The Equine Hoof: Laminitis, Progenitor (Stem) Cells, and Therapy Development

The equine hoof capsule, composed of modified epidermis and dermis, is vital for protecting the third phalanx from forces of locomotion. There are descriptions of laminitis, defined as inflammation of sensitive hoof tissues but recognized as pathologic changes with or without inflammatory mediators, in the earliest records of domesticated horses. Laminitis can range from mild to serious, and signs can be acute, chronic, or transition from acute, severe inflammation to permanently abnormal tissue. Damage within the intricate dermal and epidermal connections of the primary and secondary lamellae is often associated with lifelong changes in hoof growth, repair, and conformation. Decades of research contribute to contemporary standards of care that include systemic and local therapies as well as mechanical hoof support. Despite this, consistent mechanisms to restore healthy tissue formation following a laminitic insult are lacking. Endogenous and exogenous progenitor cell contributions to healthy tissue formation is established for most tissues. There is comparably little information about equine hoof progenitor cells. Equine hoof anatomy, laminitis, and progenitor cells are covered in this review. The potential of progenitor cells to advance in vitro equine hoof tissue models and translate to clinical therapies may significantly improve prevention and treatment of a devastating condition that has afflicted equine companions throughout history.

Wound healing complications in oncological patients: perspectives for cellular therapy

Various types of cancer are nowadays a serious medical and social problem and a great challenge for modern medicine. The majority of anticancer therapy is based on traditional chemotherapy and radiotherapy. Both of these highly non-specific types of treatment have a number of serious side effects including wound healing complications. Radiotherapy and chemotherapy mostly affect rapidly dividing skin cells (e.g. keratinocytes), as well as fibroblasts, melanocytes, endothelial and immune cells. Currently, there are many strategies to improve wound healing in oncological patients, including various types of dressings, biomaterials, growth factors, and cell therapies.

Transcriptional profile of in vitro expanded human epidermal progenitor cells for the treatment of non-healing wounds

BACKGROUND

Epidermal progenitor cells (EPCs) have been under extensive investigation due to their increasing potential of application in medicine and biotechnology. Cultured human EPCs are used in the treatment of chronic wounds and have recently became a target for gene therapy and toxicological studies. One of the challenges in EPCs culture is to provide a high number of undifferentiated, progenitor cells displaying high viability and significant biological activity.

OBJECTIVES

The goal of this study was to characterize the in vitro cultured progenitor cells and to assess whether the cells with the progenitor phenotype are able to enhance wound healing. Additionally, we aimed to establish the complete procedure of the culture, analysis and clinical application of epidermal progenitor cells.

METHODS

In this study we present a method of cell isolation and culture followed by a technique of transplantation of the cultured cells onto the wound bed. The applied isolation technique involves two enzymatic steps (dispase, trypsin) and it is characterized by a high yield of cells. The obtained cells were cultured in vitro up to the second passage in serum-free and xeno-free keratinocytes-dedicated medium. Key stem cell markers were determined with means of flow cytometry and quantitative real-time PCR.

RESULTS

The in vitro expanded cells displayed high proliferative activity without features of neither apoptosis nor necrosis. The flow cytometry and transcriptomic analyses showed enhanced expression of stem cell markers (i.e. proteins: ΔNp63, CD29, CD49f and BNC1, CDKN1A transcripts) in the expanded cells. In the presented compassionate use study, cultured autologous cells from an oncological patient were suspended in fibrin sealant and transplanted directly to a non-healing wound, resulting in wound closure within 2 months.

CONCLUSION

The cells cultured in serum-free media display epidermal stem cells features and a potential to stimulate wound healing. This promising procedure of isolation, culture and application warrants further clinical trials in the treatment of chronic wounds.

Novel role for the testis-enriched HSPA2 protein in regulating epidermal keratinocyte differentiation

HSPA2, a poorly characterized member of the HSPA (HSP70) chaperone family, is a testis-enriched protein involved in male germ cell differentiation. Previously, we revealed that HSPA2 is present in human stratified epithelia, including epidermis, however the contribution of this protein to epithelial biology remained unknown. Here, we show for the first time that HSPA2 is expressed in basal epidermal keratinocytes, albeit not in keratinocytes exhibiting features attributed to primitive undifferentiated progenitors, and participates in the keratinocyte differentiation process. We found that HSPA2 is dispensable for protection of HaCaT keratinocytes against heat shock-induced cytotoxicity. We also shown that lentiviral-mediated shRNA silencing of HSPA2 expression in HaCaT cells caused a set of phenotypic changes characteristic for keratinocytes committed to terminal differentiation such as reduced clonogenic potential, impaired adhesiveness and increased basal and confluency-induced expression of differentiation markers. Moreover, the fraction of undifferentiated cells that rapidly adhered to collagen IV was less numerous in HSPA2-deficient cells than in the control. In a 3D reconstructed human epidermis model, HSPA2 deficiency resulted in accelerated development of a filaggrin-positive layer. Collectively, our results clearly show a link between HSPA2 expression and maintenance of keratinocytes in an undifferentiated state in the basal layer of the epidermis. It seems that HSPA2 could retain keratinocytes from premature entry into the terminal differentiation process. Overall, HSPA2 appears to be necessary for controlling development of properly stratified epidermis and thus for maintenance of skin homeostasis.

α6 Integrin (α6high)/Transferrin Receptor (CD71)low Keratinocyte Stem Cells Are More Potent for Generating Reconstructed Skin Epidermis Than Rapid Adherent Cells

The epidermis basal layer is composed of two keratinocyte populations: Keratinocyte Stem cells (KSC) and Transitory Amplifying (TA) cells that arise from KSC division. Unfortunately, no specific marker exists to differ between KSC and TA cells. Here, we aimed at comparing two different methods that pretended to isolate these two populations: (i) the rapid adhesion method on coated substrate and (ii) the flow cytometry method, which is based on the difference in cell surface expressions of the α6 integrin and transferrin receptor (CD71). Then, we compared different parameters that are known to discriminate KSC and TA populations. Interestingly, we showed that both methods allow enrichment in stem cells. However, cell sorting by flow cytometry (α6^high/CD71^low) phenotype leads to a better enrichment of KSC since the colony forming efficiency is five times increased versus total cell suspension, whereas it is only 1.4 times for the adhesion method. Moreover, α6^high/CD71^low cells give rise to a thicker pluristratified epithelium with lower seeding density and display a low Ki67 positive cells number, showing that they have reached the balance between proliferation and differentiation. We clearly demonstrated that cells isolated by a rapid adherent method are not the same population as KSC isolated by flow cytometry following α6^high/CD71^low phenotype.