Biochemical indicators of implantation success of tissue-engineered oral mucosa

Noninvasive Optical Assessment of Implanted Tissue-Engineered Construct Success In Situ

Quantitative diffuse reflectance spectroscopy (DRS) was developed for label-free, noninvasive, and real-time assessment of implanted tissue-engineered devices manufactured from primary human oral keratinocytes (six batches in two 5-patient cohorts). Constructs were implanted in a murine model for 1 and 3 weeks. DRS evaluated construct success in situ using optical absorption (hemoglobin concentration and oxygenation, attributed to revascularization) and optical scattering (attributed to cellular density and layer thickness). Destructive pre- and postimplantation histology distinguished experimental control from stressed constructs, whereas noninvasive preimplantation measures of keratinocyte glucose consumption and residual glucose in spent culture media did not. In constructs implanted for 1 week, DRS distinguished control due to stressed and compromised from healthy constructs. In constructs implanted for 3 weeks, DRS identified constructs with higher postimplantation success. These results suggest that quantitative DRS is a promising, clinically compatible technology for rapid, noninvasive, and localized tissue assessment to characterize tissue-engineered construct success in vivo. Impact statement Despite the recent advance in tissue engineering and regenerative medicine, there is still a lack of nondestructive tools to longitudinally monitor the implanted tissue-engineered devices. In this study, we demonstrate the potential of quantitative diffuse reflectance spectroscopy as a clinically viable technique for noninvasive, label-free, and rapid characterization of graft success in situ.

Noninvasive measurement of cell/colony motion using image analysis methods to evaluate the proliferative capacity of oral keratinocytes as a tool for quality control in regenerative medicine

Image-based cell/colony analyses offer promising solutions to compensate for the lack of quality control (QC) tools for noninvasive monitoring of cultured cells, a regulatory challenge in regenerative medicine. Here, the feasibility of two image analysis algorithms, optical flow and normalised cross-correlation, to noninvasively measure cell/colony motion in human primary oral keratinocytes for screening the proliferative capacity of cells in the early phases of cell culture were examined. We applied our software to movies converted from 96 consecutive time-lapse phase-contrast images of an oral keratinocyte culture. After segmenting the growing colonies, two indices were calculated based on each algorithm. The correlation between each index of the colonies and their proliferative capacity was evaluated. The software was able to assess cell/colony motion noninvasively, and each index reflected the observed cell kinetics. A positive linear correlation was found between cell/colony motion and proliferative capacity, indicating that both algorithms are potential tools for QC.

Living cell-based regenerative medicine technologies for periodontal soft tissue augmentation

The cultivation of human living cells into scaffolding matrices has progressively gained popularity in the field of periodontal wound healing and regeneration. Living cellular constructs based on fibroblasts, keratinocytes alone or in combination have been developed and used as alternatives to autogenous soft tissue grafts in keratinized tissue augmentation and in root coverage procedures. Their promising advantages include reduced patient morbidity, unlimited graft availability, and comparable esthetics. This manuscript reviews soft tissue augmentation and root coverage procedures using bioengineered living cellular therapy and highlights their expected clinical, esthetic, and patient-related outcomes.

Noninvasive Optical Assessment of Implanted Engineered Tissues Correlates with Cytokine Secretion

Fluorescence lifetime sensing has been shown to noninvasively characterize the preimplantation health and viability of engineered tissue constructs. However, current practices to monitor postimplantation construct integration are either qualitative (visual assessment) or destructive (tissue histology). We employed label-free fluorescence lifetime spectroscopy for quantitative, noninvasive optical assessment of engineered tissue constructs that were implanted into a murine model. The portable system was designed to be suitable for intravital measurements and included a handheld probe to precisely and rapidly acquire data at multiple sites per construct. Our model tissue constructs were manufactured from primary human cells to simulate patient variability based on a standard protocol, and half of the manufactured constructs were stressed to create a range of health states. Secreted amounts of three cytokines that relate to cellular viability were measured in vitro to assess preimplantation construct health: interleukin-8 (IL-8), human β-defensin 1 (hBD-1), and vascular endothelial growth factor (VEGF). Preimplantation cytokine secretion ranged from 1.5 to 33.5 pg/mL for IL-8, from 3.4 to 195.0 pg/mL for hBD-1, and from 0.1 to 154.3 pg/mL for VEGF. In vivo optical sensing assessed constructs at 1 and 3 weeks postimplantation. We found that at 1 week postimplantation, in vivo optical parameters correlated with in vitro preimplantation secretion levels of all three cytokines (p < 0.05). This correlation was not observed in optical measurements at 3 weeks postimplantation when histology showed that the constructs had re-epithelialized, independent of preimplantation health state, supporting the lack of a correlation. These results suggest that clinical optical diagnostic tools based on label-free fluorescence lifetime sensing of endogenous tissue fluorophores could noninvasively monitor postimplantation integration of engineered tissues.

Soft Tissue Augmentation Techniques and Materials Used in the Oral Cavity: An Overview

PURPOSE

Oral soft tissue augmentation or grafting procedures are often necessary to achieve proper wound closure after deficits resulting from tumor excision, clefts, trauma, dental implants, and tooth recessions.

MATERIALS AND METHODS

Autologous soft tissue grafts still remain the gold standard to acquire a functionally adequate zone of keratinized attached gingiva. However, soft tissue substitutes are more commonly used because they minimize morbidity and shorten surgical time.

RESULTS

This review aimed to assess soft tissue grafting techniques and materials used in the oral cavity from existing literature. There are a large variety of materials and techniques, including grafts, local flaps, allogenic derived matrices such as acellular dermal allograft, xenogenic tissue matrices from animal origin, and synthetic materials.

CONCLUSIONS

Tissue engineering of oral mucosa represents an interesting alternative to obtain sufficient autologous tissue for reconstructing oral wounds using biodegradable scaffolds, and may improve vascularization and epithelialization, which are critical for successful outcomes.

Proceedings of the American Association of Oral and Maxillofacial Surgeons 2015 Research Summit

The Fifth Biennial Research Summit of the American Association of Oral and Maxillofacial Surgeons and its Committee on Research Planning and Technology Assessment was held in Rosemont, Illinois on May 6 and 7, 2015. The goal of the symposium is to provide a forum for the most recent clinical and scientific advances to be brought to the specialty. The proceedings of the events of that summit are presented in this report.