Clinical features of COVID-19 convalescent patients with re-positive nucleic acid detection.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a pandemic that has rapidly spread worldwide. Increasingly, confirmed patients being discharged according to the current diagnosis and treatment protocols, follow-up of convalescent patients is important to knowing about the outcome. METHODS: A retrospective study was performed among 98 convalescent patients with COVID-19 in a single medical center. The clinical features of patients during their hospitalization and 2-week postdischarge quarantine were collected. RESULTS: Among the 98 COVID-19 convalescent patients, 17 (17.3%) were detected positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid during 2-week postdischarge quarantine. The median time from discharge to SARS-CoV-2 nucleic acid re-positive was 4 days (IQR, 3-8.5).The median time from symptoms onset to final respiratory SARS-CoV-2 detection of negative result was significantly longer in re-positive group (34 days [IQR, 29.5-42.5]) than in non-re-positive group (19 days [IQR, 16-26]). On the other hand, the levels of CD3-CD56 + NK cells during hospitalization and 2-week postdischarge were higher in re-positive group than in non-re-positive group (repeated measures ANOVA, P = .018). However, only one case in re-positive group showed exudative lesion recurrence in pulmonary computed tomography (CT) with recurred symptoms. CONCLUSION: It is still possible for convalescent patients to show positive for SARS-CoV-2 nucleic acid detection, but most of the re-positive patients showed no deterioration in pulmonary CT findings. Continuous quarantine and close follow-up for convalescent patients are necessary to prevent possible relapse and spread of the disease to some extent.

Differentiation of bMSCs on Biocompatible, Biodegradable, and Biomimetic Scaffolds for Largely Defected Tissue Repair.

Biocompatible, biodegradable, and biomimetic scaffolds in combination with stem cells are of great importance for tissue engineering, especially the repairing and regeneration of defected organs. As a case in point, esophageal diseases have become serious clinical problems because of the poor self-repairing ability of the organ. It is crucial to prepare artificial replacements with biological function for serious lesions of the esophagus. However, the pH value, mechanical strength, thickness, and other physical conditions are very different in different organs or different parts of the same organ, which pose high difficulty for successful tissue engineering. In this work, bone marrow mesenchymal stem cells (bMSCs) were isolated from rabbits and transfected with green fluorescent protein (GFP) to follow their capabilities of growth, stemness, and differentiation in ex vivo culture. These bMSCs were seeded on biocompatible, biodegradable, and biomimetic scaffolds to detect the tissue regenerative capability of the esophagus with multilayer hierarchical structure. According to the esophageal bilayer muscle architecture, we designed discontinuous and continuous microchannel patterned scaffolds with medical level polyurethane (PU) as the matrix to guide the inner-circular and outer-longitudinal muscle growth. The gap on the discontinuous walls not only helped cells to communicate with each other but also assisted cells to infiltrate through the gap and grew into the inner circular muscle. The graft of silk fibroin on the scaffold surface using the aminolysis and glutaraldehyde cross-linking method enhanced the substrate's hydrophilicity and biocompatibility. Mucosa-submucosa tissue of rabbit's esophagus was decellularized to obtain the extracellular matrix (ECM) and implanted in situ after recellularizing with bMSCs to repair the partially defected rabbits' esophagus. On the basis of both in vitro and in vivo results, we concluded that esophagus regeneration was promoted by the differentiation of bMSCs on the biocompatible, biodegradable, and biomimetic scaffolds, starting from tissue "niches", to repair the largely defected esophagus, which paves the way for tissue engineering and defected organ treatments.

[Fabrication of hydrophilic medical catheter with hydrogel grafting and the in vivo evaluation of its histo-compatibility].

The biocompatible hydrogel was fabricated under suitable conditions with natural dextran and polyethylene glycol (PEG) as the reaction materials. The oligomer (Dex-AI) was firstly synthesized with dextran and allylisocyanate (AI). This Dex-AI was then reacted with poly (ethyleneglycoldiacrylate) (PEGDA) under the mass ratio of 4∶6 to get hydrogel (DP) with the maximum water absorption of 810%. This hydrogel was grafted onto the surface of medical catheter via diphenyl ketone treatment under ultraviolet (UV) initiator. The surface contact angle became lower from (97 ± 6.1)° to (25 ± 4.2)° after the catheter surface was grafted with hydrogel DP, which suggests that the catheter possesses super hydrophilicity with hydrogel grafting. The in vivo evaluation after they were implanted into ICR rats subcutaneously verified that this catheter had less serious inflammation and possessed better histocompatibility comparing with the untreated medical catheter. Therefore, it could be concluded that hydrogel grafting is a good technology for patients to reduce inflammation due to catheter implantation, esp. for the case of retention in body for a relative long time.

The growth and pluripotency of mesenchymal stem cell on the biodegradable polyurethane synthesized with ferric catalyst.

Polyurethane (PU) is a class of polymers that have been applied for tissue-engineering scaffolds. Cross-linked poly(ester urethane) (CPU), synthesized with ferric catalyst in our laboratory, was modified by silk fibroin (SF) grafting using our aminolysis and glutaradehyde crosslinking method. The physical and chemical properties of the materials were investigated by scanning electron microscope (SEM), atomic force microscope (AFM) and tensile tester. The results showed that SF grafted CPU possessed good strain and strength (4.29 ± 0.18 MPa/382.38 ± 0.71%). Its surface chemistry and roughness were fine to well support the growth of bone marrow mesenchymal stem cells (BMSC). The cells were verified to maintain the pluripotency after they were cultured in vitro for 2 weeks, which supplied us a good technology to keep cell's stemness but proliferate cell's number. These results are valuable for us to further study esophageal tissue engineering with BMSC and polyurethane materials as the components.

[Hyaluronic acid production by Streptococcus iniae and its application in rabbit skin's regeneration].

Hyaluronic acid (HA) is an important biomaterial as the extracellular matrix in human body. We produced HA by fermentation of Streptococcus iniae (Strep.). Production of HA by Strep. was evaluated and further improved by strain mutation by ultraviolet. One strain with higher HA yield and lower content of protein was obtained. Its HA yield increased from (82.3±3.3) mg/L to (120±10.6) mg/L, and protein decreased from (0.178±0.011) mg/L to (0.032±0.017) mg/L. The molecular weight (MW) of HA yield from Strep. is about 3.0×105 Da. Using the method of freezing and thawing, HA aqueous solution was transferred into hydrogel. This HA hydrogel, casted on sterilized non-woven fabric, was applied to repair rabbit skin with full-thickness defect. The preliminary results of the animal tests displayed that HA hydrogel obviously reduced the inflammation around the wound and promoted the skin regeneration comparing with the control tests.

Constitution and in vivo test of micro-porous tubular scaffold for esophageal tissue engineering.

Current clinical techniques in treating long-gap esophageal defects often lead to complications and high morbidity. Aiming at long-gap synthetic esophageal substitute, we had synthesized a biodegradable copolymer, poly(L-lactide-co-caprolactone) (PLLC), with low glass transition temperature. In this work, we developed a tubular PLLC porous scaffold using a self-designed tubular mold and thermal induced phase separation (TIPS) method. In order to enhance the interaction between tissue and scaffold, fibrin, a natural fibrous protein derived from blood fibrinogen, was coated on the scaffold circumferential surface. The fibrin density was measured to be 1.23 ± 0.04 mg/cm(2). Primary epithelial cell culture demonstrated the improved in vitro biocompatibility. In animal study with partial scaffold implantation, in situ mucosa regeneration was observed along the degradation of the scaffold. These indicate that fibrin incorporated PLLC scaffold can greatly improve epithelial regeneration in esophagus repair, therefore serve as a good candidate for long-term evaluation of post-implantation at excision site.

[Clinical observation of arthroscopic medial patellofemoral ligament overlap and lateral patellar retinaculum release in treatment of patellofemoral pain syndrome].

OBJECTIVE: To explore the therapeutic results of surgical treatment for patellofemoral pain syndrome. METHODS: One hundred patients (35 males and 65 females, ranging from 50 to 70 years old with an average age of 63 years) with patellofemoral pain syndrome were randomly and equally divided into treatment group and control group. All patients underwent arthroscopic treatment. The patients in treatment group were treated with medial patellofemoral ligament overlap and lateral patellar retinaculum release, and the patients in control group were just treated with lateral patella retinaculum release which is a current widespread operation. RESULTS: All patients were followed-up with the mean time of 13 months, and were evaluated with HSS (hospital for special surgery) scoring system for the therapeutic effect. The mean score of treatment group (73.52+/-11.17) and control group (65.50+/-13.70) had statistical difference (P<0.05), which indicated that the therapeutic effect of medial patellofemoral ligament overlap and lateral patellar retinaculum release for treatment of patellofemoral pain syndrome was satisfying. CONCLUSION: Compared with lateral patellar retinaculum release, this procedure is superior in correcting the abnormal movement of patellofemoral joint, easily balancing patellofemoral joint space, effectively relieving the pain of anterior knee. No postoperative complications occur, such as intraarticular haematoma, necrosis and dislocation of patella and so on.

[Comparative study on effects of combined massage-smouldering-washing therapy and mini-invasive surgery in treating knee osteoarthritis].

OBJECTIVE: To comparatively study the curative effects of combined massage-smouldering-washing therapy (MSW) and mini-invasive surgery in treating knee osteoarthritis (KOA) of mild-moderate degree so as to provide a suitable therapeutic protocol. METHODS: Sixty patients with KOA were assigned to two groups. The treatment group was treated with MSW once a day for 10 days as one course, and 4 courses were applied totally with an interval of 3 days between courses. The control group was treated with mini-invasive surgery by arthroscopic mopping, followed with post-operational intra-articular cavity injection with sodium hyaluronate injection, 20 mg every week for 5 times continuously. The therapeutic effect and the changes in scores of clinical symptoms and signs before and after treatment in the two groups were observed and compared. RESULTS: Outcome of 3-month follow-up showed the effective rate was 90% in the treatment group and 93.33% in the control group; scores of clinical symptoms and signs effectively improved in both groups, but the improvement on the 4 items (joint pain, swelling, soreness of loin and knee, and cold aversion of knee) was superior in the treatment group, while that on the other 4 items (pain during squatting or half-squatting, up stairs or down stairs, joint stiffiness and joint kinetic capacity) was superior in the control group (P < 0.05). CONCLUSION: Both MSW and mini-invasive surgery have definite curative effect on KOA but with different particularities.