Yo-Shen Chen

Laminin-alginate beads as preadipocyte carriers to enhance adipogenesis in vitro and in vivo

The use of autologous fat grafting in breast reconstruction still requires optimization. Fat survival and calcification are the main issues that affect the outcomes of the procedure. In this study, a cell-based therapy utilizing laminin-alginate beads (LABs) as carriers was proposed to promote cell survival and adipogenesis by providing short-term physical support and facilitate nutrient diffusion of the implants. Laminin-modified alginate beads were fabricated by immobilizing laminin onto ring-opened alginate, used to encapsulate 3T3-L1 preadipocytes, and evaluated in vitro and in vivo. LABs as preadipocyte carriers showed better biocompatibility and stability than unmodified alginate beads. Preadipocytes in LABs had higher survival rate and enhanced adipogenesis than those in unmodified alginate beads. In vivo studies showed that LABs gradually degraded and the sites were replaced by newly formed fat tissues, and new blood vessels were also observed. 7T-MRI study mimicking clinical fat grafting showed that LABs carrying adipose stem cells improved the results of conventional fat grafts. Therefore, we believe that LABs represent promising cell carriers and can be potentially used for the reconstruction of breasts or other soft tissues in the future.

Modifying alginate with early embryonic extracellular matrix, laminin, and hyaluronic acid for adipose tissue engineering

Extracellular matrix provides both mechanistic and chemical cues that can influence cellular behaviors such as adhesion, migration, proliferation, and differentiation. In this study, a new material, HA-L-Alg, was synthesized by linking developmentally essential ECM constituents hyaluronic acid (HA) and laminin(L) to alginate (Alg). The fabrication of HA-L-Alg was confirmed by FTIR spectroscopy, and it was used to form 3D cell-carrying beads. HA-L-Alg beads had a steady rate of degradation and retained 63.25% of mass after 9 weeks. HA-L-Alg beads showed biocompatibility comparable to beads formed by Alg-only with no obvious cytotoxic effect on the embedded 3T3-L1 preadipocytes. HA-L-Alg encapsulated 3T3-L1 cells were found to have a higher proliferation rate over those in Alg-only beads. These cells also showed better differentiation capacity after 2 weeks of adipogenic induction within HA-L-Alg beads. These results support that HA-L-Alg facilitated cell survival and proliferation, as well as stimulated and maintained cell differentiation. Our results suggest that HA-L-Alg has a great clinical potential to be used as stem cell carrier for adipose tissue engineering.

Evaluation of a laminin-alginate biomaterial, adipocytes, and adipocyte-derived stem cells interaction in animal autologous fat grafting model using 7-Tesla magnetic resonance imaging

Biomaterials are often added to autologous fat grafts both as supporting matrices for the grafted adipocytes and as cell carrier for adipose-derived stem cells (ADSCs). This in vivo study used an autologous fat graft model to test a lamininalginate biomaterial, adipocytes, and ADSCs in immune-competent rats. We transplanted different combinations of shredded autologous adipose tissue [designated “A” for adipose tissue]), laminin-alginate beads [designated “B” for bead], and ADSCs [designated “C” for cell]) into the backs of 15 Sprague-Dawley rats. Group A received only adipocytes, Group B received only laminin-alginate beads, Group AB received adipocytes mixed with laminin-alginate beads, Group BC received laminin-alginate beads encapsulating ADSCs, and Group ABC received adipocytes and laminin-alginate beads containing ADSCs. Seven-tesla magnetic resonance imaging was used to evaluate the rats at the 1st, 6th, and 12th weeks after transplantation. At the 12th week, the rats were sacrificed and the implanted materials were retrieved for gross examination and histological evaluation. The results based on MRI, gross evaluation, and histological data all showed that implants in Group ABC had better resorption of the biomaterial, improved survival of the grafted adipocytes, and adipogenic differentiation of ADSCs. Volume retention of grafts in Group ABC (89%) was also significantly greater than those in Group A (58%) (p < 0.01). Our findings support that the combination of shredded adipose tissue with ADSCs in laminin-alginate beads provided the best overall outcome.

Abdominal and/or Flank Necrotizing Fasciitis Secondary to Intra-abdominal Processes-NTUH Series

We present a unique case of necrotizing fasciitis of the abdomen with bilateral flank involvement, which was secondary to a fistula formation between the colon and the rectus muscle fascia, Group B Salmonella infection is believed to be the cause of initial colon perforation that led to the subsequent fistula formation. To the best of our knowledge, such a case has never been reported in the literatures. This unique case led us further to question if isolated abdominal and/or flank necrotizing fasciitis without previous history of trauma or operation are intra-abdominal origin. We retrieved all record of patients diagnosed with necrotizing fasciitis in our hospital from January 1992 to January 2002. A total of 150 patients was identified and confirmed. We found that isolated abdominal and/or flank necrotizing fasciitis without previous trauma or operation is in deed a rare occurrence, and only six such patient was identified (3 male, 3 female) counting for a mere 4 percent of 150 patient of necrotizing fasciitis. All six cases of isolated abdominal and/or flank necrotizing fasciitis presented as a spontaneous, isolated event, and all were intra-abdominal origin. Unfortunately, five cases resulted in mortality. From this review, we suggest that (1) necrotizing fasciitis involving the abdominal wall carries a very poor prognosis than the necrotizing fasciitis involving other regions; and (2) when presented with a seemingly spontaneous and isolated abdominal and/or flank necrotizing fasciitis, an entry from the digestive tract should be greatly suspected.

A Simple Perforator Classification of Anterolateral Thigh Flap and Its Correlation with the Preoperative Doppler Examination

Anterolateral thigh flap is often the first choice for the reconstruction of soft tissue defects, and it is also known for its variable anatomy of the vascular pedicle and the relatively difficult dissection when dealing with intramuscular perforators. Many classifications have been proposed based on its proximal branching pattern of its vascular pedicle, yet these classifications often have no correlation with clinical practices. We proposed a simple classification for the perforator of anterolateral thigh flap according to the routes and distance taken by the perforator in between the skin paddle and the pedicle. From this study, the preoperative Doppler examination has not only shown its value for locating the cutaneous perforators, but also for identifying of certain type of the perforator. Linear Dopple signal of 3cm or above preoperatively has positive correlation with intramuscular perforator greater than 6 cm intraoperatively.