Revitalization of Biostatic Tissue Allografts: New Perspectives in Tissue Transplantology

Investigations of Human Fascia Lata Elemental Composition-the Effect of Different Preservation and Mineralisation Methods

Influence of fixation medium and storage conditions as well as impact of sample mineralisation procedure on determination of minerals in human fascia lata was examined and discussed. Freezing and storage in 10% neutral buffered formalin solution and in 2.5% glutaraldehyde were used as the preservation methods of the samples. The concentrations of, both essential and toxic, elements were measured by ICP-OES method in fascia lata samples mineralised with concentrated nitric acid in a closed microwave system and in open vessels heated on a hot plate. Freezing was found as the best preserving method of fascia lata samples because of the number of elements determined and determination precision. The trace element (Cd, Cr, Cu, Fe, Ni, Sr, Zn) concentrations obtained in samples decomposed using the conventional hot plate were different from analogous measurements in solutions obtained after application of closed vessels and microwave energy assistance. Differences between the mineral compositions of fascia samples variously preserved and mineralised were statistically evaluated and discussed. Interelement correlations were analysed taking into account an impact of various methods of sample conservation. Strong, positive association between element content was discovered for Cr-Ba, Mn-Ba, P-Ba, Sr-Ba, Sr-Ca, Zn-Ca, Mn-Cr, Pb-Cr, Sr-Cr, Mg-Fe, P-Fe, Pb-Ni, Ti-Ni and Sr-P pairs of elements.

Regeneration of Tracheal Tissue in Partial Defects Using Porcine Small Intestinal Submucosa

Background

Surgical correction of tracheal defects is a complex procedure when the gold standard treatment with primary end-to-end anastomosis is not possible. An alternative treatment may be the use of porcine small intestinal submucosa (SIS). It has been used as graft material for bioengineering applications and to promote tissue regeneration. The aim of this study was to evaluate whether SIS grafts improved tracheal tissue regeneration in a rabbit model of experimental tracheostomy.

Methods

Sixteen rabbits were randomized into two groups. Animals in the control group underwent only surgical tracheostomy, while animals in the SIS group underwent surgical tracheostomy with an SIS graft covering the defect. We examined tissues at the site of tracheostomy 60 days after surgery using histological analysis with hematoxylin and eosin (H&E) staining and analyzed the perimeter and area of the defect with Image-Pro® PLUS 4.5 (Media Cybernetics).

Results

The average perimeter and area of the defects were smaller by 15.3% (p = 0.034) and 21.8% (p = 0.151), respectively, in the SIS group than in the control group. Histological analysis revealed immature cartilage, pseudostratified ciliated epithelium, and connective tissue in 54.5% (p = 0.018) of the SIS group, while no cartilaginous regeneration was observed in the control group.

Conclusions

Although tracheal SIS engraftment could not prevent stenosis in a rabbit model of tracheal injury, it produced some remarkable changes, efficiently facilitating neovascularization, reepithelialization, and neoformation of immature cartilage.

Intratendinous Injection of Hydrogel for Reseeding Decellularized Human Flexor Tendons

BACKGROUND

Decellularized cadaveric tendons are a potential source for reconstruction. Reseeding to enhance healing is ideal; however, cells placed on the tendon surface result in inadequate delivery. The authors used an injection technique to evaluate intratendinous cell delivery.

METHODS

Decellularized tendons were reseeded with adipose-derived stem cells in culture, and injected with fetal bovine serum or hydrogel. PKH26-stained cells in cross-section were quantified. To evaluate cell viability, the authors delivered luciferase-labeled cells and performed bioluminescent imaging. To evaluate synthetic ability, the authors performed immunohistochemistry of procollagen. Adipose-derived stem cells' ability to attract tenocytes was assessed using transwell inserts. Cell-to-cell interaction was assessed by co-culturing, measuring proliferation and collagen production, and quantifying synergy. Finally, tensile strength was tested.

RESULTS

Both fetal bovine serum (p < 0.001) and hydrogel (p < 0.001) injection led to more cells inside the tendon compared with culturing. Hydrogel injection initially demonstrated greater bioluminescence than culturing (p < 0.005) and fetal bovine serum injection (p < 0.05). Injection groups demonstrated intratendinous procollagen staining correlating with the cells' location. Co-culture led to greater tenocyte migration (p < 0.05). Interaction index of proliferation and collagen production assays were greater than 1 for all co-culture ratios, demonstrating synergistic proliferation and collagen production compared with controls (p < 0.05). There were no differences in tensile strength.

CONCLUSIONS

Hydrogel injection demonstrated the greatest intratendinous seeding efficiency and consistency, without compromising tensile strength. Intratendinous cells demonstrated synthetic capabilities and can potentially attract tenocytes inside the tendon, where synergy would promote intrinsic tendon healing.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Optimized Repopulation of Tendon Hydrogel: Synergistic Effects of Growth Factor Combinations and Adipose-Derived Stem Cells

Background: Tendon-derived extracellular matrix (ECM) hydrogel has been shown to augment tendon healing in vivo. We hypothesized that reseeding of the gel with adipose-derived stem cells (ASCs) could further assist repopulation of the gel and that combinations of growth factors (GFs) would improve the survival of these cells after reseeding. Methods: A tendon-specific ECM solution was supplemented with varying concentrations of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), and platelet-derived growth factor-BB (PDGF-BB). Gels were then seeded with ASCs transfected with a green fluorescent protein/luciferin construct. Cell proliferation was determined using the MTT assay and histology, and GF and ASC augmented gels were injected into the back of Sprague Dawley rats. Bioluminescence of seeded gels was continuously followed after reseeding, and cell counts were performed after the gels were explanted at 14 days. Results: Synergistic effects of the GFs were seen, and an optimal combination was determined to be 10 ng/mL bFGF, 100 ng/mL IGF-1, and 100 ng/mL PDGF-BB (2.8-fold increase; P < .05). In vivo bioluminescence showed an improved initial survival of cells in gels supplemented with the optimal concentration of GF compared with the control group (10.6-fold increase at 8 days; P < .05). Cell counts of explants showed a dramatic endogenous repopulation of gels supplemented by GF + ASCs compared with both gels with GF but no ASCs (7.6-fold increase) and gels with ASCs but no GF (1.6-fold increase). Conclusion: Synergistic effects of GFs can be used to improve cellular proliferation of ASCs seeded to a tendon ECM gel. Reseeding with ASCs stimulates endogenous repopulation of the gel in vivo and may be used to further augment tendon healing.

Autologous osteoblast transplantation, an innovative method of bone defect treatment: role of a tissue and cell bank in the process

BACKGROUND

The idea of cell treatment of various diseases and medical conditions has become very popular. Some procedures are well established, as is autologous chondrocyte implantation, whereas others are still in the process of early development, laboratory experiments, and some clinical trials.

METHODS

This report is devoted to an example of an emerging cell treatment: bone augmentation with the use of autologous cells and its legal and technical background. Various requirements set by law must be met by tissue banks performing cell seeding of grafts. In Europe, the requirements are described in directives 2004/23/EC, 2006/17/EC, 2006/86/EC, and in the regulation 2007/1394/EC.

RESULTS

Revitalization of biostatic allografts gives new, promising tools for creation of functional parts of organs; brings the methodology used in tissue banks closer to tissue engineering; places the enterprise in the mainstream of advanced biotechnology; allows the full potential of tissue allografts; and opens a new, large area for clinical and laboratory research. Cell and tissue processing also have a financial impact on the treatment: it produces additional expenditures.

CONCLUSIONS

Clinical effectiveness will be the most decisive factor of whether this innovative treatment will be applied in a particular type of medical condition. From a tissue establishment perspective, the most important issue is to develop a procedure that ensures safety for the patient in graft quality terms.

Naturally Occurring Extracellular Matrix Scaffolds for Dermal Regeneration: Do They Really Need Cells?

The pronounced effect of extracellular matrix (ECM) scaffolds in supporting tissue regeneration is related mainly to their maintained 3D structure and their bioactive components. These decellularized matrix scaffolds could be revitalized before grafting via adding stem cells, fibroblasts, or keratinocytes to promote wound healing. We reviewed the online published literature in the last five years for the studies that performed ECM revitalization and discussed the results of these studies and the related literature. Eighteen articles met the search criteria. Twelve studies included adding cells to acellular dermal matrix (ADM), 3 studies were on small intestinal mucosa (SIS), one study was on urinary bladder matrix (UBM), one study was on amniotic membrane, and one study included both SIS and ADM loaded constructs. We believe that, in chronic and difficult-to-heal wounds, revitalizing the ECM scaffolds would be beneficial to overcome the defective host tissue interaction. This belief still has to be verified by high quality randomised clinical trials, which are still lacking in literature.

Tendon grafts: their natural history, biology and future development

The use of tendon grafts has diminished as regimes of primary repairs and rehabilitation have improved, but they remain important in secondary reconstruction. Relatively little is known about the cellular biology of grafts, and the general perception is that they have little biological activity. The reality is that there is a wealth of cellular and molecular changes occurring with the process of engraftment that affect the quality of the repair. This review highlights the historical perspectives and modern concepts of graft take, reviews the different attachment techniques and revisits the biology of pseudosheath formation. In addition, we discuss some of the future directions in tendon reconstruction by grafting, which include surface modification, vascularized tendon transfer, allografts, biomaterials and cell-based therapies.

The past, present and future in scaffold-based tendon treatments

Tendon injuries represent a significant clinical burden on healthcare systems worldwide. As the human population ages and the life expectancy increases, tendon injuries will become more prevalent, especially among young individuals with long life ahead of them. Advancements in engineering, chemistry and biology have made available an array of three-dimensional scaffold-based intervention strategies, natural or synthetic in origin. Further, functionalisation strategies, based on biophysical, biochemical and biological cues, offer control over cellular functions; localisation and sustained release of therapeutics/biologics; and the ability to positively interact with the host to promote repair and regeneration. Herein, we critically discuss current therapies and emerging technologies that aim to transform tendon treatments in the years to come.

Effect of autogenous and fresh-frozen bone grafts on osteoblast differentiation

OBJECTIVE

Fresh-frozen bone allograft (FFBA) is an alternative to autogenous bone (AB) for reconstructing maxillary bone. Despite the promising clinical results, cell responses to FFBA and AB were not evaluated. Thus, our aim was to compare cells harvested from maxillary reconstructed sites with either AB or FFBA in terms of osteoblast differentiation and to evaluate the effect of culturing cells in contact with FFBA.

METHODS

Cells harvested from three patients submitted to bilateral maxillary reconstruction with AB and FFBA were cultured to evaluate: proliferation, alkaline phosphatase activity, extracellular matrix mineralization and gene expression of osteoblastic markers. The effect of FFBA on osteoblast differentiation was studied by culturing cells harvested from AB in contact with FFBA and evaluating the same parameters. Data were compared using either two-way ANOVA followed by Tukey-b test or Student's t test (p≤0.05).

RESULTS

Cell proliferation was higher in cultures from AB grafted sites and extracellular matrix mineralization was higher in cultures derived from FFBA grafted sites. The gene expression of alkaline phosphatase, RUNX2, bone sialoprotein and osteocalcin was higher in cells derived from FFBA compared with cells from AB grafted sites. However, the exposure of cells derived from AB to FFBA particles did not have any remarkable effect on osteoblast differentiation.

CONCLUSIONS

These results indicate the higher osteogenic activity of cells derived from FFBA compared with AB reconstructed sites, offering an explanation at cellular level of why FFBA could be a suitable alternative to AB for reconstructing maxillary bone defects.

Trapezium excision and suture suspensionplasty (TESS) for the treatment of thumb carpometacarpal arthritis

Basilar thumb arthritis, or first carpometacarpal arthritis, is a common condition affecting older women and some men. It is estimated that as many as one third of postmenopausal woman are affected. Surgical treatment of this condition includes options ranging from arthrodesis to prosthetic arthroplasty. Intermediate options include complete or partial trapezial excision with or without interposition of a cushioning/stabilizing material (auto source, allo source, synthetic source). A multitude of methods appear to offer similar end results, although some methods definitely involve more surgical work and perhaps greater patient risk. Through retrospective evaluation of a cohort of patients who underwent suture suspensionplasty, we determined the postoperative effect on strength, motion, patient satisfaction, complications, and radiographic maintenance of the scaphoid-metacarpal distance. This review shows the method to be clinically effective and, by comparison with a more traditional ligament reconstruction trapezial interposition arthroplasty, the method does not require use of autograft or allograft tendon and has fewer surgical steps. Forty-four patients were included in this retrospective study. The results showed that 91% of patients were satisfied with the procedure. Pinch and grip strength remained the same preoperatively and postoperatively. A Disabilities of the Arm, Shoulder, and Hand patient-reported outcome instrument (DASH) scores averaged 30 at final follow-up. Three patients developed a late complication requiring further surgical intervention. In summary, this technique appears to be technically reproducible, requires no additional tendon material, and achieves objectively and subjectively similar results to other reported procedures used to manage first CMC Arthritis.

Reconstruction of the tendon-bone insertion with decellularized tendon-bone composite grafts: comparison with conventional repair

PURPOSE

Injuries involving the tendon-bone interface (TBI) are difficult to address. Standard techniques typically lead to diminished strength of the healed insertion site. We hypothesized that these injuries would benefit from being reconstructed with decellularized composite grafts replacing both tendon and bone. To test this hypothesis, decellularized grafts were compared with conventional pullout repairs in an in vivo animal model.

METHODS

We harvested 48 Achilles TBI grafts from rats and decellularized them. Tendon-bone interface graft reconstruction and pullout repairs were compared using a pair-matched design. Biomechanical properties were evaluated at 2, 4, 8, and 12 weeks. We evaluated histological analysis of insertion morphology and collagen type I/III content.

RESULTS

There was a significant increase in ultimate failure load (35 ± 11 vs 24 ± 7 N) and ultimate tensile stress (1.5 ± 0.3 vs 1.0 ± 0.4 N/mm(2)) of the TBI grafts compared with pullout repairs at 2 weeks. These differences remained at 4 weeks. At 12 weeks, both TBI grafts and pullout repairs were as strong as native tissue and not significantly different from each other. Histology showed a more organized extracellular matrix in the TBI graft group at the early time points. Repopulation of the decellularized grafts increased over time. At 12 weeks, the insertion points of both groups were richly populated with cells that possessed morphologies similar to those found in native TBI.

CONCLUSIONS

This study showed that decellularized TBI grafts were stronger compared with conventional pullout repairs at 2 and 4 weeks but were comparable at 12 weeks. A more organized extracellular matrix and different collagen composition in the early time points may explain the observed differences in strength.

CLINICAL RELEVANCE

In the future, decellularized TBI grafts may be used to reconstruct tendon-bone insertion tears in multiple areas including the flexor tendon system.

Repopulation of intrasynovial flexor tendon allograft with bone marrow stromal cells: an ex vivo model

PURPOSE

Delayed healing is a common problem whenever tendon allografts are used for tendon or ligament reconstruction. Repopulating the allograft with host cells may accelerate tendon regeneration, but cell penetration into the allograft tendon is limited. Processing the tendon surface with slits that guide cells into the allograft substrate may improve healing. The purpose of this study was to describe a surface modification of allograft tendon that includes slits to aid cell repopulation and lubrication to enhance tendon gliding.

METHODS

Canine flexor digitorum profundus tendons were used for this study. Cyclic gliding resistance was measured over 1000 cycles. Tensile stiffness was assessed for normal tendon, tendon decellularized with trypsin and Triton X-100 (decellularized group), tendon decellularized and perforated with multiple slits (MS group) and tendon decellularized, perforated with slits and treated with a carbodiimide-derivatized hyaluronic acid and gelatin (cd-HA-gelatin) surface modification (MS-SM group). To assess tendon repopulation, bone marrow stromal cells (BMSCs) were used in the decellularized and MS groups. DNA concentration and histology were evaluated and compared to normal tendons and nonseeded decellularized tendons.

RESULTS

The gliding resistance of the decellularized and MS groups was significantly higher compared with the normal group. There was no significant difference in gliding resistance between the decellularized and MS group. Gliding resistance of the normal group and MS-SM group was not significantly different. The Young's modulus was not significantly different among the four groups. The DNA concentration in the MS group was significantly lower than in normal tendons, but significantly higher than in decellularized tendons, with or without BMSCs. Viable BMSCs were found in the slits after 2 weeks in tissue culture.

CONCLUSIONS

Tendon slits can successfully harbor BMSCs without compromising their survival and without changing tendon stiffness. Surface modification restores normal gliding function to the slit tendon.

CLINICAL RELEVANCE

A multislit tendon reseeded with BMSCs, with a surface treatment applied to restore gliding properties, may potentially promote tendon revitalization and accelerate healing for tendon or ligament reconstruction applications.