Multipotent Stromal Cell and Fibroblast Co‐Transplantation Alter Wound Microenvironment to Normalize Aged‐Deficient Wound Healing

Skin scarring can be debilitating to the patient and both localized and systemic conditions present many challenges for treatment, increasingly so in advanced aged. Many strategies have been developed over the past century to minimize scarring. The fibroblast rebuilds the extracellular matrix, which makes up the connective tissue. At the injury site, fibroblasts serve key roles in inflammation modulation, immune cell recruitment, and aiding endothelial cells in facilitating angiogenesis. As such, fibroblasts have been studied as cellular targets and therapies to improve the pathological response to injury. However, currently the single target approaches for the treatment of excessive healing have been less then optimal mostly due to the numerous factors at play, including the native environmental cues. In contrast, Multipotent Stromal Cells (MSCs) have been proposed as therapies for lost tissues, due to the potential to differentiate into multiple cell types and replace the missing tissues. While preclinical models have been promising, the inability to find these cells incorporated into the repaired tissue has led to questions of whether the improvements are due to production of bioactive factors and modulation of immune/inflammatory responses, or a combination thereof. Thus, we proposed that MSC‐fibroblast co‐transplantation could “educate” the wound micro‐environment by affecting the mechanisms underlying the tissue/injury diversity to normalize aberrant healing. We used Hylan A dermal filler hydrogel containing collagen I (Col I) and tenascin‐C (TNC) for delivery and to increase survival of transplanted cells. We found that co‐transplantation of MSCs with fibroblasts enhances healing and overcomes aged defective healing and extracellular matrix remodeling in our chemokine receptor CXCR3‐deficient murine model. The collagen‐tenascin‐C matrix improved survival of MSCs and fibroblasts; both in vitro in the face of serum deprivation and pro‐inflammatory challenge, and in vivo implantation onto murine excisional wounds led to fewer onset inflammatory cells in the wound as determined by FASC analysis and immunohistochemistry. More interestingly, we found the that co‐transplantation influences macrophage M1 and M2 subset polarization and repolarization during late remodeling. Transplanted MSCs amplify fibroblast proliferation, migration, and ECM deposition within the wound, which advance closure and reduced inflammation following wounding. Overall, the combined cell treatment overcame the extracellular matrix induced excessive scarring that follows the healing of wounds in CXCR3‐deficient mice. Using the encapsulated MSCs‐fibroblasts hydrogel matrix on CXCR3‐deficient mice, we were able to determine that fibroblasts could overcome endogenous deficiencies associated with age to generate a more physiological form dermal tissue. These findings provide insight into cellular therapies as a viable method for age‐dependent healing effects, especially in diseases that increase with age such as type 2 diabetes, by showing that transiently engrafted cells can have long term impact via matrix modulation and education of other tissue cells. Support or Funding Information This work was supported by grants from NIGMS and NIAMS (GM69668 AW and AR68317 CCY), and support in kind from the Pittsburgh VA Medical Center and the School of Nursing.