Cellular therapeutics and immunotherapies in wound healing - on the pulse of time?

Chronic, non-healing wounds represent a significant challenge for healthcare systems worldwide, often requiring significant human and financial resources. Chronic wounds arise from the complex interplay of underlying comorbidities, such as diabetes or vascular diseases, lifestyle factors, and genetic risk profiles which may predispose extremities to local ischemia. Injuries are further exacerbated by bacterial colonization and the formation of biofilms. Infection, consequently, perpetuates a chronic inflammatory microenvironment, preventing the progression and completion of normal wound healing. The current standard of care (SOC) for chronic wounds involves surgical debridement along with localized wound irrigation, which requires inpatient care under general anesthesia. This could be followed by, if necessary, defect coverage via a reconstructive ladder utilizing wound debridement along with skin graft, local, or free flap techniques once the wound conditions are stabilized and adequate blood supply is restored. To promote physiological wound healing, a variety of approaches have been subjected to translational research. Beyond conventional wound healing drugs and devices that currently supplement treatments, cellular and immunotherapies have emerged as promising therapeutics that can behave as tailored therapies with cell- or molecule-specific wound healing properties. However, in contrast to the clinical omnipresence of chronic wound healing disorders, there remains a shortage of studies condensing the current body of evidence on cellular therapies and immunotherapies for chronic wounds. This review provides a comprehensive exploration of current therapies, experimental approaches, and translational studies, offering insights into their efficacy and limitations. Ultimately, we hope this line of research may serve as an evidence-based foundation to guide further experimental and translational approaches and optimize patient care long-term.

Impact of Nicotine Replacement Therapy on Breast Surgery Outcomes

BACKGROUND

 Smoking cessation therapy, including nicotine replacement therapy (NRT), is used perioperatively to assist patients to reduce their tobacco smoke intake and consequently decrease their risk of smoking-associated complications. There are, however, theoretical concerns that nicotine-induced peripheral vasoconstriction could impair wound healing. This study investigated the effect of NRT on postoperative outcomes in patients undergoing breast surgery.

METHODS

 A retrospective chart review of patients undergoing breast surgery within the Yale New Haven Health System from the years 2014 to 2020 was performed. Documented smoking status within 6 months before surgery, use or prescription of NRT, type of surgery, and surgical complications of infection, wound dehiscence, tissue necrosis, hematoma, seroma, fat necrosis, and return to operating room within 30 days were recorded. Demographic and complication data were compared between patients with NRT usage and those without using t-tests and chi-square analyses. Multivariable logistic regression models were created to predict the effect of NRT usage on the occurrence of any complication.

RESULTS

 A total of 613 breast procedures met inclusion criteria, of which 105 (17.2%) had documented NRT use. The NRT cohort and the non-NRT cohort were well balanced with respect to demographics and procedural variables. Upon multivariable modeling for risk of any surgical complication, NRT was not a significant predictor (odds ratio [OR]: 1.199, p = 0.607 and OR: 0.974, p = 0.912, respectively), whereas procedure type, increased body mass index, and increased age were.

CONCLUSION

 NRT use was not associated with an increased risk of postoperative complications compared with not using NRT as part of smoking cessation therapy prior to operation.

Apoptosis recognition receptors regulate skin tissue repair in mice

Apoptosis and clearance of apoptotic cells via efferocytosis are evolutionarily conserved processes that drive tissue repair. However, the mechanisms by which recognition and clearance of apoptotic cells regulate repair are not fully understood. Here, we use single-cell RNA sequencing to provide a map of the cellular dynamics during early inflammation in mouse skin wounds. We find that apoptotic pathways and efferocytosis receptors are elevated in fibroblasts and immune cells, including resident Lyve1+ macrophages, during inflammation. Interestingly, human diabetic foot wounds upregulate mRNAs for efferocytosis pathway genes and display altered efferocytosis signaling via the receptor Axl and its ligand Gas6. During early inflammation in mouse wounds, we detect upregulation of Axl in dendritic cells and fibroblasts via TLR3-independent mechanisms. Inhibition studies in vivo in mice reveal that Axl signaling is required for wound repair but is dispensable for efferocytosis. By contrast, inhibition of another efferocytosis receptor, Timd4, in mouse wounds decreases efferocytosis and abrogates wound repair. These data highlight the distinct mechanisms by which apoptotic cell detection coordinates tissue repair and provides potential therapeutic targets for chronic wounds in diabetic patients.

Innovations in Stem Cell Therapy for Diabetic Wound Healing

Significance: The global burden of diabetic wounds, particularly diabetic foot ulcers, continues to have large economic and social impact throughout the world. Current strategies are not sufficient to overcome this burden of disease. Finding newer, more advanced regenerative cell and tissue-based strategies to reduce morbidity remains paramount. Recent Advances: Recent advances in stem cell therapies are discussed. We also highlight the practical issues of translating these advancing technologies into the clinical setting. Critical Issues: We discuss the use of somatic and induced pluripotent stem cells and the stromal vascular fraction, as well as innovations, including the use of 3D bioprinting of skin. We also explore related issues of using regenerative techniques in clinical practice, including the current regulatory landscape and translatability of in vivo research. Future Directions: Advances in stem cell manipulation showcase the best therapeutic resources available to enhance mechanisms of wound healing such as angiogenesis, cell proliferation, and collagen synthesis; potential methods include changing the scaffold microenvironment, including relative oxygen tension, and the use of gene modification and nanotechnology. Secretome engineering, particularly the use of extracellular vesicles, may be another potential cell-derived therapeutic that may enable use of cell-free translational therapy.

TNF-α Preconditioning Promotes a Proangiogenic Phenotype in hiPSC-Derived Vascular Smooth Muscle Cells

Introduction

hiPSC-VSMCs have been suggested as therapeutic agents for wound healing and revascularization through the secretion of proangiogenic factors. However, methods of increasing cell paracrine secretion and survivability have thus far yielded inconsistent results. This study investigates the effect of pre-conditioning of hiPSC-VSMCs with TNF-α and their integration into 3D collagen scaffolds on cellular viability and secretome.

Methods

hiPSC-VSMCs were dual-plated in a 2D environment. TNF-α was introduced to one plate. Following incubation, cells from each plate were divided and added to type-I collagen scaffolds. TNF-α was introduced to two sets of scaffolds, one from each 2D plate. Following incubation, scaffolds were harvested for their media, tested for cell survivability, cytotoxicity, and imaged. Intra-media VEGF and bFGF levels were evaluated using ELISA testing.

Results

hiPSC-VSMCs exposed to TNF-α during collagen scaffold proliferation and preconditioning showed an increase in cell viability and less cytotoxicity compared to non-exposed cells and solely-preconditioned cells. Significant increases in bFGF expression were found in pre-conditioned cell groups with further increases found in cells subsequently exposed during intra-scaffold conditioning. A significant increase in VEGF expression was found in cell groups exposed during both pre-conditioning and intra-scaffold conditioning. Fibroblasts treated with any conditioned media demonstrated increased migration potential.

Conclusions

Conditioning hiPSC-VSMCs embedded in scaffolds with TNF-α improves cellular viability and increases the secretion of paracrine factors necessary for wound healing mechanisms such as migration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00764-0.

Coronavirus Disease 2019 and the Yale Response: A Semistructured Interview Study on Plastic Surgery Resident Education and Departmental Adaptation to the Lockdown

BACKGROUND

Sooner-than-expected progression to statewide lockdown at the height of the coronavirus disease 2019 pandemic left minimal time for medical specialty boards, including The American Board of Plastic Surgery, to issue guidance for their respective programs. As a result, programs were tasked with developing creative alternatives to their standard resident curricula and department schedules.

OBJECTIVE

To capture attending and resident experience of the coronavirus disease 2019 lockdown in narrative form and to understand what specific changes enacted to maintain adequate education should be considered for continuation after the pandemic's conclusion.

METHODS

Qualitative, semistructured interviews of residents, fellows, and faculty of the Section of Plastic and Reconstructive Surgery during 2019 to 2020 academic year were conducted on the following topics: (1) general reflection on lockdown, (2) resident maintenance of daily logs, (3) multi-institutional collaborative lectures, (4) modified didactic curriculum, (5) virtual 3-dimensional craniofacial planning sessions, (6) maintenance of department camaraderie, and (7) effect on preparation to become a surgeon.

RESULTS

Twenty interviews (response rate 77%) were conducted between October 2020 and February 2021. Of residents, 100% felt observing the craniofacial planning sessions was beneficial, with many explicitly noting it provided a unique perspective into the surgeon's thought process behind planned manipulations, to which they usually are not privy. Of residents, 100% felt confident at the time of the interview that the lockdown would have no lasting effects on their preparation to become a surgeon.

CONCLUSIONS

Rapid changes enacted at Yale enabled resident training to advance, and documentation of the success of these changes can inform future curriculum design.

Multifunctional Elastin-Like Polypeptide Fusion Protein Coacervates Inhibit Receptor-Mediated Proinflammatory Signals and Promote Angiogenesis in Mouse Diabetic Wounds

Objective: Chronic skin wounds are one of the most devastating complications in diabetic patients due to the formation of advanced glycation end-products (AGEs) resulting from nonenzymatic glycation of proteins and lipids in hyperglycemia. AGEs, upon binding their receptors (RAGEs), trigger proinflammatory signals that impair wound healing in diabetes and contribute to the pathology of chronic skin wounds. Approach: We previously developed a recombinant fusion protein containing the binding domain of RAGE (vRAGE) linked to elastin-like polypeptides (ELPs) that acts as a competitive inhibitor of AGEs, and another ELP fusion protein containing stromal cell-derived factor 1 (SDF1) that promotes revascularization. In this study, we report the effects of protein coacervates incorporating both vRAGE-ELP and SDF1-ELP on wound healing in an in vitro diabetes-mimicking cell culture system, and in in vivo in full-thickness wounds on diabetic mice. Results: The combination of vRAGE-ELP and SDF1-ELP increased cell metabolic activity in AGE-stimulated endothelial cells, promoted in vitro tube formation and accelerated healing in an in vitro cell migration assay. When used in a single topical application on full-thickness excisional skin wounds in diabetic mice, wound closure in the combination groups reached almost 100% on postwounding day 35, compared to 62% and 85% on the same days in animals treated with fibrin gel control and vehicle control consisting of ELP alone. Innovation: To our knowledge, this is the first study that attempts to reverse the AGE-RAGE-mediated signaling as well as to promote cell proliferation and vascularization in one single treatment. Conclusion: The codelivery of vRAGE-ELP and SDF1-ELP has potential for the treatment of diabetic wounds.

The Impact of Social Determinants of Health on Pressure Injury Progression: A Retrospective Chart and Scoping Review

OBJECTIVE

To understand the effects of nutrition security and social determinants of health (SDOHs) on pressure injury (PI) progression through a scoping review and retrospective review of patients reporting to New England's largest healthcare system.

METHODS

Authors performed a scoping review for full-text, original articles reporting outcomes data specific to PIs in patients with socially informed nutrition insecurity. Investigators also performed a retrospective review of all patients from 2012 to 2021 to search for patients with PI documentation and International Classification of Diseases, Tenth Revision Z codes related to the SDOHs.

RESULTS

A full-text review of 2,323 articles from 1965 to 2020 failed to locate any eligible studies. Investigators identified 1,044 patients who met the inclusion criteria; 50.7% were men, 74.3% were White, and 13.3% had evidence of detrimental SDOHs. The average PI duration was 12.13 days (interquartile range, 6 days). Multivariate regression analysis revealed that PI duration was longer in men, Black patients, and patients with evidence of detrimental SDOHs compared with their converse counterparts (P < .0001). The presence of detrimental SDOHs independently predicted an increased duration of disease by 13.07 days (95% CI, 8.99-17.15; t = 6.29, P < .0001).

CONCLUSIONS

A patient's SDOH history has a significant and considerably stronger correlation with disease progression than predictors that are traditionally studied such as sex, race, or body mass index. These findings are novel, as highlighted by the absence of data uncovered in the literature. These data carry relevance for plastic surgeons wishing to prevent early recurrence following operative closure of PI-related wounds.

Unlocking the Potential of Induced Pluripotent Stem Cells for Wound Healing: The Next Frontier of Regenerative Medicine

Significance: Nonhealing wounds are a significant burden for the health care system all over the world. Existing treatment options are not enough to promote healing, highlighting the urgent need for improved therapies. In addition, the current advancements in tissue-engineered skin constructs and stem cell-based therapies are facing significant hurdles due to the absence of a renewable source of functional cells. Recent Advances: Induced pluripotent stem cell technology (iPSC) is emerging as a novel tool to develop the next generation of personalized medicine for the treatment of chronic wounds. The iPSC provides unlimited access to various skin cells to generate complex personalized three-dimensional skin constructs for disease modeling and autologous grafts. Furthermore, the iPSC-based therapies can target distinct wound healing phases and have shown accelerating wound closure by enhancing angiogenesis, cell migration, tissue regeneration, and modulating inflammation. Critical Issues: Since the last decade, iPSC has been revolutionizing the field of wound healing and skin tissue engineering. Despite the current progress, safety and heterogeneity among iPSC lines are still major hurdles in addition to the lack of large animal studies. These challenges need to be addressed before translating an iPSC-based therapy to the clinic. Future Directions: Future considerations should be given to performing large animal studies to check the safety and efficiency of iPSC-based therapy in a wound healing setup. Furthermore, strategies should be developed to overcome variation between hiPSC lines, develop an efficient manufacturing process for iPSC-derived products, and generate complex skin constructs with vasculature and skin appendages.

Human iPSC-Vascular smooth muscle cell spheroids demonstrate size-dependent alterations in cellular viability and secretory function

Human-induced pluripotent stem cells (hiPSC) and their differentiated vascular cells have been revolutionizing the field of regenerative wound healing. These cells are shown to be rejuvenated with immense potentials in secreting paracrine factors. Recently, hiPSC-derived vascular smooth muscle cells (hiPSC-VSMC) have shown regenerative wound healing ability via their paracrine secretion. The quest to modulate the secretory function of these hiPSC-VSMC is an ongoing effort and involves the use of both biochemical and biophysical stimuli. This study explores the development and optimization of a reproducible, inexpensive protocol to form hiPSC-VSMC derived spheroids to investigate the implications of spheroid size on viability and paracrine secretion. Our data show the successful formation of different sizes of spheroids using various amount of hiPSC-VSMC. The hiPSC-VSMC spheroids formed with 10,000 cells strike an ideal balance between overall cell health and maximal paracrine secretion. The conditioned medium from these spheroids was found to be bioactive in enhancing human dermal fibroblast cell proliferation and migration. This research will inform future studies on the optimal spheroid size for regenerative wound healing applications.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Single cell transcriptomic landscape of diabetic foot ulcers

Diabetic foot ulceration (DFU) is a devastating complication of diabetes whose pathogenesis remains incompletely understood. Here, we profile 174,962 single cells from the foot, forearm, and peripheral blood mononuclear cells using single-cell RNA sequencing. Our analysis shows enrichment of a unique population of fibroblasts overexpressing MMP1, MMP3, MMP11, HIF1A, CHI3L1, and TNFAIP6 and increased M1 macrophage polarization in the DFU patients with healing wounds. Further, analysis of spatially separated samples from the same patient and spatial transcriptomics reveal preferential localization of these healing associated fibroblasts toward the wound bed as compared to the wound edge or unwounded skin. Spatial transcriptomics also validates our findings of higher abundance of M1 macrophages in healers and M2 macrophages in non-healers. Our analysis provides deep insights into the wound healing microenvironment, identifying cell types that could be critical in promoting DFU healing, and may inform novel therapeutic approaches for DFU treatment.

Human iPSC-Derived Vascular Smooth Muscle Cells in a Fibronectin Functionalized Collagen Hydrogel Augment Endothelial Cell Morphogenesis

Tissue-engineered constructs have immense potential as autologous grafts for wound healing. Despite the rapid advancement in fabrication technology, the major limitation is controlling angiogenesis within these constructs to form a vascular network. Here, we aimed to develop a 3D hydrogel that can regulate angiogenesis. We tested the effect of fibronectin and vascular smooth muscle cells derived from human induced pluripotent stem cells (hiPSC-VSMC) on the morphogenesis of endothelial cells. The results demonstrate that fibronectin increases the number of EC networks. However, hiPSC-VSMC in the hydrogel further substantiated the number and size of EC networks by vascular endothelial growth factor and basic fibroblast growth factor secretion. A mechanistic study shows that blocking αvβ3 integrin signaling between hiPSC-VSMC and fibronectin impacts the EC network formation via reduced cell viability and proangiogenic growth factor secretion. Collectively, this study set forth initial design criteria in developing an improved pre-vascularized construct.

Integrin β3 targeting biomaterial preferentially promotes secretion of bFGF and viability of iPSC-derived vascular smooth muscle cells

Human-induced pluripotent stem cell-derived-vascular smooth muscle cells (hiPSC-VSMC) and their secretome have been shown to promote angiogenesis and wound healing. However, there is a paucity of research on how the extracellular matrix (ECM) microenvironment may impact the hiPSC-VSMC's functions. In this study, we investigated the effect of specific ECM ligand-integrin interaction on hiPSC-VSMC's paracrine secretion, cell viability, and morphology. Here, we show precise modulation of hiPSC-VSMC in a fibronectin functionalized fibrillar collagen scaffold by targeting their integrin β3. The secretion of proangiogenic growth factor, basic fibroblast growth factor (bFGF) was found to be fibronectin-dependent via αvβ3 integrin interactions. In addition, our data show the possible role of a positive feedback loop between integrin β3, bFGF, and matrix metalloproteinase-2 in regulating hiPSC-VSMC's morphology and cell viability. Finally, the secretome with enhanced bFGF shows potential for future wound healing applications.

Self-assembled elastin-like polypeptide fusion protein coacervates as competitive inhibitors of advanced glycation end-products enhance diabetic wound healing

Chronic and non-healing skin wounds are some of the most significant complications in patients with advanced diabetes. A contributing mechanism to this pathology is the non-enzymatic glycation of proteins due to hyperglycemia, leading to the formation of advanced glycation end products (AGEs). AGEs bind to the receptor for AGEs (RAGE), which triggers pro-inflammatory signals that may inhibit the proliferative phase of wound healing. Soluble forms of RAGE (sRAGE) may be used as a competitive inhibitor of AGE-mediated signaling; however, sRAGE is short-lived in the highly proteolytic wound environment. We developed a recombinant fusion protein containing the binding domain of RAGE (vRAGE) linked to elastin-like polypeptides (ELPs) that self-assembles into coacervates at around 30-31 °C. The coacervate size was concentration and temperature-dependent, ranging between 500 and 1600 nm. vRAGE-ELP reversed several AGE-mediated changes in cultured human umbilical vein endothelial cells, including a decrease in viable cell number, an increase in levels of reactive oxygen species (ROS), and an increased expression of the pro-inflammatory marker, intercellular adhesion molecule-1 (ICAM-1). vRAGE-ELP was stable in elastase in vitro for 7 days. When used in a single topical application on full-thickness excisional skin wounds in diabetic mice, wound closure was accelerated, with 90% and 100% wound closure on post-wounding days 28 and 35, respectively, compared to 62% and 85% on the same days in animals treated with vehicle control, consisting of ELP alone. This coacervate system topically delivering a competitive inhibitor of AGEs has potential for the treatment of diabetic wounds.

Self-Assembled Nanomaterials for Chronic Skin Wound Healing

Significance: Chronic wounds are one of the major burdens of the U.S. health care system with an annual cost of $31.7 billion and affecting an estimated 2.4-4.5 million people. Several underlying molecular and cellular pathophysiological mechanisms, including poor vascularization, excessive extracellular matrix (ECM) degradation by proteases, decreased growth factor activity, and bacterial infection can lead to chronic wounds. More effective wound therapies need to address one or more of these mechanisms to significantly advance wound care. Recent Advances: Self-assembled nanomaterials may provide new therapeutic options for chronic wound healing applications as those materials generally exhibit excellent biocompatibility and can bear multiple functionalities, such as ECM-mimicking properties, drug delivery capabilities, and tunable mechanics. Furthermore, self-assembled nanomaterials can be produced at low cost, and owing to their ability to self-organize, generate complex multifunctional structures that can be tailored to the varying sizes and shapes of chronic wounds. Self-assembled nanomaterials have been engineered to serve as wound dressings, growth factor delivery systems, and antimicrobials. Critical Issues: As there are many different types of self-assembled nanomaterials, which in turn have different mechanisms of self-assembly and physiochemical properties, one type of self-assembled nanomaterials may not be sufficient to address all underlying mechanisms of chronic wounds. However, self-assembled nanomaterials can be easily tailored, and developing multifunctional self-assembled nanomaterials that can address various targets in chronic wounds will be needed. Future Directions: Future studies should investigate combinations of various self-assembled nanomaterials to take full advantage of their multifunctional properties.

Prelamination of Vascularized Tensor Fascia Lata for Complex Abdominal Wall Reconstruction

ABSTRACT

There are 2 to 5 million laparotomies performed in the United States annually. Of these, 250,000 to 350,000 will undergo a ventral hernia repair. Repairs are often complicated by recurrence and infection. These risks are significantly increased in previously infected repairs, with reported recurrence rates varying from 17% to 28% after repair of infected ventral hernias, double the rates reported for first-time uninfected repairs. We describe here a novel treatment strategy involving the creation then use of bilateral prelaminated permanent mesh-reinforced tensor fascia latae flaps for abdominal wall reconstruction in patients who have recurrent ventral hernias and had undergone previous repairs complicated by infection. Previous repairs included anterior components separation, thereby making subsequent fascial release techniques and achievement of a reinforced repair extremely unlikely. Three patients were treated by a single surgeon using this 2-stage technique. There have been no incidences of recurrence and no infections after 2 to 10 years. In these patients, the only conventional option would have been a bridged repair with absorbable mesh. Combining the advantages of permanent mesh and well-vascularized autologous tissue optimizes the repair's tensile strength while mitigating the chance of recurrent infection associated with the use of permanent mesh. We propose that this strategy may be an appropriate treatment option for patients with recurrent ventral hernias that have not responded to other conventional modalities of treatment.

Does the Presence of a Preexisting Open Wound Increase Complication Risk for Implant Procedures?

ABSTRACT

Despite limited evidence, a common belief in surgical practice is that patients should not undergo elective surgery until any open wounds heal because of the risk of seeding infection to the new surgical site. To our knowledge, this is the first study to analyze postoperative complication rates for implants placed in the context of open wounds using the American College of Surgeons National Surgical Quality Improvement Program database. We examined 30-day postoperative infections for breast, hip, knee, and spine implants using the 2012-2016 American College of Surgeons National Surgical Quality Improvement Program database. Patients were excluded for missing data and propensity matched 1:10 for demographics and comorbidities to minimize confounders. Complication rates were assessed using Pearson χ2 tests. Of 475,101 patients who received breast, hip, knee, or spine implants, 1491 did so with an open wound. After propensity score matching, the overall complication rate remained higher with the open wound cohort (6.7% vs 3.8%, P < 0.001). Although the presence of an open wound was associated with an increased risk of superficial surgical site infection, it was not associated with an increased risk of organ space surgical site infection, the site best correlated with infection at the implant. Nor was the presence of an open wound associated with a statistically significantly increased risk of deep incisional surgical site infection or wound dehiscence. After controlling for demographics, preoperative comorbidities, and surgical factors, the presence of an open wound before implant surgery is associated with an increased risk of complications, readmission, and reoperation, but not necessarily infection at the surgical site.

An in situ collagen-HA hydrogel system promotes survival and preserves the proangiogenic secretion of hiPSC-derived vascular smooth muscle cells

Human-induced pluripotent stem cell-derived vascular smooth muscle cells (hiPSC-VSMCs) with proangiogenic properties have huge therapeutic potential. While hiPSC-VSMCs have already been utilized for wound healing using a biomimetic collagen scaffold, an in situ forming hydrogel mimicking the native environment of skin offers the promise of hiPSC-VSMC mediated repair and regeneration. Herein, the impact of a collagen type-I-hyaluronic acid (HA) in situ hydrogel cross-linked using a polyethylene glycol-based cross-linker on hiPSC-VSMCs viability and proangiogenic paracrine secretion was investigated. Our study demonstrated increases in cell viability, maintenance of phenotype and proangiogenic growth factor secretion, and proangiogenic activity in response to the conditioned medium. The optimally cross-linked and functionalized collagen type-I/HA hydrogel system developed in this study shows promise as an in situ hiPSC-VSMC carrier system for wound regeneration.

A Dense Fibrillar Collagen Scaffold Differentially Modulates Secretory Function of iPSC-Derived Vascular Smooth Muscle Cells to Promote Wound Healing

The application of human-induced pluripotent stem cells (hiPSCs) to generate vascular smooth muscle cells (hiPSC-VSMCs) in abundance is a promising strategy for vascular regeneration. While hiPSC-VSMCs have already been utilized for tissue-engineered vascular grafts and disease modeling, there is a lack of investigations exploring their therapeutic secretory factors. The objective of this manuscript was to understand how the biophysical property of a collagen-based scaffold dictates changes in the secretory function of hiPSC-VSMCs while developing hiPSC-VSMC-based therapy for durable regenerative wound healing. We investigated the effect of collagen fibrillar density (CFD) on hiPSC-VSMC's paracrine secretion and cytokines via the construction of varying density of collagen scaffolds. Our study demonstrated that CFD is a key scaffold property that modulates the secretory function of hiPSC-VSMCs. This study lays the foundation for developing collagen-based scaffold materials for the delivery of hiPSC-VSMCs to promote regenerative healing through guiding paracrine signaling pathways.

Induced pluripotent stem cell-derived smooth muscle cells increase angiogenesis and accelerate diabetic wound healing

Aim:

To assess the potential of human induced pluripotent stem cell-derived smooth muscle cells (hiPSC-SMC) to accelerate diabetic wound healing.

Methods:

hiPSC-SMC were embedded in 3D collagen scaffolds and cultured in vitro for 72 h; scaffolds were then applied to diabetic, nude mouse, splinted back wounds to assess in vivo healing. Cultured medium after scaffold incubation was collected and analyzed for expression of pro-angiogenic cytokines.

Results:

hiPSC-SMC secrete increased concentration of pro-angiogenic cytokines, compared with murine adipose derived stem cells. Delivery of hiPSC-SMC-containing collagen scaffolds accelerates diabetic wound healing and is associated with an increased number of total and M2 type macrophages.

Conclusion:

hiPSC-SMC promote angiogenesis and accelerate diabetic wound healing, making them a promising new candidate for treatment of diabetic wounds.

The potential and limitations of induced pluripotent stem cells to achieve wound healing

Wound healing is the physiologic response to a disruption in normal skin architecture and requires both spatial and temporal coordination of multiple cell types and cytokines. This complex process is prone to dysregulation secondary to local and systemic factors such as ischemia and diabetes that frequently lead to chronic wounds. Chronic wounds such as diabetic foot ulcers are epidemic with great cost to the healthcare system as they heal poorly and recur frequently, creating an urgent need for new and advanced therapies. Stem cell therapy is emerging as a potential treatment for chronic wounds, and adult-derived stem cells are currently employed in several commercially available products; however, stem cell therapy is limited by the need for invasive harvesting techniques, immunogenicity, and limited cell survival in vivo. Induced pluripotent stem cells (iPSC) are an exciting cell type with enhanced therapeutic and translational potential. iPSC are derived from adult cells by in vitro induction of pluripotency, obviating the ethical dilemmas surrounding the use of embryonic stem cells; they are harvested non-invasively and can be transplanted autologously, reducing immune rejection; and iPSC are the only cell type capable of being differentiated into all of the cell types in healthy skin. This review focuses on the use of iPSC in animal models of wound healing including limb ischemia, as well as their limitations and methods aimed at improving iPSC safety profile in an effort to hasten translation to human studies.

Mouse Model of Pressure Ulcers After Spinal Cord Injury

Pressure ulcers (PUs) are common debilitating complications of traumatic spinal cord injury (SCI) and tend to occur in soft tissues around bony prominences. There is, however, little known about the impact of SCI on skin wound healing in the context of animal models in controlled experimental settings. In this study, a simple, non-invasive, reproducible and clinically relevant mouse model of PUs in the context of complete SCI is presented. Adult male mice (Balb/c, 10 weeks old) were shaved and depilated. Post-depilation (24 h), mice were subjected to laminectomy followed by complete spinal cord transection (T9-T10 vertebrae). Immediately after, a skin fold on the back of the mice was lifted and sandwiched between two magnetic discs held in place for next 12 h, thus creating an ischemic area that developed into a PU over the following days. The wounded areas demonstrated tissue edema and epidermal disappearance by day 3 post-magnet application. PUs spontaneously developed and healed. Healing was, however, slower in the SCI mice compared to control non-SCI mice when the wound was created below the level of SCI. Conversely, no difference in healing was seen between SCI and control non-SCI mice when the wound was created above the level of SCI. This model is a potentially useful tool to study the dynamics of skin PU development and healing after SCI, as well as to test therapeutic approaches that may help heal such wounds.

Myofibroblast proliferation and heterogeneity are supported by macrophages during skin repair

During tissue repair, myofibroblasts produce extracellular matrix (ECM) molecules for tissue resilience and strength. Altered ECM deposition can lead to tissue dysfunction and disease. Identification of distinct myofibroblast subsets is necessary to develop treatments for these disorders. We analyzed profibrotic cells during mouse skin wound healing, fibrosis, and aging and identified distinct subpopulations of myofibroblasts, including adipocyte precursors (APs). Multiple mouse models and transplantation assays demonstrate that proliferation of APs but not other myofibroblasts is activated by CD301b-expressing macrophages through insulin-like growth factor 1 and platelet-derived growth factor C. With age, wound bed APs and differential gene expression between myofibroblast subsets are reduced. Our findings identify multiple fibrotic cell populations and suggest that the environment dictates functional myofibroblast heterogeneity, which is driven by fibroblast-immune interactions after wounding.

Fibroblast growth factor receptor is a mechanistic link between visceral adiposity and cancer

Epidemiological evidence implicates excess adipose tissue in increasing cancer risk. Despite a steeply rising global prevalence of obesity, how adiposity contributes to transformation (stage a non-tumorigenic cell undergoes to become malignant) is unknown. To determine the factors in adipose tissue that stimulate transformation, we used a novel ex vivo system of visceral adipose tissue (VAT)-condition medium-stimulated epithelial cell growth in soft agar. To extend this system in vivo, we used a murine lipectomy model of ultraviolet light B-induced, VAT-promoted skin tumor formation. We found that VAT from mice and obese human donors stimulated growth in soft agar of non-tumorigenic epithelial cells. The difference in VAT activity was associated with fibroblast growth factor-2 (FGF2) levels. Moreover, human and mouse VAT failed to stimulate growth in soft of agar in cells deficient in FGFR-1 (FGF2 receptor). We also demonstrated that circulating levels of FGF2 were associated with non-melanoma tumor formation in vivo. These data implicate FGF2 as a major factor VAT releases to transform epithelial cells—a novel, potential pathway of VAT-enhanced tumorigenesis. Strategies designed to deplete VAT stores of FGF2 or inhibit FGFR-1 in abdominally obese individuals may be important cancer prevention strategies as well as adjuvant therapies for improving outcomes.

Soluble Receptor for Advanced Glycation End Products Improves Stromal Cell-Derived Factor-1 Activity in Model Diabetic Environments

Objective: In diabetes, hyperglycemia causes the accumulation of advanced glycation end products (AGEs) that trigger reactive oxygen species (ROS) generation through binding the receptor for AGEs (RAGE). Because exogenous growth factors have had little success in enhancing chronic wound healing, we investigated whether hyperglycemia-induced AGEs interfere with cellular responses to extracellular signals. We used stromal cell-derived factor-1 (SDF-1), an angiogenic chemokine also known to promote stem cell recruitment in skin wounds. Approach: Human leukemia-60 (HL-60) cells and mouse peripheral blood mononuclear cells (PBMCs), which express the SDF-1 receptor CXCR-4, were incubated for 24 h in medium supplemented with 25 mM d-glucose. Soluble RAGE (sRAGE) was used to block RAGE activation. Response to SDF-1 was measured in cellular migration and ROS assays. A diabetic murine excisional wound model measured SDF-1 liposome and sRAGE activity in vivo. Results: Hyperglycemia led to significant accumulation of AGEs, decreased SDF-1-directed migration, and elevated baseline ROS levels; it suppressed the ROS spike normally triggered by SDF-1. sRAGE decreased the ROS baseline and restored both the SDF-1-mediated spike and cell migration. Topically applied sRAGE alone promoted healing and enhanced the effect of exogenous SDF-1 on diabetic murine wounds. Innovation: While there is interest in using growth factors to improve wound healing, this strategy is largely ineffective in diabetic wounds. We show that sRAGE may restore signaling, thus potentiating the effect of exogenously applied growth factors. Conclusion: Blocking RAGE with sRAGE restores SDF-1-mediated cellular responses in hyperglycemic environments and may potentiate the effectiveness of SDF-1 applied in vivo.

SDF-1 liposomes promote sustained cell proliferation in mouse diabetic wounds

Chronic skin wounds are a common complication of diabetes. When standard wound care fails to heal such wounds, a promising approach consists of using decellularized matrices and other porous scaffold materials to promote the restoration of skin. Proper revascularization is critical for the efficacy of such materials in regenerative medicine. Stromal cell-derived factor-1 (SDF-1) is a chemokine known to play a key role for angiogenesis in ischemic tissues. Herein we developed nanosized SDF-1 liposomes, which were then incorporated into decellularized dermis scaffolds used for skin wound healing applications. SDF-1 peptide associated with liposomes with an efficiency of 80%, and liposomes were easily dispersed throughout the acellular dermis. Acellular dermis spiked with SDF-1 liposomes exhibited more persistent cell proliferation in the dermis, especially in CD31(+) areas, compared to acellular dermis spiked with free SDF-1, which resulted in increased improved wound closure at day 21, and increased granulation tissue thickness at day 28. SDF-1 liposomes may increase the performance of a variety of decellularized matrices used in tissue engineering.

The fate of internalized α5 integrin is regulated by matrix-capable fibronectin

BACKGROUND

Assembly of fibronectin matrices is associated with integrin receptor turnover and is an important determinant of tissue remodeling. Although it is well established that fibronectin is the primary ligand for α5β1 receptor, the relationship between fibronectin matrix assembly and the fate of internalized α5 integrin remains poorly characterized.

MATERIALS AND METHODS

To evaluate the effect of fibronectin matrix on the fate of internalized α5 integrin, fibronectin-null Chinese hamster ovary and mouse embryo fibroblast cells were used to track the fate of α5 after exposure to exogenous fibronectin.

RESULTS

In the absence of matrix-capable fibronectin dimer, levels of internalized α5 decreased rapidly over time. This correlated with a decline in total cellular α5 and was associated with the ubiquitination of α5 integrin. In contrast, internalized and total cellular α5 protein levels were maintained when matrix-capable fibronectin was present in the extracellular space. Further, we show that ubiquitination and degradation of internalized α5 integrin in the absence of fibronectin require the presence of two specific lysine residues in the α5 cytoplasmic tail.

CONCLUSIONS

Our data demonstrate that α5 integrin turnover is dependent on fibronectin matrix assembly, where the absence of matrix-capable fibronectin in the extracellular space targets the internalized receptor for rapid degradation. These findings have important implications for understanding tissue-remodeling processes found in wound repair and tumor invasion.

Modulation of cell-fibronectin matrix interactions during tissue repair

Environmental signals from the extracellular matrix (ECM) are transmitted by cell surface receptors that connect to the actin cytoskeleton and to multiple intracellular signaling pathways. To dissect how the ECM regulates cell functions, we are using a three-dimensional (3D) fibrin-fibronectin matrix, resembling the wound provisional matrix. Fibroblasts adhere to fibronectin in this matrix via concomitant engagement of alpha 5 beta 1 integrin receptors and syndecan-4, a transmembrane proteoglycan. An adhesive phenotype is developed with actin stress fibers and activation of focal adhesion kinase (FAK) and Rho GTPase. Lack of syndecan-4 engagement, as occurs in the presence of the ECM protein tenascin-C, promotes a motile phenotype; FAK and Rho signaling are downregulated and filopodia are extended. Fibronectin matrices have distinct effects on two other receptors: alpha 4 beta 1 and beta v beta 3 integrins. Although alpha 4 beta 1 does not naturally support strong cell interactions with a fibrin-fibronectin matrix, binding is dramatically enhanced by proteolytic cleavage of fibronectin. Conversely, activity of alpha v beta 3 is stimulated by multimeric fibronectin fibrils showing that the organization of fibronectin differentially affects integrin functions. Thus, deposition of additional ECM components, expression of co-receptors for ECM, cleavage of adhesive proteins, and the architecture of the ECM microenvironment are different mechanisms for modulating cell responses to fibronectin matrix.

Adenoviral-mediated expression and local deposition of recombinant tenascin-C perturbs cell-dependent matrix contraction

BACKGROUND

To mimic the wound environment, we have developed a three-dimensional (3-D) fibrin-fibronectin (FN) matrix model that is formed in vitro from purified proteins and approximates the provisional matrix. Tenascin-C, a large extracellular matrix (ECM) glycoprotein, is expressed transiently in tissue adjacent to areas of injury and contacts the provisional matrix in vivo. We have constructed a novel recombinant adenovirus vector (Ad-70Ten) to up-regulate local expression and secretion of a recombinant form of tenascin-C.

METHODS

Ad-70Ten and a control vector were constructed and used to infect cultured mammalian cells. Post-infection monitoring of expression was accomplished by immunoblot and immunohistochemical techniques. Local protein deposition was examined by immunofluorescence. Cell contractility was assessed by ability of infected cells to contract 3-D fibrin-FN matrices. Some matrices also contained lysophosphatidic acid (LPA), an activator of Rho GTPase.

RESULTS

Adenovirus-infected cells demonstrated high recombinant tenascin-C expression and deposited protein at sites of cell-matrix contacts resulting in significantly reduced contractility with 2.5-fold lower contraction of the matrix compared with control cells. Matrix contraction could be restored by treatment with LPA.

CONCLUSION

These results show that endogenous expression of tenascin-C down-regulates cell contractility and strongly suggest that it exerts its effects via a Rho GTPase signaling pathway. Taken with previous findings, these results suggest that tenascin-C acts in both a paracrine and autocrine manner via Rho GTPase pathways. This report demonstrates that recombinant adenovirus infection is a feasible method to induce high expression of large matrix proteins in mammalian cells, allowing better approximation of in vivo circumstances for investigations of locally secreted matrix protein. While the current vector has been constructed for research purposes, it also represents a proof in principle that adenoviral vectors encoding large proteins may have potential benefit in clinical applications.

Fibronectin fragmentation promotes α4β1 integrin-mediated contraction of a fibrin–fibronectin provisional matrix

In injured tissues, the fibrin-fibronectin (FN) provisional matrix provides a framework for cell adhesion, migration, and repair. Effective repair and remodeling require a proper balance between extracellular matrix (ECM) deposition, contraction, and turnover. We utilized a three-dimensional (3D) fibrin-FN provisional matrix model to determine the contributions of the FN-binding integrin receptors alpha5beta1 and alpha4beta1 to matrix contraction. CHOalpha5 cells expressing alpha5beta1, a receptor for FN's RGD cell-binding domain, were highly contractile, and cells were well spread on a 3D fibrin-FN matrix. In contrast, CHOalpha4 cells expressing the alpha4beta1 receptor for FN's alternatively spliced V region attached less efficiently to FN and were deficient in fibrin-FN matrix contraction. Surprisingly, cell adhesion and matrix contraction by CHOalpha4 cells were dramatically enhanced, to levels equivalent to CHOalpha5 cells, when proteolyzed FN was used in place of intact FN in the fibrin-FN matrix. Similar enhancement was observed when ligand binding by alpha4beta1 integrins was activated by treatment with Mn(++), but not by stimulation of actin organization with LPA. Therefore, alpha4beta1-dependent cell responses to the provisional matrix are modulated by cleavage of matrix components.

Coregulation of fibronectin signaling and matrix contraction by tenascin-C and syndecan-4

Syndecan-4 is a ubiquitously expressed heparan sulfate proteoglycan that modulates cell interactions with the extracellular matrix. It is transiently up-regulated during tissue repair by cells that mediate wound healing. Here, we report that syndecan-4 is essential for optimal fibroblast response to the three-dimensional fibrin-fibronectin provisional matrix that is deposited upon tissue injury. Interference with syndecan-4 function inhibits matrix contraction by preventing cell spreading, actin stress fiber formation, and activation of focal adhesion kinase and RhoA mediated-intracellular signaling pathways. Tenascin-C is an extracellular matrix protein that regulates cell response to fibronectin within the provisional matrix. Syndecan-4 is also required for tenascin-C action. Inhibition of syndecan-4 function suppresses tenascin-C activity and overexpression of syndecan-4 circumvents the effects of tenascin-C. In this way, tenascin-C and syndecan-4 work together to control fibroblast morphology and signaling and regulate events such as matrix contraction that are essential for efficient tissue repair.

Differences in breast shape preferences between plastic surgeons and patients seeking breast augmentation

There has been little discussion in the published literature regarding breast shape preferences. This study was conducted to ascertain previously undocumented differences in breast shape preferences between plastic surgeons and patients seeking breast augmentation, with respect to upper-pole contour. Sixty-six respondents, grouped into three cohort categories (plastic surgeons, breast augmentation patients, and lay people), were asked to evaluate a series of 12 nonptotic breast profiles representing a range of upper-pole contours. Five profiles exhibited convex upper-pole contours, five exhibited concave contours, and two exhibited upper poles with flat slopes. A five-point Likert-type scale was used to rate attractiveness, naturalness, how close the shape was to each respondent's personal ideal, and how close the shape was to what the respondent believed was our society's ideal. Statistical comparisons were made among the three cohorts. The plastic surgeon cohort (n = 11) rated concave upper-pole contours significantly higher than did the patient cohort (n = 13) for attractiveness, naturalness, and personal ideal (p < 0.01). For convex contours, the plastic surgeon cohort gave significantly lower scores than did the patient cohort (p < 0.01). The lay category (n = 42) demonstrated preferences intermediate between those of the other groups. There are no known studies in the literature documenting the breast shape preferences of plastic surgeons and their patients. This study suggests that plastic surgeons and patients seeking breast augmentation may have drastically different images in mind regarding what constitutes an attractive, natural, and ideal breast shape. These findings have potential implications for patient treatment and satisfaction.

Transvaginal uterine cervical dilation with fluoroscopic guidance: preliminary results in patients with infertility

PURPOSE

To assess efficacy of uterine cervical dilation performed with fluoroscopic guidance to treat patients with infertility who have cervical stenosis, false channels within the endocervical canal, or both.

MATERIALS AND METHODS

Fifteen patients in whom infertility was diagnosed were referred because the uterine lumen could not be accessed. Three of the patients had endometriosis. With fluoroscopic guidance, the cervix was cannulated and the endocervical canal was dilated with an angioplasty balloon or with dilators. Five patients underwent simultaneous fallopian tube recanalization. Five of 15 patients who underwent dilation subsequently underwent in vitro fertilization for embryo transfer (IVF-ET) or intrauterine insemination.

RESULTS

Four patients became pregnant. Of those four, one underwent IVF-ET and one underwent intrauterine insemination. Two patients became pregnant spontaneously. In the five patients who underwent IVF-ET or intrauterine insemination and in the remaining eight patients, the cervix could be easily cannulated up to 7 months after dilation.

CONCLUSION

Dilation of the uterine cervix may provide options for treatment in selected patients with infertility. The effect of dilation on patients with other sequelae of cervical obstruction such as endometriosis remains uncertain.

The effects of chronic administration of indomethacin and misoprostol on renal function in cirrhotic patients with and without ascites

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) often cause renal dysfunction in cirrhotic patients with ascites through inhibition of prostaglandin synthesis. However, their renal effects in cirrhotic patients without ascites are controversial. In addition, the role of prostaglandins in cirrhotic patients with ascites and in non-ascitic cirrhotic patients receiving NSAIDs also remains elusive. Thus we evaluated the chronic renal effects of indomethacin and misoprostol in 9 cirrhotic patients with ascites (protocol 1) and 21 cirrhotic patients without ascites (protocol 2).

METHODS

The patients of protocol 1 received 200 micrograms of misoprostol every 6 h for 7 consecutive days. In protocol 2, 11 patients received 25 mg indomethacin three times a day for 7 consecutive days. The other 10 patients received 25 mg indomethacin three times a day plus 200 micrograms misoprostol every 6 h for 7 consecutive days. Renal function tests, plasma renin activity, and plasma aldosterone concentration were measured before and after treatment.

RESULTS

In protocol 1, misoprostol tended to reduce the urinary sodium excretion (p = 0.08). In protocol 2, indomethacin alone greatly impaired renal plasma flow (p < 0.05), creatinine clearance (p < 0.05), blood urea nitrogen (p < 0.05), and serum creatinine (p = 0.06) in 11 patients. Similar magnitudes of renal dysfunction were observed in the other 10 patients despite the concomitant misoprostol treatment.

CONCLUSION

Chronic administration of misoprostol may have caused a negative natriuretic effect in cirrhotic patients with ascites. In cirrhotic patients without ascites chronic administration of indomethacin may induce a renal dysfunction that cannot be reversed by misoprostol.

Pharmacological characterization of bradykinin receptors in canine cultured tracheal smooth muscle cells

1. [3H]-bradykinin was used to characterize the bradykinin receptors associated with canine cultured tracheal smooth muscle cells (TSMCs). Receptor binding assay showed that TSMCs had specific, saturable, high-affinity binding sites for [3H]-bradykinin. 2. The specific [3H]-bradykinin binding increased linearly with increasing cell concentrations. The equilibrium for association of [3H]-bradykinin with the bradykinin receptors was attained within 2 h at 4 degrees C and 1 h at room temperature, respectively. 3. Analysis of binding isotherms yielded an apparent equilibrium dissociation constant (KD) of 2.5 +/- 0.3 nM and a maximum receptor density (Bmax) of 25.1 +/- 0.3 fmol mg-1 protein. The Hill coefficient for [3H]-bradykinin binding was 1.00 +/- 0.02. The association (K1) and dissociation (K-1) rate constants were (8.67 +/- 2.60) x 10(6) M-1 min-1 and 0.024 +/- 0.005 min-1, respectively. KD, calculated from the ratio of K-1 and K1 was 2.8 +/- 0.5 nM, a value close to that of KD calculated from Scatchard plots of binding isotherms. 4. The B1 receptor selective agonist, (des-Arg9-bradykinin, 0.1 nM-10 microM) and antagonist ([Leu8, des-Arg9]-bradykinin, 0.1 nM-10 microM) did not did not inhibit the [3H]-bradykinin binding to TSMCs, which excludes the presence of B1 receptors in canine TSMCs. 5. The specific binding of [3H]-bradykinin to canine TSMCs was inhibited by B2 receptor selective antagonists ([D-Arg0, Hyp3, Thi5, D-Tic7, Oicl-bradykinin, Hoe 140, 0.1 nM-10 micro M and [D-Arg0, Hyp3,Thi5,8, D-Phe7-bradykinin, 0.1 nM-10 micro M) and agonists (bradykinin and kallidin, 0.1 nM-10 micro M) with a best fit by a one-binding site model. The order of potency for the inhibition of [3H]-bradykinin binding was kallidin = bradykinin = Hoe 140> [D-Arg0, Hyp3, Thi5,8, D-Phel-bradykinin.6. Preincubation of TSMCs with forskolin for 24 h led to an up-regulation of B2 receptors, increasing in Bmax from 25.1 +/- 0.3 to 218 +/- 24 fmol mg-1 protein without changing the KD values. [3H]-bradykinin binding to TSMCs was inhibited by the B2 receptor selective antagonists and agonists, but not by the B1 receptor selective reagents. The up-regulation of the B2 receptor by forskolin was mediated through protein synthesis, since cycloheximide blocked this response.7 It is concluded that the pharmacological characteristics of the bradykinin receptors in canine cultured TSMCs are primarily of the B2 receptor subtype.

Bradykinin-stimulated calcium mobilization in cultured canine tracheal smooth muscle cells

Bradykinin (BDK)-induced increases in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) using a fluorescent Ca2+ indicator, Fura-2. BDK and kallidin caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner, with half-maximal stimulation (log EC50) obtained at -8.10 M and -8.04 M, respectively. The BDK-induced rise in [Ca2+]i was not affected by the BDK B1 receptor antagonist, des-Arg9[Leu8]-BDK (10 microM). However, the BDK B2 receptor antagonists des-Arg[Hyp3, Thi5,8, D-Phe7]-BDK and Hoe 140 had high affinity in antagonizing BDK with pKB values of 7.5 +/- 0.3 and 8.7 +/- 0.3, respectively. The sustained phase of the rise in [Ca2+]i was dependent on the presence of external Ca2+, as evidenced by a decline to the resting level on addition of EGTA. In the absence of external Ca2+, only an initial transient peak was seen which then declined to the resting level; a sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of BDK. Ca2+ influx was required for the changes in [Ca2+]i, since Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to BDK. In conclusion, these findings indicate that the initial increase in [Ca2+]i stimulated by BDK acting on BDK B2 receptors is due to the release of Ca2+ from internal stores, followed by the influx of external Ca2+ into the cells. The influx of extracellular Ca2+ partially involves a diltiazem- and verapamil-sensitive Ca2+ channel.

The effect of cyclic AMP elevating agents on bradykinin- and carbachol-induced signal transduction in canine cultured tracheal smooth muscle cells

1. The effects of cholera toxin (CTX), forskolin and dibutyryl cyclic AMP on bradykinin (BK)- and carbachol-induced accumulation of inositol phosphates (IPs) and Ca2+ mobilization were investigated in canine cultured tracheal smooth muscle cells (TSMCs). The BK-induced responses were mediated via a G protein which was not inhibited by CTX or pertussis toxin treatment. 2. BK-stimulated IPs accumulation and Ca2+ mobilization were potentiated by CTX (10 micrograms ml-1) pretreatment which was time-dependent. Maximal increase of these responses occurred after 24 h treatment with CTX. The concentration-effect relationship of BK-induced responses were shifted to the left and BK was substantially more effective in CTX-treated cells than in the control cells. This enhancing effect of CTX did not occur with carbachol. 3. Short-term (< 4 h) treatment with forskolin (10 microM) or dibutyryl cyclic AMP (1 mM) failed to accentuate BK-induced responses, but long-term (> 4 h) treatment of TSMCs with these agents mimicked the enhancing effect of CTX, suggesting that CTX-induced enhancement of BK responsiveness might be due to a rise in cyclic AMP. 4. Prolonged treatment of TSMCs with these agents was accompanied by an increase in cell surface [3H]-BK binding sites, which was inhibited by concurrent incubation with cycloheximide, an inhibitor of protein biosynthesis. Cycloheximide also abolished the potentiating actions of CTX, forskolin, and dibutyryl cyclic AMP on BK-induced IPs formation and Ca2+ mobilization. 5. The locus of this enhancement was further investigated by examining the effects of CTX, forskolin and dibutyryl cyclic AMP on A1F4(-)-induced IPs accumulation in canine TSMCs. AIF4-induced IPs accumulation was not affected by CTX, forskolin, or dibutyryl cyclic AMP treatment, supporting the contention that this stimulatory effect is located at the BK receptor level.6. These results demonstrate that the augmentation of BK-induced IPs accumulation and Ca2+mobilization produced by CTX, forskolin and dibutyryl cyclic AMP involves a cyclic AMP-dependent mechanism which is induced by a sustained increase in the level of intracellular cyclic AMP. CTX and forskolin may promote an increase of the synthesis of BK receptors, and thereby enhance BK-induced responses.

Relationships between the severity of cirrhosis and haemodynamic values in patients with cirrhosis

The relationship between the severity of cirrhosis and systemic and hepatic haemodynamic values was evaluated in 193 patients with cirrhosis, most of whom were diagnosed with post-necrotic cirrhosis. It was found that the hepatic venous pressure gradient and cardiac output in Pugh's A patients (13.6 +/- 4.8 mmHg and 6.2 +/- 1.6 L/min, mean +/- s.d.) were significantly lower than in both Pugh's B (16.8 +/- 4.3 mmHg and 7.3 +/- 2.1 L/min) and Pugh's C (18.8 +/- 5.5 mmHg and 7.4 +/- 2.3 L/min) patients (P < 0.01), respectively. In contrast, the systemic vascular resistance in Pugh's A patients (1232 +/- 369 dyn/s per cm5) was significantly higher than in both Pugh's B (1016 +/- 345 dyn/s per cm5) and Pugh's C (935 +/- 234 dyn/s per cm5) patients (P < 0.01), respectively. Additionally, not only was there a positive correlation found between Pugh's score and cardiac output and hepatic venous pressure gradient, but a negative correlation was found between Pugh's score and systemic vascular resistance. It was also confirmed that the degree of portal hypertension and the hyperdynamic circulation were more severe in patients with ascites than in those without ascites. However, there were no statistically significant differences in hepatic venous pressure gradient among patients with F1, F2 and F3 esophageal varices (15.7 +/- 4.0, 17.0 +/- 4.8 and 18.0 +/- 4.8 mmHg, respectively). It is concluded that in those patients with cirrhosis, the severity of cirrhosis is closely related to the degree of the hyperkinetic circulatory state and portal hypertension.

Bradykinin-stimulated phosphoinositide metabolism in cultured canine tracheal smooth muscle cells

1. Stimulation of bradykinin (BK) receptors coupled to phosphoinositide (PI) hydrolysis was investigated in canine cultured tracheal smooth muscle cells (TSMCs). BK, kallidin, and des-Arg9-BK, stimulated [3H]-inositol phosphates (IPs) accumulation in a dose-dependent manner with half-maximal responses (EC50) at 20 +/- 5, 13 +/- 4, and 2.3 +/- 0.7 nM, (n = 5), respectively. 2. D-Arg[Hyp3, D-Phe7]-BK and D-Arg[Hyp3, Thi5,8, D-Phe7]-BK, B2 receptor antagonists, were equipotent in blocking the BK-induced IPs accumulation with pKB = 7.1 and 7.3, respectively. 3. Short-term exposure of TSMCs to phorbol 12-myristate 13-acetate (PMA, 1 microM) attenuated BK-stimulated IPs accumulation. The concentrations of PMA that gave half-maximal and maximal inhibition of BK-induced IPs accumulation were 15 +/- 4 nM and 1 microM, n = 3, respectively. The inhibitory effect of PMA on BK-induced response was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC. 4. Prolonged incubation of TSMCs with PMA for 24 h, resulted in a recovery of receptor responsiveness which may be due to down-regulation of PKC. The inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate at 1 microM, did not inhibit this response. 5. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the G protein(s) can be directly activated by AlF4-, which is uncoupled from phospholipase C by PMA treatment. 6. Incubation of TSMCs in the absence of external Ca2+ or upon removal of Ca2+ by addition of EGTA, caused a decrease in IPs accumulation without changing the basal levels. Addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs stimulated IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) or BK. The combination of GTP gamma S and BK caused an additive effect on IPs accumulation.7. Pretreatment of TSMCs with cholera toxin enhanced BK-stimulated IPs accumulation, whereas there was no effect with pertussis toxin.8. These data suggest that BK-stimulated PI metabolism is mediated by the activation of BK B2 receptors coupling to a G protein which is not blocked by cholera toxin or pertussis toxin treatment and dependent on external Ca2+. The transduction mechanism of BK coupled to PI hydrolysis is sensitive to feedback regulation by PKC.

Hepatic hemodynamic features in patients with esophageal or gastric varices

One hundred and fifty cirrhotic patients with or without esophageal varices and/or gastric varices were investigated by endoscopy and hepatic venous catheterization to evaluate differences in the degree of portal hypertension, main portal venous diameter and frequency of portal systemic encephalopathy. Hemodynamic values were correlated with varices size as assessed by endoscopy. Patients with large gastric varices had wedged hepatic venous pressures and hepatic venous pressure gradients which were lower than patients with esophageal varices only, but similar to patients without varices. In addition, in patients with large gastric varices, a decrease in the diameter of the main portal vein and an increase in the incidence of chronic portal systemic encephalopathy were noted. Our results implied that patients with large gastric varices presented different hemodynamic features including the degree of portal hypertension and the incidence of portal systemic encephalopathy from patients with esophageal varices only.

Changes of sex hormone levels in patients with hepatitis B virus-related postnecrotic cirrhosis: relationship to the severity of portal hypertension

The effect of portal hypertension on plasma sex steroid levels was studied in 49 patients with hepatitis B virus-related postnecrotic cirrhosis. In accordance with the Child-Pugh classification, 18 patients were classified as grade A, 15 grade B and 16 grade C. At the same time, 25 males who were admitted for physical check-up served as normal controls. Serum testosterone levels decreased (3.31 +/- 2.03 vs. 5.65 +/- 0.13 ng/ml) and estrone levels increased (0.16 +/- 0.08 vs. 0.09 +/- 0.02 ng/ml) significantly in patients with cirrhosis compared to the levels obtained in the controls. Moreover, these changes were associated with an increased severity of cirrhosis (P < 0.05 when severity increased from grade A to C). Hemodynamic values regarding hepatic venous pressure gradient and cardiac output demonstrated significant differences in patients from grade A to C, but the correlation between these two parameters was poor (r = 0.3242). The hepatic venous pressure gradient, the only direct measurement of portal hypertension, did not correlate with any of the measured hormone levels in patients with cirrhosis. There was, however, a highly significant negative correlation between cardiac output and testosterone levels (r = -0.8754, P < 0.01) and a positive correlation between cardiac output and estrone levels (r = 0.7522, P < 0.05) in grade C patients. On the basis of these results, we concluded that gonadal dysfunction is a common finding in patients with hepatitis B related postnecrotic cirrhosis, especially in those with decompensated liver function. The relationship between cardiac output and severity of liver disease suggests that the degree of portosystemic shunting probably increases as liver disease worsens.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of hepatic and systemic haemodynamics following somatostatin administration in patients with hepatitis B-related cirrhosis

Somatostatin has been used to effectively control acute variceal haemorrhage, with conjectured mechanisms on portal hypertension. We, therefore, evaluated the effects of somatostatin on hepatic and systemic haemodynamics in 15 patients with hepatitis B-related cirrhosis and portal hypertension. All patients received an intravenous, continuous infusion of somatostatin 250 micrograms/h, following a bolus injection of 250 micrograms. In systemic haemodynamics, the mean arterial pressure (MAP) increased (P < 0.05), associated with a reflex bradycardia within 3 min following bolus injections, compared with basal values. The right atrial pressure, pulmonary capillary wedge pressure, inferior vena cava pressure, cardiac index, and systemic vascular resistance remained unaffected after drug infusion. In hepatic haemodynamics, the wedge hepatic vein pressure remained unchanged after drug administration. However, there was an increase in free hepatic vein pressure (FHVP; P < 0.05), and a trend toward a decrease in the hepatic vein pressure gradient (HVPG; P = 0.063), within 3 min after bolus injection. Furthermore, the hepatic blood flow decreased significantly at 10 and 30 min after somatostatin infusion (P < 0.05). The effective sinusoidal perfusion assessed by indocyanine green infusion also decreased progressively at 10 min (P = 0.057) and 30 min (P < 0.05). We concluded that somatostatin, at the dose used in this study, caused a transient and bolus-related vasoconstrictive effect, resulting in increases in MAP and FHVP, a decrease in heart rate, and a trend toward lower HVPG. In addition, somatostatin reduced the hepatic blood flow and effective sinusoidal perfusion which may be hazardous to cirrhotic patients during variceal haemorrhage.

A randomized controlled trial comparing octreotide and vasopressin in the control of acute esophageal variceal bleeding

This randomized controlled trial was conducted to compare the efficacy of intravenous infusion of octreotide (a synthetic long-acting somatostatin analogue) with vasopressin in 48 cirrhotic patients with endoscopically proven bleeding esophageal varices. Twenty-four patients received a continuous infusion of octreotide 25 micrograms/h for 24 h after an initial bolus of 100 micrograms and another 24 patients received a continuous infusion of vasopressin 0.4 U/min for 24 h. Bleeding was initially controlled after 6 h of drug infusion in 88% (21/24) and 54% (13/24) of the patients treated with octreotide and vasopressin respectively (p = 0.03). Complete control of bleeding after 24 h of drug infusion was achieved in 15 (63%) patients receiving octreotide and in 11 (46%) patients receiving vasopressin (p > 0.05). Side effects during drug infusion such as headache, chest pain and abdominal pain were significantly lower in the octreotide group (3/24) than in the vasopressin group (11/24). Serum gastrin and insulin levels fell significantly following octreotide infusion, but plasma glucose levels remained unchanged. Mortality related to bleeding esophageal varices was no different between the two groups. This report showed that octreotide infusion was more effective and had fewer side effects than vasopressin in initial controlling of acute esophageal variceal bleeding until an elective endoscopic sclerotherapy could be performed.