Bioengineering Methods Research Articles

Study the Native Vegetation around the <i>Al Hosh</i> Highway Slope in Sudan (Gezira State) as Bioengineering Method of Slope Erosion Protection

Soil erosion occurs due to rainfall intensity and soil movement had become one of the disasters faced by Al Hosh highway today. And the carelessness (Where there is no any type of protection) it has also caused occur the soil erosion due unprotected embankment side slope of the Al Hosh highway, which affect widely of the loss of human lives according to traffic accidents, the destruction of cars and large vehicles. Although the area is usually categorized as eroded area because of high rainfall intensity during the autumn season time, the Middle East states of the Sudan as Gezira state is known by the heavy rainfall. As stabilization of slopes using mechanical structures is costly to establish and maintain, biotechnical slope protection is an alternative which is more aesthetically pleasing and cost effective. Hence, in this research, an overall study on the positive impacts of the presence of native vegetation for the slope stability were studied in the Al Hosh embankment side slope. Trying to use native vegetation as the local grasses to restore the Al Hosh highway slope as a new bio-engineering method in Sudan. This paper explores the review the native vegetation and its ability to use it in protecting Al Hosh slope erosion with different slope angles by identification, categorization and studying of the salient features of them according to the soil classification for relevant slope by using both Unified Soil Classification System and US Department of Agriculture. This research recommends suitable native vegetation against soil erosion and subsequent slope failures in cut slopes.

Slope Processes, Mass Movement and Soil Erosion: A Review

Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorphological processes. This paper reviews slope processes associated with mass movement and soil erosion and contributory factors, including physical and human agents. Acting together, these cause diverse geomorphological features. Slope processes are illustrated by reference to case studies from Brazil and UK. The causes and impacts of erosion are discussed, along with appropriate remedial bioengineering methods and the potential of the measures to prevent these types of environmental degradation. Although there are several agents of erosion, water is the most important one. Cultivation can promote soil erosion, due to ploughing and harvesting, which moves soil down slopes. Soil erosion and mass movement data would inform the viability of soil conservation practices. Integrated management of drainage basins offers a promising way forward for effective soil conservation and soil remedial bioengineering in Brazil and UK.

Development of a Functional Biohybrid Implant Formed from Periodontal Tissue Utilizing Bioengineering Technology.

Current osseointegrated dental implants have been widely used for the rehabilitation of tooth loss. Although dental implants are considered an available treatment in the paradigm shift from traditional dental therapies, such as fixed dental bridges and removable dentures, the fundamental problems must be overcome before their clinical use in young patients who are still undergoing jawbone growth. Here, we show a novel bioengineering method for a functional biohybrid implant that is combined with adult-derived periodontal tissue and attached with bone tissue as a substitute for cementum. This biohybrid implant was successfully engrafted using the bioengineered periodontal ligament, and it restored physiological function, such as orthodontic movement through bone remodeling and appropriate responsiveness to noxious stimuli. Thus, this study represents the functional biohybrid implant's potential for clinical use as a next-generation dental implant using adult-derived tissues.

Implementation of eco-engineering design into existing slope stability design practices

Eco-engineering techniques involve the use of both plants and inert materials where, in the latter, non-treated wood is usually present. The two different elements will both evolve with time and change their mechanical properties differently. On one hand, the wood will degrade decreasing its effective cross sectional area with time. On the other hand, the live plant material will grow and propagate new roots as time progresses. Both root development and inert material changes must be accounted for in order to realistically simulate a bioengineered slope evolution and design effective eco-engineering solutions.The dynamic nature of a bioengineered work sets different scenarios throughout the slope design life. All these different stages must be taken into account in the work design process. In this work, we propose an adaptation of the existing routines and procedures of both geotechnical practice and civil engineering design scheme in order to closely reflect the inclusion of bioengineering methods in the classic geotechnical engineering problems. A design methodology covering different critical points within the lifecycle of a bioengineered slope is proposed and put into practice into the design stage for a case study in Scotland. By detecting critical points at the design stage the proposed methodology was proven to offer an improved eco-engineering work design scheme. With the use of the proposed method both external and internal stability checks with their corresponding safety factor values increase with time and there are no conflicts between the two evolving processes involved in this kind of works.

Generation of bioengineered feather buds on a reconstructed chick skin from dissociated epithelial and mesenchymal cells.

Various kinds of in vitro culture systems of tissues and organs have been developed, and applied to understand multicellular systems during embryonic organogenesis. In the research field of feather bud development, tissue recombination assays using an intact epithelial tissue and mesenchymal tissue/cells have contributed to our understanding the mechanisms of feather bud formation and development. However, there are few methods to generate a skin and its appendages from single cells of both epithelium and mesenchyme. In this study, we have developed a bioengineering method to reconstruct an embryonic dorsal skin after completely dissociating single epithelial and mesenchymal cells from chick skin. Multiple feather buds can form on the reconstructed skin in a single row in vitro. The bioengineered feather buds develop into long feather buds by transplantation onto a chorioallantoic membrane. The bioengineered bud sizes were similar to those of native embryo. The number of bioengineered buds was increased linearly with the initial contact length of epithelial and mesenchymal cell layers where the epithelial-mesenchymal interactions occur. In addition, the bioengineered bud formation was also disturbed by the inhibition of major signaling pathways including FGF (fibroblast growth factor), Wnt/β-catenin, Notch and BMP (bone morphogenetic protein). We expect that our bioengineering technique will motivate further extensive research on multicellular developmental systems, such as the formation and sizing of cutaneous appendages, and their regulatory mechanisms.

Impact of chemical peeling combined with negative pressure on human skin.

In vivo changes in skin barrier function after chemical peeling with alpha hydroxyacids (AHAs) have been previously reported. However, the additional effects of physical treatment with chemical agents on skin barrier function have not been adequately studied. This study measured the degree of acute skin damage and the time required for skin barrier repair using non-invasive bioengineering methods in vivo with human skin to investigate the additional effect of a 4% AHA chemical jet accelerated at supersonic velocities. Thirteen female subjects (average age: 29.54 ± 4.86 years) participated in this study. The faces of the subjects were divided into half according to the block randomization design and were then assigned to receive AHA peeling alone or AHA peeling combined with pneumatic pressure on each side of the face. Transepidermal water loss (TEWL), skin colour and skin blood flow were evaluated at baseline and at 30 min, 2, 5 and 7 days after treatment. The TEWL and skin blood flow were significantly increased after 30 min in chemodermabrasion compared with chemical peeling alone (P < 0.05). The TEWL and skin blood flow recovered to baseline after 2 days, and TEWL was significantly decreased at 7 days compared with chemical peeling alone (P < 0.05). Chemodermabrasion can temporarily impair skin barriers, but it is estimated that it can enhance the skin barrier function after 7 days compared to the use of a chemical agent alone. In addition, chemodermabrasion has a more effective impact in the dermis and relatively preserves the skin barrier.

Improvement of the sizing methods of riverbank bioengineering following an empirical approach

Improvement of the sizing methods of riverbank bioengineering following an empirical approach

The effective bioengineering method of implantation decellularized renal extracellular matrix scaffolds.

End stage renal disease (ESRD) is a progressive loss of kidney function with a high rate of morbidity and mortality. Transplantable organs are hard to come by and hold a high risk of recipient immune rejection. We intended to establish a more effective and faster method to decellularize and recellularize the kidney scaffold for transplant and regeneration. We successfully produced renal scaffolds by decellularizing rat kidneys with 0.5% sodium dodecyl sulfate (SDS), while still preserving the extracellular matrix (ECM) 3D architecture, an intact vascular tree and biochemical components. We recellularized the kidney scaffolds with mouse embryonic stem (ES) cells that then populated and proliferated within the glomerular, vascular, and tubular structures. After in vivo implantation, these recellularized scaffolds were easily reperfused, tolerated blood pressure and produced urine with no blood leakage. Our methods can successfully decellularize and recellularize rat kidneys to produce functional renal ECM scaffolds. These scaffolds maintain their basic components, retain intact vasculature and show promise for kidney regeneration.

Randomized, double-blinded, vehicle-controlled, split-face study to evaluate the effects of topical application of a Gold Silk Sericin/Niacinamide/Signaline complex on biophysical parameters related to skin ageing.

To investigate the effects of topical application of a Gold Silk Sericin (GSS) complex on biophysical parameters related to skin ageing. A range of non-invasive bioengineering methods were deployed in an 8-week randomized, double-blinded, vehicle-controlled, split-face study among 40 female subjects aged 40-70. Endpoints measured included expert grades of skin condition, stratum corneum (SC) hydration, SC barrier function, elasticity and surface topography. The GSS complex produced significant single-variable (P < 0.05) improvements in SC hydration, barrier function, elasticity and surface topography compared with the Vehicle control. The GSS complex examined in this study represents an interesting new cosmetic topical technology with which to address multiple aspects of aged/photoaged female facial skin.

Functional salivary gland regeneration as the next generation of organ replacement regenerative therapy.

Oral health is maintained by the coordinated function of many organs including the teeth and salivary glands. Dysfunction of these organs causes many problems, such as dental caries, swallowing dysfunction and periodontal disease. Regenerative therapy for salivary gland tissue repair and whole-salivary gland replacement is currently considered a novel therapeutic concept that may have potential for the full recovery of salivary gland function. Salivary gland tissue stem cells are thought to be candidate cell sources for salivary gland tissue repair therapies. In addition, whole-salivary gland replacement therapy may become a novel next-generation organ regenerative therapy. Almost all organs arise from reciprocal epithelial and mesenchymal interactions of the germ layers. We developed a novel bioengineering method, an organ germ method that can reproduce organogenesis through the epithelial-mesenchymal interaction. A bioengineered salivary gland germ can regenerate a structurally correct salivary gland in vitro, and bioengineered salivary glands successfully secrete saliva into the oral cavity from ducts in the recipient through the reestablishment of the afferent-efferent neural network. The bioengineered salivary gland can also improve the symptoms of xerostomia, such as bacterial infection and swallowing dysfunction. In this review, we describe recent findings and technological developments of salivary gland regenerative therapy.

Blood and immune cell engineering: Cytoskeletal contractility and nuclear rheology impact cell lineage and localization: Biophysical regulation of hematopoietic differentiation and trafficking.

Clinical success with human hematopoietic stem cell (HSC) transplantation establishes a paradigm for regenerative therapies with other types of stem cells. However, it remains generally challenging to therapeutically treat tissues after engineering of stem cells in vitro. Recent studies suggest that stem and progenitor cells sense physical features of their niches. Here, we review biophysical contributions to lineage decisions, maturation, and trafficking of blood and immune cells. Polarized cellular contractility and nuclear rheology are separately shown to be functional markers of a hematopoietic hierarchy that predict the ability of a lineage to traffic in and out of the bone marrow niche. These biophysical determinants are regulated by a set of structural molecules, including cytoplasmic myosin-II and nuclear lamins, which themselves are modulated by a diverse range of transcriptional and post-translational mechanisms. Small molecules that target these mechanobiological circuits, along with novel bioengineering methods, could prove broadly useful in programming blood and immune cells for therapies ranging from blood transfusions to immune attack of tumors.

Renal Stem Cells, Tissue Regeneration, and Stem Cell Therapies for Renal Diseases.

Kidney diseases are a global public health problem, with an incidence that has reached epidemic proportions and continues to climb in the USA and worldwide. This trend is projected to grow in correlation with the global rise in the aged population and the increasing prevalence of conditions that cause renal complications, such as cardiovascular disease, hypertension, and diabetes. Current treatment options for acute and chronic kidney disease include dialysis, which is also associated with substantial morbidity and mortality, and kidney transplantation, which is limited by the supply of compatible organs. Consequently, new methods to alleviate, cure, or prevent renal disease are urgently required to reduce the exponentially growing burden due to acute and chronic kidney disorders and offer alternative therapeutic options to improve patients' survival and quality of life. Several potential regenerative cell-based therapies for the treatment of renal failure are currently under development. The first one is the direct application of stem cells (SCs) to the diseased kidney, which relies on the inherent capabilities of SCs to differentiate, organize, and integrate into the existing tissues to restore function. To this aim different stem cell types have been investigated for their potential to contribute to renal regeneration. In their article “WNT/β-Catenin Signaling Is Required for Integration of CD24+ Renal Progenitor Cells into Glycerol-Damaged Adult Renal Tubules,” Z. Zhang et al. described how the endogenous canonical β-catenin/TCF pathway is reactivated during recovery from AKI and is required for the engraftment of exogenous CD24+ embryonic renal progenitor cells into damaged tubular areas upon injury. These events appear to recapitulate the WNT-dependent inductive process which drives primary nephrogenesis. Review article by F. O. Arcolino et al. entitled “Human Urine as a Noninvasive Source of Kidney Cells” summarizes the recent data regarding human urine-derived cells. Urine contains various types of kidney cells such as podocytes, proximal tubule cells, or renal stem/progenitor cells, which can be easily as well as noninvasively isolated and cultured in vitro. Although the characteristics of each cell population are not totally understood, this paper suggests the potential of urine-derived kidney cells as a tool of clinical application for the treatment of various kidney diseases. Stem cell therapy contributes for kidney regeneration not only through direct differentiation and replacement of injured cells but also by secretion of renoprotective or trophic factors. These data are summarized by K. Tsuji and S. Kitamura in their review article “Trophic Factors from Tissue Stem Cells for Renal Regeneration.” Another strategy is based on the prospective design of a therapeutic approach focused on modulation of endogenous kidney regenerative properties by conventional chemical and biological agents able to modulate the activity of resident progenitor cells. Although understanding of regeneration of the nephron may have significance to explore new therapeutic approaches, the process of regeneration of nephron has yet been poorly understood. The review article “Atlas of Cellular Dynamics during Zebrafish Adult Kidney Regeneration” by K. K. McCampbell et al. provides an essential foundation for future work aimed at elucidating the mechanisms that regulate kidney regeneration following acute kidney injury using adult zebrafish, which maintains the regenerative ability. Akito Maeshima et al. in their review “Diverse Cell Populations Involved in Regeneration of Renal Tubular Epithelium following Acute Kidney Injury” describe recent advances in understanding the regeneration mechanisms of renal tubules, particularly the characteristics of various cell populations contributing to tubular regeneration and highlight the targets for the development of regenerative medicine for treating kidney diseases in humans. Additional information on the renal regeneration capacity could be inferred from studies on kidney organ culture. The review article “Organ In Vitro Culture: What Have We Learned about Early Kidney Development?” by A. Rak-Raszewska et al. provides an introduction to the organ culture method and a summary of the progress in the field of kidney developmental biology based on it. Finally, a great advance on the comprehension of the mechanisms of renal regeneration, in particular podocyte regeneration, and on the role of putative population of renal stem/progenitor cells could be obtained from transgenic mouse models, as summarized by D. Lombardi and Laura Lasagni in their review “Transgenic Strategies to Study Podocyte Loss and Regeneration.” Finally, a number of different approaches have been applied toward tissue engineering of the kidney as a mean to replace renal function. S. Yamanaka and Takashi Yokoo in their review article “Current Bioengineering Methods for Whole Kidney Regeneration” summarized recent researches involving the use of renal stem cells and renal bioengineering to regenerate functional whole kidneys de novo. The editors hope that the original and review articles integrated in this special issue provide more insights into the advancements and challenges faced by this rapidly expanding field of regenerative medicine and will be helpful and educational for interested readers. Benedetta Bussolati Akito Maeshima Janos Peti-Peterdi Takashi Yokoo Laura Lasagni

Current Bioengineering Methods for Whole Kidney Regeneration

Kidney regeneration is likely to provide an inexhaustible source of tissues and organs for immunosuppression-free transplantation. It is currently garnering considerable attention and might replace kidney dialysis as the ultimate therapeutic strategy for renal failure. However, anatomical complications make kidney regeneration difficult. Here, we review recent advances in the field of kidney regeneration, including (i) the directed differentiation of induced pluripotent stem cells/embryonic stem cells into kidney cells; (ii) blastocyst decomplementation; (iii) use of a decellularized cadaveric scaffold; (iv) embryonic organ transplantation; and (v) use of a nephrogenic niche for growing xenoembryos for de novo kidney regeneration from stem cells. All these approaches represent potentially promising therapeutic strategies for the treatment of patients with chronic kidney disease. Although many obstacles to kidney regeneration remain, we hope that innovative strategies and reliable research will ultimately allow the restoration of renal function in patients with end-stage kidney disease.

METHODS TO QUANTITATE ATRIAL ELECTRICAL ACTIVITY USING ELECTROGRAMS ACQUIRED DURING ATRIAL FIBRILLATION

Herein, commonly used quantitative bioengineering methods that have been developed to analyze fractionated electrograms recorded from the surface of the atria during atrial fibrillation (AF) are described. Techniques were categorized as time-domain and frequency-domain methods. The main time-domain method is peak counting. Its variations based on preprocessing and thresholding are discussed. The main frequency-domain method is spectral analysis. Two spectral estimators, the discrete Fourier transform (DFT) and the new spectral estimator (NSE) are described. The ability of each estimator to detect the main periodic component of fractionated atrial electrograms is compared. Several spectral parameters that are used for analysis of atrial electrograms including the dominant frequency (DF), dominant amplitude (DA) and mean spectral profile (MP) are defined. Mean values of these parameters are compared in paroxysmal versus persistent AF fractionated electrograms based upon the results of several studies. Time-domain methods are shown to work best for analysis with deterministic, not fractionated atrial electrograms. For fractionated atrial electrograms, frequency-domain methods are often used. The DF, DA and MP spectral parameters are significantly different in paroxysmal versus longstanding persistent AF recordings. The DF and the DA are significantly higher, and the MP is significantly lower, in persistent AF electrogram recordings. The higher DF and DA parameter values reflect substrate remodeling in persistent AF, which increases the stability of the electrical activation pattern. The lower MP value in persistent AF reflects the lower spectral noise floor, indicative of a less complex and more periodic pattern of electrical activity.

Time course of skin features and inflammatory biomarkers after liquid sulfur mustard exposure in SKH-1 hairless mice

Sulfur mustard (SM) is a strong bifunctional alkylating agent that produces severe tissue injuries characterized by erythema, edema, subepidermal blisters and a delayed inflammatory response after cutaneous exposure. However, despite its long history, SM remains a threat because of the lack of effective medical countermeasures as the molecular mechanisms of these events remain unclear. This limited number of therapeutic options results in part of an absence of appropriate animal models. We propose here to use SKH-1 hairless mouse as the appropriate model for the design of therapeutic strategies against SM-induced skin toxicity. In the present study particular emphasis was placed on histopathological changes associated with inflammatory responses after topical exposure of dorsal skin to three different doses of SM (0.6, 6 and 60mg/kg) corresponding to a superficial, a second-degree and a third-degree burn. Firstly, clinical evaluation of SM-induced skin lesions using non invasive bioengineering methods showed that erythema and impairment of skin barrier increased in a dose-dependent manner. Histological evaluation of skin sections exposed to SM revealed that the time to onset and the severity of symptoms including disorganization of epidermal basal cells, number of pyknotic nuclei, activation of mast cells and neutrophils dermal invasion were dose-dependent. These histopathological changes were associated with a dose- and time-dependent increase in expression of specific mRNA for inflammatory mediators such as interleukins (IL1β and IL6), tumor necrosis factor (TNF)-α, cycloxygenase-2 (COX-2), macrophage inflammatory proteins (MIP-1α, MIP-2 and MIP-1αR) and keratinocyte chemoattractant (KC also called CXCL1) as well as adhesion molecules (L-selectin and vascular cell adhesion molecule (VCAM)) and growth factor (granulocyte colony-stimulating factor (Csf3)). A dose-dependent increase was also noted after SM exposure for mRNA of matrix metalloproteinases (MMP9) and laminin-γ2 which are associated with SM-induced blisters formation. Taken together, our results show that SM-induced skin histopathological changes related to inflammation is similar in SKH-1 hairless mice and humans. SKH-1 mouse is thus a reliable animal model for investigating the SM-induced skin toxicity and to develop efficient treatment against SM-induced inflammatory skin lesions.

Development of the stratum corneum.

In 2015, Professor Ronald (Ronnie) Marks will celebrate his 80th birthday and the 35th year since assuming the Chair of Dermatology at the University of Wales College of Medicine in Cardiff, Wales. Ronnie's long and prolific career is well deserving of a celebratory Festschrift. Among his many accomplishments, Marks was an early champion of quantitative measurements and the application of bioengineering methods to clinical skin science, with particular focus on stratum corneum biology and the measurement of skin appearance. Appealing to Ronnie's wry sense of humour, I would characterize his career in the words of the native Welshman, Dylan Thomas, who published an unfinished novel in 1955 entitled Adventures in the Skin Trade. Ronnie Marks has been a quintessential and imaginative adventurer in the 'skin trade', and he continues to forge new trails for others to follow. The areas highlighted below are emblematic of Ronnie's varied research interests and his impact on stimulating experimental questions for me and future investigators of epidermal differentiation and stratum corneum development.

11-2 Biophysical effects after cutaneous application of dermatological products made from sediment of mineral waters Lanjarón-Capuchina by skin bioengineering methods

11-2 Biophysical effects after cutaneous application of dermatological products made from sediment of mineral waters Lanjarón-Capuchina by skin bioengineering methods

Use of Live Poles for Stabilization of a Shallow Slope Failure

AbstractSoil bioengineering methods consisting of live poles and brush layers were used to stabilize shallow slides and control erosion on an embankment slope in eastern Ohio. Plant survival rates, slope movement, soil moisture content, and soil suction were measured. Load tests were performed to evaluate resistance of the poles, and results were used to estimate the stability of the repaired slope. Seven years after the repair was completed, vegetation is well established and the slope is stable, which is in agreement with calculated safety factors. This study indicates that soil bioengineering methods can be used for stabilization of shallow failures; however, the method may not be immediately effective, and the time of installation and soil moisture conditions are important for survival of the poles.

Methods to quantitate videocapsule endoscopy images in celiac disease.

In this work, bioengineering methods that can be used to quantitatively analyze videocapsule endoscopy images that have been acquired from celiac patients versus controls are described. For videocapsule endoscopic analysis, each patient swallows a capsule which contains an imaging device and light source. In celiac and control patients, images are acquired and analyzed at the level of the small intestine. The data used for videocapsule analysis consisted of high resolution images of dimension 576 × 576 pixels, acquired twice per second. The goal of the quantitative analysis is to detect abnormality in celiac patient images as compared with controls. Several types of abnormality can exist at the level of the small intestine in celiac patients. In untreated patients, and often even after treatment with a gluten-free diet, there can be villous atrophy, as well as presence of fissures and a mottled appearance. To detect and discern these abnormalities, several methods of statistical and structural feature extraction and selection are described. It was found that there is a significantly greater variation in image texture and average brightness level in celiac patients as compared with controls (p < 0.05). Celiac patients have a longer dominant period as compared with controls, averaging 6.4 ± 2.6 seconds versus 4.7 ± 1.6 seconds in controls (p = 0.001). This suggests that overall motility is slower in the celiac patients. Furthermore, the mean number of villous protrusions per image was found to be 402.2 ± 15.0 in celiac patients versus 420.8 ± 24.0 in control patients (p < 0.001). The average protrusion width was 14.66 ± 1.04 pixels in celiacs versus 13.91 ± 1.47 pixels in controls (p = 0.01). The mean protrusion height was 3.10 ± 0.26 grayscale levels for celiacs versus 2.70 ± 0.43 grayscale levels for controls (p < 0.001). Thus celiac patients tended to have fewer protrusions, and these were more varied in shape, tending to be blunted, as compared with controls, which more often had fine, uniform protrusions. A variety of computerized methods are now available to quantitate videocapsule images for comparison of celiac versus control patients. Since these methods are based on computer algorithms, they can be automated and there is no variation in the results due to observer bias. These methods readily lend themselves to automation, so that it may be possible to map the entire small intestine for presence of abnormality in real-time. It is also possible to develop an automated, quantitative clinical score which can be displayed with real-time update during the procedure. This would be useful to determine progress in celiac patients on a gluten-free diet, and to better understand the properties of the healing process in these patients.

Development and Prospects of Organ Replacement Regenerative Therapy

Current approaches for the development of regenerative therapies have been influenced by our understanding of embryonic development, stem cell biology, and tissue engineering technology. The ultimate goal of regenerative therapy is to develop fully functioning bioengineered organs to replace lost or damaged organs that result from disease, injury, or aging. Almost all organs including ectodermal organs, such as teeth, hair, salivary glands, and lacrimal glands, arise from organ germs induced by reciprocal epithelial-mesenchymal interactions in the developing embryo. A novel concept to generate a bioengineered organ is to recreate organogenesis and thereby develop fully functioning bioengineered organs from the resulting bioengineered organ germ generated via 3-dimensional cell manipulation using immature stem cells in vitro. We have previously developed a bioengineering method for forming a 3-dimensional organ germ in the early developmental stages, termed the "bioengineered organ germ method." Recently, we reported fully functioning bioengineered tooth replacements after transplantation of a bioengineered tooth germ or a mature tooth unit comprising the bioengineered tooth and periodontal tissues. This concept could be adopted to generate not only teeth but also bioengineered hair follicles, salivary glands, and lacrimal glands. These studies emphasize the potential for bioengineered organ replacement in future regenerative therapies. In this review, we will summarize the strategies and the recent progress of research and development for the establishment of organ replacement regenerative therapies.