Tumorigenesis by Millipore filters in mice: histology and ultrastructure of tissue reactions as related to pore size

Wireless Battery-free and Fully Implantable Organ Interfaces

Advances in soft materials, miniaturized electronics, sensors, stimulators, radios, and battery-free power supplies are resulting in a new generation of fully implantable organ interfaces that leverage volumetric reduction and soft mechanics by eliminating electrochemical power storage. This device class offers the ability to provide high-fidelity readouts of physiological processes, enables stimulation, and allows control over organs to realize new therapeutic and diagnostic paradigms. Driven by seamless integration with connected infrastructure, these devices enable personalized digital medicine. Key to advances are carefully designed material, electrophysical, electrochemical, and electromagnetic systems that form implantables with mechanical properties closely matched to the target organ to deliver functionality that supports high-fidelity sensors and stimulators. The elimination of electrochemical power supplies enables control over device operation, anywhere from acute, to lifetimes matching the target subject with physical dimensions that supports imperceptible operation. This review provides a comprehensive overview of the basic building blocks of battery-free organ interfaces and related topics such as implantation, delivery, sterilization, and user acceptance. State of the art examples categorized by organ system and an outlook of interconnection and advanced strategies for computation leveraging the consistent power influx to elevate functionality of this device class over current battery-powered strategies is highlighted.

Unraveling and Harnessing the Immune Response at the Cell-Biomaterial Interface for Tissue Engineering Purposes

Biomaterials are defined as "engineered materials" and include a range of natural and synthetic products, designed for their introduction into and interaction with living tissues. Biomaterials are considered prominent tools in regenerative medicine that support the restoration of tissue defects and retain physiologic functionality. Although commonly used in the medical field, these constructs are inherently foreign toward the host and induce an immune response at the material-tissue interface, defined as the foreign body response (FBR). A strong connection between the foreign body response and tissue regeneration is suggested, in which an appropriate amount of immune response and macrophage polarization is necessary to trigger autologous tissue formation. Recent developments in this field have led to the characterization of immunomodulatory traits that optimizes bioactivity, the integration of biomaterials and determines the fate of tissue regeneration. This review addresses a variety of aspects that are involved in steering the inflammatory response, including immune cell interactions, physical characteristics, biochemical cues, and metabolomics. Harnessing the advancing knowledge of the FBR allows for the optimization of biomaterial-based implants, aiming to prevent damage of the implant, improve natural regeneration, and provide the tools for an efficient and successful in vivo implantation.

Granular Hydrogels for Harnessing the Immune Response

This review aims to understand the current progress in immune-instructive granular hydrogels and identify the key features used as immunomodulatory strategies. Published work is systematically reviewed and relevant information about granular hydrogels used throughout these studies is collected. The base polymer, microgel generation technique, polymer crosslinking chemistry, particle size and shape, annealing strategy, granular hydrogel stiffness, pore size and void space, degradability, biomolecule presentation, and drug release are cataloged for each work. Several granular hydrogel parameters used for immune modulation: porosity, architecture, bioactivity, drug release, cell delivery, and modularity, are identified. The authors found in this review that porosity is the most significant factor influencing the innate immune response to granular hydrogels, while incorporated bioactivity is more significant in influencing adaptive immune responses. Here, the authors' findings and summarized results from each section are presented and suggestions are made for future studies to better understand the benefits of using immune-instructive granular hydrogels.

Eta polycaprolactone (ε-PCL) implants appear to cause a partial differentiation of breast cancer lung metastasis in a murine model

BACKGROUND

Cells in every epithelium can be roughly divided in three compartments: stem cell (SC) compartment, transient amplifying cell (TA) compartment and terminally differentiated (TD) compartment. Maturation of stem cells is characterized by epithelial stromal interaction and sequential maturational movement of stem cell's progeny through those compartments. In this work we hypothesize that providing an artificial stroma, which murine breast cancer metastatic cells can infiltrate, will induce their differentiation.

METHODS

BALB/c female mice were injected with 10⁶ isogenic 4T1 breast cancer cells labeled with GFP. After 20 days primary tumors were removed, and artificial ε-PCL implants were implanted on the contralateral side. After 10 more days mice were sacrificed and implants along with lung tissue were harvested. Mice were divided in four groups: tumor removal with sham implantation surgery (n = 5), tumor removal with ε-PCL implant (n = 5), tumor removal with VEGF enriched ε-PCL implant (n = 7) and mice without tumor with VEGF enriched ε-PCL implant (n = 3). Differentiational status of GFP + cells was assessed by Ki67 and activated caspase 3 expression, thus dividing the population in SC like cells (Ki67^+/dim aCasp3^-), TA like cells (Ki67^+/dim aCasp3^+/dim) and TD like cells (Ki67^- aCasp3^+/dim) on flow cytometry.

RESULTS

Lung metastatic load was reduced by 33% in mice with simple ε-PCL implant when compared to tumor bearing group with no implant. Mice with VEGF enriched implants had 108% increase in lung metastatic load in comparison to tumor bearing mice with no implants. Likewise, amount of GFP + cells was higher in simple ε-PCL implant in comparison to VEGF enriched implants. Differentiation-wise, process of metastasizing to lungs reduces the average fraction of SC like cells when compared to primary tumor. This effect is made more uniform by both kinds of ε-PCL implants. The opposite process is mirrored in TA like cells compartment when it comes to averages. Effects of both types of implants on TD like cells were negligible. Furthermore, if gene expression signatures that mimic tissue compartments are analyzed in human breast cancer metastases, it turns out that TA signature is associated with increased survival probability.

CONCLUSION

ε-PCL implants without VEGF can reduce metastatic loads in lungs, after primary tumor removal. Both types of implants cause lung metastasis differentiation by shifting cancer cells from SC to TA compartment, leaving the TD compartment unaffected.

The Application of Porous Scaffolds for Cardiovascular Tissues

As the number of arteriosclerotic diseases continues to increase, much improvement is still needed with treatments for cardiovascular diseases. This is mainly due to the limitations of currently existing treatment options, including the limited number of donor organs available or the long-term durability of the artificial organs. Therefore, tissue engineering has attracted significant attention as a tissue regeneration therapy in this area. Porous scaffolds are one of the effective methods for tissue engineering. However, it could be better, and its effectiveness varies depending on the tissue application. This paper will address the challenges presented by various materials and their combinations. We will also describe some of the latest methods for tissue engineering.

Vascular Grafts: Technology Success/Technology Failure

Vascular prostheses (grafts) are widely used for hemodialysis blood access, trauma repair, aneurism repair, and cardiovascular reconstruction. However, smaller-diameter (≤4 mm) grafts that would be valuable for many reconstructions have not been achieved to date, although hundreds of papers on small-diameter vascular grafts have been published. This perspective article presents a hypothesis that may open new research avenues for the development of small-diameter vascular grafts. A historical review of the vascular graft literature and specific types of vascular grafts is presented focusing on observations important to the hypothesis to be presented. Considerations in critically reviewing the vascular graft literature are discussed. The hypothesis that perhaps the "biocompatible biomaterials" comprising our vascular grafts-biomaterials that generate dense, nonvascularized collagenous capsules upon implantation-may not be all that biocompatible is presented. Examples of materials that heal with tissue reconstruction and vascularity, in contrast to the fibrotic encapsulation, are offered. Such prohealing materials may lead the way to a new generation of vascular grafts suitable for small-diameter reconstructions.

Medical Applications of Porous Biomaterials: Features of Porosity and Tissue-Specific Implications for Biocompatibility

Porosity is an important material feature commonly employed in implants and tissue scaffolds. The presence of material voids permits the infiltration of cells, mechanical compliance, and outward diffusion of pharmaceutical agents. Various studies have confirmed that porosity indeed promotes favorable tissue responses, including minimal fibrous encapsulation during the foreign body reaction (FBR). However, increased biofilm formation and calcification is also described to arise due to biomaterial porosity. Additionally, the relevance of host responses like the FBR, infection, calcification, and thrombosis are dependent on tissue location and specific tissue microenvironment. In this review, the features of porous materials and the implications of porosity in the context of medical devices is discussed. Common methods to create porous materials are also discussed, as well as the parameters that are used to tune pore features. Responses toward porous biomaterials are also reviewed, including the various stages of the FBR, hemocompatibility, biofilm formation, and calcification. Finally, these host responses are considered in tissue specific locations including the subcutis, bone, cardiovascular system, brain, eye, and female reproductive tract. The effects of porosity across the various tissues of the body is highlighted and the need to consider the tissue context when engineering biomaterials is emphasized.

Paradoxical Behavior of Oncogenes Undermines the Somatic Mutation Theory

The currently accepted theory on the influence of DNA mutations on carcinogenesis (the Somatic Mutation Theory, SMT) is facing an increasing number of controversial results that undermine the explanatory power of mutated genes considered as "causative" factors. Intriguing results have demonstrated that several critical genes may act differently, as oncogenes or tumor suppressors, while phenotypic reversion of cancerous cells/tissues can be achieved by modifying the microenvironment, the mutations they are carrying notwithstanding. Furthermore, a high burden of mutations has been identified in many non-cancerous tissues without any apparent pathological consequence. All things considered, a relevant body of unexplained inconsistencies calls for an in depth rewiring of our theoretical models. Ignoring these paradoxes is no longer sustainable. By avoiding these conundrums, the scientific community will deprive itself of the opportunity to achieve real progress in this important biomedical field. To remedy this situation, we need to embrace new theoretical perspectives, taking the cell-microenvironment interplay as the privileged pathogenetic level of observation, and by assuming new explanatory models based on truly different premises. New theoretical frameworks dawned in the last two decades principally focus on the complex interaction between cells and their microenvironment, which is thought to be the critical level from which carcinogenesis arises. Indeed, both molecular and biophysical components of the stroma can dramatically drive cell fate commitment and cell outcome in opposite directions, even in the presence of the same stimulus. Therefore, such a novel approach can help in solving apparently inextricable paradoxes that are increasingly observed in cancer biology.

Biocompatibility Evolves: Phenomenology to Toxicology to Regeneration

The word "biocompatibility," is inconsistent with the observations of healing for so-called biocompatible biomaterials. The vast majority of the millions of medical implants in humans today, presumably "biocompatible," are walled off by a dense, avascular, crosslinked collagen capsule, hardly suggestive of life or compatibility. In contrast, one is now seeing examples of implant biomaterials that lead to a vascularized reconstruction of localized tissue, a biological reaction different from traditional biocompatible materials that generate a foreign body capsule. Both the encapsulated biomaterials and the reconstructive biomaterials qualify as "biocompatible" by present day measurements of biocompatibility. Yet, this new generation of materials would seem to heal "compatibly" with the living organism, where older biomaterials are isolated from the living organism by the dense capsule. This review/perspective article will explore this biocompatibility etymological conundrum by reviewing the history of the concepts around biocompatibility, today's standard methods for assessing biocompatibility, a contemporary view of the foreign body reaction and finally, a compendium of new biomaterials that heal without the foreign body capsule. A new definition of biocompatibility is offered here to address advances in biomaterials design leading to biomaterials that heal into the body in a facile manner.

Bleeding "sarcomatosis" as a rare presentation of vascular graft-related angiosarcoma: case report and review of the literature

Background

Angiosarcoma is a rare malignant tumor, originating from vascular endothelial cells, accounting for approximatively 1–2% of soft tissue sarcomas. It is characterized by a rapid proliferation and high metastatic potential. Some cases of angiosarcoma are described in association with vascular prosthesis, orthopedic devices and foreign bodies. Hereby, we report a case of a patient treated with the endovascular placement of a PTFE aorto bis-iliac prosthesis for aortic aneurysm, who developed a graft-related angiosarcoma with bone and peritoneal localizations. The peritoneal “sarcomatosis” led to an acute presentation with hemoperitoneum and anemia. We perform a thorough review of the literature summarizing the description of similar cases, their epidemiology and the possibilities for treatment.

Case presentation

An 84-year-old male with a history of abdominal aortic aneurysm endovascular repair presented to our emergency department complaining with low back pain radiating to the left limb. He underwent a type II endoleak embolization of the aneurysmal sac nine days before. During hospitalization he underwent a spine MRI which documented a vertebral alteration of non-univocal interpretation. Vertebral biopsy was performed revealing groups of cells of uncertain nature. He lately underwent percutaneous L2–L4 arthrodesis. Forty-two days after admission, he developed acute anemia. Emergency laparotomy revealed a massive hemoperitoneum and actively bleeding peritoneal nodules. Abdominal packing was performed, and several nodules were sent for definitive histological examination. After surgery, he developed progressive and severe hypovolemic shock and expired on postoperative day 5.

Conclusions

Angiosarcoma associated with foreign bodies, especially vascular prosthesis, is a very rare entity. In patients who have a history of prosthetic vascular graft placement that present with lumbar pain, osteolytic changes at radiologic imaging or the development of ascites, angiosarcoma should be considered in the differential diagnosis. Despite the poor prognosis, a prompt diagnosis might give access to an adequate treatment planning, with the aim for disease control and increased survival.

Challenges in diagnosing aortic leiomyosarcoma post endovascular repair of abdominal aortic aneurysm

Primary aortic tumors after endovascular aortic repair are rarely reported in the literature. Here, we report an elderly male with abdominal aortic leiomyosarcomas (LMS) after an endovascular aneurysm repair in 2012 for a 5-cm symptomatic abdominal aortic aneurysm using an Endurant II aortic stent graft (Medtronic, Minneapolis, Minn). The autopsy confirmed the aortic LMS after the patient rapidly deteriorated and succumbed to death. The vascular LMS are rapidly progressive and diagnostically challenging malignant soft tissue tumors with poor prognosis, which necessitates a strong clinical suspicion and attentiveness to radiologic signs for prompt diagnosis.

Effects of age-related shifts in cellular function and local microenvironment upon the innate immune response to implants

The host macrophage response is now well recognized as a predictor of the success or failure of biomaterial implants following placement. More specifically, shifts from an "M1" pro-inflammatory towards a more "M2-like" anti-inflammatory macrophage polarization profile have been shown to result in enhanced material integration and/or tissue regeneration downstream. As a result, a number of biomaterials-based approaches to controlling macrophage polarization have been developed. However, the ability to promote such activity is predicated upon an in-depth, context-dependent understanding of the host response to biomaterials. Recent work has shown the impacts of both tissue location and tissue status (i.e. underlying pathology) upon the host innate immune response to implants, representing a departure from a focus upon implant material composition and form. Thus, the ideas of "biocompatibility," the host macrophage reaction, and ideal material requirements and modification strategies may need to be revisited on a patient, tissue, and disease basis. Immunosenescence, dysregulation of macrophage function, and delayed resolution of immune responses in aged individuals have all been demonstrated, suggesting that the host response to biomaterials in aged individuals should differ from that in younger individuals. However, despite the increasing usage of implantable medical devices in aged patients, few studies examining the effects of aging upon the host response to biomaterials and the implications of this response for long-term integration and function have been performed. The objective of the present manuscript is to review the putative effects of aging upon the host response to implanted materials and to advance the hypothesis that age-related changes in the local microenvrionement, with emphasis on the extracellular matrix, play a previously unrecognized role in determining the host response to implants.

Tumors arise from the excessive repair of damaged stem cells

Although many hypotheses for tumorigenesis have been proposed, none can explain the occurrence and development of tumors comprehensively until now. We put forward a new hypothesis: tumors arise from the excessive repair of damaged stem cells. There are stem cells in all tissues and organs, and the stem cells have perfect damage repair mechanisms, including damage repair systems and repair-inhibiting systems. Tumors arise from the excessive repair of damaged stem cells, i.e., carcinogens induce stem cell damage, leading to overexpression of damage repair systems, and simultaneous inactivation of repair-inhibiting systems through genetic or non-genetic mechanisms, finally forming tumors. The outcome (forming clinically significant tumors or death) and development (tumor recurrence, metastasis or spontaneous healing) of the tumor cells depends on whether the injury and the excessive repair persists, whether immune surveillance function is normal and the tumor microenvironment is appropriate. This hypothesis not only addresses the issues of where tumor cells arise from, how tumors form and where they go, but also provides a reasonable explanation for many unresolved issues in tumor occurrence, development, metastasis or healing. In addition, this hypothesis could guide the early diagnosis, reasonable treatment and effective prevention of tumors.

Effects of aging upon the host response to implants

Macrophage polarization during the host response is now a well-accepted predictor of outcomes following material implantation. Immunosenescence, dysregulation of macrophage function, and delayed resolution of immune responses in aged individuals have all been demonstrated, suggesting that host responses to materials in aged individuals should differ from those in younger individuals. However, few studies examining the effects of aging upon the host response have been performed. The present work sought to elucidate the impacts of aging upon the host response to polypropylene mesh implanted into 8-week-old and 18-month-old mice. The results showed that there are significant differences in macrophage surface marker expression, migration, and polarization during the early host macrophage response and delayed resolution of the host response in 18-month-old versus 8-week-old mice. These differences could not be attributed to cell-intrinsic defects alone, suggesting that the host macrophage response to implants is likely also dictated to a significant degree by the local tissue microenvironment. These results raise important questions about the design and testing of materials and devices often intended to treat aged individuals and suggest that an improved understanding of patient- and context-dependent macrophage responses has the potential to improve outcomes in aged individuals. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1281-1292, 2017.

Primary Intimal Sarcoma of the Aorta Associated With a Dacron Graft and Resulting in Arterial Rupture

Primary arterial neoplasms are rare lesions which have been most frequently associated with local or constitutional symptomatology, and with distal embolization. Perirenal aortic disruption with pseudoaneurysm formation due to an intimal sarcoma adjacent to a previously placed prosthetic graft is reported in a 66-year-old man. This case supports the premise that the presence of a vascular prosthesis might result in the induction of an arterial wall malignancy. This should be considered when an intraluminal mass is identified in the absence of other arterial pathology. Although the prognosis of these tumors is poor, their preoperative recognition may enhance treatment outcomes.

A pore way to heal and regenerate: 21st century thinking on biocompatibility

This article raises central questions about the definition of biocompatibility, and also about how we assess biocompatibility. We start with the observation that a porous polymer where every pore is spherical, ∼40 microns in diameter and interconnected, can heal into vascularized tissues with little or no fibrosis and good restoration of vascularity (i.e., little or no foreign body reaction). The same polymer in solid form will trigger the classic foreign body reaction characterized by a dense, collagenous foreign body capsule and low vascularity. A widely used definition of biocompatibility is ‘the ability of a material to perform with an appropriate host response in a specific application’. With precision-porous polymers, in direct comparison with the same polymer in solid form, we have the same material, in the same application, with two entirely different biological reactions. Can both reactions be ‘biocompatible?’ This conundrum will be elaborated upon and proposals will be made for future considerations and measurement of biocompatibility.

A cancer theory kerfuffle can lead to new lines of research

The standard viewpoint that cancer is a genetic disease is often stated as a fact rather than a theory. By not acknowledging that it is a theory, namely the Somatic Mutation Theory (SMT), researchers are limiting their progress. An attractive alternative to SMT is the tissue organization field theory (TOFT), which is summarized as "development gone awry." To initiate a kerfuffle, I discuss the interpretation of various results under both TOFT and SMT, including recurrent mutations, hereditary cancers, induction of tumors in transgenic experiments, remission of tumors following the inhibition of enzymes activated by mutated genes, nongenotoxic carcinogens, denervation experiments, foreign-body carcinogenesis, transplantation experiments, and tumors with zero mutations. Thinking in terms of TOFT can spur new lines of research; examples are given related to the early detection of cancer.

Role of the host stroma in cancer and its therapeutic significance

Current cancer research focuses mainly upon the cancer cells in malignant tumours and is providing a growing database about aberrations in their genetic composition. However, tumours also contain non-cancerous host tissue, referred to as the stroma, which plays an active and indispensable role in tumour growth and influences the virulence of the neoplasm towards the host. Many cell types inhabit the stroma, amidst apparently inert fibrous and viscous matrix material, composed of complex polysaccharides, proteins and other molecules. Actually, all of these elements are in constant turnover, causing unpredictable evolution in the properties of the community. This article provides pathologic observations and data on reciprocal interactions between these stromal and neoplastic components of tumours and how they change during the course of the disease. Malignant progression depends upon dauntingly intricate communications between different specialised lineages within the cellular society, which enable rapid adaptation to changing circumstances. Opportunistic misuse of such communication networks enables tumour cells to recruit and incorporate adjacent normal stroma into their midst, so that they may grow, infiltrate and parasitise the host. The absolute dependency of primary tumours and metastases on their diverse stromal components for survival and their insatiable need to continuously recruit more stroma to support expansion, renders them vulnerable to strategies capable of disrupting the cellular interactions involved. This dependency is of critical importance for cancer therapy research, and proposed methods for turning this parasitic behaviour of tumours against themselves are suggested below.

[Cancer research: a privileged field of investigation on chance, reductionism and holism]

The debate between reductionism and anti-reductionism, dealing with the ultimate constituents of the world, is one of the fundamental issues in the philosophy of science. However, in biology, reductionism is less of an ontological and more of an epistemological question: it argues that the explanation of biological processes resides in deciphering the genetic code of living entities. This position is still prevalent in cancer biology, which has long been defined as a cellular process where genetic alterations are responsible for aberrant proliferation. While the hypothesis of somatic mutations remains the central theoretical model, a bundle of experimental data reveals how important the disturbances of tissue organisation are in cancer development, leading to a renewal of holistic and organicist approaches. This latter perspective in particular attempts to contextualise and rethink the centrality of the genetic level by proposing a new conception of cancerogenesis as a tissue disease.

Engineering biomaterials to integrate and heal: the biocompatibility paradigm shifts

This article focuses on one of the major failure routes of implanted medical devices, the foreign body reaction (FBR)--that is, the phagocytic attack and encapsulation by the body of the so-called "biocompatible" biomaterials comprising the devices. We then review strategies currently under development that might lead to biomaterial constructs that will harmoniously heal and integrate into the body. We discuss in detail emerging strategies to inhibit the FBR by engineering biomaterials that elicit more biologically pertinent responses.

Origins of injection-site sarcomas in cats: the possible role of chronic inflammation-a review

The etiology of feline injection-site sarcomas remains obscure. Sarcomas and other tumors are known to be associated with viral infections in humans and other animals, including cats. However, the available evidence suggests that this is not the case with feline injection-site sarcomas. These tumors have more in common with sarcomas noted in experimental studies with laboratory animals where foreign materials such as glass, plastics, and metal are the causal agent. Tumors arising with these agents are associated with chronic inflammation at the injection or implantation sites. Similar tumors have been observed, albeit infrequently, at microchip implantation sites, and these also are associated with chronic inflammation. It is suggested that injection-site sarcomas in cats may arise at the administration site as a result of chronic inflammation, possibly provoked by adjuvant materials, with subsequent DNA damage, cellular transformation, and clonal expansion. However, more fundamental research is required to elucidate the mechanisms involved.

Plausibility of stromal initiation of epithelial cancers without a mutation in the epithelium: a computer simulation of morphostats

BACKGROUND

There is experimental evidence from animal models favoring the notion that the disruption of interactions between stroma and epithelium plays an important role in the initiation of carcinogenesis. These disrupted interactions are hypothesized to be mediated by molecules, termed morphostats, which diffuse through the tissue to determine cell phenotype and maintain tissue architecture.

METHODS

We developed a computer simulation based on simple properties of cell renewal and morphostats.

RESULTS

Under the computer simulation, the disruption of the morphostat gradient in the stroma generated epithelial precursors of cancer without any mutation in the epithelium.

CONCLUSION

The model is consistent with the possibility that the accumulation of genetic and epigenetic changes found in tumors could arise after the formation of a founder population of aberrant cells, defined as cells that are created by low or insufficient morphostat levels and that no longer respond to morphostat concentrations. Because the model is biologically plausible, we hope that these results will stimulate further experiments.

Carcinogenesis induced by foreign bodies

This review deals with the contemporary investigations of carcinogenesis induced by foreign bodies. The main attention is given to the interactions of macrophages with an implanted foreign body and their possible role in tumorigenesis.

Paradoxes in carcinogenesis: new opportunities for research directions

Background

The prevailing paradigm in cancer research is the somatic mutation theory that posits that cancer begins with a single mutation in a somatic cell followed by successive mutations. Much cancer research involves refining the somatic mutation theory with an ever increasing catalog of genetic changes. The problem is that such research may miss paradoxical aspects of carcinogenesis for which there is no likely explanation under the somatic mutation theory. These paradoxical aspects offer opportunities for new research directions that should not be ignored.

Discussion

Various paradoxes related to the somatic mutation theory of carcinogenesis are discussed: (1) the presence of large numbers of spatially distinct precancerous lesions at the onset of promotion, (2) the large number of genetic instabilities found in hyperplastic polyps not considered cancer, (3) spontaneous regression, (4) higher incidence of cancer in patients with xeroderma pigmentosa but not in patients with other comparable defects in DNA repair, (5) lower incidence of many cancers except leukemia and testicular cancer in patients with Down's syndrome, (6) cancer developing after normal tissue is transplanted to other parts of the body or next to stroma previously exposed to carcinogens, (7) the lack of tumors when epithelial cells exposed to a carcinogen were transplanted next to normal stroma, (8) the development of cancers when Millipore filters of various pore sizes were was inserted under the skin of rats, but only if the holes were sufficiently small. For the latter paradox, a microarray experiment is proposed to try to better understand the phenomena.

Summary

The famous physicist Niels Bohr said "How wonderful that we have met with a paradox. Now we have some hope of making progress." The same viewpoint should apply to cancer research. It is easy to ignore this piece of wisdom about the means to advance knowledge, but we do so at our peril.

A calcium-based theory of carcinogenesis

Most human cancers are initiated by chronic injuries that repeatedly kill cells and must, therefore, repeatedly raise cell calcium within nearby survivors. They may also raise calcium in distant cells via calcium waves. Here it is argued that these calcium increases initiate oncogenesis by breaking gap junctions and thus disorganizing tissues and by activating proto-oncogenes. It is also argued that these calcium increases become self-perpetuating in part through the development of an ability of cells to divide in reduced extracellular calcium, i.e., habituation to reduced extracellular calcium. I propose to test these calcium-based theories by using aequorinated mice.

Undifferentiated Intimal Sarcoma of Large Systemic Blood Vessels

Intimal sarcoma (IS) is defined as a malignant tumor arising in the tunica intima of large blood vessels. In systemic circulation, the majority of IS develop in the aorta, where close to three fourths of published cases lack specific differentiation and are called undifferentiated intimal sarcomas (UIS). The remaining cases are intima-associated sarcomas of recognized types, also called differentiated intimal sarcomas (DIS). In this report, we further characterize UIS, including its immunohistochemical profile and results of comparative genomic hybridization. A total of 14 cases of UIS were collected from 17 medical institutions, including slides, blocks, electron photomicrographs, clinical abstracts, and reports of surgical pathology specimens and autopsies. The patients, 7 women and 7 men, were 41 to 85 years of age (median, 65.6 years). Twelve tumors arose from the aorta, one from the left external iliac and femoral arteries, and one in a large systemic vein (the venous tumor was included due to histologic similarity with the arterial lesions). Tumors ranged from 1 cm to over 10 cm in diameter. Histopathology was that of a largely necrotic, poorly differentiated epithelioid and pleomorphic malignant neoplasm relating to the tunica intima. Usually there was only a thin layer of viable tumor cells overlying a large thrombus. All tumors stained at least focally with the endothelial markers CD31 and Fli-1; however, there was otherwise considerable variability in immunophenotype. The distinctive histopathologic appearance of the primary luminal lesion was lost whenever tumor invaded outside the vessel wall (into adventitia and beyond) or in metastatic sites. Such extravascular tumors assumed a variety of patterns reminiscent of undifferentiated pleomorphic sarcoma (UPS; in older literature also known as pleomorphic malignant fibrous histiocytoma, MFH) or other distinct types of sarcomas, including osteosarcoma, angiosarcoma, and rhabdomyosarcoma. The results of comparative genomic hybridization were nonspecific. Eleven patients died of the disease, in an average of 11 months after diagnosis. Three patients are still alive and free of disease at 4, 16, and 27 years. UIS of large systemic vessels represents a distinct clinical entity where intraluminal sarcoma presents with thrombosis and occlusion of large vessels. It is associated with a highly characteristic, although not entirely specific, histology and immunohistochemical phenotype. The histogenesis of UIS is not certain; however, it seems that the cell of origin must leave the confines of the vessel wall to show altered morphology. Although there are rare long-term survivors, UIS behaves as a fully malignant neoplasm that is almost uniformly associated with metastases and tumor-related death.

Novel mechanism of tumorigenesis: Increased transforming growth factor-?1 suppresses the expression of connexin 43 in BALB/cJ mice after implantation of poly-L-lactic acid

Poly-L-lactic acid (PLLA) is a widely used promising material for surgical implants such as tissue-engineered scaffolds. In this study, we aimed to determine the in vivo effect of PLLA plates on the cellular function of subcutaneous tissue in the two mouse strains, BALB/cJ and SJL/J, higher and lower tumorigenic strains, respectively. Gap-junctional intercellular communication (GJIC) and the expression of connexin 43 (Cx43) protein were significantly suppressed, whereas the secretion of transforming growth factor-beta 1 (TGF-beta 1) level was significantly increased in PLLA-implanted BALB/cJ mice compared with BALB/cJ controls. However, no significant difference in TGF-beta 1 secretion was observed between the SJL/J-implanted and SJL/J control mice. We found for the first time that a significant difference was observed between the two strains; thus, the PLLA increased the secretion of TGF-beta 1 and suppressed the mRNA expression of Cx43 at the earlier stage after implantation into the higher-tumorigenic strain, BALB/cJ mice. This novel mechanism might have a vital role in the inhibition of GJIC and promote the tumorigenesis in BALB/cJ mice.

Compromised production of extracellular matrix in mice lacking secreted protein, acidic and rich in cysteine (SPARC) leads to a reduced foreign body reaction to implanted biomaterials

SPARC (secreted protein, acidic and rich in cysteine), a matricellular glycoprotein, modulates the interaction of cells with the extracellular matrix (ECM). Recently, accelerated cutaneous wound closure and altered deposition of collagen were reported in SPARC-null mice. Herein we asked whether SPARC might influence the foreign body reaction to biomaterial implants. Polydimethylsiloxane (silicone rubber) disks and cellulose Millipore filters were implanted into wild-type and SPARC-null mice. In wild-type animals, significant levels of SPARC were observed in the cells and the ECM comprising the capsules around the implants. After 4 weeks, SPARC-null mice exhibited a significant decrease in the thickness of the foreign body capsule, as compared to that observed in wild-type mice. A significant reduction in capsular vascular density was also associated with the silicone implants in the SPARC-null animals. Electron microscopy revealed that collagen fibers in the capsules produced by SPARC-null mice were smaller and more uniform in size than those in wild-type animals. Furthermore, staining with picrosirius-red showed that the collagen fibers were less mature in SPARC-null than in wild-type mice. The altered ECM resulting in decreased capsular thickness, indicative of an altered foreign body reaction in SPARC-null mice, implicates SPARC as an important modulator of the encapsulation of implanted biomaterials.

Reducing capsular thickness and enhancing angiogenesis around implant drug release systems

Biological encapsulation and the foreign body reaction can impair the performance of implanted drug release devices. In this article, the classic definition of biocompatibility is questioned. Examples are presented of biomaterials showing unique healing behavior. A new paradigm for biomaterials healing is proposed in which non-specific protein adsorption is inhibited and matricellular proteins are controlled at the surfaces of implants.

A method for evaluating the influence of porosity on the early reactions of blood with materials

A method is presented for evaluating the influence of porosity on the early reactions of blood with polymer membranes of cellulose acetate and polyethersulfone with two different pore sizes, 0.1-0.2 microm and 0.8 microm. A system of two phases consisting of capillary blood and Dulbecco's phosphate buffered saline was constructed. Platelet adhesion and exposure of thrombospondin was examined by immunofluorescence. Platelet adhesion was higher on the membrane with 0.8 microm pore size. Leukocyte adhesion and viability was measured by fluorescein diacetate/propidium iodide staining, and the respiratory burst response to PMA and opsonized zymosan was measured by chemiluminescence. Leukocyte viability was higher on the membranes with 0.8 microm pore size and higher on the cellulose membrane for exposures upto 2 h. After 3 h the leukocyte viability was highest on the polyethersulfone membrane with a pore size of 0.8 microm. The respiratory burst response of membrane-adhering leukocytes could not be triggered by opsonized zymosan on any of the tested membranes. A response was seen after stimulation with PMA of cells adhering to the cellulose membrane with a pore size of 0.8 microm.

Long-term implantation test and tumorigenicity of polyvinyl alcohol hydrogel plates

Two types of flat plates made from a polyvinyl alcohol (PVA) hydrogel with a water content of 80 and 20 (PVA-H80, PVA-H20), 20 x 10 x 1 mm in size, were subcutaneously implanted into each of 50 young, male Wistar rats. As a control, a sham operation was done on another set of 50 rats (Sham Op group). The shape and transparency of the PVA hydrogel were unchanged for up to 24 months. Tumors arose in 14 rats from the PVA-H80 group. In the PVA-H20 group, tumors appeared in 15 rats. The average tumor latency was 598 +/- 109 days in the PVA-H80 and 637 +/- 94 days in the PVA-H20. There was no difference in tumor incidence between the PVA-H20 and PVA-H80 groups (p < 0.05). In the Sham Op group, no malignant tumors appeared. Histopathologically, the tumors induced by hydrogel plates were malignant tumors resembling fibrosarcoma or malignant fibrous histiocytoma. This indicates that PVA hydrogel implants also induce solid state carcinogenesis at a similarly high rate to medical grade hydrophobic material reported in a previous study.

Tissue response to single-polymer fibers of varying diameters: evaluation of fibrous encapsulation and macrophage density

An in vivo study was conducted to assess the sensitivity of fibrous capsule thickness and macrophage density to polymer fiber diameter. Single polypropylene fibers of diameters ranging from 2.1 to 26.7 microm were implanted in the subcutaneous dorsum of Sprague-Dawley rats. Results at 5 weeks demonstrated reduced fibrous capsule thickness for small fibers. Capsule thickness was 0.6 (+/-1.8) microm, 11.7 (+/-12.0) microm, 20.3 (+/-11.6) microm, and 25.5 (+/-10.0) microm for fibers in the ranges of 2.1 to 5.9, 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, respectively. Fibers very near to blood vessels had smaller capsules than did those with local vasculature further away. The macrophage density in tissue with fiber diameters 2.1 to 5.9 microm (23.03 +/- 8.67%) was comparable to that of unoperated contralateral control skin (18.72+/-10.06%). For fibers with diameters in the ranges of 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, macrophage densities were 33.90+/-13.08%, 34.40+/-15.77%, and 41.68+/-13.98%, respectively, all of which were significantly larger (p<0.002) than that for the control. The reduced fibrous capsule thickness and macrophage density for small fibers (<6 microm) compared with large fibers could be due to the reduced cell-material contact surface area or to a curvature threshold effect that triggers cell signaling. A next step will be to extend the analysis to meshes to evaluate fiber-spacing effects on small-fiber biomaterials.

Studies on the mechanisms of tumorigenesis induced by polyetherurethane in rats: production of superoxide, tumor necrosis factor, and interleukin 1 from macrophages cultured on different polyetherurethanes

Interaction of macrophages (Mos) with polyetherurethane (PEU) was investigated to clarify the role of the Mos in the early stage of tumorigenesis of PEUs. As for the inflammatory cytokines produced from Mos, the amount of tumor necrosis factor (TNF) produced on three PEUs (PU-4, 6, and 8) was similar, but less than that on a control glass dish. Interleukin 1 (IL-1) production levels on the PEUs, especially on PU-6, also decreased in comparison with the glass dish. Superoxide (O(2)(-)) release from Mos on the PEUs was similar or more than that on the glass dishes within 24 h incubation. In particular, the O(2)(-) release on PU-6, possessing the lowest tumorigenic potential in vivo, reached the highest level among the PEUs tested. To clarify the causes that enhanced O(2)(-) release from Mos, the methanol extracts of the three PEUs and chemicals that constitute the PEUs were tested. The extracts and 1,4-butanediol did not show an effect on O(2)(-) release. However, 4, 4'-di(ethoxycarboamide) diphenylmethane, a model hard segment of PEU, was remarkably enhanced, whereas poly(tetramethyleneoxide), a soft segment of PEU, reduced the O(2)(-) release in a dose-dependent manner. From these results, although it is still unclear what affects different types of O(2)(-) production, lower tumorigenic potentials of PU-6 may be caused by O(2)(-) release from Mos, which play an important role in the tumoricidal process. Further, the low IL-1 production on PU-6 suggests that PU-6 suppresses inflammatory responses other than O(2)(-) production in vivo, resulting in lower tumorigenic potentials. On the other hand, TNF production was almost similar when Mos were cultured on three PEUs, suggesting TNF did not play a role in the different tumorigenic potentials of PEUs.

Epithelioid angiosarcoma associated with a Dacron vascular graft

Angiosarcoma developed at the site of a Dacron vascular prosthesis 8 years after an aortobifemoral bypass graft insertion. The tumor was composed of epithelioid cells, which showed positive staining for cytokeratin and expression of the common endothelial markers CD31, CD34, and von Willebrand factor. Ultrastructural examination showed aggregates of large cells with intercellular lumina and focal perinuclear whorls of intermediate filaments. The patient, who had abdominal pain and weight loss, died of disseminated pelvic and abdominal disease 6 months after diagnosis. Sarcomas associated with vascular Dacron grafts and angiosarcomas associated with metal or polymer foreign bodies are rare. Their development is probably analogous to the common experimental development of foreign body-associated sarcomas in rodents. Physicians caring for patients with vascular grafts or metal foreign bodies should be aware of this complication.

Mice that lack the angiogenesis inhibitor, thrombospondin 2, mount an altered foreign body reaction characterized by increased vascularity

Disruption of the thrombospondin 2 gene (Thbs2) in mice results in a complex phenotype characterized chiefly by abnormalities in fibroblasts, connective tissues, and blood vessels. Consideration of this phenotype suggested to us that the foreign body reaction (FBR) might be altered in thrombospondin 2 (TSP2)-null mice. To investigate the participation of TSP2 in the FBR, polydimethylsiloxane (PDMS) and oxidized PDMS (ox-PDMS) disks were implanted in TSP2-null and control mice. Growth of TSP2-null and control skin fibroblasts in vitro also was evaluated on both types of disks. Normal fibroblasts grew as a monolayer on both surfaces, but attachment of the cells to ox-PDMS was weak and sensitive to movement. TSP2-null fibroblasts grew as aggregates on both surfaces, and their attachment was further compromised on ox-PDMS. After a 4-week implantation period, both types of PDMS elicited a similar FBR with a collagenous capsule in both TSP2-null and control mice. However, strikingly, the collagenous capsule that formed in TSP2-null mice was highly vascularized and thicker than that formed in normal mice. In addition, abnormally shaped collagen fibers were observed in capsules from mutant mice. These observations indicate that the presence or absence of an extracellular matrix component, TSP2, can influence the nature of the FBR, in particular its vascularity. The expression of TSP2 therefore could represent a molecular target for local inhibitory measures when vascularization of the tissue surrounding an implanted device is desired.

Effect of 3 growth control substances on foreign body sarcomagenesis: IFN, IUdR, MGBG

The purpose was to observe the effect on sarcomagenesis of 3 substances reported to inhibit neoplastic growth--interferon alpha-2/alpha-1 hybrid (IFN), 5-iodo-2-deoxyuridine (IUdR) and methylglyoxal bis(guanylhydrazone) (MGBG). Inhibitory effect might help diminish the sarcoma risk of human implants. The substances were applied respectively to groups of 25mm cellulose filters which were implanted subcutaneously 1 per animal in randomly assigned respective groups of 50 female BALB/c mice. The implant sites were palpated weekly. On detection of a tumour the animal was sacrificed. The number of tumours arising and the accumulated weeks of exposure to the implants were recorded per group and compared to those of controls with untreated filters. Tumour incidence in the 2 IFN groups was 33/45 and 35/48 mice--160 per cent that of the controls, 22/48 (chi-square p < 0.05). In the IUdR group tumour incidence was 24/44 mice--194 per cent that of controls (p < 0.05), and in the MGBG group 15/43--122 per cent that of controls (p < 0.75). Although the substances inhibit tumour growth in man, they did not inhibit but increased film sarcomagenesis, not significant for MGBG. Observation of the effects of such substances with dual neoplastic activity may furnish clues to the control processes of neoplasia.

Biodegradation and tumorigenicity of implanted plates made from a copolymer of epsilon-caprolactone and L-lactide in rat

Flat plates made from a copolymer of epsilon-caprolactone and L-lactide (P-CL-LA) [50:50 (w/w), molecular weight 1.62 x 10(5); 20 x 10 x 1 mm size] were subcutaneously implanted into 50 young, male Wistar rats (P-CL-LA group). After 24 months the plates had become a mass of small pieces, which were concentrated in an area of 3 x 2 x 1 mm. For comparison, 50 rats were implanted with medical-grade polyethylene plates (PE group) while another set of 50 rats was subjected to the same operation but without an implant (Sham Op group). Tumors arose in 25 rats from the P-CL-LA group: 24 were malignant mesenchymal tumors at the implant sites. In the PE group, tumors appeared in 16 rats (14 at the implant sites and two ectopically). The average tumor latency was 578+/-84 days in the P-CL-LA group and 452+/-102 days in the PE group. There was no difference in tumor incidence between the P-CL-LA and PE groups (p < 0.05). In the Sham Op group, two malignant tumors appeared over 2 years. Pathologically, these induced tumors arose from the inflammatory cells surrounding the degrading fragments of P-CL-LA within the tissue capsule. This indicates that relatively slowly degrading material can induce malignant tumors at a similarly high rate to nonabsorbable medical grade PE, at least in this animal model.