Regeneration Patches Research Articles

Electrohydrodynamic Printing of Microscale Fibrous Scaffolds with a Sinusoidal Structure for Enhancing the Contractility of Cardiomyocytes.

Mimicking the curved collagenous fibers in the cardiac extracellular matrix to fabricate elastic scaffolds in vitro is important for cardiac tissue engineering. Here, we developed sinusoidal polycaprolactone (PCL) fibrous scaffolds with commendable flexibility and elasticity to enhance the contractility of primary cardiomyocytes by employing melt-based electrohydrodynamic (EHD) printing. Microscale sinusoidal PCL fibers with an average diameter of ∼10 μm were printed to mimic the collagenous fibers in the cardiac ECM. The sinusoidal PCL fibrous scaffolds were EHD-printed in a layer-by-layer manner and exhibited outstanding flexibility and elasticity compared with the straight ones. The sinusoidal PCL scaffolds provided an elastic microenvironment for the attaching and spreading of primary cardiomyocytes, which facilitated their synchronous contractive activities. Primary cardiomyocytes also showed improved gene expression and maturation on the sinusoidal PCL scaffolds under electrical stimulation for 5 days. It is envisioned that the proposed flexible fibrous scaffold with biomimetic architecture may serve as a suitable patch for tissue regeneration and repair of damaged hearts after myocardial infarction.

Ameliorating impaired cardiac function in myocardial infarction using exosome-loaded gallic-acid-containing polyurethane scaffolds

Myocardial infarction (MI) can be tackled by implanting cardiac patches which provide mechanical support to the heart. However, most tissue-engineered scaffolds face difficulty in attenuating oxidative stress, maintaining mechanical stability, and regenerating damaged cardiomyocytes. Here, we fabricated elastic cryogels using polyurethane modified with antioxidant gallic acid in its backbone (PUGA) and further coated them with decellularized extracellular matrix (dECM) to improve adhesiveness, biocompatibility and hemocompatibility. The scaffold was functionalized with exosomes (EXO) isolated from adipose-derived stem cells having regenerative potential. PUGA-dECM + EXO was tested in a rat model with induced MI where echocardiography after 8 weeks of implantation showed significant recovery in treatment group. Histological analysis revealed a decrease in fibrosis after application of patch and promotion of angiogenesis with reduced oxidative stress was shown by immunostaining. Expression of cardiac tissue contractile function marker was also observed in treatment groups. Thus, the proposed biomaterial has a promising application to be utilized as a patch for cardiac regeneration. More detailed studies with larger animal species are needed for using these observations for specific applications.

Three-Dimensionally Printed Hydrogel Cardiac Patch for Infarct Regeneration Based on Natural Polysaccharides

Myocardial infarction is one of the more common cardiovascular diseases, and remains the leading cause of death, globally. Hydrogels (namely, those using natural polymers) provide a reliable tool for regenerative medicine and have become a promising option for cardiac tissue regeneration due to their hydrophilic character and their structural similarity to the extracellular matrix. Herein, a functional ink based on the natural polysaccharides Gellan gum and Konjac glucomannan has, for the first time, been applied in the production of a 3D printed hydrogel with therapeutic potential, with the goal of being locally implanted in the infarcted area of the heart. Overall, results revealed the excellent printability of the bioink for the development of a stable, porous, biocompatible, and bioactive 3D hydrogel, combining the specific advantages of Gellan gum and Konjac glucomannan with proper mechanical properties, which supports the simplification of the implantation process. In addition, the structure have positive effects on endothelial cells’ proliferation and migration that can promote the repair of injured cardiac tissue. The results presented will pave the way for simple, low-cost, and efficient cardiac tissue regeneration using a 3D printed hydrogel cardiac patch with potential for clinical application for myocardial infarction treatment in the near future.

Are seed dispersal and seedling establishment distance- and/or density-dependent in naturally regenerating larch patches? A within-patch scale analysis using an eigenvector spatial filtering approach

The success of natural regeneration in silviculture depends on the complex interactions between interventions of stand structure, the natural seed-dispersal processes, and seedling development. Particularly, the spatial patterns of seed dispersal, seedling establishment and growth, and microenvironmental factors are closely interrelated, controlling the outcomes of natural regeneration practices. wWe performed a within-patch scale spatial analysis and modeling for seed dispersal and seedling development on four different natural regeneration patches (seed tree, grouped seed tree, reserved seed tree, and strip clear-cut methods) of Japanese larch (Larix kaempferi) using an eigenvector spatial filtering (ESF) approach. Our spatial analysis allowed us to determine whether seed fall, seedling establishment, and seedling growth are distance- rather than density-dependent, corresponding to the Janzen–Connell hypothesis. The ESF model revealed that gentle slope, moderate soil moisture, and low crown closure were essential in achieving potential seedling establishment and growth. In addition, the ESF based spatially varying coefficient (ESF-SVC) model provided the difference in impacts of those environmental factors across the regeneration patches. The strategy of planting a large number of evenly distributed remnant seed trees in the regeneration patch of the reserved seed trees was effective in improving seed dispersal, while no remnant seed tree in the regeneration patch of the strip clear-cut method contributed to seedling growth. These findings indicate that ESF-based approaches may represent a feasible way of natural regeneration modeling with more reliable statistical estimations and interpretations by accounting for spatial autocorrelation and heterogeneity.

Fabrication, characterization and in vivo assessment of cardiogel loaded chitosan patch for myocardial regeneration

Cell therapy is one of the promising approaches for cardiac repair, subsequently after infarction or injury. However, contemporary mesenchymal stromal/stem cell (MSCs) delivery strategies result in low retention and poor engraftment of donor cells, thus limiting the therapeutic efficacy. Here, we developed an engineered biomimetic cardiogel patch (EBCP) comprising of the native decellularized cardiac extracellular matrix (ECM) “cardiogel” and chitosan, leading to the efficient regeneration of injured myocardium. We also developed novel bio-adhesive that is capable of suture-free epicardial placement of EBCP to injured myocardium. We have illustrated the potential of the mussels-inspired bioadhesive system, which comprises gelatin catechol and partially oxidized chitosan, which relies on self-crosslinking capability, to promote wet adhesion. In vitro studies with isolated cardiogel promoted cell proliferation, adhesion, and migration while aiding cardiomyogenic differentiation. The EBCP's ability to protect cells from abrasion due to surrounding tissues in the myocardial infarction (MI) rat model makes it more desirable.Furthermore, the epicardial implantation of the EBCP loaded with MSCs improves the initial retention of cells and subsequent functional cardiac recovery with enhanced myocardial tissue restoration. Histological examination showed the presence of EBCP and infiltration of cells to the infarcted heart tissue. The fast and facile synthesis of bioadhesive and major therapeutic benefits of EBCP make it a potential candidate for recuperating the ailing heart.

Chitosan-Heparin Polyelectrolyte Multilayer-Modified Poly(vinyl alcohol) Vascular Patches based on a Decellularized Scaffold for Vascular Regeneration.

Vascular patches play an important role in vascular reparation and cardiovascular diseases therapy. Recently, decellularized scaffold (DCS)-based vascular patches have drawn attention for their good biocompatibility and blood compatibility. In this work, we developed a poly(vinyl alcohol)-coated DCS as a vascular patch for vascular regeneration. Polyelectrolyte multilayers (PEMs) were further decorated on the surface via layer-by-layer (LbL) self-assembly to improve the biocompatibility of the vascular patch. According to the in vitro experiment, the vascular patch exhibited rapid endothelialization and good hemocompatibility. Compared with unmodified poly(vinyl alcohol)/DCS, the PEM-modified vascular patch possesses improved hemocompatibility, for example, enhanced anti-platelet adhesion ability, prolonged in vitro coagulation time, and decreased hemolysis rate. Therefore, this vascular patch is conducive to the proliferation and attachment of endothelial progenitor cells. Meanwhile, the in vivo performance in a porcine model was investigated with the in vivo computed tomography angiography and B ultrasound was used to further confirm the vascular regeneration. Excitedly, the porcine artery could remain unblocked for 5 months after implantation. Our current research provides a potential strategy for treating diseased blood vessels in clinical surgery.

Abundance and Diversity of Woody Undergrowth Reservoir as Indicator of Suitable Vegetation Patch for Natural Regeneration

The diversity, abundance and height structure of naturally regenerated woody species were analyzed and compared for undergrowth reservoir associated with vegetation patches as bowal, shrubland and woodland for understanding the effect of vegetation conditions on spatial distribution of woody plants in Sudanian ecosystem. All undergrowth individuals (height 2) laid out in each vegetation patch during rainy season. In total 52 undergrowth species and 2224 stems arranged in 38 genera and 21 families out of which 25, 36 and 38 species were found in bowal, shrubland and woodland respectively and 15 shared species. Combretaceae, Caesalpiniaceae and Mimosaceae families were the most abundant and species density was significantly higher (P < 0.05) in shrubland and woodland than bowal, and increase diversity in only shrubland (P = 0.002) comparing with bowal. Undergrowth was abundantly concentrated in small height class as canopy benefit and indicate a specific-site distribution. Results also showed that bowal had a particular vegetation which vary in function of tree community characters in place (P < 0.05) while woodland and shrubland are similar vegetation patches. As conclusion, the study vegetation patches form suitable regeneration niches for the undergrowth reservoir of limited number of species which in return can be predictor of species richness and abundance and thus the structure of tree community. Woody undergrowth community could be considered in biodiversity management and degraded land restoration. Supplementary works could be undertaken to understand the characteristics of seed bank for bowal, shrubland and woodland regarding the undergrowth and tree communities.

A Polycaprolactone (PCL)-Supported Electrocompacted Aligned Collagen Type-I Patch for Annulus Fibrosus Repair and Regeneration.

Deformity or fissure within the annulus fibrosus (AF) lamellar structure often results in disc herniation leading to the extrusion of nucleus pulposus (NP), which pushes the adjacent nerve, causing low back pain. Low back pain, frequently associated with the degeneration of the intervertebral disc (IVD), affects around 80% of the population worldwide. The difficulty in mimicking the unique structural characteristics of the native AF tissue presents several challenges to the tissue engineering field for the development of the long-term effective therapeutic strategy for AF tissue regeneration. The AF cell niche possesses less reparative capacity for regeneration and thus compels to develop a strategy to recapitulate damaged AF tissues. We have fabricated a polycaprolactone-supported electrocompacted type-I collagen patch (A-PCL-NH2+Col-I) using surface-modified electrospun-aligned polycaprolactone (A-PCL) nanofibers cross-linked with an electro-compacted type-I collagen patch (Col-I) using EDAC-NHS (1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride and N-hydroxy succinimide). This subtle approach offered a 3D biodegradable scaffold with dense aggregates of anisotropic collagen-I nanofibrils coupled with electrospun-aligned PCL nanofibers, which provide high tensile strength (4.21 ± 1.07 MPa), moduli (24.496 ± 4.85 MPa), low subsidence to failure, and high-water absorption ability. The systemic organization of both the polymers within the scaffold, evident from attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, revealed a uniform degree of fiber alignment assessed by differential interference contrast (DIC) microscopy, field-emission scanning electron microscopy (FE-SEM), and cryo-SEM. The aminolysis of A-PCL nanofibers was established by energy-dispersive X-ray analysis (EDX), while circular dichroic spectra showed that the electro-compacted Col-I patch displayed a triple helical structure, characteristic of collagens. Moreover, the scaffold revealed more hydrophilic, rough nano-features, which provided ample ligands for cell attachment supporting adequate proliferation of primary goat annulus fibrosus (AF) cells, oriented along the fiber direction, and also favored sufficient production of collagen type-I (+32-fold change) and a glycosaminoglycan extracellular matrix (+2.3-fold change) as compared to cell control, respectively. This study thus demonstrates for the first time the practicability of creating an aligned polycaprolactone-supported electrocompacted type-I collagen hydrogel (A-PCL-NH2+Col-I) with significant biomechanical properties, which can be used as an alternative to repair and regenerate AF fissures in degenerated IVD.

Modular Microneedle Patch for Local Immunomodulation and Periodontal Tissue Regeneration

Periodontal diseases affect over 50% of people and are caused by microbial infection and the recruitment of destructive immune cells such as macrophages and T cells. Current therapies for periodontitis mainly deal with bacteria elimination, but immunomodulation and tissue regeneration remains a challenge. Here we developed a modular and multifunctional microneedle (MN) patch that can deliver small molecules and immunomodulatory cytokines into the local gingival tissue. This MN patch included a quickly dissolvable gelatin membrane for a burst release of tetracycline and biodegradable GelMA microneedles that contained poly(lactic-co-glycolic acid) nanoparticles and silica microparticles for a sustained release of tetracycline and cytokines respectively. Antibiotic release completely inhibited bacteria growth, and the sustained release of IL-4 and TGF-β induced the repolarization of anti-inflammatory macrophages and the formation of regulatory T cells in vitro. In vivo placement of MN patch into periodontal tissues not only reduced local inflammatory signals but also modulated local immune cells to promote tissue healing. This work demonstrated a modular MN delivery platform for immunomodulation and tissue regeneration, which will have broad applications in regenerative medicine.

Analyzing Spatial Distribution Patterns of European Beech (Fagus sylvatica L.) Regeneration in Dependence of Canopy Openings

The use of natural regeneration techniques is one of the key elements of modern (close-to-nature) forestry. In natural forests, changes in canopy cover, such as the emergence and successive re-closure of canopy gaps are particularly important, as they influence the light availability on the forest floor. Creating canopy gaps of different size is a promising silvicultural tool allowing the regulation of the light availability in managed forests in order to control regeneration composition and development. In this study, we used terrestrial laser scanning data to investigate the relationship between canopy-gap dimensions and emerging natural regeneration along a gradient of management in forests dominated by European beech (Fagus sylvatica, L.). We analyzed the spatial distribution and height of regeneration patches in dependence of gap characteristics. Mean regeneration height decreases progressively from the gap polygon over a transition zone towards the area under the canopy, while the tallest regeneration plants were placed in positions midway between center and gap edge, and not directly in the gap center as we initially assumed. The centers of regeneration patches were not displaced when compared to the associated canopy gap centers, as has been reported in other studies conducted on the northern hemisphere for various tree species. The observed patterns did not depend on management strategies, indicating that regeneration responded equally to naturally created gaps and gaps that were caused by logging. We conclude that establishment and development of shade-tolerant European beech regeneration in forest stands is driven by gap openings, but not necessarily direct radiation. If at all, pronounced direct radiation mainly occurs at the northern edge of large gaps. Neither regeneration patch center, nor regeneration tree height pointed in that direction. Our study suggests that in the investigated beech-dominated forests the effect of increased light availability at the northern edge of a gap is overruled by other factors increasing towards the gap edge, such as increased belowground competition of the overstory trees.

Patchiness in old-growth oriental beech forests across development stages at multiple neighborhood scales

The patch mosaic–development stage model posits the unity of patches and development stages in primeval temperate forests and links patchiness to the synchronized, coarse-scale canopy senescence, and breakup processes that initiate the demographic transition to new regeneration patches that then asynchronously progress through sequential development stages. Subtle structural differences and inconsistent transitions among development stages observed in primeval forests such as Oriental beech (Fagus orientalis Lipsky) set expected coarse-scale canopy senescence against observed, predominantly fine-scale canopy-gap dynamics. Applying a multi-scale approach to quantify the extent to which stages are characterized by the interspersion of neighborhoods of variously sized trees (i.e., patch types), we investigated patchiness and structural differences in nine Oriental beech stands classified into Initial, Optimum, and Decay stages. Differences among stages in patch type richness and composition occurred primarily at the finest scales and diminished rapidly with increasing scale. Most patch types were ubiquitous and the few patch types unique to a particular stage occurred at very low abundances. Patch types composed of advance regeneration were most prevalent in the Initial stage, but were absorbed into the matrix structure at scales > 500 m2. In all three stages, the most heterogeneous patch type encompassed > 90% of all trees at scales > 100 m2. To portray fine-scale dynamics resulting in similar patch type compositions and structures across development stages, we introduce and discuss the new patch mosaic–gap reabsorption model that avoids the unity of patch and “demographic” stage to focus instead on “structural” stages.

Chemical Engineering of Cell Therapy for Heart Diseases.

Cardiovascular disease (CVD) is a major health problem worldwide. Since adult cardiomyocytes irreversibly withdraw from the cell cycle soon after birth, it is hard for cardiac cells to proliferate and regenerate after myocardial injury, such as that caused myocardial infarction (MI). Live cell-based therapies, which we term as first generation of therapeutic strategies, have been widely used for the treatment of many diseases, including CVD. However, cellular approaches have the problems of poor retention of the transplanted cells and the significant entrapment of the cells in the lungs when delivered intravenously. Another big problem is the low storage/shipping stability of live cells, which limits the manufacturability of living cell products. The field of chemical engineering focuses on designing large-scale processes to convert chemicals, raw materials, living cells, microorganisms, and energy into useful forms and products. By definition, chemical engineers conceive and design processes to produce, transform, and transport materials. This matches the direction that cell therapies are heading toward: "produce", from live cells to synthetic artificial cells; "transform", from bare cells to cell/matrix/factor combinations; and "transport". from simple systemic injections to targeted delivery. Thus, we hereby introduce the "chemical engineering of cell therapies" as a concept. In this Account, we summarize our recent efforts to develop chemical engineering approaches to repair injured hearts. To address the limitations of poor cellular retention and integration, the first step was the artificial manipulation of stem cells before injections (we term this the second generation of therapeutic strategies). For example, we took advantage of the natural infarct-targeting ability of platelet membranes by fusing them onto the surface of cardiac stromal/stem cells (CSCs). By doing so, we improved the rate at which they were delivered through the vasculature to sites of MI. In addition to modifying natural CSCs, we described a bioengineering approach that involved the encapsulation of CSCs in a polymeric microneedle patch for myocardium regeneration. The painless microneedle patches were used as an in situ delivery device, which directly transported the loaded CSCs to the MI heart. In addition to low cell retention, there are some other barriers that need to be addressed before further clinical application is viable, including the storage/shipping stability of and the evident safety concerns about live cells. Therefore, we developed the third generation of therapeutic strategies, which utilize cell-free approaches for cardiac cell therapies. Numerous studies have indicated that paracrine mechanisms reasonably explain stem cell based heart repair. By imitating or adapting natural stem cells, as well as their secretions, and using them in conjunction with biocompatible materials, we can simulate the function of natural stem cells while avoiding the complications association with the first and second generation therapeutic options. Additionally, we can develop approaches to capture endogenous stem cells and directly transport them to the infarct site. Using these third generation therapeutic strategies, we can provide unprecedented opportunities for cardiac cell therapies. We hope that our designs will promote the use of chemical engineering approaches to transform, transport, and fabricate cell-free systems as novel cardiac cell therapeutic agents for clinical applications.

Patchy Fires Promote Regeneration of Longleaf Pine (Pinus palustris Mill.) in Pine Savannas

Research Highlights: Spatial patterns of fire spread and severity influence survival of juvenile pines in longleaf pine savannas. Small areas that do not burn during frequent fires facilitate formation of patches of even-aged longleaf pine juveniles. These regeneration patches are especially associated with inner portions of openings (gaps) and where canopy trees have died in recent decades. Patterns of prescribed fire can thus have an important influence on stand dynamics of the dominant tree in pine savannas. Background and Objectives: Savannas are characterized by bottlenecks to tree regeneration. In pine savannas, longleaf pine is noted for recruitment in discrete clusters located within gaps away from canopy trees. Various mechanisms promoting this pattern have been hypothesized: light limitations, soil moisture, soil nutrients, pine needle mulching, competition with canopy tree roots, and fire severity associated with pine needle litter. We tested the hypothesis that regeneration patches are associated with areas that remain unburned during some prescribed fires, as mediated by gaps in the canopy, especially inner portions of gaps, and areas re-opened by death of canopy trees. Materials and Methods: We mapped areas that were unburned during prescribed fires applied at 1–2 year intervals from 2005–2018 in an old-growth pine savanna in Georgia, USA. We compared the maps to locations of longleaf pine juveniles (&lt;1.5 m height) measured in 2018 and canopy cover and canopy tree deaths using a long-term (40 year) tree census. Results: Logistic regression analysis showed juveniles to be associated with unburned areas, gaps, inner gaps, and areas where canopy trees died. Conclusions: Patterns of fire spread and severity limit survival of longleaf pine juveniles to patches away from canopy trees, especially where canopy trees have died in recent decades. These processes contribute to a buffering mechanism that maintains the savanna structure and prevents transition to closed canopy forest or open grassland communities.

Tree spatial patterns modulate peak snow accumulation and snow disappearance

Forests and snow covered regions frequently co-occur across the northern hemisphere. In these environments, forests are structurally and spatially complex mosaics of tree neighborhoods that are intrinsically linked to ecosystem functions. Tree and canopy structures influence snow accumulation and disappearance processes through interception and radiation attenuation. However, it is unclear if spatial heterogeneity within the forest canopy induces heterogeneity in snow accumulation and persistence. We quantitatively identified different tree neighborhoods and tested the differential effects of these within-stand neighborhoods on snow processes. Neighborhood types included individual ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii) and western larch (Larix occidentalis) trees, dense overstory tree clumps, openings, and regeneration patches. Intensive measurements of snow accumulation (density and depth) and persistence (disappearance date) were made within replicate neighborhoods for three years. Overall, neighborhood type and year had a significant effect on accumulation and snow disappearance. Openings were significantly different from clumps and individuals, always accumulating more snow. Openings retained snow significantly later than clumps but were not significantly different from individuals. Within the individual tree neighborhood type, a nested species effect indicated no differences in accumulation but significant differences in disappearance between deciduous and evergreen conifers, with snow persisting longer beneath deciduous western larch. Our results suggest that canopy interception is the primary mechanism driving the accumulation phase, while snow disappearance patterns are largely a consequence of spatial variation of longwave radiation. Reducing canopy interception and longwave radiation by increasing the abundance of widely spaced single trees and small openings with silvicultural treatments should increase snow depth and duration, and thus snow water storage. Maintaining a heterogeneous canopy structure that includes tree clumps can be used to meet multiple objectives such as provision of ungulate winter range habitat, and heterogenous understory plant phenology.

Composición florística y relaciones ecológicas de las especies de borde, parches y árboles aislados de un bosque seco tropical en Colombia. Implicaciones para su restauración ecológica

El Bosque Seco Tropical (bs-T) es uno de los ecosistemas más amenazados en el mundo, debido a procesos de fragmentación y pérdida de hábitat. La restauración ecológica es necesaria para mantener y recuperar la funcionalidad de los remanentes de bosque y los servicios ecosistémicos que ofrecen. El bs-T actual presenta un paisaje heterogéneo con elementos como bordes, parches y árboles aislados, con especies de gran potencial para ser implementadas en la restauración. Se evaluó la composición florística de un bosque seco, y la estructura de parches y bordes con un análisis de distribución de clases. Los síndromes de dispersión de las especies creciendo en estos elementos fueron comparados y con análisis de correspondencia sin tendencia (DCA por sus siglas en inglés) se obtuvieron grupos de especies para cada elemento del paisaje. El análisis de la estructura y los porcentajes de síndromes de dispersión, permitieron establecer una hipótesis de cómo se forman los parches en regeneración. Con base en esta hipótesis, los grupos de especies otorgados por el DCA, y literatura sobre restauración en bosques tropicales, proponemos tres estrategias de restauración que aumenten la conectividad entre los elementos del paisaje, permitan recuperar la estructura, y a la vez conservar especies claves en la conservación del bosque seco tropical (bs-T).

Photolithographic-stereolithographic-tandem fabrication of 4D smart scaffolds for improved stem cell cardiomyogenic differentiation

4D printing is a highly innovative additive manufacturing process for fabricating smart structures with the ability to transform over time. Significantly different from regular 4D printing techniques, this study focuses on creating novel 4D hierarchical micropatterns using a unique photolithographic-stereolithographic-tandem strategy (PSTS) with smart soybean oil epoxidized acrylate (SOEA) inks for effectively regulating human bone marrow mesenchymal stem cell (hMSC) cardiomyogenic behaviors. The 4D effect refers to autonomous conversion of the surficial-patterned scaffold into a predesigned construct through an external stimulus delivered immediately after printing. Our results show that hMSCs actively grew and were highly aligned along the micropatterns, forming an uninterrupted cellular sheet. The generation of complex patterns was evident by triangular and circular outlines appearing in the scaffolds. This simple, yet efficient, technique was validated by rapid printing of scaffolds with well-defined and consistent micro-surface features. A 4D dynamic shape change transforming a 2-D design into flower-like structures was observed. The printed scaffolds possessed a shape memory effect beyond the 4D features. The advanced 4D dynamic feature may provide seamless integration with damaged tissues or organs, and a proof of concept 4D patch for cardiac regeneration was demonstrated for the first time. The 4D-fabricated cardiac patch showed significant cardiomyogenesis confirmed by immunofluorescence staining and qRT-PCR analysis, indicating its promising potential in future tissue and organ regeneration applications.

Natural regeneration of oriental beech (Fagus orientalis Lipsky) trees in canopy gaps and under closed canopy in a forest in northern Iran

For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies. A systematic 50 × 50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies. Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps. Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy. Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps. Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured. The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration. The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.

Different facets of tree sapling diversity influence browsing intensity by deer dependent on spatial scale.

Browsing of tree saplings by deer hampers forest regeneration in mixed forests across Europe and North America. It is well known that tree species are differentially affected by deer browsing, but little is known about how different facets of diversity, such as species richness, identity, and composition, affect browsing intensity at different spatial scales. Using forest inventory data from the Hainich National Park, a mixed deciduous forest in central Germany, we applied a hierarchical approach to model the browsing probability of patches (regional scale) as well as the species‐specific proportion of saplings browsed within patches (patch scale). We found that, at the regional scale, the probability that a patch was browsed increased with certain species composition, namely with low abundance of European beech (Fagus sylvatica L.) and high abundance of European ash (Fraxinus excelsior L.), whereas at the patch scale, the proportion of saplings browsed per species was mainly determined by the species’ identity, providing a “preference ranking” of the 11 tree species under study. Interestingly, at the regional scale, species‐rich patches were more likely to be browsed; however, at the patch scale, species‐rich patches showed a lower proportion of saplings per species browsed. Presumably, diverse patches attract deer, but satisfy nutritional needs faster, such that fewer saplings need to be browsed. Some forest stand parameters, such as more open canopies, increased the browsing intensity at either scale. By showing the effects that various facets of diversity, as well as environmental parameters, exerted on browsing intensity at the regional as well as patch scale, our study advances the understanding of mammalian herbivore–plant interactions across scales. Our results also indicate which regeneration patches and species are (least) prone to browsing and show the importance of different facets of diversity for the prediction and management of browsing intensity and regeneration dynamics.

Local neighborhood communities in the understory play a critical role by affecting regeneration niches and subsequent community assembly in a montane cloud forest

AbstractRegeneration niches for tree seedlings are defined as possessing the biotic and abiotic requirements to successfully replace adults. However, two critical discrepancies obscure our understanding of the role of regeneration niches in forest community assembly: a weak association between seedling assemblages and environmental factors, and an uncoupling between seedling and adult‐tree assemblages. However, understory plants, which may interact with microenvironments and seedlings, may be a better spatial descriptor of regeneration habitats. To test this, the spatial variations of seedling assemblages in a montane cloud forest of Taiwan were analyzed in terms of their association with neighborhood assemblages of understory plants, the shrub layer, and overstory trees, as well as environmental variables. We found that the understory plant spatial structure contributed most in explaining spatial variations of the seedling assemblages (especially for widespread Lauraceae and patchy Fagaceae) and facilitated the identification of patches of different regeneration habitats for specific seedling assemblages. Moreover, among these regeneration patches, tall herbs affected seedling density and diversity differently. We found segregation between tall herbs and Lauraceae seedlings, indicating that tall herbs shape seedling assemblages and uncouple the association between seedling and adult stages. However, positive covariations between seedlings/tall herbs and between seedlings/adults were found for Fagaceae and Pentaphylacaceae in different regeneration patches, suggesting that positive, neighboring effects and dispersal limitation may cause the patchy distribution of seedling assemblages and affect their coupling with adults. Thus, the understory plant spatial structure shapes seedling assemblages and provides a better link to spatial associations with regeneration habitats.

Assessment Capability Forest Regeneration in Different Geographical Aspects Approach Landscape Ecology

In order to determine the relationship between physiographical factors and regeneration changes in forests, and to improve and model natural regeneration status, Gorazbon district in Kheyrod Forest was selected for the study. All available regeneration patches in the area were selected. To achieve spatial structure and quantify metrics related to regeneration patches, the analysis of landscape metrics was used. The results show that 692 regeneration patches were identified at the level of different directions. LAND Metric show the most regeneration percent is related to the western (9%), southern (8.66%), flat areas (8.33%), northern (5.68%) and eastern (4.73%), respectively. In total, the patch coverage level percentage was calculated in the landscape (8.31%). The results related to patch shape metric show that most shapes of patches follow polygon structures and do not have fixed shapes. Results related to the average area of the patch metric show that the average level of patches is between 4 and 5 R. The maximum and minimum distance between patches was observed in the survey between 39 and 520 m respectively. According to the results of the distance average between patch metric, the distribution of patches is random in the southern and western directions, flat areas and pile, but it is uniform in northern directions. It should be noted that the distribution and structure of patches in the northern directions has a better distribution and homogeneity than the other directions. Its canals are used as a natural regeneration model to follow the natural phenomena in forest sustainable management.