Solid Free-Form Fabrication-Based PCL/HA Scaffolds Fabricated with a Multi-head Deposition System for Bone Tissue Engineering

In this study, we fabricated polycaprolactone/hydroxyapatite (PCL/HA) scaffolds with a multi-head deposition system, a solid free-form fabrication technology that was developed in our previous study. The bone regeneration potential of the scaffolds was compared with that of PCL scaffolds fabricated with the same system. The fabricated scaffolds had a pore size of 400 μm and a porosity of 66.7%. The PCL/HA scaffolds had higher mechanical strength and modulus than the PCL scaffolds. To compare the osteogenic potential, the two types of scaffolds were seeded with rat osteoblasts and cultured in vitro or implanted subcutaneously into athymic mice. The cells cultured on PCL/HA scaffolds expressed higher levels of osteopontin and osteonectin, both of which are osteogenic proteins. The PCL/HA scaffolds resulted in larger bone area and calcium deposition in the implants compared to the PCL scaffolds.     

Immunology of the central nervous system

Abstract

Immunology of the central nervous system (CNS) is a growing field of study. Until recently the brain was considered an 'immunologically privileged' site. It is increasingly apparent that the CNS has a significant but tightly regulated capability to mount an inflammatory and immune response. This article serves as an introduction to the special section at the start of this issue on neuroimmunology. We also focus on several immunological concepts that are particularly relevant in the context of neuroimmunology—cross-reactivity, the immunological synapse and the nature of the immune response to transplantation in the CNS. We conclude that the fundamental concepts are common to all branches of immunology. Better understanding of the basic mechanisms will blur the borders between the different areas of immunology.     

PROLIFERATION AND DIFFERENTIATION OF NEURAL STEM CELLS IN ADULT RATS AFTER CEREBRAL INFARCTION

Objective To investigate proliferation and differentiation of neural stem cells in adult rats after cerebral infarction. Methods Models of cerebral infarction in rats were made and the time-course expression of bromodeoxyuridine (BrdU), Musashil, glial fibrillary acidic protein (GFAP), and neuronal nuclear antigen (NeuN) were determined by immunohistochemistry and immunofluorescence staining. BrdU and Musashil were used to mark dividing neural stem cells. GFAP and NeuN were used to mark differentiating neural stem cells. Results Compared with controls, the number of BrdU-labeled and BrdU-labeled with Musashil-positive cells increased strikingly 1 day after cerebral infarction; approximately 6 fold with a peak 7 days later; markedly decreased 14 days later, but was still elevated compared with that of controls; decling to the control level 28 days later. The number of BrdU-labeled with GFAP-positive cells nearly remained unchanged in the hippocampus after cerebral infarction. The number of BrdU-labeled with NeuN-positive cells increased strikingly 14 days after cerebral infarction, reached maximum peak in the hippocampus 28 days after cerebral infarction in rats. Conclusion Cerebral infarction stimulate proliferation of inherent neural stem cells and most proliferated neural stem cells differentiate into neurons.     

巴戟天离体培养及植株再生的研究

以巴戟天无菌苗的茎尖、带节茎、无节茎为材料进行离体培养。结果表明 :外植体表面消毒采用70 %乙醇预处理 30s ,再用 0 .1%的升汞浸泡 10～ 15min ,效果较好。茎尖和带节茎培养 ,于含有 6-苄基氨基嘌呤 ( 6-benzylaminopurine。BA)的MurashigeandTucker (MT)培养基上 ,均能直接出芽 ,带节茎出芽率最高 ,为 97.5%。适宜的BA浓度为 1mg·L- 1,BA浓度升高 ,出芽率下降。根的诱导 ,以MT加 0 .2～0 .5mg·L- 1的萘乙酸 (naphthleneaceticacid ,NAA)培养基较好 ,生根率可达 80 .0 %以上     

Mouse Digit Tip Regeneration Is Mechanical Load Dependent

Amputation of the mouse digit tip results in blastema-mediated regeneration. In this model, new bone regenerates de novo to lengthen the amputated stump bone, resulting in a functional replacement of the terminal phalangeal element along with associated non-skeletal tissues. Physiological examples of bone repair, such as distraction osteogenesis and fracture repair, are well known to require mechanical loading. However, the role of mechanical loading during mammalian digit tip regeneration is unknown. In this study, we demonstrate that reducing mechanical loading inhibits blastema formation by attenuating bone resorption and wound closure, resulting in the complete inhibition of digit regeneration. Mechanical unloading effects on wound healing and regeneration are completely reversible when mechanical loading is restored. Mechanical unloading after blastema formation results in a reduced rate of de novo bone formation, demonstrating mechanical load dependence of the bone regenerative response. Moreover, enhancing the wound-healing response of mechanically unloaded digits with the cyanoacrylate tissue adhesive Dermabond improves wound closure and partially rescues digit tip regeneration. Taken together, these results demonstrate that mammalian digit tip regeneration is mechanical load-dependent. Given that human fingertip regeneration shares many characteristics with the mouse digit tip, these results identify mechanical load as a previously unappreciated requirement for de novo bone regeneration in humans. © 2021 American Society for Bone and Mineral Research (ASBMR).     

Comparison between NRT-based MAPs and behaviourally measured MAPs at different stimulation rates – a multicentre investigation

Abstract

Seventeen adult subjects participated in a multicentre trial to compare the performance between an NRT-based MAP and their behavioural MAP. The NRT-based MAP was made using a correction factor to predict T/C levels, calculated from the difference between the ECAP threshold ('T-NRT') and the measured T/C levels at electrode 10, as described by Brown et al. (2000). A secondary aim was to compare T/C levels in behavioural MAPs at different stimulation rates with the predicted T/C levels in NRT-based MAPs. Performance with both MAPs was evaluated using CNC words and sentences. Variations in the T/C levels between all MAPs were found, although results of the speech discrimination tests demonstrated no statistically significant difference between behavioural and NRT-based MAPs.     

Apatite-Coated Porous Poly(lactic-co-glycolic acid) Microspheres as an Injectable Bone Substitute

Previously, we developed an apatite-coated non-porous poly(lactic-co-glycolic acid) (PLGA) microsphere (ANPM) as an injectable bone substitute. We hypothesized that an apatite-coated porous PLGA microsphere (APPM) would have enhanced osteogenic potential compared to that of an ANPM. To test the hypothesis, critical-sized bone defects were made in mouse calvaria, and APPMs and ANPMs were implanted in the defects for 8 weeks. New bone formed around both types of bone substitutes implanted in mouse calvarial defects. Importantly, the portion of bone-like tissue area in the implant cross-sectional area was significantly higher in the APPM group than in the ANPM group (36.9% versus 14.6%, P < 0.001). Fluorochrome-labeling analysis showed that bone regeneration occurred in the pores of implanted APPMs. The results show that APPM may be useful as a bone substitute in orthopedic applications.     

Effects of Epimedium flavonoids on proliferation and differentiation of neural stem cells in vitro

Abstract

Objective: The purpose of this study is to investigate the effects of Epimedium flavonoids (EF), which is extracted from a traditional Chinese Epimedium herb, and its effect on the proliferation and differentiation of neural stem cells (NSCs) in vitro.

Methods: The single cells isolated from the hippocampi of 1 day old neonatal rats were cultured in a serum-free condition medium DMEM/F12 (1 : 1) with different concentrations of EF or 20 ng/ml epidermal growth factor (EGF) and 10 ng/ml basic fibroblast growth factor (bFGF). After 7 and 28 days, the neurospheres' diameters were measured. The formed neurospheres were cultured in the differentiation medium containing EF or 10% fetal bovine serum (FBS). After 12 hours and 7 days, immunofluorescent studies for nestin, Musashi-1, BrdU, β-III-tubulin, NF-200 and GFAP were performed. The number and lengths of 10–15 axons of NF-200 immunopositive cells were measured.

Results: The results showed that the isolated cells had the ability to propagate as neurospheres in the medium with 200 and 400 m g/ml EF, but without any EGF or bFGF, and the volume of neurospheres increase gradually from 7 to 28 days. In comparison with FBS control, the number of NF-200 positive neurons had significantly increased in the EF groups where the newborn neurons were morphologically more mature and able to migrate farther away from neurospheres than in the FBS control.

Discussion: The results demonstrate that EF effectively promotes the proliferation and differentiation of NSCs in vitro, suggesting that EF may have new properties of regulating central nervous system function by neurogenesis.     

Folate stimulates ERK1/2 phosphorylation and cell proliferation in fetal neural stem cells

Abstract

Cellular events for neural progenitor cells, such as proliferation and differentiation, are regulated by multiple intrinsic and extrinsic cell signals. Folate plays central roles in central nervous system development, so folate, as an extrinsic signal, may affect neural stem cell (NSC) proliferation and differentiation. In this study, we have investigated the effect of folate on extracellular signal-regulated kinase (ERK1/2) phosphorylation, cell proliferation and apoptosis in fetal NSCs. The results showed that treatment of neurospheres with folate increased ERK1/2 phosphorylation and cell proliferation in a concentration-dependent manner. Folate also decreased the percentage of apoptotic cells. All of these effects of folate were prevented by a selective inhibitor (U0126) of mitogen-activated/ERK kinase 1/2. In conclusion, fetal NSCs respond to folate with ERKl/2 phosphorylation, cell proliferation and decreased apoptosis. This mechanism may mediate the regulation by folate of neurogenesis in the central nervous system.     

Three-dimensional porous hydroxyapatite/collagen composite with rubber-like elasticity

A three-dimensional porous hydroxyapatite/collagen (HAp/Col) composite with a random pore structure was fabricated using freeze-drying processes; the self-organized HAp/Col nanocomposite with a weight ratio of 80.5:19.5, freeze-dried, was kneaded in 100 mM sodium phosphate buffer, frozen at ?20°C and freeze-dried. The cross-linkage of Col molecules was introduced dehydrothermally at 140°C in vacuo. The porous composite had a porosity of 94.7% with pore sizes between 200 and 500 μm. The compressive stress for the wet porous composite in phosphate buffer saline (PBS) was gradually decreased during 20 days incubation with a small amount of weight loss. The cyclic and time-course compression tests showed good repeatability of stress and well-recovery of its height, and caused no collapse of the porous composite. The implantation of the porous composite in rat bone holes showed the biodegradable property and new bone formation occurred in the pores without inflammatory response. The porous composite fabricated has good flexibility and rubber-like elasticity, and is a promising bone regenerative material.