Chen-Chen Li

The number of pet dogs is increasing, and the number of working dogs (e.g., guide dogs, police dogs) is also gradually increasing. Skin wounds are a common clinical problem in dogs and tend to be more common in the clinic as mechanical wounds. The healing process of skin wounds is often influenced by a variety of factors, including infection, nutritional status, and immune response, while wound healing is more difficult in dogs with diabetes or aging dogs. Mesenchymal stem cells (MSCs) play an important role in skin healing and regeneration with their multidirectional differentiation potential and immunomodulatory function. However, the application of MSCs alone for the treatment of skin wounds may have certain limitations, such as low cell survival and a lack of localization. Therefore, it is important to find methods that can enhance the therapeutic effect of MSCs. Secreted protein acidic and rich in cysteine (SPARC), an extracellular matrix protein widely involved in regulating biological processes such as cell proliferation, migration, and matrix production, may enhance the efficacy of MSCs in skin wound healing. This study aims to systematically evaluate the therapeutic efficacy of SPARC-overexpressing adipose-derived mesenchymal stem cells (ADSCs) in promoting skin wound healing by establishing wound models in normal, diabetic, and aged mice and dogs, thereby validating their potential under diverse physiological and pathological conditions. For in vitro validation, we used hydrogen peroxide (H₂O₂) to induce Human Umbilical Vein Endothelial Cell (HUVEC) and Human Keratinocyte Cell (HaCaT) injury. All animals were randomly assigned to six experimental groups as follows: (1) Model group: Untreated wound (negative control); (2) HY group: Hydrogel alone (vehicle control); (3) Con group: Control-ADSCs (cell control); (4) Con-Exo&HY group: Control-ADSC exosomes in hydrogel; (5) SPARC group: oe-SPARC-ADSCs (treatment); (6) SPARC-Exo&HY group: oe-SPARC-ADSC exosomes in hydrogel (treatment). Separately, HUVEC and HaCaT cells were assigned to four experimental conditions: a blank control group, a model group, a control-ADSC-treated group, and an oe-SPARC-ADSC-treated group. ADSCs modified by SPARC significantly promoted re-epithelialization integrity, collagen deposition, inflammation reduction, angiogenesis, and hair follicle regeneration during wound healing in dog skin. HUVEC and HaCaT cells proliferated after adding oe-SPARC-ADSCs cell supernatant. Meanwhile, quantitative proteomic sequencing data analysis showed that SPARC could promote skin wound healing by enhancing cell adhesion, hyaluronic acid binding, and vascular smooth muscle contraction of ADSCs. Both in vitro cellular assays and in vivo wound-healing models suggest that the combination of SPARC and ADSCs for the treatment of skin wounds has broad application prospects.

The existing treatment modalities for skin injuries mainly include dressings, negative-pressure wound treatment, autologous skin grafting, and high-pressure wound treatment. All of these therapies have limitations such as high time cost, the inability to remove inactivated tissue in a timely manner, surgical debridement, and oxygen toxicity. Mesenchymal stem cells have a unique self-renewal ability and wide differentiation potential, and they are one of the most promising stem cell types in cell therapy and have great application prospects in the field of regenerative medicine. Collagen exerts structural roles by promoting the molecular structure, shape, and mechanical properties of cells, and adding it to cell cultures can also promote cell proliferation and shorten the cell doubling time. The effects of collagen on MSCs were examined using Giemsa staining, EdU staining, and growth curves. Mice were subjected to allogeneic experiments and autologous experiments to reduce individual differences; all animals were separated into four groups. Neonatal skin sections were detected by HE staining, Masson staining, immunohistochemical staining, and immunofluorescence staining. We found that the MSCs pretreated with collagen accelerated the healing of skin wounds in mice and canines by promoting epidermal layer repair, collagen deposition, hair follicle angiogenesis, and an inflammatory response. Collagen promotes the secretion of the chemokines and growth factors associated with skin healing by MSCs, which positively influences skin healing. This study supports the treatment of skin injuries with MSCs cultured in medium with collagen added.