Long-term survival of free fat grafts in muscle: an experimental study in rats

Histologic Comparison of Autologous Fat Processing Methods

PURPOSE

To perform a quantitative analysis of adipocyte viability after fat processing during autologous fat transfer, comparing the processing methods of washing, centrifuging, and sedimentation.

METHODS

An experimental study was conducted in which 24 fat samples were obtained after processing from 22 patients undergoing autologous fat transfer. Histologic analysis of periodic acid-Schiff-stained specimens was then performed.

RESULTS

Cell counts per high-powered field of intact adipocytes and nucleated adipocytes and adipocyte cross-sectional area were significantly greater in samples processed by sedimentation, compared with those by centrifuging or washing.

CONCLUSIONS

Of the various processing techniques currently used during autologous fat transfer, sedimentation appears to yield a higher proportion of viable adipocytes than does washing or centrifuging.

Cryopreservation of human fat for soft tissue augmentation: viability requires use of cryoprotectant and controlled freezing and storage

BACKGROUND

Autologous fat transfer for soft tissue augmentation has been increasing in recent years. Graft longevity may vary greatly from patient to patient, requiring repeat procedures, often using frozen adipose tissue. Storage usually involves placing syringes of fat directly into a -20 degrees C freezer. However, the viability of fat frozen in this way is controversial.

OBJECTIVE

This study tested methods for the optimal storage of adipose tissue harvested by tumescent liposuction.

MATERIALS AND METHODS

Aliquots of washed adipose tissue were frozen directly at -20 degrees C or mixed with cryoprotectants, frozen at 1 degree C/min, and subsequently stored in liquid nitrogen vapor phase. Aliquots were subsequently thawed, and adipocyte viability was determined by staining and culture methods.

RESULTS

Viability of adipocytes frozen at -20 degrees C was very low when analyzed by staining, and no cultures could be established from any of the specimens. In contrast, viable adipocytes were recovered from samples that were controlled-rate frozen in the presence of cryoprotectants and stored in nitrogen vapor. CONCLUSION. Our results indicate that fat frozen at -20 degrees C is not viable and thus provides no advantage over inert fillers. The methods here described could readily be transferred to the clinical setting after further laboratory study.

Fat Injection: A 20-Year Revision

In the last 20 years, several different techniques of lipoinjection have been developed. Nevertheless, a standard procedure has not been adopted by all practitioners. There is no agreement as to the best way of processing the fat to ensure maximal take and viability of the graft. Other controversial issues include the ideal cannula for harvesting and reinjection, the presence of blood in the transplanted fat, trauma, air exposure, contamination of the graft, durability, and fat cell survival. Newly emerging approaches to fat tissue engineering with the use of cultured autologous preadipocytes may improve the technique of fat injection and transplant.

The Role of Recipient Sites in Fat-Graft Survival

The survival of fat grafts depends on many factors, 1 of the major being early revascularization. Early studies showed that adipose tissue has a low tolerance to ischemia. Some methods have been described to increase the tolerance of adipose tissue to ischemia. This study was designed to compare volume maintenance of the transplanted fat graft in different recipient sites of the rabbit face. Three groups of 5 New Zealand white rabbits were studied. Fat grafts harvested from the right inguinal fat pad were transplanted to the buccomandibular area of the rabbit's face. Three different recipient sites (subcutaneous, supramuscular, and submuscular) were dissected on each side of the face, and groups were formulated based on this difference of recipient sites. Morphometric, as well as histopathologic, analyses were done, and the results revealed a statistically significant increase of fat graft survival in supramuscular layer (81.95% +/- 4.40%) than in subcutaneous (41.62% +/- 3.29%) and submuscular layer (37.31% +/- 5.77%) (P<0.05). This study demonstrates that selection of an "appropriate recipient site" should enhance ultimate fat-graft survival.

Facteurs influençant la survie de la greffe d’adipocytes

Most authors supported the theory of adipocyte survival. The viability of these cells has been demonstrated by various experimental clinical, radiological and biochemical studies. After a review of the literature, the authors report the various factors, which influence the survival of the transplanted adipocytes. These factors are presented according to their chronology in the operative procedure. The techniques used are very diverse. The reference technique chosen is that described by Coleman (Lipostructure). The following factors are studied: type of anaesthesia, infiltration, donor site of adipose tissue, method of harvesting, method of refining adipose tissue, anabolic complements, receiving site, reinjection technique, number of grafting sessions, freezing of adipose tissue and complementary postoperative treatments. It seems imperative that each phase of the operative procedure should be carried out without damage to the adipocytes, in particular their harvesting, refining and reinjection. All the other factors studied require comparative analysis in order to demonstrate their true importance. This opens up various directions of research aiming to improve the survival of the transplanted adipocytes.

The fate of intramuscularly injected fat autografts: an experimental study in rabbits

An experimental study was designed to assess the viability and revascularization of intramuscularly injected fat autografts. For the study, 18 rabbits were divided into two groups. In the first group, fat was injected intramuscularly (12 rabbits). Autologous fat was obtained from the inguinal area and subsequently injected into the thigh muscle. In the second group, physiologic saline was injected intramuscularly to determine the effects of cannulation and pressure on muscle tissue (6 rabbits). Fat autografts were performed on the right side of the animal, and the left side was used as the control. Scintigraphic imaging and histopathologic examination of the limbs were performed after injection of adipose tissue on days 15, 30, 45, 60, 90, and 120. On the technetium-99m ((99m)Tc) hexamethylpropylene amine oxime scintigraphy, whereas similar activity distribution was observed between the left and right thigh on days 15, 30, and 45, there was increased uptake at the right thigh on days 60, 90, and 120. This increased uptake indicates that there is viable fat tissue in this region. Histopathologic evaluation showed that microcysts resulting from degeneration of some adipocytes and inflammatory changes on day 15 additionally increased vascularity and fibrosis in some animals on day 30, as well as fibrosis, microcysties, and focal calcification areas in adipose tissue on day 45 and later. It was observed that adipose tissue survived in more than 50% of the graft area in all the animals. These findings show that fat autografts can survive in muscle tissue with less than 50% fibrotic change.

No-touch technique for autologous fat harvesting

A new technique for autologous fat harvesting is presented. It is termed the "no-touch" technique because the concentrated fat graft is obtained with no handling of fatty tissue. With the no-touch technique, fat aspiration is performed under tourniquet. There is no need for any mechanical manipulations such as centrifugation, washing, whisking, filtering, or straining. The medial aspect of the knee is used as the donor area. Fat is aspirated through a disposable 10-ml syringe and a 14-gauge microcannula, which consists of a curved, semiblunted tip such as that of the Tuohy needle. What remains in the syringe is the concentrated fat without blood, serum, or lidocaine. The authors report their experience with 30 patients.

Measurement in vivo of the survival rate in autologous adipocyte transplantation

Up until now, research on fat cells has been unable to prove their survival rate objectively in vivo. In this article, the first application of the cell surface marker PKH26 in the fat cells of rats is reported. In a study of 48 Lewis rats, this method enabled the objective stereometry of viable and necrotic grafts after variable follow-up times in groups of eight animals each. The best survival rate was 30.41 percent, and the best implantation site was the interscapular subcutis. During follow-up, a characteristic change in size of the viable fat cells matched the in vitro findings of various investigators. Because of the surface marking, it could be proved that the viable cells found after 6 months were transplanted cells that had undergone a cycle of fat deprivation and regaining. This is proof of the cell survival theory postulated by Peer in 1950.

Applications of the classic dermal fat graft in primary and secondary facial rejuvenation

Volumetric facial aging occurs primarily as a descent of facial soft tissues, followed by their secondary atrophy. Proper volumetric facial rejuvenation, therefore, demands effective superior redistribution of fallen soft tissues, for which the author prefers malar imbrication. Only then do augmentative adjustments become appropriate, including solid facial protheses, "soft-tissue" fillers, dermal fat grafts, free-fat micrografts, and Erol's "tissue-cocktail." Of these, the author prefers the time-honored dermal fat graft for all primary volumetric augmentations within the surgical field, reserving free-fat micrografts for adjustments outside the field and those performed secondarily. Dermal fat grafts are added to the face in three categories: "camouflage" grafts from the anterior face lift discard specimen to correct contour irregularities in the sculpted subcutaneous cheek in half of patients; "transition" grafts from the suprapubic abdomen to the zone between the midface and lower face in 5 percent of patients with an emaciated quality to their aging; and "secondary" grafts from the abdomen in occasional patients with volumetric deformities following inexpert face lift and other forms of trauma. All grafts were harvested, prepared, and placed according to 10 straightforward technical principles. The grafts were highly effective and predictable in their ability to augment contour; none of 283 total grafts were regarded as a treatment failure. The use of such grafts was extremely safe, with complications limited to cyst formation in 1.5 percent of grafts, all of which were treated nonoperatively. The use of the dermal fat graft is seen as safe, effective, and convenient when the subcutaneous plane of the face is exposed during facial rejuvenation. The majority of grafts were derived from the face lift discard specimen. Although those that came from outside the head and neck presented extra inconvenience and operative time, their use was limited to occasional and challenging circumstances that justified extra investment.

Simultaneous rhytidoplasty and lipoinjection: a comprehensive aesthetic surgical strategy

Fat autografting is an accepted technique in the treatment of depressions or augmenting thin soft tissues. Aging soft tissues become thin, among them the subcutaneous fat layer, muscles, and fasciae, and these tissues in addition become flaccid. Therefore, to get better results in rejuvenation plastic surgery, a good alternative is the combination of lifting the flaccid tissues and thickening the thin soft tissues with a lack of contour and definition, which enhances the aspect of the entire face and neck. For 10 years in our practice, we have been combining rhytidoplasty (which includes systematizing superficial musculoaponeurotic system and platysma plication) with lipoinjection, placing thin rolls of autologous fat into the facial and cervical muscles, or at least under the fasciae. The results reveal a very high success rate with few minor complications. Proper diagnosis, patient selection, and adequate surgical technique produce predictable and favorable aesthetic results. A concurrent retrospective study of 357 consecutive patients who underwent simultaneous rhytidoplasty and lipoinjection was conducted over a 10-year period (1985 to 1995). The purpose of this article is to show our experience with this method, including long follow-up observations.