Tissue Micro-channels Formed by Collagen Fibers and their Internal Components: Cellular Evidence of Proposed Meridian Conduits in Vertebrate Skin.

In order to clarify fine structures of the hypothetical meridian conduits of Chinese traditional medicine (CTM) in the skin, the present study used light and transmission electron microscopy to examine fasciae in different vertebrate species. Collagen fiber bundles and layers were arranged in a crisscross pattern, which developed into a special tissue micro-channel (TMC) network, in a manner that was analogs to the proposed skin meridian conduits. It was further revealed that tissue fluid in lateral TMC branches drained into wide longitudinal channels, which were distinctly different from lymphatic capillary. Mast cells, macrophages, and extracellular vesicles such as ectosomes and exosomes were distributed around telocytes (TCs) and their long processes (Telopodes, Tps) within the TMC. Cell junctions between TCs developed, which could enable the communication between contiguous but distant Tps. On the other hand, winding free Tps without cell junctions were also uncovered inside the TMC. Tissue fluid, cell junctions of TCs, mast cells, macrophages, and extracellular vesicles within the TMC corresponded to the circulating "" ("Qi-Xue", i.e., information, message, and energy) of meridian conduits at the cytological level. These results could provide morphological evidence for the hypothesis that "meridians are the conduit for Qi-Xue circulation" in CTM.

Dynamics of actinotrichia regeneration in the adult zebrafish fin.

The skeleton of adult zebrafish fins comprises lepidotrichia, which are dermal bones of the rays, and actinotrichia, which are non-mineralized spicules at the distal margin of the appendage. Little is known about the regenerative dynamics of the actinotrichia-specific structural proteins called Actinodins. Here, we used immunofluorescence analysis to determine the contribution of two paralogous Actinodin proteins, And1/2, in regenerating fins. Both proteins were detected in the secretory organelles in the mesenchymal cells of the blastema, but only And1 was detected in the epithelial cells of the wound epithelium. The analysis of whole mount fins throughout the entire regenerative process and longitudinal sections revealed that And1-positive fibers are complementary to the lepidotrichia. The analysis of another longfin fish, a gain-of-function mutation in the potassium channel kcnk5b, revealed that the long-fin phenotype is associated with an extended size of actinotrichia during homeostasis and regeneration. Finally, we investigated the role of several signaling pathways in actinotrichia formation and maintenance. This revealed that the pulse-inhibition of either TGFß/Activin-ßA or FGF are sufficient to impair deposition of Actinodin during regeneration. Thus, the dynamic turnover of Actinodin during fin regeneration is regulated by multiple factors, including the osteoblasts, growth rate in a potassium channel mutant, and instructive signaling networks between the epithelium and the blastema of the regenerating fin.

Non-Fourier thermal transport induced structural hierarchy and damage to collagen ultrastructure subjected to laser irradiation.

Comprehending the mechanism of thermal transport through biological tissues is an important factor for optimal ablation of cancerous tissues and minimising collateral tissue damage. The present study reports detailed mapping of the rise in internal temperature within the tissue mimics due to NIR (1064 nm) laser irradiation, both for bare mimics and with gold nanostructures infused. Gold nanostructures such as mesoflowers and nanospheres have been synthesised and used as photothermal converters to enhance the temperature rise, resulting in achieving the desired degradation of malignant tissue in targeted region. Thermal history was observed experimentally and simulated considering non-Fourier dual phase lag (DPL) model incorporated Pennes bio-heat transfer equation using COMSOL Multiphysics software. The gross deviation in temperature i.e. rise from the classical Fourier model for bio-heat conduction suggests additional effects of temperature rise on the secondary structures and morphological and physico-chemical changes to the collagen ultrastructures building the tissue mass. The observed thermal denaturation in the collagen fibril morphologies have been explained based on the physico-chemical structure of collagen and its response to thermal radiation. The large shift in frequency of amides A and B is pronounced at a depth of maximum temperature rise compared with other positions in tissue phantom. Observations for change in band of amide I, amide II, and amide III are found to be responsible for damage to collagen ultra-structure. Variation in the concentration of gold nanostructures shows the potentiality of localised hyperthermia treatment subjected to NIR radiation through a proposed free radical mechanism.

Dentin Topographic Features following Chemomechanical Caries Removal in Primary Teeth.

AIM: Study the topographic features of dentin after caries removal with a chemomechanical agent (Papacarie) compared with the conventional drilling method. STUDY DESIGN: The sample included 7 exfoliated and extracted primary teeth with carious dentin lesions, not reaching the pulp. Each tooth was sectioned longitudinally through the center of the carious lesions into two halves. The teeth were then divided into two groups according to the method of caries removal. Following caries removal, dentin topography and the cut section were examined using the scanning electron microscope. RESULTS: Papacarie produced an irregular, porous, rough and globular dentin appearance. The dentin surfaces were generally free of smear layer, visible bacteria and the dentinal tubules were opened. The dentin cut surfaces showed patent dentinal tubules with open orifices. The drilling method created a smooth and amorphous surface with a continuous smear layer occluding the dentinal tubules. Numerous bacteria were also observed. The cut dentin surfaces showed patent dentinal tubules with their orifices plugged with smear layer. CONCLUSIONS: Papacarie produced a rough and porous surface with partial or complete removal of the smear layer and opened dentinal tubules, while the drill produced a smooth surface with uniform smear layer occluding the dentinal tubules.

Development and characterization of a rapid polymerizing collagen for soft tissue augmentation.

A liquid collagen has been developed that fibrilizes upon injection. Rapid polymerizing collagen (RPC) is a type I porcine collagen that undergoes fibrillization upon interaction with ionic solutions, such as physiological solutions. The ability to inject liquid collagen would be beneficial for many soft tissue augmentation applications. In this study, RPC was synthesized and characterized as a possible dermal filler. Transmission electron microscopy, ion induced RPC fibrillogenesis tests, collagenase resistance assay, and injection force studies were performed to assess RPC's physicochemical properties. An in vivo study was performed which consisted of a 1-, 3-, and 6-month study where RPC was injected into the ears of miniature swine. The results demonstrated that the liquid RPC requires low injection force (<7 N); fibrillogenesis and banding of collagen occurs when RPC is injected into ionic solutions, and RPC has enhanced resistance to collagenase breakdown. The in vivo study demonstrated long-term biocompatibility with low irritation scores. In conclusion RPC possesses many of the desirable properties of a soft tissue augmentation material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 758-767, 2016.

Massage may initiate tendon structural changes--a preliminary study.

BACKGROUND: Physical exercise is now a widely known and studied factor of the proper functioning of living organisms. Many questions remain unanswered concerning various aspects of the changes in the morphology of structures subjected to chronic physical exercise. MATERIALS AND METHODS: This study was conducted on fifty Buffalo strain rats, randomly divided into two equal (experimental and control) groups. All animals were subjected to physical training on a running track for 10 weeks, whereas only in the experimental group, massage was additionally applied five-times per week. RESULTS: An increase in the percentage of collagen fibers in tendons with the smallest diameter (≤100 nm) was observed only in the experimental group in week 3, followed by a decrease in weeks 5 and 7. A subsequent repeated increase was observed in week 10 of the study. No significant differences were observed for either study group in the number of collagen fibers based on fiber diameter (101-200 nm, 201-300 nm and 301-400 nm). CONCLUSION: The results of this preliminary study showed that long-term massage performed during running training may initiate for small structural changes in the rat tendon. Further morphological studies with prolonged observation periods are recommended.

Meniscal biomechanical alterations in an ACLT rabbit model of early osteoarthritis.

OBJECTIVE: The purpose of this study was to analyze the early biomechanical alterations of menisci during the early stage of osteoarthritis (OA) development and to correlate them with the chemical composition and matrix alteration. A particular focus was paid to pathological changes in glycosaminoglycan (GAG) content and collagen fiber architecture. DESIGN: Menisci (n = 24) were removed from rabbits' knee joints 6 weeks following surgical anterior cruciate ligament transection (ACLT). Both the anterior and posterior regions of medial and lateral menisci were characterized using indentation tests, Raman microspectroscopy (RM), biphotonic confocal microscopy (BCM) and histology. RESULTS: Mechanical and matrix alterations occurred in both regions of medial and lateral menisci. A significant decrease in the mechanical properties was observed in OA menisci, with a mean reduced modulus from 2.3 to 1.1 MPa. Microstructural observations revealed less organized and less compact collagen bundles in operated menisci than in contralateral menisci, as well as a loss of fiber tension. GAG content was increased in OA menisci, especially in the damaged areas. Neither changes in the secondary structure of collagen nor mineralization were detected through RM at this stage of OA. CONCLUSION: ACLT led to a disorganization of the collagen framework at the early stage of OA development, which decreases the mechanical resistance of the menisci. GAG content increases in response to this degradation. All of these results demonstrate the strong correlation between matrix and mechanical alterations.

Acupuncture increases the diameter and reorganisation of collagen fibrils during rat tendon healing.

BACKGROUND: Our previous study showed that electroacupuncture (EA) increases the concentration and reorganisation of collagen in a rat model of tendon healing. However, the ultrastructure of collagen fibrils after acupuncture is unknown. OBJECTIVES: To assess the effect of acupuncture protocols on the ultrastructure of collagen fibrils during tendon healing. METHODS: Sixty-four rats were divided into the following groups: non-tenotomised (normal group), tenotomised (teno group), tenotomised and subjected to manual acupuncture at ST36 (ST36 group), BL57 (BL57 group) and ST36+BL57 (SB group) and EA at ST36+BL57 (EA group). The mass-average diameter (MAD) and the reorganisation of collagen fibril diameters were determined during the three phases of tendon healing (at 7, 14 and 21 days). RESULTS: The MAD increased during the three phases of healing in the SB group. In the EA group, MAD increased initially but was reduced at day 21. The reorganisation of collagen fibrils was improved in the EA and SB groups at days 14 and 21, respectively. EA at day 21 appeared to reduce the reorganisation. CONCLUSIONS: These results indicate that the use of EA up to day 14 and manual acupuncture at ST36+BL57 up to day 21 improve the ultrastructure of collagen fibrils, indicating strengthening of the tendon structure. These data suggest a potential role for acupuncture in rehabilitation protocols.

The effect of calcium phosphate composite scaffolds on the osteogenic differentiation of rabbit dental pulp stem cells.

The objective of this study is to compare the effects of the two calcium phosphate composite scaffolds on the attachment, proliferation, and osteogenic differentiation of rabbit dental pulp stem cells (DPSCs). One nano-hydroxyapatite/collagen/poly (l-lactide) (nHAC/PLA), imitating the composition and the micro-structure characteristics of the natural bone, was made by Beijing Allgens Medical Science & Technology Co., Ltd. (China). The other beta-tricalcium phosphate (ß-TCP), being fully interoperability globular pore structure, was provided by Shanghai Bio-lu Biomaterials Co, Ltd. (China). We compared the absorption water rate and the protein adsorption rate of two scaffolds and the characterization of DPSCs cultured on the culture plate and both scaffolds under osteogenic differentiation media (ODM) treatment. The constructs were then implanted subcutaneously into the back of severely combined immunodeficient (SCID) mice for 8 and 12 weeks to compare their bone formation capacity. The results showed that the ODM-treated DPSCs expressed osteocalcin (OCN), bone sialoprotein (BSP), type I collagen (COLI) and osteopontin (OPN) by immunofluorescence staining. Positive alkaline phosphatase (ALP) staining, calcium deposition and calcium nodules were also observed on the ODM-treated DPSCs. The absorption water rate and protein adsorption rate of nHAC/PLA was significantly higher than ß-TCP. The initial attachment of DPSCs seeded onto nHAC/PLA was significantly higher than that onto ß-TCP; and the proliferation rate of the cells was also significantly higher than that of ß-TCP on 1, 3, and 7 days of cell culture. The ALP activity, calcium/phosphorus content and mineral formation of DPSCs + ß-TCP were significantly higher than DPSCs + nHAC/LA. When implanted into the back of SCID mice, nHAC/PLA alone had no new bone formation, newly formed mature bone and osteoid were only observed in ß-TCP alone, DPSCs + nHAC/PLA and DPSCs + ß-TCP, and this three groups displayed increased bone formation over the 12-week period. The percentage of total bone formation area had no difference between DPSCs + ß-TCP and DPSCs + nHAC/PLA at each time point, but the percentage of mature bone formation area of DPSCs + ß-TCP was significantly higher than that of DPSCs + nHAC/PLA. Our results demonstrated that the DPSCs on nHAC/PLA had a better proliferation, and that the DPSCs on ß-TCP had a more mineralization in vitro, much more newly formed mature bones in vivo were presented in DPSCs + ß-TCP group. These findings have provided a further knowledge that scaffold architecture has different influence on the attachment, proliferation and differentiation of cells. This study may provide insight into the clinical periodontal bone tissue repair with DPSCs + ß-TCP construct.

Anomalous subsurface thermal behavior in tissue mimics upon near infrared irradiation mediated photothermal therapy.

Photothermal therapy using (Near Infrared) NIR region of EM spectrum is a fast emerging technology for cancer therapy. Different types of nanoparticles may be used for enhancing the treatment. Though the treatment protocols are developed based on experience driven estimated temperature increase in the tissue, it is not really known what spatiotemporal thermal behavior in the tissue is. In this work, this thermal behavior of tissue models is investigated with and without using nanoparticles. An increased temperature inside tissue compared to surface is observed which is counter intuitive from the present state of knowledge. It is shown from fiber level microstructure that this increased temperature leads to enhanced damage at the deeper parts of biomaterials. Nanoparticles can be utilized to control this temperature increase spatially. A multiple scattering based physical model is proposed to explain this counterintuitive temperature rise inside tissue. The results show promising future for better understanding and standardizing the protocols for photothermal therapy.

Character of skin on photo-thermal response and its regeneration process using second-harmonic generation microscopy.

Quantitative characterization of skin collagen on photo-thermal response and its regeneration process is an important but difficult task. In this study, morphology and spectrum characteristics of collagen during photo-thermal response and its light-induced remodeling process were obtained by second-harmonic generation microscope in vivo. The texture feature of collagen orientation index and fractal dimension was extracted by image processing. The aim of this study is to detect the information hidden in skin texture during the process of photo-thermal response and its regeneration. The quantitative relations between injured collagen and texture feature were established for further analysis of the injured characteristics. Our results show that it is feasible to determine the main impacts of phototherapy on the skin. It is important to understand the process of collagen remodeling after photo-thermal injuries from texture feature.

Critical appraisal: Cross-linkers and the dentin matrix.

The formation of a hybrid layer is essential for successful dentin bonding and is achieved by adhesive penetration between exposed collagen fibrils in the demineralized dentin. Incomplete infiltration of the adhesive within the collagen network results in exposed fibrils, which may suffer enzymatic degradation over time. Methods to increase collagen resistance to proteinases (enzymes that degrade proteins) have been studied. One particular approach is to use collagen cross-linking agents that modify collagen through addition of specific or random amino acid linkage between and within its molecules. This Critical Appraisal provides information on the effects of various cross-linkers on dentin collagen stability, dentin properties, and resin-dentin bond strengths, and calls for critical thinking on the potential effects of this therapeutic approach.

An ex vivo study of arrested primary teeth caries with silver diamine fluoride therapy.

OBJECTIVES: This ex vivo study compared the physico-chemical structural differences between primary carious teeth biannually treated with silver diamine fluoride (SDF) and carious teeth without such treatment. METHOD: Twelve carious primary upper-central incisors were collected from 6-year-old children. Six teeth had arrested caries after 24-month biannual SDF applications and 6 had active caries when there was no topical fluoride treatment. The mineral density, elemental contents, surface morphology, and crystal characteristics were assessed by micro-computed tomography (micro-CT), energy-dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). RESULTS: Micro-CT examination revealed a superficial opaque band approximately 150µm on the arrested cavitated dentinal lesion. This band was limited in the active carious lesion. EDX examination detected a higher intensity of calcium and phosphate of 150µm in the surface zone than in the inner zone, but this zone was restricted in the active cavitated dentinal lesion. SEM examination indicated that the collagens were protected from being exposed in the arrested cavitated dentinal lesion, but were exposed in the active cavitated dentinal lesion. TEM examination suggested that remineralised hydroxyapatites were well aligned in the arrested cavitated dentinal lesion, while those in the active cavitated dentinal lesion indicated a random apatite arrangement. CONCLUSIONS: A highly remineralised zone rich in calcium and phosphate was found on the arrested cavitated dentinal lesion of primary teeth with an SDF application. The collagens were protected from being exposed in the arrested cavitated dentinal lesion. CLINICAL SIGNIFICANCE: Clinical SDF application positively influences dentine remineralisation.

Exposed collagen in resin bonds to caries-affected dentin after dentin treatment with aqueous and alcoholic chlorhexidine solutions.

PURPOSE: To evaluate the effect of saturation of demineralized dentin with aqueous and alcoholic excipients of chlorhexidine (CHX) on the exposure of collagen fibrils in resin-dentin bonds in sound and caries-affected dentin. MATERIALS AND METHODS: Flat midcoronal dentin surfaces were prepared from 24 noncarious molars, and artificial caries was induced in half of the sample. For each substrate, the surfaces were assigned to 4 groups (n = 3) according to the saturation solution of the dentin: water, ethanol, 1% CHX aqueous or alcoholic solution. Infected dentin was removed by abrasive papers. After acid etching, the dentin surface was saturated with each solution for 60 s followed by application of Single Bond. The specimens were processed for Goldner's trichrome staining and the thickness of the exposed collagen zone (ECZ) at the resin/dentin interfaces was measured under optical microscopy. Data were analyzed statistically by Kruskal-Wallis and Mann-Whitney tests (α = 0.05). RESULTS: Regardless of the saturation solution, caries-affected dentin presented a thicker ECZ at the bottom of the hybrid layer than did sound dentin. For both substrates, 100% ethanol had a negative influence on collagen exposure in comparison with water, but the same was not observed for the CHX alcoholic solution. CHX solutions did not differ significantly from each other or from their respective solvents. CONCLUSION: The saturation of phosphoric acid-demineralized dentin with either CHX aqueous or alcoholic solutions did not affect the exposure of collagen fibrils in the resin-dentin bonds produced in sound and caries-affected dentin. A thicker zone of exposed collagen was found in hybridized caries-affected dentin compared to noncarious dentin.

Exogenous bFGF promotes articular cartilage repair via up-regulation of multiple growth factors.

OBJECTIVE: To investigate the roles of exogenous basic fibroblast growth factor (bFGF) on the repair of full-thickness articular cartilage defects in rabbits. DESIGN: In the present study, a double-layered collagen membrane sandwiched with bFGF-loaded-nanoparticles between a dense layer and a loose layer was implanted into full-thickness articular cartilage defects in rabbits. By grafting the membrane in a different direction, the dense layer or the loose layer facing the surface of the subchondral bone, the effects of the released bFGF on the defects and the profiles of nine growth factors (GFs) in synovial fluid (SF) were investigated using histological methods and antibody arrays, respectively. RESULTS: In the group with the loose layer facing the surface of the subchondral bone, fast release of bFGF was observed, and early high levels of endogenous transforming growth factor-ß2 (TGF-ß2), vascular endothelial growth factor (VEGF), bFGF, bone morphogenetic protein 2 (BMP-2), BMP-3, and BMP-4 in SF were detected by antibody arrays, especially on day 3. Chondrocyte-like cells were also observed in this group at an early stage. As a result, this group showed better levels of repair, as compared to the other groups in which low GF levels were detected at an early stage, and chondrocyte-like cells appeared much later. CONCLUSIONS: Our study suggests that exogenous bFGF promotes articular cartilage repair by up-regulating the levels of multiple GFs, but administration at an early stage is required.

Direct AFM force mapping of surface nanoscale organization and protein adsorption on an aluminum substrate.

We investigate the nanoscale organization of a superficially hydroxylated Al substrate and its effect on subsequent protein adsorption using atomic force microscopy (AFM). For this purpose we used a mode which allows a direct mapping of a variety of surface properties (adhesion, elasticity, dissipation, etc.) to be probed simultaneously with topographical images. The hydroxylation treatment leads to a drastic modification of the surface morphology, owing to the formation of AlOOH compounds. In air, AFM images revealed the formation of regular nanorod-like structures randomly distributed, inducing the appearance of nanoporous domains on the surface. In buffer solution, prior to the adsorption of proteins, the surface nanoscale organization is preserved, mainly due to the chemical stability of AlOOH compounds under these conditions. The adsorption of proteins on the obtained nanostructured surface was performed using either a globular (ß-lactoglobulin) or a fibrillar (collagen) protein and by modulating the adsorbed amount through the incubation time or the concentration of proteins in solution. At low amounts, collagen adsorbs on the whole surface without preferential localization. The surface topography remains similar to the bare surface, while significant changes were evidenced on adhesion and elasticity maps. This is due to the fact that the surface became adhesive and less stiff, owing to the presence of a soft and hydrated protein layer. By contrast, ß-lactoglobulin tends to diffuse into the nanoporous domains, leading to their filling up, and the surface is blurred with a thick and dense protein layer upon increasing the amount of adsorbed molecules. Our findings demonstrate the interest in using AFM for surface mapping to investigate the mechanism of protein adsorption at the nanoscale on materials with high surface roughness.

Percentage exposure of root dentin collagen after application of two irrigation protocols with manual or rotary instrumentation and two methacrylate resin-based sealers.

PURPOSE: To compare the percentage of collagen exposed in dentin root thirds after two irrigation protocols with manual or rotary instrumentation using two methacrylate resin-based sealers. MATERIALS AND METHODS: Forty-eight single-root human teeth were prepared with manual (n = 24) or nickeltitanium ProFile rotary (n = 24) instrumentation, using 5% NaOCl between instruments and 5 ml 17% EDTA as final irrigant or 20% citric acid + 2% chlorhexidine (CHX) between instruments and as the final irrigant. RealSeal or EndoREZ were used as filling materials. One 1-mm slice per third was abraded and stained with Masson's trichrome method. Mean exposed collagen values were obtained in four areas from each section (at 60X magnification) and a complete factorial ANOVA was used to analyze the influence of the study variables. Non-parametric Mann-Whitney's test was used to compare groups. Differences with p < 0.05 were considered significant. RESULTS: A significantly higher percentage of collagen was exposed in all thirds with the use of the 20% citric acid + 2% CHX protocol with rotary vs manual instrumentation, but percent collagen exposed did not differ as a function of the filling material. After the 5% NaOCl + 17% EDTA protocol, the percentage of collagen exposed did not differ between rotary and manual instrumentation but was higher with the use of RealSeal. CONCLUSION: The highest percentage exposure of collagen was with 20% citric acid + 2% CHX using rotary instrumentation, regardless of the filling material.

Effect of androgenic-anabolic steroids and heavy strength training on patellar tendon morphological and mechanical properties.

Combined androgenic-anabolic steroids (AAS) and overloading affects tendon collagen metabolism and ultrastructure and is often associated with a higher risk of injury. The aim of this prospective study was to investigate whether such effects would be reflected in the patellar tendon properties of individuals with a history of long-term resistance training and AAS abuse (RTS group), compared with trained (RT) and untrained (CTRL) nonsteroids users. Tendon cross-sectional area (CSA), stiffness, Young's modulus, and toe limit strain were measured in vivo, from synchronized ultrasonography and dynamometry data. The patellar tendon of RT and RTS subjects was much stiffer and larger than in the CTRL group. However, stiffness and modulus were higher in the RTS group (26%, P < 0.05 and 30%, P < 0.01, respectively) than in the RT group. Conversely, tendon CSA was 15% (P < 0.05) larger in the RT group than in RTS, although differences disappeared when this variable was normalized to quadriceps maximal isometric torque. Yet maximal tendon stress was higher in RTS than in RT (15%, P < 0.05), without any statistical difference in maximal strain and toe limit strain between groups. The present lack of difference in toe limit strain does not substantiate the hypothesis of changes in collagen crimp pattern associated with AAS abuse. However, these findings indicate that tendon adaptations from years of heavy resistance training are different in AAS users, suggesting differences in collagen remodeling. Some of these adaptations (e.g., higher stress) could be linked to a higher risk of tendon injury.

Effect of the Arrabidaea chica extract on collagen fiber organization during healing of partially transected tendon.

AIMS: After undergoing lesions, tendons have disorganized collagen fibers compared to undamaged tendons. Arrabidaea chica leaves have the aglycones carajurin and carajurone, components of the antocyanins, with a strong pharmacological potential due to their healing properties. Thus, the aim of this study was to investigate the effect of topical application of A. chica extract during tendon healing. MAIN METHODS: The calcaneal tendon of Wistar rats was partially transected with subsequent treatment with A. chica extract (2.13 g/mL) followed by excision on the 7th, 14th and 21st days. Control rats received only saline treatment. KEY FINDINGS: Transmission electron microscopy analysis showed the presence of a large amount of small segments of collagen fibrils in the transected region of the tendons on the 7th day in both the control and plant-treated groups. Considering the organization of the collagen fibers, higher values of birefringence were observed under polarization microscopy in the tendons of the plant-treated group on the 14th day compared to the control group. A larger quantity of dermatan sulfate was also detected after plant treatment in the same period. However, lesser dermatan and chondroitin sulfate were detected in the plant-treated group than in the control group on the 21st day. No differences were found in the values of birefringence between these groups. Intense metachromasy was observed in both transected groups on the 21st day. SIGNIFICANCE: In conclusion, the use of A. chica extract improves collagen organization and increases the quantity of dermatan sulfate on the 14th day of the tendon healing.