Stem cell- and scaffold-based tissue engineering approaches to osteochondral regenerative medicine

In osteochondral tissue engineering, cell recruitment, proliferation, differentiation, and patterning are critical for forming biologically and structurally viable constructs for repair of damaged or diseased tissue. However, since constructs prepared ex vivo lack the multitude of cues present in the in vivo microenvironment, cells often need to be supplied with external biological and physical stimuli to coax them toward targeted tissue functions. To determine which stimuli to present to cells, bioengineering strategies can benefit significantly from endogenous examples of skeletogenesis. As an example of developmental skeletogenesis, the developing limb bud serves as an excellent model system in which to study how osteochondral structures form from undifferentiated precursor cells. Alongside skeletal formation during embryogenesis, bone also possesses innate regenerative capacity, displaying remarkable ability to heal after damage. Bone fracture healing shares many features with bone development, driving the hypothesis that the regenerative process generally recapitulates development. Similarities and differences between the two modes of bone formation may offer insight into the special requirements for healing damaged or diseased bone. Thus, endogenous fracture healing, as an example of regenerative skeletogenesis, may also inform bioengineering strategies. In this review, we summarize the key cellular events involving stem and progenitor cells in developmental and regenerative skeletogenesis, and discuss in parallel the corresponding cell- and scaffold-based strategies that tissue engineers employ to recapitulate these events in vitro.     

Primary cortical brain cells influence osteoblast activity

The presence of neuropeptides and neuroreceptors in the bone have been reported in several studies. Bone turn-over seems to be controlled by the nervous system. The actual pathway or the control mechanism is still under investigation. In this study we investigate the changes in osteoblast cells if they are in co-culture with primary cortical brain cells. After seven days in co-culture with the primary fetal brain cells the osteoblast cells exhibited hypertrophic morphological changes and showed stronger ALP activity.     

Cloning and expression of rabbit CCT subunits eta and beta in healing cutaneous wounds

We have previously identified the CCT subunit eta as specifically reduced in healing fetal skin wounds by differential display, and observed that this reduction is not seen with any other CCT subunit. We now report the cloning and characterization of the cDNAs for rabbit CCT-eta and its closest evolutionary homolog, CCT-beta. Quantitative examination of CCT-eta and –beta message expression in healing fetal and adult wounds at 12 h post-injury confirms that CCT-eta mRNA is decreased in fetal wound tissues, but actually elevated in adult wound tissues. CCT-beta mRNA, in contrast, remains unchanged in both fetal and adult wound tissues. CCT-eta mRNA remains persistently elevated in healing adult wounds for 28 days following injury, whereas CCT-beta mRNA remains invariant throughout. CCT-eta protein is similarly increased, whereas CCT-beta protein remains unchanged. -smooth muscle actin (-SMA), a recognized substrate of CCT known to be important in integumentary wound healing, was also measured over the course of wound healing, and both mRNA and protein levels were elevated throughout the 28 days.     

唾液富组氨酸蛋白

唾液富组氨酸蛋白（histidine-rich protein, HRPs）是由人类和高等灵长动物的腮腺、下颌下腺、舌下腺分泌到唾液中的碱性小分子多肽,分子量为4 kD左右,其氨基酸序列富含组氨酸,分子表面带有正电荷和稳定的α螺旋结构．唾液富组氨酸蛋白具有广谱抗菌性,对革兰氏阴性菌、革兰氏阳性菌及真菌都有杀伤作用,其抗菌机制是作用线粒体呼吸通路,诱发ATP的释放．此外,唾液富组氨酸蛋白具有促进伤口愈合的能力,其作用机制与细胞内信号调节激酶1/2通路相关．同时,它也具有金属离子结合能力、机体免疫调节能力,其作用机制与分子表面本身结构特点和阻滞下游信号通路相关．唾液富组氨酸蛋白是一种天然的功能性蛋白质,有望应用在相关疾病的治疗上,本文对唾液富组氨酸蛋白的结构特点、功能机制、应用前景作一简要论述,为后续功能蛋白质的研发和应用奠定了理论基础．     

Activin B regulates adipose-derived mesenchymal stem cells to promote skin wound healing via activation of the MAPK signaling pathway

Adipose-derived stem cells (ADSCs) are multipotent stromal cells that can differentiate into a variety of cell types, including skin cells, and they can provide an abundant source of cells for skin tissue engineering and skin wound healing. The purpose of this study is to explore the therapeutic effects of activin B in combination with ADSCs and the possible signaling mechanism. In this study, we found that activin B was able to promote ADSC migration by inducing actin stress fiber formation in vitro. In vivo, activin B in combination with ADSCs was capable of enhancing α-SMA expression and wound closure. This combined treatment also promoted fibroblast and keratinocyte proliferation and accelerated re-epithelialization and collagen deposition. Moreover, activin B in combination with ADSCs boosted angiogenesis in the wound area. Further study of the mechanism revealed that activation of JNK and ERK signaling, but not p38 signaling, were required for activin B-induced ADSC actin stress fiber formation and cell migration. These results showed that activin B was able to activate JNK and ERK signaling pathways to induce actin stress fiber formation and ADSC migration to promote wound healing. These results suggest that combined treatment with activin B and ADSCs is a promising therapeutic strategy for the management of serious skin wounds.     

基于自组装交联的水凝胶在皮肤损伤中的应用

自组装水凝胶具有高吸水性、高保水性、良好的生物相容性、生物降解性和三维立体结构等物理优势,同时具备止血、抗菌、抗炎、抗氧化等功能优势。因此自组装水凝胶作为一种新型伤口敷料,在皮肤损伤的创面愈合和调节再生中具有广阔的应用前景。本文通过分析讨论自组装水凝胶的交联机制,阐述自组装水凝胶的功能,明确其作为伤口敷料在皮肤损伤中的优势,总结自组装水凝胶在皮肤损伤应用中的发展趋势,展望自组装水凝胶的未来方向,有助于更全面地了解自组装水凝胶,为自组装水凝胶的多技术联合应用提供新思路。     

Effects of genistein on early-stage cutaneous wound healing

Wound healing occurs in three sequential phases: hemostasis and inflammation, proliferation, and remodeling. Inflammation, the earliest phase, is considered a critical period for wound healing because immune cells remove damaged tissues, foreign debris, and remaining dead tissue. Wound healing would be delayed without inflammation, and this phase is affected by antioxidation capacity. Therefore, we hypothesized that genistein, which has an antioxidant effect, might modulate the wound healing process by altering the inflammatory response. After three days of acclimation, mice were divided into three groups: control, 0.025% genistein, and 0.1% genistein. After two weeks of an experimental diet, skin wounds were induced. Wounded skin areas were imaged, and the healing rate calculated. To measure lipid peroxidation, antioxidant enzyme expression and activity, and pro-inflammatory cytokine expression, skin and liver tissues were harvested at 12, 24, 48, and 72 h. Genistein did not affect body weight. The rate of wound closure in mice fed genistein was significantly faster than in the control group during the early stage of wound healing, especially in first three days. Cu, Zn-SOD and Mn-SOD expression in wound skin tissue in the 0.1% genistein group was lower than in the control group. However, CAT expression did not differ among groups. We also found that genistein modulated NF-κB and TNF-α expression during the early stage of wound healing. The genistein group had significantly lower hepatic lipid peroxidation and higher SOD, CAT, and GPx activities than the control group. These results suggest that genistein supplementation reduces oxidative stress by increasing antioxidant capacity and modulating proinflammatory cytokine expression during the early stage of wound healing.     

Wound healing and blastema formation in regenerating digit tips of adult mice

Amputation of the distal region of the terminal phalanx of mice causes an initial wound healing response followed by blastema formation and the regeneration of the digit tip. Thus far, most regeneration studies have focused in embryonic or neonatal models and few studies have examined adult digit regeneration. Here we report on studies that include morphological, immunohistological, and volumetric analyses of adult digit regeneration stages. The regenerated digit is grossly similar to the original, but is not a perfect replacement. Re-differentiation of the digit tip occurs by intramembranous ossification forming a trabecular bone network that replaces the amputated cortical bone. The digit blastema is comprised of proliferating cells that express vimentin, a general mesenchymal marker, and by comparison to mature tissues, contains fewer endothelial cells indicative of reduced vascularity. The majority of blastemal cells expressing the stem cell marker SCA-1, also co-express the endothelial marker CD31, suggesting the presence of endothelial progenitor cells. Epidermal closure during wound healing is very slow and is characterized by a failure of the wound epidermis to close across amputated bone. Instead, the wound healing phase is associated with an osteoclast response that degrades the stump bone allowing the wound epidermis to undercut the distal bone resulting in a novel re-amputation response. Thus, the regeneration process initiates from a level that is proximal to the original plane of amputation.     

Mallotus philippinensis bark extracts promote preferential migration of mesenchymal stem cells and improve wound healing in mice

In the present study, we report the effects of the ethanol extract from Mallotus philippinensis bark (EMPB) on mesenchymal stem cell (MSC) proliferation, migration, and wound healing in vitro and in a mouse model. Chemotaxis assays demonstrated that EMPB acted an MSC chemoattractant and that the main chemotactic activity of EMPB may be due to the effects of cinnamtannin B-1. Flow cytometric analysis of peripheral blood mononuclear cells in EMPB-injected mice indicated that EMPB enhanced the mobilization of endogenous MSCs into blood circulation. Bioluminescent whole-animal imaging of luciferase-expressing MSCs revealed that EMPB augmented the homing of MSCs to wounds. In addition, the efficacy of EMPB on migration of MSCs was higher than that of other skin cell types, and EMPB treatment improved of wound healing in a diabetic mouse model. The histopathological characteristics demonstrated that the effects of EMPB treatment resembled MSC-induced tissue repair. Taken together, these results suggested that EMPB activated the mobilization and homing of MSCs to wounds and that enhancement of MSC migration may improve wound healing.