Treating a collagen scaffold with a low concentration of nicotine promoted angiogenesis and wound healing

Sympathetic System in Wound Healing: Multistage Control in Normal and Diabetic Skin

In this review, we discuss sympathetic regulation in normal and diabetic wound healing. Experimental denervation studies have confirmed that sympathetic nerve endings in skin have an important and complex role in wound healing. Vasoconstrictor neurons secrete norepinephrine (NE) and neuropeptide Y (NPY). Both mediators decrease blood flow and interact with inflammatory cells and keratinocytes. NE acts in an ambiguous way depending on receptor type. Beta2-adrenoceptors could be activated near sympathetic endings; they suppress inflammation and re-epithelialization. Alpha1- and alpha2-adrenoceptors induce inflammation and activate keratinocytes. Sudomotor neurons secrete acetylcholine (ACh) and vasoactive intestinal peptide (VIP). Both induce vasodilatation, angiogenesis, inflammation, keratinocytes proliferation and migration. In healthy skin, all effects are important for successful healing. In treatment of diabetic ulcers, mediator balance could be shifted in different ways. Beta2-adrenoceptors blockade and nicotinic ACh receptors activation are the most promising directions in treatment of diabetic ulcers with neuropathy, but they require further research.

Annexin A1-derived peptide Ac2-26 facilitates wound healing in diabetic mice

Impaired wound healing is a common complication of diabetes. In diabetic wounds, macrophages present dysfunctional efferocytosis and abnormal phenotypes, which could result in excessive neutrophil accumulation and prolonged inflammation, thereby eventually hindering wound repair. ANXA1 N-terminal peptide Ac2-26 exhibits a high potential in mitigating inflammation and improving repair; however, its efficacy in diabetic wound repair remains unclear. In this study, a cutaneous excisional wound model was built in genetically diabetic mice. Ac2-26 or a vehicle solution was employed locally in wound sites. Subsequently, wound zones were measured and sampled at different time intervals post-wounding. Using hematoxylin-eosin and Masson's trichrome staining, we observed the histopathological variations and collagen deposition in wound samples. Based on immunohistochemistry and immunofluorescence, the numbers of neutrophils, macrophages, and CD206-positive macrophages in the wound samples were determined. Cytokine expression in wound samples was studied by immunoblot assay. Results showed that Ac2-26 treatment could facilitate diabetic wound closure, down-regulate the number of neutrophils, and improve angiogenesis and collagen deposition. In addition, Ac2-26 application expedited macrophage recruitment and up-regulated the percentage of macrophages expressing CD206, which is a marker for M2 macrophages. Moreover, Ac2-26 inhibited the expressions of TNF-α and IL-6 and up-regulated the expressions of IL-10, TGF-β, and VEGFA during diabetic wound healing. Hence, based on the aforementioned findings, Ac2-26 application in diabetic wounds could exert anti-inflammatory and pro-repair effects by reducing neutrophil accumulation and facilitating M2 macrophage development.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

Physical Properties of Implanted Porous Bioscaffolds Regulate Skin Repair: Focusing on Mechanical and Structural Features

Porous bioscaffolds are applied to facilitate skin repair since the early 1990s, but a perfect regeneration outcome has yet to be achieved. Until now, most efforts have focused on modulating the chemical properties of bioscaffolds, while physical properties are traditionally overlooked. Recent advances in mechanobiology and mechanotherapy have highlighted the importance of biomaterials' physical properties in the regulation of cellular behaviors and regenerative processes. In skin repair, the mechanical and structural features of porous bioscaffolds are two major physical properties that determine therapeutic efficacy. Here, first an overview of natural skin repair with an emphasis on the major biophysically sensitive cell types involved in this multistage process is provided, followed by an introduction of the four roles of bioscaffolds as skin implants. Then, how the mechanical and structural features of bioscaffolds influence these four roles is discussed. The mechanical and structural features of porous bioscaffolds should be tailored to balance the acceleration of wound closure and functional improvements of the repaired skin. This study emphasizes that decoupling and precise control of the mechanical and structural features of bioscaffolds are significant aspects that should be considered in future biomaterial optimization, which can build a foundation to ultimately achieve perfect skin regeneration outcomes.

The Effects of Isopropyl Methylphosphono-Fluoridate (IMPF) Poisoning on Tumor Growth and Angiogenesis in BALB/C Mice

Background

Acetylcholinesterase (AChE) and cholinergic receptors have an important role in the immune system and angiogenesis. This work evaluated the effects of isopropyl methylphosphonofluoridate (IMPF), an irreversible inhibitor of AChE, on tumor growth and selected parameters associated with tumor angiogenesis.

Material/Methods

Experiments were performed on male BALB/c mice exposed to IMPF (study group) or saline buffer (control group) and inoculated with L-1 sarcoma; the number of new blood vessels (TIA test) and the level of αvβ3 integrin (¹³¹I-MAb-antiβ3 assay) were analyzed at seven, 14, or 21 days after implantation of the tumor cells.

Results

The IMPF poisoning affected tumor angiogenesis (TIA test). There was a statistically significant increase in the number of newly forming blood vessels in the group subjected to IMPF and inoculated with tumor cells.

Conclusions

This study showed that IMPF had a significant effect on the regulation of lymphocyte-induced angiogenesis and the modulation of angiogenic and pro-inflammatory cytokines secretion. The observed effects suggest involvement of neuronal and/or non-neuronal cholinergic signaling pathway.

Current Advancements and Strategies in Tissue Engineering for Wound Healing: A Comprehensive Review

Significance: With an aging population leading to an increase in diabetes and associated cutaneous wounds, there is a pressing clinical need to improve wound-healing therapies. Recent Advances: Tissue engineering approaches for wound healing and skin regeneration have been developed over the past few decades. A review of current literature has identified common themes and strategies that are proving successful within the field: The delivery of cells, mainly mesenchymal stem cells, within scaffolds of the native matrix is one such strategy. We overview these approaches and give insights into mechanisms that aid wound healing in different clinical scenarios. Critical Issues: We discuss the importance of the biomimetic niche, and how recapitulating elements of the native microenvironment of cells can help direct cell behavior and fate. Future Directions: It is crucial that during the continued development of tissue engineering in wound repair, there is close collaboration between tissue engineers and clinicians to maintain the translational efficacy of this approach.

Efficacy of gelatin gel sheets in sustaining the release of basic fibroblast growth factor for murine skin defects

BACKGROUND

Gelatin has been used as a material sustaining the release of basic fibroblast growth factor (bFGF), which promotes fibroblast proliferation and capillary formation and accelerates wound healing. In the application of these materials, bFGF is impregnated immediately before application, and it is difficult to conform the shape to the wound. In this study, we prepared a pliable and plastic gelatin gel sheet (GGS) that sustains bFGF and conforms to the shape of the wound as a result of cross-linking just before application. In addition, we examined the sustained release profile of bFGF from GGS and its effect on wound healing in murine skin defects.

MATERIALS AND METHODS

A 13-wt% gelatin solution was mixed with bFGF before cross-linking with 1% glutaraldehyde solution. GGSs impregnated with 7 μg/cm(2) of bFGF were incubated in phosphate-buffered saline and collagenase solution, and GGS degradation and bFGF release were evaluated. In the murine experiments, GGSs treated without bFGF and GGSs impregnated with 1, 3.5, 7, or 14 μg/cm(2) of bFGF were applied to full-thickness skin defects created on the backs of C57BL/6JJcl mice, and the wound closure, epithelial length, extent of granulation tissue and capillary formation were compared.

RESULTS

bFGF was released according to the degradation of GGS in phosphate-buffered saline, and the remaining bFGF was released in collagenase solution. In the animal studies, epithelialization was accelerated in the GGSs treated with 1 and 3.5 μg/cm(2) of bFGF, and granulation tissue formation and angiogenesis were promoted based on the amount of bFGF impregnated into the GGS.

CONCLUSIONS

GGS impregnated with bFGF is capable of sustaining the release of bFGF, with consequent accelerated epithelialization, granulation tissue formation, and angiogenesis in vivo. GGS is a novel and promising wound dressing that sustains bFGF and can be adapted to the shape of various wounds in the treatment of both acute and chronic wounds.

Efficacy of gelatin gel sheets sustaining epidermal growth factor for murine skin defects

BACKGROUND

Epidermal growth factor (EGF) plays an important role in wound healing. However, EGF must be applied daily due to rapid inactivation in vivo. We investigated the sustained release of EGF from gelatin gel sheets (GGSs) and the efficacy of GGSs impregnated with EGF for promoting wound healing.

MATERIALS AND METHODS

GGSs impregnated with EGF were prepared by cross-linking via glutaraldehyde to gelatin solution containing EGF. The sustained release of EGF and the bioactivity of released EGF were evaluated. Then, three kinds of GGSs containing NSS (normal saline solution; NSS group), 2.5 μg of EGF (EGF-L group), or 25 μg of EGF (EGF-H group) were applied to full-thickness skin defects created on the backs of mice. The wounds covered with polyurethane film without GGS were used as a control (PUF group). The wound area, neoepithelium length, regenerated granulation tissue, and newly formed capillaries were evaluated.

RESULTS

EGF was sustained and released from GGS as it degraded. The bioactivity of released EGF was confirmed. EGF-L group promoted the neoepithelium length, regenerated granulation tissue, and newly formed capillaries compared with those in the PUF and NSS groups. The area of regenerated granulation tissue in the NSS group (week 1: 2.6 + 0.2 mm(2), week 2: 2.8 + 0.3 mm(2)) was larger than that in the PUF group (week 1: 0.6 + 0.1 mm(2), week 2: 1.0 + 0.1 mm(2)). The area of newly formed capillaries in the EGF-L group (9967 + 1903 μm(2)) was larger than that of the EGF-H group (3485 + 1050 μm(2)).

CONCLUSIONS

GGSs impregnated with EGF-L showed promising results regarding wound healing.

Exploration of the wound healing effect of topical administration of nicotine in combination with collagen scaffold in a rabbit model

Nicotine has been reported to prolong the wound healing; however, we showed that the topical application of 10(-4) M nicotine promoted murine wound healing. The objective of this study was to explore the wound healing effects of nicotine in combination with collagen scaffold using skin defects in rabbit. Three full-thickness skin defects 8 mm in diameter were made on the rabbit auricle. Artificial dermis was applied to the defects, and 10 μl of nicotine solution (10(-5), 10(-4), and10(-3) M), bFGF solution (0.5 μg/10 μl), and both bFGF and 10(-4) M nicotine solutions were injected into the artificial dermis once daily for 7 days. Rabbits were sacrificed on day 10, 15, or 20, and the wound healing process was evaluated. bFGF was superior in the formation of the dermis-like tissue and capillaries. In nicotine groups, the epithelial length and the dermis-like tissue formations in the 10(-4) M group were superior, in contrast, those were inhibited in the 10(-3) M group. The synergistic effect of bFGF and 10(-4) M nicotine was not confirmed. This study suggests that the topical application of 10(-4) M nicotine promoted wound healing in rabbit, but the effect was not apparent compared with murine models.

Biomaterials as carrier, barrier and reactor for cell-based regenerative medicine

Cell therapy has achieved tremendous success in regenerative medicine in the past several decades. However, challenges such as cell loss, death and immune-rejection after transplantation still persist. Biomaterials have been designed as carriers to deliver cells to desirable region for local tissue regeneration; as barriers to protect transplanted cells from host immune attack; or as reactors to stimulate host cell recruitment, homing and differentiation. With the assistance of biomaterials, improvement in treatment efficiency has been demonstrated in numerous animal models of degenerative diseases compared with routine free cell-based therapy. Emerging clinical applications of biomaterial assisted cell therapies further highlight their great promise in regenerative therapy and even cure for complex diseases, which have been failed to realize by conventional therapeutic approaches.

Mechanisms of growth-promoting and tumor-protecting effects of epithelial nicotinic acetylcholine receptors

Although the role of nicotine as a carcinogen is debatable, it is widely accepted that it contributes to cancer by promoting growth and survival of mutated cell clones and protecting them from the chemo- and radiotherapy-induced apoptosis. On the cell membrane (cm), the nicotinic acetylcholine (ACh) receptors (nAChRs) implement upregulation of proliferative and survival genes. Nicotine also can permeate cells and activate mitochondrial (mt)-nAChRs coupled to inhibition of the mitochondrial permeability transition pore (mPTP) opening, thus preventing apoptosis. In this study, we sought to pin down principal mechanisms mediating the tumor-promoting activities of nicotine resulting from activation of cm- and mt-nAChRs in oral and lung cancer cells, SCC25 and SW900, respectively. Activated cm-nAChRs were found to form complexes with receptors for EGF and VEGEF via the α7 and β2 nAChR subunits, respectively, whereas activated mt-nAChRs physically associated with the intramitochondrial protein kinases PI3K and Src via the α7 and β4 subunits. This was associated with upregulated expression of cyclin D1/activation of ERK1/2 and inhibition of mPTP opening, respectively, as well as upregulated proliferation and resistance to H(2)O(2)-induced apoptosis. The molecular synergy between cm-nAChRs and growth factor receptors helps explain how one biological mediator, such as ACh, can modulate activity of the other, such as a growth factor, and vice versa. Establishment of functional coupling of mt-nAChRs to regulation of mPTP opening provides a novel mechanism of nicotine-dependent protection from cell death. Further elucidation of this novel mechanism of tumor-promoting activities of nicotine should have a strong translational impact, because extraneuronal nAChRs may provide a novel molecular target to prevent, reverse, or retard progression of both nicotine-related and unrelated cancers.

Mechanisms of tumor-promoting activities of nicotine in lung cancer: synergistic effects of cell membrane and mitochondrial nicotinic acetylcholine receptors

Background

One of the major controversies of contemporary medicine is created by an increased consumption of nicotine and growing evidence of its connection to cancer, which urges elucidation of the molecular mechanisms of oncogenic effects of inhaled nicotine. Current research indicates that nicotinergic regulation of cell survival and death is more complex than originally thought, because it involves signals emanating from both cell membrane (cm)- and mitochondrial (mt)-nicotinic acetylcholine receptors (nAChRs). In this study, we elaborated on the novel concept linking cm-nAChRs to growth promotion of lung cancer cells through cooperation with the growth factor signaling, and mt-nAChRs — to inhibition of intrinsic apoptosis through prevention of opening of mitochondrial permeability transition pore (mPTP).

Methods

Experiments were performed with normal human lobar bronchial epithelial cells, the lung squamous cell carcinoma line SW900, and intact and NNK-transformed immortalized human bronchial cell line BEP2D.

Results

We demonstrated that the growth-promoting effect of nicotine mediated by activation of α7 cm-nAChR synergizes mainly with that of epidermal growth factor (EGF), α3 — vascular endothelial growth factor (VEGF), α4 — insulin-like growth factor I (IGF-I) and VEGF, whereas α9 with EGF, IGF-I and VEGF. We also established the ligand-binding abilities of mt-nAChRs and demonstrated that quantity of the mt-nAChRs coupled to inhibition of mPTP opening increases upon malignant transformation.

Conclusions

These results indicated that the biological sum of simultaneous activation of cm- and mt-nAChRs produces a combination of growth-promoting and anti-apoptotic signals that implement the tumor-promoting action of nicotine on lung cells. Therefore, nAChRs may be a promising molecular target to arrest lung cancer progression and re-open mitochondrial apoptotic pathways.

Connections of nicotine to cancer

This Opinion article discusses emerging evidence of direct contributions of nicotine to cancer onset and growth. The list of cancers reportedly connected to nicotine is expanding and presently includes small-cell and non-small-cell lung carcinomas, as well as head and neck, gastric, pancreatic, gallbladder, liver, colon, breast, cervical, urinary bladder and kidney cancers. The mutagenic and tumour-promoting activities of nicotine may result from its ability to damage the genome, disrupt cellular metabolic processes, and facilitate growth and spreading of transformed cells. The nicotinic acetylcholine receptors (nAChRs), which are activated by nicotine, can activate several signalling pathways that can have tumorigenic effects, and these receptors might be able to be targeted for cancer therapy or prevention. There is also growing evidence that the unique genetic makeup of an individual, such as polymorphisms in genes encoding nAChR subunits, might influence the susceptibility of that individual to the pathobiological effects of nicotine. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the evaluation of regulations on nicotine product manufacturing, distribution and marketing.

Is nicotine still the bad guy? Summary of the effects of smoking on patients with head and neck cancer in the postoperative period and the uses of nicotine replacement therapy in these patients

Smoking has long been implicated in the development and progression of numerous postoperative complications. The cause is largely thought to be the presence of reactive oxygen species (ROS) in cigarette smoke, which attenuates inflammation and affects neutrophil function. Wound healing is further compromised by deficiencies in vitamins C and E, which result from a higher vitamin turnover secondary to the oxidative stress produced by smoking. However, studies recently have found that the effects of nicotine may benefit healing if used in isolation. We summarise the effects that smoking and abstaining from smoking can have on inflammation and wound healing, and describe the possible benefits that nicotine replacement and antioxidant supplements can give.