The prolonged survival of fibroblasts with forced lipid catabolism in visceral fat following encapsulation in alginate-poly-L-lysine.

Biomaterials. 2012 Aug;33(22):5638-49. doi: 10.1016/j.biomaterials.2012.04.035. Epub 2012 May 9.

Yang F, Zhang X, Maiseyeu A, Mihai G, Yasmeen R, DiSilvestro D, Maurya SK, Periasamy M, Bergdall KV, Duester G, Sen CK, Roy S, Lee LJ, Rajagopalan S, Ziouzenkova O.



Although alginate-poly-L-lysine (APL) encapsulation of cells producing bioactive peptides has been widely tested, it is unknown whether APL supports lasting catabolic functions of encapsulated cells in adipose tissue, which are required for obesity reduction. We tested functions of APL-encapsulated fibroblasts isolated from wild-type (WT) and aldehyde dehydrogenase 1a1 knockout mice (KO), which resist obesity on a high-fat (HF) diet, have a higher metabolic rate, and express increased levels of thermogenic uncoupling protein-1 (Ucp1) in their deleterious visceral fat depots compared to WT mice. To enable in vivo detection and quantification, fibroblasts were stably transfected with green-fluorescent protein. WT- or KO-containing microcapsules were injected into two visceral depots of WT mice fed an HF diet. Eighty days after transplantation, microcapsules were located in vivo using magnetic resonance imaging. KO microcapsules prevented weight gain in obese WT mice compared to a mock- and WT capsule-injected groups on an HF diet. The weight loss in KO-treated mice corresponded to lipid reduction and induction of thermogenesis in the injected visceral fat. The non-treated subcutaneous fat was not altered. Our data suggest that the APL polymer supports long-term catabolic functions of genetically-modified fibroblasts, which can be potentially used for depot-specific obesity treatment.


DiSilvestro D and Ziouzenkova O.

Obesity is growing worldwide problem [1]. Obesity increases the risk of cancer, diabetes, cardiovascular disease, and mortality [2]. Obesity is a disease of excess white adipose tissue (WAT) that stores fat and produces an array of bioactive molecules (adipokines). Secreted adipokines can increase chronic inflammation, decrease glucose tolerance, and promote other pathological conditions [2, 3].  WAT can be categorized into two groups, subcutaneous and visceral fat (VF).  Increased VF, also known as abdominal fat, has been linked to increased inflammation and increased risk of obesity related diseases, such as type II diabetes and cardiovascular disease [3]. In contrast, subcutaneous fat, also known as peripheral fat, generates cytokines that can decrease inflammation and reduce the risk for type II diabetes [4].  Diet and exercise may reduce body WAT; however, they cannot preferentially reduce VF. Furthermore, treating obesity by implementing lifestyle changes may not be sufficient to successfully treat severely obese patients that are elderly or have disabilities.  We developed a novel obesity therapy that targets VF and would improve health outcomes when traditional therapies, such as diet and exercise fail [5].

In the body, substantial energy expenditure could be achieved through heat production (thermogenesis).  This is mediated by brown adipose tissue or specific rare cells known as thermocytes, beige, or bright adipocytes in WAT.  Thermocytes and brown fat adipocytes express uncoupling protein 1 (UCP1) that dissipates energy for heat instead of producing ATP.  Increased UCP1 expression in WAT, results in a lean phenotype [6, 7].  On the contrary, a decrease in thermogenesis in WAT can cause obesity [8].  Many studies suggest that thermogenic proteins, like UCP1, are novel targets of obesity therapy [9]. Our goal was to locally increase thermogenesis within VF and reduce fat storage in this deleterious fat depot. To accomplish this, thermocytes could be implanted into VF to directly increase thermogenesis within the VF depot.

To create a thermogenic cell line, we used GFP labeled fibroblasts that are genetically deficient in aldehyde dehydrogenase 1a1 (Aldh1a1), a gene involved in vitamin A metabolism [5].  Aldh1a1-/- female mice develop less VF on a high fat diet than WT mice fed the same diet due to a markedly increased number of thermocytes in VF. In order to use immortalized Aldh1a1-/- fibroblasts these cells as a therapy, the genetically different Aldh1a1-/- fibroblasts need to be protected or they would be destroyed by the host’s immune system. To overcome this, we used APL encapsulation technology to place thermogenic engineered fibroblasts into VF in an attempt to change the microenvironment of the VF tissue.  APL-encapsulation provides a vehicle to deliver cells to a specific location in the body.  The protective APL-capsule surrounds the encapsulated cells allowing nutrients to pass through, as well as providing protection from the host’s immune system.

GFP labeled Aldh1a1-/- thermogenic fibroblasts (GKO) and lipogenic wild-type fibroblasts (GWT) were encapsulated and injected into the VF of WT mice.  For a control, WT mice were injected with phosphate buffered saline.  To maintain obesogenic conditions, all mouse groups were kept on a HF diet .The groups that had encapsulated cells (GKO and GWT) immediately lost weight.  The weight loss most likely was not due to the capsules themselves because mice injected with empty (acellular) capsules did not lose weight.  As time passed the GKO group maintained weight loss, whereas WT mice injected with GWT began to gain weight.  Furthermore, thermogenic GKO-treated group’s weight was statistically the same when comparing the weight at injection to the weight 80 days after injection, whereas both the control and GWT-treated groups gained weight over this time.  Injection of encapsulated thermogenic GKO cells had stimulated UCP1 expression and thermogenic remodeling of VF in the host WT mice.  Images confirmed that there were UCP1 positive cells located in areas close to the GKO capsules.  The GKO injected mice had a greater metabolic rate as well as better glucose sensitivity than the GWT and control mouse groups. It seems as though the encapsulated GKO fibroblasts affected the surrounding tissue and had a positive health effect on the overall body lipid and glucose metabolism (Fig. 1).

While there was some success in attenuating weight gain, more research needs to be done using this encapsulation technology.  Another more thermogenic cell lines or cell lines controlling appetite and food consumption could be developed.

Regardless these results show that it is possible to attenuate weight gain in a tissue and fat-depot specific fashion through encapsulation technology.  Similar technology has already been used to encapsulate islet cells to generate insulin for people with type I diabetes [10].  Encapsulation provides a means to deliver treatment to a specific area, unlike drugs and other treatments that have undesired systemic responses. If developed carefully APL-encapsulation may provide safer treatment options for obesity and other diseases.

biomaterial fig1Figure 1: Mice were fed a high fat diet and injected with capsules containing thermocytes or adipocytes.  The mice with thermocyte-containing capsules exhibited a resistance to weight and fat gain as well as a greater metabolic rate than mice injected with adipocyte containing capsules or a control group of mice fad same high-fat diet.



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