[Ocular surface reconstruction in limbal stem cell deficiency : Transplantation of cultivated limbal epithelium]

Midterm results of conjunctival reconstruction with buccal mucosa and amniotic membrane after resecting ocular surface squamous neoplasia of the fornix

OBJECTIVE

To evaluate the midterm results of tumour resection with or without adjunctive therapy for ocular surface squamous neoplasia of the fornix, including conjunctival reconstruction with buccal mucosa and amniotic membrane.

METHODS

A retrospective case-series analysis including slit-lamp examination, photographic documentation, and biopsy results (repeated when clinical findings changed). Analysis centred on eye function, complications, additional procedures, and recurrence rate. Surgical technique included tumour resection and subsequent reconstruction of lost conjunctiva with buccal mucosa and amniotic membrane.

RESULTS

We included 83 affected eyes from 76 patients (mean age, 63.10 ± 14.45 years; 34 females) seen over a mean follow-up period of 26.56 ± 21.17 months. We achieved bulbus oculi salvage in 82 eyes (98.79%) and typically preserved visual acuity (mean 0.2 ± 0.5 logMAR and 0.3 ± 0.5 logMAR at presentation and last follow-up, respectively). Moreover, only 23 patients (27.71%) required corrective surgery for clinically relevant complications. The main complications included symblepharon (9.64%; n = 8), cicatricial ectropion (9.64%; n = 8), pannus (9.64%; n = 8), and corneal decompensation (8.43%; n = 7). Local tumour recurrence was seen in 23 patients (27.71%).

CONCLUSIONS

These midterm results confirm the efficacy of conjunctival reconstruction with amniotic membrane and buccal mucosa after resection of ocular surface squamous neoplasia from the fornix with palpebral and bulbar conjunctiva involvement. We not only achieved good tumour control and organ salvage with high levels of organ preservation but we also achieved good functional outcomes and acceptable recurrence rates. All clinically significant complications could be corrected in separate procedures.

Recent perspectives on the delivery of biologics to back of the eye

INTRODUCTION

Biologics are generally macromolecules, large in size with poor stability in biological environments. Delivery of biologics to tissues at the back of the eye remains a challenge. To overcome these challenges and treat posterior ocular diseases, several novel approaches have been developed. Nanotechnology-based delivery systems, like drug encapsulation technology, macromolecule implants and gene delivery are under investigation. We provide an overview of emerging technologies for biologics delivery to back of the eye tissues. Moreover, new biologic drugs currently in clinical trials for ocular neovascular diseases have been discussed. Areas covered: Anatomy of the eye, posterior segment disease and diagnosis, barriers to biologic delivery, ocular pharmacokinetic, novel biologic delivery system Expert opinion: Anti-VEGF therapy represents a significant advance in developing biologics for the treatment of ocular neovascular diseases. Various strategies for biologic delivery to posterior ocular tissues are under development with some in early or late stages of clinical trials. Despite significant progress in the delivery of biologics, there is unmet need to develop sustained delivery of biologics with nearly zero-order release kinetics to the back of the eye tissues. In addition, elevated intraocular pressure associated with frequent intravitreal injections of macromolecules is another concern that needs to be addressed.

Transcriptome and proteome characterization of surface ectoderm cells differentiated from human iPSCs

Surface ectoderm (SE) cells give rise to structures including the epidermis and ectodermal associated appendages such as hair, eye, and the mammary gland. In this study, we validate a protocol that utilizes BMP4 and the γ-secretase inhibitor DAPT to induce SE differentiation from human induced pluripotent stem cells (hiPSCs). hiPSC-differentiated SE cells expressed markers suggesting their commitment to the SE lineage. Computational analyses using integrated quantitative transcriptomic and proteomic profiling reveal that TGFβ superfamily signaling pathways are preferentially activated in SE cells compared with hiPSCs. SE differentiation can be enhanced by selectively blocking TGFβ-RI signaling. We also show that SE cells and neural ectoderm cells possess distinct gene expression patterns and signaling networks as indicated by functional Ingenuity Pathway Analysis. Our findings advance current understanding of early human SE cell development and pave the way for modeling of SE-derived tissue development, studying disease pathogenesis, and development of regenerative medicine approaches.

Telocytes in regenerative medicine

Telocytes (TCs) are a distinct type of interstitial cells characterized by a small cell body and extremely long and thin telopodes (Tps). The presence of TCs has been documented in many tissues and organs (go to http://www.telocytes.com). Functionally, TCs form a three-dimensional (3D) interstitial network by homocellular and heterocellular communication and are involved in the maintenance of tissue homeostasis. As important interstitial cells to guide or nurse putative stem and progenitor cells in stem cell niches in a spectrum of tissues and organs, TCs contribute to tissue repair and regeneration. This review focuses on the latest progresses regarding TCs in the repair and regeneration of different tissues and organs, including heart, lung, skeletal muscle, skin, meninges and choroid plexus, eye, liver, uterus and urinary system. By targeting TCs alone or in tandem with stem cells, we might promote regeneration and prevent the evolution to irreversible tissue damage. Exploring pharmacological or non-pharmacological methods to enhance the growth of TCs would be a novel therapeutic strategy besides exogenous transplantation for many diseased disorders.

Telocytes and stem cells in limbus and uvea of mouse eye

The potential of stem cell (SC) therapies for eye diseases is well-recognized. However, the results remain only encouraging as little is known about the mechanisms responsible for eye renewal, regeneration and/or repair. Therefore, it is critical to gain knowledge about the specific tissue environment (niches) where the stem/progenitor cells reside in eye. A new type of interstitial cell–telocyte (TC) (http://www.telocytes.com) was recently identified by electron microscopy (EM). TCs have very long (tens of micrometres) and thin (below 200 nm) prolongations named telopodes (Tp) that form heterocellular networks in which SCs are embedded. We found TCs by EM and electron tomography in sclera, limbus and uvea of the mouse eye. Furthermore, EM showed that SCs were present in the anterior layer of the iris and limbus. Adhaerens and gap junctions were found to connect TCs within a network in uvea and sclera. Nanocontacts (electron-dense structures) were observed between TCs and other cells: SCs, melanocytes, nerve endings and macrophages. These intercellular ‘feet’ bridged the intercellular clefts (about 10 nm wide). Moreover, exosomes (extracellular vesicles with a diameter up to 100 nm) were delivered by TCs to other cells of the iris stroma. The ultrastructural nanocontacts of TCs with SCs and the TCs paracrine influence via exosomes in the epithelial and stromal SC niches suggest an important participation of TCs in eye regeneration.

[Short-term and long-term complications after transplantation of cultivated limbal epithelium]

Recent advances in tissue engineering have facilitated the development of new strategies in ocular surface reconstruction. Limitations and possibilities of ex vivo cultivation and limbal epithelium cell culture techniques as well as the short and long-term complications after transplantation of ex vivo expansion of cultivated limbal epithelium for the treatment of limbal stem cell deficiency are summarized in this review.