Different types of stem cells have been used in various ways in several research projects to find the optimal procedure to regenerate the human corneal stroma. It included several approaches which can be classified as intrastromal implantation of stem cells (1) alone, (2) together with a biodegradable scaffold, (3) with a non-biodegradable scaffold, or (4) with a decellularized corneal stromal scaffold. The complex structure of the corneal stroma has not been yet replicated, and there are well-known drawbacks to the use of synthetic scaffold-based designs. Recently, several corneal decellularization techniques have been described, which provide an acellular corneal extracellular matrix (ECM). These scaffolds have gained attention in the last few years. The scaffold provides a more natural environment for the growth and differentiation of cells when compared with synthetic scaffolds. In addition, components of the ECM are generally conserved among species and are tolerated well even by xenogeneic recipients. Keratocytes are essential for remodeling the corneal stroma and for normal epithelial physiology. This highlights the importance of transplanting a cellular substitute together with the structural support (acellular ECM) to undertake these critical functions in corneal homeostasis. To the best of the investigators' knowledge, all attempts to repopulate decellularized corneal scaffolds have used corneal cells, but these cells have major drawbacks that preclude their autologous use in clinical practice (damage of the donor tissue, lack of cells, and inefficient cell subcultures), thus the efforts to find an extraocular source of autologous cells. A recent study by the investigators has shown a perfect bio integration of human decellularized corneal stromal laminas (100 µm thickness) with and without h-ADASCs colonization inside the rabbit cornea in vivo, without observing any rejection response despite the graft being xenogeneic. The investigators also demonstrated the differentiation of h-ADASCs into functional keratocytes inside these implants in vivo, which then achieved their proper biofunctionalization. According to the investigator's opinion, the transplant of stem cells together with decellularized corneal ECM would be the best technique to effectively restore the thickness of a diseased human cornea, like in keratoconus. Through this technique, and using extraocular mesenchymal stem cells from patients, it is possible to transform allergenic grafts into functional autologous grafts, theoretically avoiding the risk of rejection.

The process flow is defined as following: (1) the file study: which start by receiving the file of the patient, the file will be forwarded to appointed physicians coordinators for review and submission of medical report, then the medical report will be evaluated within the cell therapy committee and the patient will be asked for clinical examination, and after consultation a reply to the patient with medical decision will follow with an approval or not to be recruited and if yes, a brief report about the procedure will be submitted and explained in details to the patient, a consent form must be signed if the patient agree to be included in the study, (2) the patient admission: which may start by completion of the procedure forms and doing the pre-op evaluation (initial work up defined as a clinical and biological assessment upon C.A.S which may include unaided and best spectacle corrected visual acuity, refraction, slit lamp examination, intraocular pressure, fundoscopy, corneal topography, aberrometry, endothelial cell count (specular microscopy), corneal confocal microscopy, as well as blood tests), all this tests should be effectuated by an specialist and reviewed by an ophthalmologist. Then, a lipoaspiration of the subcutaneous adipose tissue to be performed by a plastic surgeon, sample processing at a cGMP facility for isolation and characterization of the stromal vascular fraction enriched with ADASCs as well as laminas preparing (the quality control assessment will be realized before and after all the steps of the procedure starting from the ADASCs collection to implantation including cell culture, cell quiescence, decellularization of human corneal lamina, recellularization of the laminas with ADASCs, and implantation; the assessment will include cell viability, cell number, cell apoptosis, immunophenotyping, infection, inflammation by analyzing the secreted cytokines from ADASCs, lamina cutting, lamina thickness, immunostaining, confocal microscopy, etc.); (3) the delivery (implantation) which starts by a peribulbar or retrobulbar anesthesia where the patient is placed under operating microscope, followed by a femtosecond laser-assisted mid-stromal lamellar dissection, then the autologous ADASCs or laminas or recellularized laminas will be placed within the pocket, and finally closed by a superior incision closure. The patient will be put under antibiotic/steroids for a defined period and followed by the team at 1 week, 2 weeks, 1 month, 3 months, 6 months.

This protocol of cell therapy will be applied exclusively at VISSUM (Alicante-Spain), Barraquer Ophthalmology Center (Barcelona-Spain), Ramon y Cajal Hospital (Madrid-Spain), Asturias Prince Hospital (Madrid-Spain), and Murcia Hospital (Murcia-Spain), in affiliation with Miguel Hernandez of Elche University (Elche-Spain).

The patient's recruitment will take place: for the lipoaspiration, processing, preparing the cellularized laminas and quality control assessments in VISSUM (Alicante-Spain), Barraquer Ophthalmology Center (Barcelona-Spain), Ramon y Cajal Hospital (Madrid-Spain), and Murcia Hospital (Murcia-Spain). All these steps are managed by VISSUM (Prof. J. ALIO).