Integrated environmental and health economic assessments of novel xeno-keratografts addressing a growing public health crisis

Study design

This study used a process-based LCA to quantify the environmental impacts of two distinct xeno-keratoplasty procedures involving native corneas and the decellularized corneal scaffolds that can be regenerated as individualized grafts. These procedures occurred at the Khalifa University’s College of Medicine and Health Sciences (KU CMHS) in Abu Dhabi, UAE. This organization is one of the top-ranked institutions involved in regenerative medicine in the UAE, generating hundreds of xenograft models annually, and is involved in primary and stem cell-based tissue engineering to address the substantial and growing need for corneal transplantation. The functional unit for the procedure was a single xeno-keratoprosthesis model involving a single ovine eye.

Xeno-keratoplasty model derived from slaughterhouse waste

All tissues were collected from the Abu Dhabi Automated Slaughterhouse, which is one of the largest slaughterhouses in the UAE, capable of accommodating around 37,000 sacrifices and carcasses. For our purposes, the ovine eyes were collected from the animals directly after slaughter and transported to KU CMHS, where they were used to create xenografts for our in vitro transplantation model, presented in Fig. 1. The model consists of allogeneic native corneas and tissue-engineering personalized xenografts derived from decellularization/recellularization techniques transplanted on extracted eyes obtained from other animals. In-depth details on native and tissue-engineering processes3,4 and transplantation27 are outlined in the literature. All experimental protocols were approved by the Animal Research Oversight Committee (AROC) at Khalifa University of Science and Technology. The study was also carried out in compliance with the ARRIVE guidelines. All methods were carried out in accordance with relevant guidelines and regulations.

Corneal processing and xenograft preparation

The protocols for processing both native corneas and tissue-engineered corneal scaffolds used in this study were based on methodologies established in our previous research3,4,28. Fresh ovine eyes were sourced from the Abu Dhabi Automated Slaughterhouse and transported to KU CMHS under sterile conditions. In earlier studies, native corneas were excised, washed in sterile saline, and treated with antibiotics to minimize contamination. These corneas were evaluated in their unmodified state, focusing on structural integrity, transparency, and biomechanical properties (reference to the relevant previous study).

We previously employed a decellularization process for the tissue-engineered corneal scaffolds using a 4% zwitterionic biosurfactant solution, followed by rigorous washing to remove residual surfactants. These decellularized scaffolds were analyzed through histological and polymerase chain reaction (PCR) assays to confirm the absence of cellular materials and pathogens. The outcomes of these assessments provided the groundwork for evaluating the potential of decellularized corneas as xenografts28.

While the current study did not directly repeat these experiments, we built on these previously validated processes to perform a comparative life cycle analysis (LCA) and cost-effectiveness analysis (CEA) of native versus decellularized corneal scaffolds derived from slaughterhouse waste. This analysis was used to assess the environmental and economic implications of utilizing these materials in clinical settings.

Product life cycle model

The Life Cycle Assessment (LCA) conducted in this study aimed to quantify the environmental impacts of xeno-keratoplasty by following a structured, multi-step approach based on the ISO 14,040 framework. The LCA included the four main stages: goal and scope definition, life cycle inventory (LCI), life cycle impact assessment (LCIA), and interpretation. Below, each parameter used in the LCA is detailed based on how it was determined and evaluated.

Goal and scope definition

The goal of the LCA was to assess the environmental impacts of a single xeno-keratoplasty procedure, from tissue harvesting to post-operative patient care. The functional unit chosen was chosen as the production of one pair of corneas derived from sheep for transplant. The system boundary was set to include all processes from sheep tissue harvesting, sterilization, packaging, and transportation to the operating room procedures and end-of-life scenarios to perform each type of keratoplasty. Exclusions included environmental impacts outside the control of the procedure itself, such as personal transportation of patients to clinics and hospital energy use unrelated to the surgery. Sensitivity analyses were conducted to evaluate the importance of these exclusions. All inputs were attributed by weight and normalized accordingly. As such, impacts associated with the processing and packaging of meat, skin, and other products were not included in this study. The system boundary is shown in Fig. S1 in the Supplementary file. It is important to note that for the subject analysis, only the attributable life of the equipment used will be considered. Assumptions regarding the useful life of the inputs and attributable proportion thereof have been provided in the Appendix. As such, some inputs (e.g., drapes) were not considered in the analysis as their life depends upon the quality of the fabric and involve inputs related to washing, ironing, and repackaging, which are beyond the scope of the current study.

Life cycle inventory (LCI)

The life cycle inventory phase involved collecting quantitative data for each stage of the xeno-keratoplasty process. Each parameter was measured, estimated, or sourced from existing LCA databases such as the Ecoinvent database. Data were gathered on sheep cornea extraction, including energy use, water consumption, and waste generation. Information regarding the sterilization process was obtained from hospital records, including energy use, chemicals involved (e.g., ethylene oxide), and water consumption. The environmental footprint of materials was derived from Ecoinvent. Transportation impacts were calculated based on the distance travelled by the harvested cornea tissue from the animal facility to the surgical center, and by considering the transportation mode (i.e., refrigerated truck). Standard emissions data for transportation were used, including fuel consumption and greenhouse gas emissions per kilometer travelled. Detailed data were collected on the surgical instruments used, including single-use items (gloves, scalpels, sutures) and their disposal. Energy consumption (electricity for lighting, HVAC, and surgical equipment) was estimated using hospital energy audits. Data on waste generation (hazardous and non-hazardous) during surgery were also documented.

Life cycle impact assessment (LCIA)

The LCIA phase translated the inventory data into environmental impacts using an impact assessment model. SimaPro software was used to estimate 18 midpoint indicators using ReCiPe methodology with a Hierarchical perspective. Where data was missing from the Ecoinvent database for individual inputs, published protocols were implemented based on chemical characteristics or functional parallels These parallels were confirmed by the owner of the case study as appropriate to the scope of the study. The equation for the contributions of individual emissions within the system, is given in equation (1).

Here Ap represents the inputs (i) into the supply chain, according to the system boundary shown in Fig. 1; this includes raw material extraction, energy use, and production processes; n is the total number of inputs (i), and Ep is the emissions intensity of the chosen impact categories outlined above, for each input (i) into the supply chain. A detailed explanation of LCA parameters has been provided in the Supplementary file.

Interpretation

The final phase of the LCA involved interpreting the results to identify the most significant contributors to the environmental impact of xeno-keratoplasty. Sensitivity analysis was conducted to explore how changes in key parameters (e.g., transportation distance, energy use) affected overall results. Recommendations for reducing the environmental impact of xeno-keratoplasty were drawn from this phase, emphasizing areas such as optimizing transportation logistics and improving energy efficiency in sterilization processes.