Possible Link Between the ABO Blood Group of Bioprosthesis Recipients and Specific Types of Structural Degeneration

Stem Cell Therapy, Artificial Heart or Xenotransplantation: What will be New “Regenerative” Strategies in Heart Failure during the Next Decade?

The main limitation of allotransplantation and in particular heart transplantation is the insufficient supply of donor organs. As alternative strategies to heart transplantation, stem cells opened the way of regenerative medicine in early 2000. While new biotechnologies tried to minimize side effects due to hemocompatibility in artificial hearts, progress in xenotransplantation allowed in 2022 to realize the first pig-to-human heart transplant on a compassionate use basis. This xenotransplantation has been successful thanks to genetically modified pigs using the CRISPR-Cas9 technology. Indeed, gene editing allowed modifications of immune responses and thrombotic potential to modulate graft and systemic reaction. Academic research and preclinical studies of xenogeneic tissues already used in clinic such as bioprosthesis valve and of new xenotransplantation options will be necessary to evaluate immune-thrombosis and organ/vascular damages more deeply to make this hope of xenotransplantation a clinical reality. Stem cells, artificial heart and xenotransplantation are all in line to overcome the lack of donor hearts. Combination of stem cell approaches and/or xenogeneic tissue and/or artificial organs are probably part of the research objectives to make these projects real in the short term.

Can Heart Valve Decellularization Be Standardized? A Review of the Parameters Used for the Quality Control of Decellularization Processes

When a tissue or an organ is considered, the attention inevitably falls on the complex and delicate mechanisms regulating the correct interaction of billions of cells that populate it. However, the most critical component for the functionality of specific tissue or organ is not the cell, but the cell-secreted three-dimensional structure known as the extracellular matrix (ECM). Without the presence of an adequate ECM, there would be no optimal support and stimuli for the cellular component to replicate, communicate and interact properly, thus compromising cell dynamics and behaviour and contributing to the loss of tissue-specific cellular phenotype and functions. The limitations of the current bioprosthetic implantable medical devices have led researchers to explore tissue engineering constructs, predominantly using animal tissues as a potentially unlimited source of materials. The high homology of the protein sequences that compose the mammalian ECM, can be exploited to convert a soft animal tissue into a human autologous functional and long-lasting prosthesis ensuring the viability of the cells and maintaining the proper biomechanical function. Decellularization has been shown to be a highly promising technique to generate tissue-specific ECM-derived products for multiple applications, although it might comprise very complex processes that involve the simultaneous use of chemical, biochemical, physical and enzymatic protocols. Several different approaches have been reported in the literature for the treatment of bone, cartilage, adipose, dermal, neural and cardiovascular tissues, as well as skeletal muscle, tendons and gastrointestinal tract matrices. However, most of these reports refer to experimental data. This paper reviews the most common and latest decellularization approaches that have been adopted in cardiovascular tissue engineering. The efficacy of cells removal was specifically reviewed and discussed, together with the parameters that could be used as quality control markers for the evaluation of the effectiveness of decellularization and tissue biocompatibility. The purpose was to provide a panel of parameters that can be shared and taken into consideration by the scientific community to achieve more efficient, comparable, and reliable experimental research results and a faster technology transfer to the market.

Modes of the bioprosthetic valve failure of the porcine and pericardial valves in the mitral position

OBJECTIVES

This study was conducted to examine the incidence and modes of the bioprosthetic valve failure of the porcine valve in the mitral position and compare them with those of the pericardial valve.

METHODS

This study included 240 patients (116 men [48.3%]; mean age, 74.87 ± 6.61 years) who underwent mitral valve replacement using the St. Jude Medical Epic bioprosthesis (Epic) (N = 125) or Carpentier-Edwards Perimount (CEP) pericardial valve (N = 115) from January 2000 to December 2020.

RESULTS

The median clinical follow-up durations in the Epic and CEP groups were 54.5 months (range, 0-111 months) and 81.5 months (range, 0-194 months), respectively. Structural valve degeneration (SVD) was observed in 9 patients (7.2%) in the Epic group and 11 patients (9.6%) in the CEP group. The rates of freedom from SVD at 3, 5 and 7 years were 97.7%, 90.5% and 75.5% in the Epic group and 100.0%, 96.1% and 90.0% in the CEP group, respectively. SVD reoperation was performed for 7 patients (5.6%) in the Epic group and 6 patients (5.2%) in the CEP group. The rates of freedom from SVD reoperation at 3, 5 and 7 years were 97.7%, 90.5% and 75.5% in the Epic group and 100%, 96.1% and 90.0% in the CEP group, respectively. Epic SVD was predominantly due to leaflet tearing, whereas CEP SVD was predominantly due to leaflet calcification and adhesion to the subvalvular apparatus.

CONCLUSIONS

SVD of the porcine valve was predominantly due to leaflet tearing. The rate of reoperation for SVD was slightly higher for the porcine valve in the mitral position than for the pericardial valve at adjusted survival analysis.

Possible Link Between the ABO Blood Group of Bioprosthesis Recipients and Specific Types of Structural Degeneration

Background Pigs/bovines share common antigens with humans: α-Gal, present in all pigs/bovines close to the human B-antigen; and AH-histo-blood-group antigen, identical to human AH-antigen and present only in some animals. We investigate the possible impact of patients' ABO blood group on bioprosthesis structural valve degeneration (SVD) through calcification/pannus/tears/perforations for patients ≤60 years at implantation. Methods and Results This was a single-center study (Paris, France) that included all degenerative bioprostheses explanted between 1985 and 1998, mostly porcine bioprostheses (Carpentier-Edwards second/third porcine bioprostheses) and some bovine bioprostheses. For the period 1998 to 2014, only porcine bioprostheses with longevity ≥13 years were included (total follow-up ≥29 years). Except for blood groups, important predictive factors for SVD were prospectively collected (age at implantation/longevity/number/site/sex/SVD types) and analyzed using logistic regression. All variables were available for 500 explanted porcine bioprostheses. By multivariate analyses, the A group was associated with an increased risk of: tears (odds ratio[OR], 1.61; P=0.026); pannus (OR, 1.5; P=0.054), pannus with tears (OR, 1.73; P=0.037), and tendency for lower risk of: calcifications (OR, 0.63; P=0.087) or isolated calcification (OR, 0.67; P=0.17). A-antigen was associated with lower risk of perforations (OR 0.56; P=0.087). B-group patients had an increased risk of: perforations (OR, 1.73; P=0.043); having a pannus that was calcified (OR, 3.0, P=0.025). B-antigen was associated with a propensity for calcifications in general (OR, 1.34; P=0.25). Conclusions Patient's ABO blood group is associated with specific SVD types. We hypothesize that carbohydrate antigens, which may or may not be common to patient and animal bioprosthetic tissue, will determine a patient's specific immunoreactivity with respect to xenograft tissue and thus bioprosthesis outcome in terms of SVD.