vitro angiogenesis. We found that EVs secreted from keratinocytes treated with mesoglycan promote fibroblasts and endothelial cells migration and invasion. Furthermore, these receiving cells acquire a mesenchymal phenotype. Additionally, the angiogenesis appears strongly enhanced in presence of this kind of EVs. In conclusion, we show that EVs deriving from keratinocytes trigger a paracrine positive feedback able to further amplify the effects of mesoglycan. This mechanism adds up to the autocrine loop previously reported and culminates with the activation of fibroblasts and endothelial cells. Particularly, this activation is amplified by the action of growth factors as FGF-2 (Fibroblast Growth Factor-2) for the fibroblasts and by VEGF (Vascular Endothelial Growth Factor) for the endothelial cells.

Scleral ossicles: angiogenic scaffolds, a novel biomaterial for regenerative medicine applications

Given the current prolonged life expectancy, various pathologies affect increasingly the aging subjects. Regarding the musculoskeletal apparatus, bone fragility induces more susceptibility to fractures, often not accompanied by good ability of self-repairing, in particular when critical-size defects (CSD) occur. Currently orthopedic surgery makes use of allografting and autografting which, however, have limitations due to the scarce amount of tissue that can be taken from the donor, the possibility of disease transmission and donor site morbidity. The need to develop new solutions has pushed the field of tissue engineering (TE) research to study new scaffolds to be functionalized in order to obtain constructs capable of promoting tissue regeneration and achieve stable bone recovery over time. This investigation focuses on the most important aspect related to bone tissue regeneration: the angiogenic properties of the scaffold to be used. As an innovative solution, scleral ossicles (SOs), previously characterized as natural, biocompatible and spontaneously decellularized scaffolds used for bone repair, were tested for angiogenic potential and biocompatibility. To reach this purpose, in ovo Chorioallantoic Membrane Assay (CAM) was firstly used to test the angiogenic potential; secondly, in vivo subcutaneous implantation of SOs (in a rat model) was performed in order to assess the biocompatibility and the inflammatory response. Finally, thanks to the analysis of mass spectrometry (LCMSQE), the putative proteins responsible for the SO angiogenic properties were identified. Thus, a novel natural biomaterial is proposed, which is (i) able to induce an angiogenic response in vivo by subcutaneous implantation in a non-immunodeficient animal model, (ii) which does not induce any inflammatory response, and (iii) is useful for regenerative medicine application for the healing of bone CSD.

Crucial Role for Endothelial Cell α2β1 Integrin Receptor Clustering in Collagen-Induced Angiogenesis

Angiogenesis is a crucial mechanism of vascular growth and regeneration that requires biosynthesis and cross-linking of collagens in vivo and is induced by collagen in vitro. Here, we use an in vitro model in which apical Type I collagen gels rapidly induce angiogenesis in endothelial monolayers. We extend previous studies demonstrating the importance of the endothelial α2β1 integrin, a key collagen receptor, in angiogenesis by investigating the roles of receptor clustering and conformational activation. Immunocytochemical localization of α2β1 integrins in endothelial monolayers showed a concentration of integrins along cell-cell borders. After inducing angiogenesis with collagen, the receptors redistributed to apical cell surfaces, aligning with collagen fibers, which were also redistributed during angiogenesis. Levels of conformationally activated α2β1 integrins were unchanged during angiogenesis and undetected on endothelial cells binding collagen in suspension. We mimicked the polyvalency of collagen fibrils using antibody-coated polystyrene beads to cluster endothelial cell surface α2β1 integrins, which induced rapid angiogenesis in the absence of collagen gels. Clustering of αvβ3 integrins and PECAM-1 but not of α1 integrins also induced angiogenesis. Soluble antibodies alone had no effect. Thus, the angiogenic property of collagen may reside in its ability to ligate and cluster cell surface receptors such as α2β1 integrins. Furthermore, synthetic substrates that promote the clustering of select endothelial cell surface receptors mimic the angiogenic properties of Type I collagen and may have applications in promoting vascularization of engineered tissues. Anat Rec, 2019. © 2019 American Association for Anatomy.

Limiting angiogenesis to modulate scar formation

Angiogenesis, the process of new blood vessel formation from existing blood vessels, is a key aspect of virtually every repair process. During wound healing an extensive, but immature and leaky vascular plexus forms which is subsequently reduced by regression of non-functional vessels. More recent studies indicate that uncontrolled vessel growth or impaired vessel regression as a consequence of an excessive inflammatory response can impair wound healing, resulting in scarring and dysfunction. However, in order to elucidate targetable factors to promote functional tissue regeneration we need to understand the molecular and cellular underpinnings of physiological angiogenesis, ranging from induction to resolution of blood vessels. Especially for avascular tissues (e.g. cornea, tendon, ligament, cartilage, etc.), limiting rather than boosting vessel growth during wound repair potentially is beneficial to restore full tissue function and may result in favourable long-term healing outcomes.

Fidgetin-Like 2 siRNA Enhances the Wound Healing Capability of a Surfactant Polymer Dressing

Microtubules (MTs) are intracellular polymers that provide structure to the cell, serve as railways for intracellular transport, and regulate many cellular activities, including cell migration. The dynamicity and function of the MT cytoskeleton are determined in large part by its regulatory proteins, including the recently discovered MT severing enzyme Fidgetin-like 2 (FL2). Downregulation of FL2 expression with small interfering RNA (siRNA) results in a more than twofold increase in cell migration rate in vitro as well as translates into improved wound-healing outcomes in in vivo mouse models. Here we utilized a commercially available surfactant polymer dressing (SPD) as a vehicle to deliver FL2 siRNA. To this end we incorporated collagen microparticles containing FL2 siRNA into SPD (SPD-FL2-siRNA) for direct application to the injury site. Topical application of SPD-FL2 siRNA to murine models of full-thickness excision wounds and full-thickness burn wounds resulted in significant improvements in the rate and quality of wound healing, as measured clinically and histologically, compared with controls. Wound healing occurred more rapidly and with high fidelity, resulting in properly organized collagen substructure. Taken together, these findings indicate that the incorporation of FL2 siRNA into existing treatment options is a promising avenue to improve wound outcomes.

Electrophilic substitution in the d-metal hexacyanoferrate(II) gelatin-immobilized matrix systems

Data of electrophilic substitution processes proceeding into the d-metal hexacyanoferrate(II) gelatin-immobilized matrix systems when they are in contact with aqueous solutions of chlorides of d-elements have been systematized and generalized. The bibliography includes 94 references.

Activation of cancer-associated fibroblasts is required for tumor neovascularization in a murine model of melanoma

Metastatic melanoma is highly fatal. Within the tumor microenvironment, the role of cancer-associated fibroblasts (CAFs) in melanoma metastasis and progression is relatively understudied. The matricellular protein CCN2 (formerly termed connective tissue growth factor, CTGF) is overexpressed, in a fashion independent of BRAF mutational status, by CAFs in melanoma. Herein, we find, in human melanoma patients, that CCN2 expression negatively correlates with survival and positively correlates with expression of neovascularization markers. To assess the role of CAFs in melanoma progression, we used C57BL/6 mice expressing a tamoxifen-dependent cre recombinase expressed under the control of a fibroblast-specific promoter/enhancer (COL1A2) to delete CCN2 postnatally in fibroblasts. Mice deleted or not for CCN2 in fibroblasts were injected subcutaneously with B16-F10 melanoma cells. Loss of CCN2 in CAFs resulted in reduced CAF activation, as detected by staining with anti-α-smooth muscle actin antibodies, and reduced tumor-induced neovascularization, as detected by micro-computed tomography (micro-CT) and staining with anti-CD31 antibodies. CCN2-deficient B16(F10) cells were defective in a tubule formation/vasculogenic mimicry assay in vitro. Mice deleted for CCN2 in CAFs also showed impaired vasculogenic mimicry of subcutaneously-injected B16-F10 cells in vivo. Our results provide new insights into the cross-talk among different cell types in the tumor microenvironment and suggest CAFs play a heretofore unappreciated role by being essential for tumor neovascularization via the production of CCN2. Our data are consistent with the hypothesis that activated CAFs are essential for melanoma metastasis and that, due to its role in this process, CCN2 is a therapeutic target for melanoma.

Fine-tuning pro-angiogenic effects of cobalt for simultaneous enhancement of vascular endothelial growth factor secretion and implant neovascularization

Rapid neovascularization of a tissue-engineered (TE) construct by the host vasculature is quintessential to warrant effective bone regeneration. This process can be promoted through active induction of angiogenic growth factor secretion or by implementation of in vitro pre-vascularization strategies. In this study, we aimed at optimizing the pro-angiogenic effect of Cobalt (Co²⁺) to enhance vascular endothelial growth factor (VEGF) expression by human periosteum-derived mesenchymal stem cells (hPDCs). Simultaneously we set out to promote microvascular network formation by co-culturing with human umbilical vein endothelial cells (HUVECs). The results showed that Co²⁺ treatments (at 50, 100 or 150 µM) significantly upregulated in vitro VEGF expression, but inhibited hPDCs growth and HUVECs network formation in co-cultures. These inhibitory effects were mitigated at lower Co²⁺ concentrations (at 5, 10 or 25 µM) while VEGF expression remained significantly upregulated and further augmented in the presence of Ascorbic Acid and Dexamethasone possibly through Runx2 upregulation. The supplements also facilitated HUVECs network formation, which was dependent on the quantity and spatial distribution of collagen type-1 matrix deposited by the hPDCs. When applied to hPDCs seeded onto calcium phosphate scaffolds, the supplements significantly induced VEGF secretion in vitro, and promoted higher vascularization upon ectopic implantation in nude mice shown by an increase of CD31 positive blood vessels within the scaffolds. Our findings provided novel insights into the pleotropic effects of Co²⁺ on angiogenesis (i.e. promoted VEGF secretion and inhibited endothelial network formation), and showed potential to pre-condition TE constructs under one culture regime for improved implant neovascularization in vivo.

STATEMENT OF SIGNIFICANT

Cobalt (Co²⁺) is known to upregulate vascular endothelial growth factor (VEGF) secretion, however it also inhibits in vitro angiogenesis through unknown Co²⁺-induced events. This limits the potential of Co²⁺ for pro-angiogenesis of tissue engineered (TE) implants. We showed that Co²⁺ upregulated VEGF expression by human periosteum-derived cells (hPDCs) but reduced the cell growth, and endothelial network formation due to reduction of col-1 matrix deposition. Supplementation with Ascorbic acid and Dexamethasone concurrently improved hPDCs growth, endothelial network formation, and upregulated VEGF secretion. In vitro pre-conditioning of hPDC-seeded TE constructs with this fine-tuned medium enhanced VEGF secretion and implant neovascularization. Our study provided novel insights into the pleotropic effects of Co²⁺ on angiogenesis and formed the basis for improving implant neovascularization.

Bone Healing Evaluation in Critical-Size Defects Treated With Xenogenous Bone Plus Porcine Collagen

PURPOSE

This study aimed to evaluate the osteoconductive features of Bio-Oss Collagen in large critical-size defects (8 mm).

MATERIALS AND METHODS

Thirty-six adult Wistar Albinus male adult rats were carried out a critical-size defect with a trephine bur of 8 mm in the calvaria. Groups were divided depending on the filling biomaterial as follows: group BO: Bio-Oss (n = 18); group BOC: Bio-Oss Collagen (n = 18). After 7, 30, and 60 days, 6 rats of each group were euthanized with anesthetic overdose. Specimens were laboratory processed for histomorphometric analysis. Histomorphometric data were statistically analyzed by analysis of variance and post-Tukey test (P < 0.05).

RESULTS

Statistical differences were found in new bone formation just in the intragroup comparison among periods after 7 and 60 postoperative days, indicating more new bone formation after 60 days (Tukey test, P = 0.029).

CONCLUSION

Under the limitation of this research, it could be concluded that Bio-Oss and Bio-Oss Collagen in this experimental model did not show osteoconductive features.

Adrenergic nerves activate an angio-metabolic switch in prostate cancer

Nerves closely associate with blood vessels and help to pattern the vasculature during development. Recent work suggests that newly formed nerve fibers may regulate the tumor microenvironment, but their exact functions are unclear. Studying mouse models of prostate cancer, we show that endothelial β-adrenergic receptor signaling via adrenergic nerve-derived noradrenaline in the prostate stroma is critical for activation of an angiogenic switch that fuels exponential tumor growth. Mechanistically, this occurs through alteration of endothelial cell metabolism. Endothelial cells typically rely on aerobic glycolysis for angiogenesis. We found that the loss of endothelial Adrb2, the gene encoding the β₂-adrenergic receptor, leads to inhibition of angiogenesis through enhancement of endothelial oxidative phosphorylation. Codeletion of Adrb2 and Cox10, a gene encoding a cytochrome IV oxidase assembly factor, prevented the metabolic shift induced by Adrb2 deletion and rescued prostate cancer progression. This cross-talk between nerves and endothelial metabolism could potentially be targeted as an anticancer therapy.