Healing of deep dermal burns by allogeneic mesenchymal stromal cell transplantation

Advancements in cell-based therapies for thermal burn wounds: a comprehensive systematic review of clinical trials outcomes

BACKGROUND

Burn trauma is one of the major causes of morbidity and mortality worldwide. The standard management of burn wounds consists of early debridement, dressing changes, surgical management, and split-thickness skin autografts (STSGs). However, there are limitations for the standard management that inclines us to find alternative treatment approaches, such as innovative cell-based therapies. We aimed to systematically review the different aspects of cell-based treatment approaches for burn wounds in clinical trials.

METHODS

A systematic search through PubMed, Medline, Embase, and Cochrane Library databases was carried out using a combination of keywords, including "Cell transplantation", "Fibroblast", "Keratinocyte", "Melanocyte", or "Stem Cell" with "Burn", "Burn wound", or "Burn injury". Firstly, titles and abstracts of the studies existing in these databases until "February 2024" were screened. Then, the selected studies were read thoroughly, and considering the inclusion and exclusion criteria, final articles were included in this systematic review. Moreover, a manual search was performed through the reference lists of the included studies to minimize the risk of missing reports.

RESULTS

Overall, 30 clinical trials with 970 patients were included in our study. Considering the type of cells, six studies used keratinocytes, nine used fibroblasts, eight used combined keratinocytes and fibroblasts, one study used combined keratinocytes and melanocytes, five used combined keratinocytes and fibroblasts and melanocytes, and one study used mesenchymal stem cells (MSCs). Evaluation of the preparation type in these studies showed that cultured method was used in 25 trials, and non-cultured method in 5 trials. Also, the graft type of 17 trials was allogeneic, and of 13 other trials was autologous.

CONCLUSIONS

Our study showed that employing cell-based therapies for the treatment of burn wounds have significant results in clinical studies and are promising approaches that can be considered as alternative treatments in many cases. However, choosing appropriate cell-based treatment for each burn wound is essential and depends on the situation of each patient.

Murine bone-derived mesenchymal stem cells undergo molecular changes after a single passage in culture

The rarity of the mesenchymal stem cell (MSC) population poses a significant challenge for MSC research. Therefore, these cells are often expanded in vitro, prior to use. However, long-term culture has been shown to alter primary MSC properties. Additionally, early passage primary MSCs in culture are often assumed to represent the primary MSC population in situ, however, little research has been done to support this. Here, we compared the transcriptomic profiles of murine MSCs freshly isolated from the bone marrow to those that had been expanded in culture for 10 days. We identified that a single passage in culture extensively altered MSC molecular signatures associated with cell cycling, differentiation and immune response. These findings indicate the critical importance of the MSC source, highlighting the need for optimization of culture conditions to minimize the impact on MSC biology and a transition towards in vivo methodologies for the study of MSC function.

Allogeneic Bone Marrow Mesenchymal Stromal Cell Transplantation Induces Dentin Pulp Complex-like Formation in Immature Teeth with Pulp Necrosis and Apical Periodontitis

INTRODUCTION

Dental pulp regeneration is challenging in endodontics. Cellular therapy is an alternative approach to induce dental pulp regeneration. Mesenchymal stromal cells (MSCs) have the capacity to induce dental pulp-like tissue formation. In this study, we evaluated the capacity of allogeneic bone marrow MSCs (BM-MSCs) to regenerate pulp following necrosis and apical periodontitis in children's permanent immature apex teeth.

METHODS

Patients aged 8 to 12 years with pulp necrosis and apical periodontitis were evaluated. The study included 15 teeth (13 incisors and 2 molars) from 14 patients (8 boys and 6 girls). Radiographic evaluation showed periapical radiolucency and immature apex teeth. There was no response to cold or electric pulp testing. The root canal of each tooth was cleaned, shaped, and Ca(OH)2 used as an interappointment medication. Cryopreserved allogeneic BM-MSCs were thawed, expanded, incorporated into preclotted platelet-rich plasma, and implanted into the tooth's pulp cavity. They were sealed with bioceramic cement and composite. Sensibility, apical foramen, calcium deposits within the root canal, and resolution of periapical lesions were evaluated in each tooth over the following 12 months.

RESULTS

Based on 9 variables established for dental pulp-like tissue regeneration, all MSC-treated teeth showed evidence of successful regeneration. Clinical and radiographic evaluation of the treated teeth showed periapical lesion healing, sensitivity to cold and electricity, decreased width of the apical foramen, and mineralization within the canal space.

CONCLUSIONS

Transplantation of allogeneic MSCs induces the formation of dental pulp-like tissue in permanent immature apex teeth with pulp necrosis and apical periodontitis. Implant of MSCs constitutes a potential therapy in regenerative endodontics in pediatric dentistry. Future studies incorporating a larger sample size may confirm these results.

Porous Collagen Sponge Loaded with Large Efficacy-Potentiated Exosome-Mimicking Nanovesicles for Diabetic Skin Wound Healing

Diabetic skin wounds are difficult to heal quickly due to insufficient angiogenesis and prolonged inflammation, which is an urgent clinical problem. To address this clinical problem, it becomes imperative to develop a dressing that can promote revascularization and reduce inflammation during diabetic skin healing. Herein, a multifunctional collagen dressing (CTM) was constructed by loading large efficacy-potentiated exosome-mimicking nanovesicles (L-Meseomes) into a porous collagen sponge with transglutaminase (TGase). L-Meseomes were constructed in previous research with the function of promoting cell proliferation, migration, and angiogenesis and inhibiting inflammation. CTM has a three-dimensional porous network structure with good biocompatibility, swelling properties, and degradability and could release L-Meseome slowly. In vitro experiments showed that CTM could promote the proliferation of fibroblasts and the polarization of macrophages to the anti-inflammatory phenotype. For in vivo experiments, on the 21st day after surgery, the wound healing rates of the control and CTM were 83.026 ± 4.17% and 93.12 ± 2.16%, respectively; the epidermal maturation and dermal differentiation scores in CTM were approximately four times that of the control group, and the skin epidermal thickness of the CTM group was approximately 20 μm, which was closest to that of normal rats. CTM could significantly improve wound healing in diabetic rats by promoting anti-inflammation, angiogenesis, epidermal recovery, and dermal collagen deposition. In summary, the multifunctional collagen dressing CTM could significantly promote the healing of diabetic skin wounds, which provides a new strategy for diabetic wound healing in the clinic.

Osteogenic organoid for bone regeneration: Healing of bone defect in congenital pseudoarthrosis of the tibia

BACKGROUND

Congenital pseudoarthrosis of the tibia (CPT) is an uncommon disease associated with failure to achieve bone union and recurrent fractures. There is evidence showing that CPT is associated with decreased osteogenesis. Based on the capacity of mesenchymal stromal cells (MSCs) to induce osteogenesis, we develop an osteogenic organoid (OstO) constituted by these cells, and other components of the bone niche, for inducing bone formation in a child diagnosed with CPT.

AIM

To evaluate the capacity of an OstO to induce bone formation in a patient with CPT.

METHODS

The OstO was fabricated with allogeneic bone marrow MSCs from a healthy donor, collagen microbeads (CM) and PRP clot. The CM and PRP function as extracellular matrix and scaffolds for MSC. The OstO was placed at the site of non-union. Internal and external fixation was placed in the tibia. Radiological evaluation was performed after MSCs transplantation.

RESULTS

After 4 months of MSCs transplantation, radiographic imaging showed evidence of osteogenesis at the site of CPT lesion. The tibia showed bone consolidation and complete healing of the non-union CPT lesion after 6 months. Functional improvement was observed after 1 year of MSC transplantation.

CONCLUSIONS

The OstO is a bone-like niche which promote osteogenesis in patients with failure in bone formation, such as CPT. To our knowledge, these results provide the first evidence showing CPT healing induced by an OstO constituted by allogeneic MSCs. Future studies incorporating a larger number of patients may confirm these results.

Nanostructured fibrin-agarose hydrogels loaded with allogeneic fibroblasts as bio-dressings for acute treatment of massive burns

The prompt management of patients with massive burns is essential to maximize survival by preventing infection, hemorrhage, fluid and heat loss, and to optimally prepare the wound bed for the application of autografts or cultured tissue-engineered artificial autologous skin. Acute treatments are typically based on temporary bio-dressings, commonly cadaveric skin allografts, but supply challenges, high costs and increasingly stringent regulatory requirements preclude their widespread use. Nanostructured fibrin-agarose hydrogels (NFAH) have been proven to be safe and effective biomaterials in preclinical and clinical studies, and show good hemostatic and biomechanical properties. Here we generated and tested NFAH with embedded allogeneic dermal fibroblasts (NFAH-F) under Good Manufacturing Practice (GMP) conditions. Fibroblasts were first expanded and characterized to create a GMP bank and the NFAH-F was manufactured on demand. Three patients with major burns were treated with this product as a temporary bio-dressing under compassionate use. Our results suggest that NFAH-F product was a safe product and no adverse reactions were observed. In all cases, the patients survived until definitive treatment. Therefore, the application of NFAH-F might be a temporary bio-dressing for patients with massive burns when cadaveric skin allografts are not available.

Wound healing by transplantation of mesenchymal stromal cells loaded on polyethylene terephthalate scaffold: Implications for skin injury treatment

BACKGROUND

Several clinical studies have shown that cellular therapy based on mesenchymal stromal cells (MSCs) transplantation may accelerate wound healing. One major challenge is the delivery system used for MSCs transplantation. In this work, we evaluated the capacity of a scaffold based on polyethylene terephthalate (PET) to maintain the viability and biological functions of MSCs, in vitro. We examined the capacity of MSCs loaded on PET (MSCs/PET) to induce wound healing in an experimental model of full-thickness wound.

METHODS

Human MSCs were seeded and cultured on PET membranes at 37 °C for 48 h. Adhesion, viability, proliferation, migration, multipotential differentiation and chemokine production were evaluated in cultures of MSCs/PET. The possible therapeutic effect of MSCs/PET on the re-epithelialization of full thickness wounds was examined at day 3 post-wounding in C57BL/6 mice. Histological and immunohistochemical (IH) studies were performed to evaluate wound re-epithelialization and the presence of epithelial progenitor cells (EPC). As controls, wounds without treatment or treated with PET were established.

RESULTS

We observed MSCs adhered to PET membranes and maintained their viability, proliferation and migration. They preserved their multipotential capacity of differentiation and ability of chemokine production. MSCs/PET implants promoted an accelerated wound re-epithelialization, after three days post-wounding. It was associated with the presence of EPC Lgr6⁺ and K6⁺.

DISCUSSION

Our results show that MSCs/PET implants induce a rapid re-epithelialization of deep- and full-thickness wounds. MSCs/PET implants constitute a potential clinical therapy for treating cutaneous wounds.

The effects of mesenchymal stromal cells and platelet-rich plasma treatments on cutaneous wound healing

Cellular therapy and platelet-rich plasma (PRP) have been used as a treatment for skin wounds. Previous evidence has shown that mesenchymal stromal cells (MSC) may improve skin wound healing. In contrast, contradictory effects have been reported by using PRP treatment on skin wound healing. However, there is evidence that PRP constitutes an excellent scaffold for tissue engineering. In this work, we aim to study the effect of MSC on skin wound healing. We used an experimental murine model of full-thickness wounds. Wounds were treated with human bone marrow-MSC contained in a PRP clot. Untreated or PRP-treated wounds were used as controls. Wound healing was evaluated by macroscopic observation and histological analysis at day 7 post-wounding. Immunohistochemical studies were performed to detect the presence of epithelial progenitor cells (EPC) and the expression of basic fibroblast growth factor (bFGF). MSC/PRP implantation induced a significant wound closure and re-epithelialization as compared with the controls. Increase of CD34⁺ cells and bFGF was observed in the wounds treated with MSC/PRP. Our results show that MSC included in PRP clot induce cutaneous wound repair by promoting re-epithelialization, migration of EPC and expression of bFGF. PRP alone does not exert a significant effect on wound healing. Our results support the possible clinical use of MSC in PRP scaffold as potential treatment of skin wounds.

Enhanced chondrogenesis from chondrocytes co-cultured on mesenchymal stromal cells: Implication for cartilage repair

Cellular therapy based on chondrocytes implantation is the most widely used procedure for inducing cartilage regeneration. However, the dedifferentiation process that these cells suffer and their limited capacity of proliferation, when they are cultured in vitro, restrict their use in cellular therapy protocols. To investigate the capacity of mesenchymal stromal cells (MSCs) to promote chondrogenesis from chondrocytes or chondrons in 2D and 3D coculture systems. Murine chondrocytes and chondrons were cocultured with MSCs at different cell ratios (100/0, 50/50, 70/30, 0/100) in two-dimensional (2D) and three-dimensional (3D) culture systems. High proliferation of cells with chondrocyte morphology, enhanced GAG production and expression of cartilage genes (aggrecan, type II collagen, and SOX-9) were observed in chondrocytes/MSCs cocultures. In contrast, fibroblastoid cells, down-regulation of cartilage gene expression and reduction of GAG production were observed in chondrons/MSCs cocultures. Chondrocytes within cartilage lacunae and surrounded by extracellular matrix were observed in chondrocytes/MSC pellets. MSCs promote the proliferation of functional chondrocytes in 2D and 3D culture systems. Transplantation of chondrogenic construct based on MSCs and chondrocytes may constitute a potential treatment for inducing cartilage repair.

The Role of MSC in Wound Healing, Scarring and Regeneration

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.