visualizing-scar-development-using-scad-assay-an-ex-situ-skin

Visualizing Scar Development Using SCAD Assay - An <em>Ex-situ</em> Skin Scarring Assay

The mammalian global response to sealing deep tissue wounds is through scar formation and tissue contraction, mediated by specialized fascia fibroblasts. ...

Helmholtz Zentrum München

Nonhealing chronic wounds in the constantly growing elderly population represent a major public health problem with high socioeconomic burden. Yet, the underlying mechanism of age-related impairment of wound healing remains elusive. Here, we show that the number of dermal cells expressing cyclin-dependent kinase inhibitor p21 was elevated upon skin injury, particularly in aged population, in both man and mouse. The nuclear expression of p21 in activated wound fibroblasts delayed the onset of the proliferation phase of wound healing in a p53-independent manner. Further, the local and transient inhibition of p21 expression by in vivo delivered p21-targeting siRNA ameliorated the delayed wound healing in aged mice. Our results suggest that the increased number of p21 wound fibroblasts enforces the age-related compromised healing, and targeting p21 creates potential clinical avenues to promote wound healing in aged population.

Local and transient inhibition of p21 expression ameliorates age-related delayed wound healing.

Mammals form scars to quickly seal wounds and ensure survival by an incompletely understood mechanism. Here we show that skin scars originate from prefabricated matrix in the subcutaneous fascia. Fate mapping and live imaging revealed that fascia fibroblasts rise to the skin surface after wounding, dragging their surrounding extracellular jelly-like matrix, including embedded blood vessels, macrophages and peripheral nerves, to form the provisional matrix. Genetic ablation of fascia fibroblasts prevented matrix from homing into wounds and resulted in defective scars, whereas placing an impermeable film beneath the skin-preventing fascia fibroblasts from migrating upwards-led to chronic open wounds. Thus, fascia contains a specialized prefabricated kit of sentry fibroblasts, embedded within a movable sealant, that preassemble together diverse cell types and matrix components needed to heal wounds. Our findings suggest that chronic and excessive skin wounds may be attributed to the mobility of the fascia matrix.

Patch repair of deep wounds by mobilized fascia.

Scars are more severe when the subcutaneous fascia beneath the dermis is injured upon surgical or traumatic wounding. Here, we present a detailed analysis of fascia cell mobilisation by using deep tissue intravital live imaging of acute surgical wounds, fibroblast lineage-specific transgenic mice, and skin-fascia explants (scar-like tissue in a dish - SCAD). We observe that injury triggers a swarming-like collective cell migration of fascia fibroblasts that progressively contracts the skin and form scars. Swarming is exclusive to fascia fibroblasts, and requires the upregulation of N-cadherin. Both swarming and N-cadherin expression are absent from fibroblasts in the upper skin layers and the oral mucosa, tissues that repair wounds with minimal scar. Impeding N-cadherin binding inhibits swarming and skin contraction, and leads to reduced scarring in SCADs and in animals. Fibroblast swarming and N-cadherin thus provide therapeutic avenues to curtail fascia mobilisation and pathological fibrotic responses across a range of medical settings.

Injury triggers fascia fibroblast collective cell migration to drive scar formation through N-cadherin.

In recent years, the discovery of ovarian germ stem cells (OGSCs) has provided a new research direction for the treatment of female infertility. The ovarian microenvironment affects the proliferation and differentiation of OGSCs, and immune cells and related cytokines are important components of the microenvironment. However, whether improving the ovarian microenvironment can regulate the proliferation of OGSCs and remodel ovarian function has not been reported. In this study, we chelated chito-oligosaccharide (COS) with fluorescein isothiocyanate (FITC) to track the distribution of COS in the body. COS was given to mice through the best route of administration, and the changes in ovarian and immune function were detected using assays of organ index, follicle counting, serum estrogen (E) and anti-Mullerian hormone (AMH) levels, and the expression of IL-2 and TNF-α in the ovaries. We found that COS significantly increased the organ index of the ovary and immune organs, reduced the rate of follicular atresia, increased the levels of E and AMH hormones, and increased the protein expression of IL-2 and TNF-α in the ovary. Then, COS and OGSCs were co-cultured to observe the combination of COS and OGSCs, and measure the survival rate of OGSCs. With increasing time, the fluorescence intensity of cells gradually increased, and the cytokines IL-2 and TNF-α significantly promoted the proliferation of OGSCs. In conclusion, COS could significantly improve the ovarian and immune function of chemotherapy model mice, and improve the survival rate of OGSCs, which provided a preliminary blueprint for further exploring the mechanism of COS in protecting ovarian function.

The role of Chito-oligosaccharide in regulating ovarian germ stem cells function and restoring ovarian function in chemotherapy mice.

Deep and voluminous skin wounds are repaired with scars, by mobilization of fibroblasts and extracellular matrix from fascia, deep below the skin. The molecular trigger of this novel repair mechanism is incompletely understood. Here we reveal that the gap junction alpha-1 protein (Connexin43, Cx43) is the key to patch repair of deep wounds. By combining full-thickness wound models with fibroblast lineage specific transgenic lines, we show Cx43 expression is substantially upregulated in specialized fibroblasts of the fascia deep beneath the skin that are responsible for scar formation. Using live imaging of fascia fibroblasts and fate tracing of the fascia extracellular matrix we show that Cx43 inhibition disrupts calcium oscillations in cultured fibroblasts and that this inhibits collective migration of fascia EPFs necessary to mobilize fascia matrix into open wounds. Cell-cell communication through Cx43 thus mediates matrix movement and scar formation, and is necessary for patch repair of voluminous wounds. These mechanistic findings have broad clinical implications toward treating fibrosis, aggravated scarring and impaired wound healing.

Connexin43 gap junction drives fascia mobilization and repair of deep skin wounds.

Internal organs heal injuries with new connective tissue, but the cellular and molecular events of this process remain obscure. By tagging extracellular matrix around the mesothelium lining in mouse peritoneum, liver and cecum, here we show that preexisting matrix was transferred across organs into wounds in various injury models. Using proteomics, genetic lineage-tracing and selective injury in juxtaposed organs, we found that the tissue of origin for the transferred matrix likely dictated the scarring or regeneration of the healing tissue. Single-cell RNA sequencing and genetic and chemical screens indicated that the preexisting matrix was transferred by neutrophils dependent on the HSF-integrin AM/B2-kindlin3 cascade. Pharmacologic inhibition of this axis prevented matrix transfer and the formation of peritoneal adhesions. Matrix transfer was thus an early event of wound repair and provides a therapeutic window to dampen scaring across a range of conditions.

Haifeng Ye

Institute of Regenerative Biology and Medicine

Helmholtz Zentrum München

Visualizing Scar Development Using SCAD Assay - An Ex-situ Skin Scarring Assay