Development of low endotoxin gelatin for regenerative medicine

Impact of anticancer drugs on the therapeutic efficacy and side effects of hepatic arterial embolization for hepatocellular carcinoma

Background and Aim

Transcatheter arterial chemoembolization (TACE) using various anticancer drugs is often performed to treat hepatocellular carcinoma (HCC). We aimed to compare the therapeutic efficacy and side effects of TACE with anticancer drugs versus transcatheter arterial embolization (TAE) without anticancer drugs for HCC.

Methods

Patients with HCC were randomized to either the TACE or TAE group. Up to five target nodules were treated in each patient. Lipiodol (Lp; 10 mL), contrast media (CM; 10 mL), epirubicin (40 mg), mitomycin C (10 mg), miliplatin (70 mg), and 1-2-mm 2-day soluble gelatin sponge particles (2D-SGS) were injected into the TACE group, whereas Lp (10 mL), CM (10 mL), and 2D-SGS were injected into the TAE group. Treatment effect (TE) of the target nodules was graded (TE1-TE4) and patient responses were assessed. Three months after treatment, blood tests were performed to compare tumor markers and adverse events.

Results

Fifty-four patients and 161 target nodules were included; 75 nodules in 28 patients were treated by TACE, and 86 nodules in 26 patients were treated by TAE. The number of nodules graded TE1, TE2, TE3, and TE4 was 1, 28, 7, and 39, respectively, in the TACE group and 2, 25, 7, and 52, respectively, in the TAE group. The response rates were 89% (25/28) and 73% (19/26) in the TACE and TAE groups, respectively. There were no significant differences in TE, response rates, or blood test results between the two groups.

Conclusion

In hepatic arterial embolization for HCC, anticancer drugs did not have any impact on the therapeutic efficacy or side effects at 3 months after embolization.

Transcatheter arterial embolization of abnormal neovessels in a swine model of knee arthritis

BACKGROUND

In recent years, transcatheter arterial embolization (TAE) using imipenem/cilastatin (IPM/CS) has attracted attention as a treatment for relieving osteoarthritis (OA) pain. However, IPM/CS is not approved by Japanese medical insurance for use as an embolic material. Therefore, it is necessary to develop new embolic materials for TAE to relieve OA pain. The purpose of this study was to develop a swine model of knee arthritis and embolize abnormal neovessels (ANs) using two different embolic materials. We compared the embolic effects and tissue damage in knees.

METHODS

Knee arthritis was induced by intra-articular injection of papain into 12 knees in six female swine. The swine were divided into two groups of three swine each (six knees per group) for embolization of ANs in the knees with either IPM/CS or soluble gelatin sponge particles (SGSs). Three days after embolization, we compared the embolic effects using angiography and the tissue damage histopathologically.

RESULTS

ANs were observed in all 12 knees at 42 days after papain injection. The ANs disappeared and the patent arteries were recanalized 3 days after TAE in all 12 knees. Histopathological evaluation revealed synovitis changes, such as synovial thickening and inflammatory cell infiltration, in all 12 knees. There was no evidence of skin or muscle necrosis in either group. The appearance of ANs, recanalization of the parent arteries, and histopathological outcomes were not significantly different between the two groups.

CONCLUSION

SGSs were as safe as IPM/CS for TAE of ANs in this swine model of knee arthritis.

Study of the immunologic response of marine-derived collagen and gelatin extracts for tissue engineering applications

The host immunologic response to a specific material is a critical aspect when considering it for clinical implementation. Collagen and gelatin extracted from marine sources have been proposed as biomaterials for tissue engineering applications, but there is a lack of information in the literature about their immunogenicity. In this work, we evaluated the immune response to collagen and/or gelatin from blue shark and codfish, previously extracted and characterized. After endotoxin evaluation, bone marrow-derived macrophages were exposed to the materials and a panel of pro- and anti-inflammatory cytokines were evaluated both for protein quantification and gene expression. Then, the impact of those materials in the host was evaluated through peritoneal injection in C57BL/6 mice. The results suggested shark collagen as the less immunogenic material, inducing low expression of pro-inflammatory cytokines as well as inducible nitric oxide synthase (encoded by Nos2) and high expression of Arginase 1 (encoded by Arg1). Although shark gelatin appeared to be the material with higher pro-inflammatory expression, it also presents a high expression of IL-10 (anti-inflammatory cytokine) and Arginase (both markers for M2-like macrophages). When injected in the peritoneal cavity of mice, our materials demonstrated a transient recruitment of neutrophil, being almost non-existent after 24 hours of injection. Based on these findings, the studied collagenous materials can be considered interesting biomaterial candidates for regenerative medicine as they may induce an activation of the M2-like macrophage population, which is involved in suppressing the inflammatory processes promoting tissue remodeling. STATEMENT OF SIGNIFICANCE: Marine-origin biomaterials are emerging in the biomedical arena, namely the ones based in marine-derived collagen/gelatin proposed as cell templates for tissue regeneration. Nevertheless, although the major cause of implant rejection in clinical practice is the host's negative immune response, there is a lack of information in the literature about the immunological impact of these marine collagenous materials. This work aims to contribute with knowledge about the immunologic response to collagen/gelatin extracted from blue shark and codfish skins. The results demonstrated that despite some differences observed, all the materials can induce a macrophage phenotype related with anti-inflammation resolution and then act as immuno-modulators and anti-inflammatory inducible materials.

Comparison of Uterine Necrosis After Uterine Artery Embolization with Soluble Gelatin Sponge Particles or Tris-acryl Gelatin Microspheres in Swine

PURPOSE

To compare the recanalization of the uterine arteries and uterine necrosis after uterine artery embolization (UAE) using either soluble gelatin sponge particles (SGS), which dissolve in saline, or tris-acryl gelatin microspheres (MS), which are permanent embolic materials, in swine.

METHODS

Fourteen uteri in seven swine were divided into two groups for embolization with either 500-1000 µm SGS (SGS group) or 500-700 µm MS (MS group) (seven uteri per group). The uterine arteries were embolized using SGS or MS, and angiography was performed to evaluate recanalization of the uterine arteries immediately, 1, 2, 3, 4, 5, and 6 h, and 3 days after embolization. On day 3, the uteri were removed to determine the macroscopic necrosis rate and for histopathologic examination.

RESULTS

In the SGS group, four uterine arteries were completely recanalized, two were partially recanalized, and one was still occluded 5 h after embolization. In contrast, all seven uterine arteries in the MS group were still occluded 6 h after embolization. The complete recanalization rate at 3 days was significantly greater in the SGS group than in the MS group (100.0% vs. 14.3%, respectively; P = .0047). The mean uterine necrosis rate was not significantly different between the SGS and MS groups (15.0 ± 15.7% vs. 26.8 ± 13.3%, respectively; P = .096). The mean smallest arterial diameter containing embolic materials was 48.2 ± 22.0 μm (range 21-109 μm) for SGS and 446.7 ± 107.0 μm (range 352-742 μm) for MS (P < .0001).

CONCLUSION

The uterine arteries recanalized earlier in the SGS group than in the MS group and the uterine necrosis rates were similar in both groups. SGS have the potential for a more distal penetration in comparison with MS.

Impact of Endotoxins in Gelatine Hydrogels on Chondrogenic Differentiation and Inflammatory Cytokine Secretion In Vitro

Gelatine methacryloyl (GelMA) hydrogels are widely used in studies aimed at cartilage regeneration. However, the endotoxin content of commercially available GelMAs and gelatines used in these studies is often overlooked, even though endotoxins may influence several cellular functions. Moreover, regulations for clinical use of biomaterials dictate a stringent endotoxin limit. We determined the endotoxin level of five different GelMAs and evaluated the effect on the chondrogenic differentiation of equine mesenchymal stromal cells (MSCs). Cartilage-like matrix production was evaluated by biochemical assays and immunohistochemistry. Furthermore, equine peripheral blood mononuclear cells (PBMCs) were cultured on the hydrogels for 24 h, followed by the assessment of tumour necrosis factor (TNF)-α and C-C motif chemokine ligand (CCL)2 as inflammatory markers. The GelMAs were found to have widely varying endotoxin content (two with >1000 EU/mL and three with <10 EU/mL), however, this was not a critical factor determining in vitro cartilage-like matrix production of embedded MSCs. PBMCs did produce significantly higher TNF-α and CCL2 in response to the GelMA with the highest endotoxin level compared to the other GelMAs. Although limited effects on chondrogenic differentiation were found in this study, caution with the use of commercial hydrogels is warranted in the translation from in vitro to in vivo studies because of regulatory constraints and potential inflammatory effects of the content of these hydrogels.

Cellular Orientation on Repeatedly Stretching Gelatin Hydrogels with Supramolecular Cross-Linkers

The cytocompatibility of biological and synthetic materials is an important issue for biomaterials. Gelatin hydrogels are used as biomaterials because of their biodegradability. We have previously reported that the mechanical properties of gelatin hydrogels are improved by cross-linking with polyrotaxanes, a supramolecular compound composed of many cyclic molecules threaded with a linear polymer. In this study, the ability of gelatin hydrogels cross-linked by polyrotaxanes (polyrotaxane–gelatin hydrogels) for cell cultivation was investigated. Because the amount of polyrotaxanes used for gelatin fabrication is very small, the chemical composition was barely altered. The structure and wettability of these hydrogels are also the same as those of conventional hydrogels. Fibroblasts adhered on polyrotaxane–gelatin hydrogels and conventional hydrogels without any reduction or apoptosis of adherent cells. From these results, the polyrotaxane–gelatin hydrogels have the potential to improve the mechanical properties of gelatin without affecting cytocompatibility. Interestingly, when cells were cultured on polyrotaxane–gelatin hydrogels after repeated stress deformation, the cells were spontaneously oriented to the stretching direction. This cellular response was not observed on conventional hydrogels. These results suggest that the use of a polyrotaxane cross-linking agent can not only improve the strength of hydrogels but can also contribute to controlling reorientation of the gelatin.

Antioxidant N-Acetylcysteine and Glutathione Increase the Viability and Proliferation of MG63 Cells Encapsulated in the Gelatin Methacrylate/VA-086/Blue Light Hydrogel System

Photoencapsulation of cells inside a hydrogel system can provide a suitable path to establish a gel in situ for soft tissue regeneration applications. However, the presence of photoinitiators and blue or UV light irradiation can result in cell damage and an increase of reactive oxygen species. We here evaluate the benefits of an antioxidant pretreatment on the photoencapsulated cells. We study this by evaluating proliferation and viability of MG63 cells, which we combined with a gelatin methacrylate (GelMA) hydrogel system, using the photoinitiator, VA-086, cured with 440 nm blue light. We found that blue light irradiation as well as the presence of 1% VA-086 reduced MG63 cell proliferation rates. Adding a short pretreatment step to the MG63 cells, consisting of the antioxidant molecules N-acetylcysteine (NAC) and reduced glutathione (GSH), and optimizing the GelMA encapsulation steps, we found that both NAC and GSH pretreatments of MG63 cells significantly increased both proliferation and viability of the cells, when using a 15% GelMA hydrogel, 1% VA-086, and 1-min blue light exposure. These findings suggest that the use of antioxidant pretreatment can counteract the negative presence of the photoinitiators and blue light exposure and result in a suitable environment for photoencapsulating cells in situ for tissue engineering and soft tissue applications.

Effect of the up-front heat treatment of gelatin particles dispersed in calcium phosphate cements on the in vivo material resorption and concomitant bone formation

Calcium phosphate cements (CPCs), consisting of a mixture of calcium phosphate powders and setting liquid, have been widely used in orthopedic applications. One of the drawbacks of CPCs is their poor resorbability in the living body, which hinders substitution with natural bones. One of the strategies to facilitate the resorption of CPCs is the incorporation of bioresorbable or water-soluble pore-generating particles (porogens), such as gelatin, in the CPC matrices. In spite of numerous reports, however, little is known about the effect of the dissolution/resorption rate of the porogens on concomitant bone regeneration. In the present study, we prepared preset CPCs dispersed with 10 mass% of low-endotoxin gelatin particles 200-500 μm in diameter having different heat-treatment histories, therefore exhibiting different dissolution rate, and then the obtained CPC/gelatin composites were evaluated for in vivo resorption and concomitant in vivo bone formation behaviors. As the results, the dispersion of gelatin particles markedly promoted in vivo resorption of CPC, and enhanced concomitant bone formation, connective tissue formation, osteoblast proliferation, and vascularization. The dissolution/resorption rate was able to be controlled by changing the up-front heat-treatment temperature. In particular, when CPC/gelatin composites were implanted in distal metaphysis of rabbits, the optimum dissolution/resorption was attained by heat-treating gelatin particles at 383 K for 24 h before dispersing in CPC. Quick resorption of calcium phosphate cement and concomitant bone formation by dispersing properly heat-treated with gelatin particles.

Synthesis of 24-h soluble gelatin sponge particles and their effect on liver necrosis following hepatic artery embolization: Results of in vitro and in vivo studies

AIM

To synthesize 24-h soluble gelatin sponge particles (SGSP) of 200-500 and 500-1000 µm, and to investigate their ischemic potency following hepatic artery embolization (HAE).

METHODS

Low-endotoxin gelatin was freeze-dried and heated at 110, 115, 118, 120, 122 and 125°C to form cross-linked gelatin sponge. We prepared 200-500- and 500-1000-µm SGSP by pulverizing and sieving the gelatin sponge. The dissolution times in saline were measured. Eight healthy pigs underwent HAE of the right and left hepatic arteries with either 200-500- or 500-1000-µm SGSP (n = 4/group).

RESULTS

The particles prepared at 110-122°C were soluble whereas particles prepared at 125°C or more were insoluble. The mean dissolution time of the particles increased with increasing temperature. In each pig, sequential arteriography confirmed that recanalization was complete 24 h after embolization. Pathological tests 48 h after HAE revealed coagulation necrosis but least damage to the biliary tract. The liver necrosis rate (mean ± standard deviation) was significantly greater in the 200-500-µm group than in the 500-1000-µm group (9.89 ± 4.04% vs 4.44 ± 0.67%, respectively; P = 0.0027). A significantly greater proportion of arteries with a diameter of 100-200 µm had residual SGSP in the 200-500-µm group than in the 500-1000-µm group (P < 0.002).

CONCLUSION

HAE with 200-500-µm SGSP had greater effects on promoting liver necrosis without biliary damage than did HAE with 500-1000-µm SGSP.

Enhancement of mechanical strength and in vivo cytocompatibility of porous β-tricalcium phosphate ceramics by gelatin coating

Background

In an attempt to prepare scaffolds with porosity and compressive strength as high as possible, we prepared porous β-tricalcium phosphate (TCP) scaffolds and coated them with regenerative medicine-grade gelatin. The effects of the gelatin coating on the compressive strength and in vivo osteoblast compatibility were investigated.

Methods

Porous β-TCP scaffolds were prepared and coated with up to 3 mass% gelatin, and then subjected to thermal cross-linking. The gelatin-coated and uncoated scaffolds were then subjected to compressive strength tests and implantation tests into bone defects of Wistar rats.

Results

The compressive strength increased by one order of magnitude from 0.45 MPa for uncoated to 5.1 MPa for gelatin-coated scaffolds. The osteoblast density in the internal space of the scaffold increased by 40 % through gelatin coating.

Conclusions

Coating porous bone graft materials with gelatin is a promising measure to enhance both mechanical strength and biomedical efficacy at the same time.

Endotoxins-the invisible companion in biomaterials research

Metal implants and polymeric devices for the application in the clinical treatment of orthopedic tissue injuries are increasingly coated with bioactive biomaterials derived from natural substances to induce desirable biological effects. Many metals and polymers used in biomaterials research show high affinity for endotoxins, which are abundant in the environment. Endotoxin contamination is indicated in the pathology of periodontitis and aseptic implant loosening, but may also affect the evaluation of a biomaterial's bioactivity by inducing strong inflammatory reactions. In this review, we discuss the high affinity of three commonly used implant biomaterials for endotoxins and how the contamination can affect the outcome of the orthopedic fixation. The chemical nature of bacterial endotoxins and some of the clinical health implications are described, as this knowledge is critically important to tackle the issues associated with the measurement and removal of endotoxins from medical devices. Commonly used methods for endotoxin testing and removal from natural substances are examined and the lack of standard guidelines for the in vitro evaluation of biomaterials is discussed.

Evaluation of the role of cisplatin-conjugated-soluble gelatin sponge: feasibility study in a swine model

PURPOSE

To evaluate the safety and the delivery function of cisplatin-conjugated-soluble gelatin sponge in a swine model.

METHODS

Fifteen healthy young swine were assigned into three groups: transarterial cisplatin infusion group, transarterial chemoembolization (TACE) with cisplatin-conjugated 120-min soluble gelatin sponge (TACE-120) group, and TACE with cisplatin-conjugated 360-min soluble gelatin sponge (TACE-360) group. A total volume of 0.8 mL/kg cisplatin in each group and 8 mg/kg soluble gelatin sponge in TACE-120 and TACE-360 groups were injected from the left hepatic artery in small increments for 10 min. Common hepatic angiography and whole-blood sampling via the left hepatic vein were conducted to explore recanalization immediately after the procedure and again at 10, 30, 60, 90, 120, 180, 240, 300, 360, and 420 min later. The area under the plasma concentration curve (AUC) of non-protein-bound platinum was compared among the three groups. Each liver was removed and cut into 10-cm-thick sections for calculating liver-damaged volume ratio.

RESULTS

Sequential angiography depicted gradual recanalization of the occluded hepatic artery and total recanalization at 120 and 360 min after embolization in the TACE-120 and TACE-360 groups, respectively. Of the three groups, AUC(0-30), AUC(30-120), and AUC(120-420) were significantly highest in the transarterial cisplatin infusion group (p < 0.001), the TACE-120 group (p < 0.001), and the TACE-360 group (p < 0.001), respectively. The liver-damaged volume ratio in the TACE-360 group was small (8.20 %) but significantly higher than that in the TACE-120 group (2.67%, p = 0.014).

CONCLUSION

Cisplatin-conjugated soluble gelatin sponge functions as a cisplatin carrier and is associated with tolerable liver damage.

A new soluble gelatin sponge for transcatheter hepatic arterial embolization

To prepare a soluble gelatin sponge (GS) and to explore the GS particles (GSPs) that inhibit development of collateral pathways when transcatheter hepatic arterial embolization is performed. The approval of the Institutional Committee on Research Animal Care of our institution was obtained. By means of 50 and 100 kDa of regenerative medicine-gelatin (RM-G), RM-G sponges were prepared by freeze-drying and heating to temperatures of 110-150°C for cross-linkage. The soluble times of RM-GSPs were measured in vitro. Eight swine for transcatheter hepatic arterial embolization were assigned into two groups: six received 135°C/50RM-GSPs, 125°C/100RM-GSPs, and 138°C/50RM-GSPs, with soluble time of 48 h or more in vitro; two swine received Gelpart GSPs (G-GSPs) with insoluble time of 14 days as a control. Transarterial chemoembolization was performed on two branches of the hepatic artery per swine. RM-GSPs heated at temperatures of 110-138°C were soluble. Mean soluble times of the RM-GSPs increased with higher temperature. Hepatic branches embolized with G-GSP remained occluded after 6 days, and development of collateral pathways was observed after 3 days. Hepatic branches embolized with 135°C/50RM-GSP and 125°C/100RM-GSP remained occluded for 4 h, and recanalization was observed after 1 day. Hepatic branches embolized with 138°C/50RM-GS remained occluded for 1 day, and recanalization was observed after 2 days with no development of collateral pathways. In RM-GSs with various soluble times that were prepared by modulating the heating temperature, 138°C/50RM-GSP was the soluble GSP with the longest occlusion time without inducing development of collateral pathways.