Adult stem cells in small animal wound healing models

Wound Healing Potential of Couroupita guianensis Aubl. Fruit Pulp Investigated on Excision Wound Model

Wound care management aims at stimulating and improving healing process without scar formation. Although various plants have been reported to possess wound healing properties in tribal and folklore medicines, there is a lack of scientific data to validate the claim. In this aspect, it becomes inevitable to prove the efficacy of naturally derived products at pharmacological levels. Couroupita guianensis as a whole plant has been reported to exhibit wound healing activity. The leaves and fruit of this plant have been utilized in folkloric medicine to cure skin diseases and infections for many years. However, to the best of our knowledge, no scientific studies have been conducted to verify the wound healing properties of C. guianensis fruit pulp. Therefore, the present study seeks to investigate the wound healing potential of C. guianensis fruit pulp using an excision wound model in Wistar albino male rats. This study indicated that the ointment prepared from crude ethanolic extract of C. guianensis fruit pulp facilitated wound contraction that were evidenced by a greater reduction in the wound area and epithelialization period and increased hydroxyproline content. The experimental groups treated with low and mid dose of C. guianensis ethanol extract (CGEE) ointments had shown a wound closure of 80.27% and 89.11% respectively within 15 days, which is comparable to the standard betadine ointment which showed 91.44% healing in the treated groups. Further, the extract influenced the expression of genes VEGF and TGF-β on post wounding days that clearly explained the strong correlation between these genes and wound healing in the experimental rats. The animals treated with 10% CGEE ointment showed a significant upregulation of both VEGF and TGF-β as compared with other test and standard groups. These findings provide credence to the conventional application of this plant in the healing of wounds and other dermatological conditions, and may represent a therapeutic strategy for the treatment of wounds.

Wound Healing Modulation through the Local Application of Powder Collagen-Derived Treatments in an Excisional Cutaneous Murine Model

Wound healing includes dynamic processes grouped into three overlapping phases: inflammatory, proliferative, and maturation/remodeling. Collagen is a critical component of a healing wound and, due to its properties, is of great interest in regenerative medicine. This preclinical study was designed to compare the effects of a new collagen-based hydrolysate powder on wound repair to a commercial non-hydrolysate product, in a murine model of cutaneous healing. Circular excisional defects were created on the dorsal skin of Wistar rats (n = 36). Three study groups were established according to the treatment administered. Animals were euthanized after 7 and 18 days. Morphometric and morphological studies were performed to evaluate the healing process. The new collagen treatment led to the smallest open wound area throughout most of the study. After seven days, wound morphometry, contraction, and epithelialization were similar in all groups. Treated animals showed reduced granulation tissue formation and fewer inflammatory cells, and induction of vasculature with respect to untreated animals. After 18 days, animals treated with the new collagen treatment showed accelerated wound closure, significantly increased epithelialization, and more organized repair tissue. Our findings suggest that the new collagen treatment, compared to the untreated control group, produces significantly faster wound closure and, at the same time, promotes a slight progression of the reparative process compared with the rest of the groups.

Melatonin pre-treated bone marrow derived-mesenchymal stem cells prompt wound healing in rat models

Bone marrow derived-mesenchymal stem cells (BMSCs)-based therapy is an outstanding candidate for cutaneous wound healing. Melatonin (MEL) has been reported for its anti-inflammatory as well as tissue regenerative properties. Existing work aimed to explore the potential healing power of BMSCs pre-treated with MEL in a skin wound model. Adult rats were allocated into control, PIO, BMSCs (1 × 10⁵ cells), and MEL/BMSCs groups. On the 21 days post-wounding, tissues were sampled for analysis. The results demonstrated that compared to the control group, MEL/BMSCs therapy induced noticeable decline in wound area and elevated rate of wound retraction. Furthermore, marked increases in tissue hydroxyproline, as well as tissue content and gene expression level of vascular endothelial growth factor in MEL/BMSCs treated-wounded animals. Compared to the untreated control group, marked increases were found in antioxidant enzymatic activities together with elevated GSH levels in wounded tissues after MEL/BMSCs treatment. Moreover, therapeutically handled wounds with MEL/BMSCs revealed low levels of MDA, NO and protein carbonyls. Combined therapy with MEL/BMSCs relieved the inflammation witnessed by decreasing IL-1β, TNF-α and NF-κB levels in wounded tissues. Furthermore, noteworthy rises in levels of TGF-β and gene expression of α-SMA were noticed after MEL/BMSCs application that reveals their anti-scarring properties. Histologically, noticeable improvement in histopathological skin lesions in wound area and elevated the collagen synthesis and deposition. Collectively, the obtained data depict that the pre-treatment of BMSCs with MEL could potentially be a successful strategy for scaling-up the wound healing outcomes more than using BMSCs monotherapy in rat models.

Blended Natural Support Materials-Collagen Based Hydrogels Used in Biomedicine

Due to their unique properties-the are biocompatible, easily accessible, and inexpensive with programmable properties-biopolymers are used in pharmaceutical and biomedical research, as well as in cosmetics and food. Collagen is one of the most-used biomaterials in biomedicine, being the most abundant protein in animals with a triple helices structure, biocompatible, biomimetic, biodegradable, and hemostatic. Its disadvantages are its poor mechanical and thermal properties and enzymatic degradation. In order to solve this problem and to use its benefits, collagen can be used blended with other biomaterials such as alginate, chitosan, and cellulose. The purpose of this review article is to offer a brief paper with updated information on blended collagen-based formulations and their potential application in biomedicine.

Experimental models and methods for cutaneous wound healing assessment

Wound healing studies are intricate, mainly because of the multifaceted nature of the wound environment and the complexity of the healing process, which integrates a variety of cells and repair phases, including inflammation, proliferation, reepithelialization and remodelling. There are a variety of possible preclinical models, such as in mice, rabbits and pigs, which can be used to mimic acute or impaired for example, diabetic and nutrition-related wounds. These can be induced by many different techniques, with excision or incision being the most common. After determining a suitable model for a study, investigators need to select appropriate and reproducible methods that will allow the monitoring of the wound progression over time. The assessment can be performed by non-invasive protocols such as wound tracing, photographic documentation (including image analysis), biophysical techniques and/or by invasive protocols that will require wound biopsies. In this article, we provide an overview of some of the most often needed and used: (a) preclinical/animal models including incisional, excisional, burn and impaired wounds; (b) methods to evaluate the healing progression such as wound healing rate, wound analysis by image, biophysical assessment, histopathological, immunological and biochemical assays. The aim is to help researchers during the design and execution of their wound healing studies.

Effects of Human Adipose-Derived Stem Cells on the Survival of Rabbit Ear Composite Grafts

Background

Composite grafts are frequently used for facial reconstruction. However, the unpredictability of the results and difficulties with large defects are disadvantages. Adipose-derived stem cells (ADSCs) express several cytokines, and increase the survival of random flaps and fat grafts owing to their angiogenic potential.

Methods

This study investigated composite graft survival after ADSC injection. Circular chondrocutaneous composite tissues, 2 cm in diameter, from 15 New Zealand white rabbits were used. Thirty ears were randomly divided into 3 groups. In the experimental groups (1 and 2), ADSCs were subcutaneously injected 7 days and immediately before the operation, respectively. Similarly, phosphate-buffered saline was injected in the control group just before surgery in the same manner as in group 2. In all groups, chondrocutaneous composite tissue was elevated, rotated 90 degrees, and repaired in its original position. Skin flow was assessed using laser Doppler 1, 3, 6, 9, and 12 days after surgery. At 1 and 12 days after surgery, the viable area was assessed using digital photography; the rabbits were euthanized, and immunohistochemical staining for CD31 was performed to assess neovascularization.

Results

The survival of composite grafts increased significantly with the injection of ADSCs (P<0.05). ADSC injection significantly improved neovascularization based on anti-CD31 immunohistochemical analysis and vascular endothelial growth factor expression (P<0.05) in both group 1 and group 2 compared to the control group. No statistically significant differences in graft survival, anti-CD31 neovascularization, or microcirculation were found between groups 1 and 2.

Conclusions

Treatment with ADSCs improved the composite graft survival, as confirmed by the survival area and histological evaluation. The differences according to the injection timing were not significant.

Optimization of an injectable tendon hydrogel: the effects of platelet-rich plasma and adipose-derived stem cells on tendon healing in vivo

INTRODUCTION

Acute and chronic tendon injuries would benefit from stronger and more expeditious healing. We hypothesize that supplementation of a biocompatible tendon hydrogel with platelet-rich plasma (PRP) and adipose-derived stem cells (ASCs) would augment the tendon healing process.

MATERIALS AND METHODS

Using 55 Wistar rats, a full-thickness defect was created within the midsubstance of each Achilles tendon with the addition of one of five experimental conditions: (i) saline control (50-μL), (ii) tendon hydrogel (50-μL), (iii) tendon hydrogel (45-μL)+PRP (5-μL), (iv) tendon hydrogel (45-μL)+2×10(6)-ASCs/mL in phosphate buffered saline (5-μL), and (v) tendon hydrogel (45-μL)+2×10(6)-ASCs/mL in PRP (5-μL). Hydrogel was developed from decellularized, human cadaveric tendons. Fresh rat PRP was obtained per Amable et al.'s technique, and green fluorescent protein/luciferase-positive rat ASCs were utilized. Rats were sacrificed at weeks 1, 2, 4, and 8 after injury. Real-time in vivo bioluminescence imaging of groups with ASCs was performed. Upon sacrifice, Achilles tendons underwent biomechanical and histological evaluation. Comparisons across groups were analyzed using the two-sample Z-test for proportions and the Student's t-test for independent samples. Significance was set at p<0.05.

RESULTS

(i) Bioluminescence imaging demonstrated that total photon flux was significantly increased for hydrogel+PRP+ASCs, versus hydrogel+ASCs for each postoperative day imaged (p<0.03). (ii) Mean ultimate failure load (UFL) was increased for hydrogel augmented with PRP and/or ASCs versus hydrogel alone at week 2 (p<0.03). By week 4, hydrogel alone reached a similar mean UFL to hydrogel augmented with PRP and/or ASCs (p>0.3). However, at week 8, hydrogel with PRP and ASCs demonstrated increased strength over other groups (p<0.05), except for hydrogel with PRP (p=0.25). (iii) Upon histological analysis, Hematoxylin and Eosin staining showed increased extracellular matrix formation in groups containing PRP and increased cellularity in groups containing ASCs. Groups containing both PRP and ASCs demonstrated both of these characteristics.

CONCLUSION

PRP and ASCs are easily accessible bioactive products that have potentiating effects on tendon hydrogel. Augmentation with these two factors encourages earlier mechanical strength and functional restoration. Thus, biochemically, tendon hydrogel augmented with PRP and/or ASCs, serves as a promising therapeutic modality for augmenting the tendon healing process after injury.

Cell recruitment by amnion chorion grafts promotes neovascularization

BACKGROUND

Nonhealing wounds are a significant health burden. Stem and progenitor cells can accelerate wound repair and regeneration. Human amniotic membrane has demonstrated efficacy in promoting wound healing, though the underlying mechanisms remain unknown. A dehydrated human amnion chorion membrane (dHACM) was tested for its ability to recruit hematopoietic progenitor cells to a surgically implanted graft in a murine model of cutaneous ischemia.

METHODS

dHACM was subcutaneously implanted under elevated skin (ischemic stimulus) in either wild-type mice or mice surgically parabiosed to green fluorescent protein (GFP) + reporter mice. A control acellular dermal matrix, elevated skin without an implant, and normal unwounded skin were used as controls. Wound tissue was harvested and processed for histology and flow cytometric analysis.

RESULTS

Implanted dHACMs recruited significantly more progenitor cells compared with controls (*P < 0.05) and displayed in vivo SDF-1 expression with incorporation of CD34 + progenitor cells within the matrix. Parabiosis modeling confirmed the circulatory origin of recruited cells, which coexpressed progenitor cell markers and were localized to foci of neovascularization within implanted matrices.

CONCLUSIONS

In summary, dHACM effectively recruits circulating progenitor cells, likely because of stromal derived factor 1 (SDF-1) expression. The recruited cells express markers of "stemness" and localize to sites of neovascularization, providing a partial mechanism for the clinical efficacy of human amniotic membrane in the treatment of chronic wounds.